fix_bbtppq: add missing space - no-op
[ardour.git] / gtk2_ardour / engine_dialog.cc
index dccffde949ded504da033637b554d000a85e93bc..8a6c42fd8c79bdb11771d4463dcfe96322fa65b3 100644 (file)
@@ -20,7 +20,6 @@
 #include <exception>
 #include <vector>
 #include <cmath>
-#include <fstream>
 #include <map>
 
 #include <boost/scoped_ptr.hpp>
 #include "ardour/audio_backend.h"
 #include "ardour/audioengine.h"
 #include "ardour/mtdm.h"
+#include "ardour/mididm.h"
 #include "ardour/rc_configuration.h"
 #include "ardour/types.h"
+#include "ardour/profile.h"
 
 #include "pbd/convert.h"
 #include "pbd/error.h"
 
+#include "opts.h"
+#include "debug.h"
 #include "ardour_ui.h"
 #include "engine_dialog.h"
 #include "gui_thread.h"
 #include "utils.h"
-#include "i18n.h"
+#include "pbd/i18n.h"
 
 using namespace std;
 using namespace Gtk;
 using namespace Gtkmm2ext;
 using namespace PBD;
 using namespace Glib;
+using namespace ARDOUR_UI_UTILS;
 
-static const unsigned int midi_tab = -1; /* not currently in use */
+#define DEBUG_ECONTROL(msg) DEBUG_TRACE (PBD::DEBUG::EngineControl, string_compose ("%1: %2\n", __LINE__, msg));
+
+static const unsigned int midi_tab = 2;
 static const unsigned int latency_tab = 1; /* zero-based, page zero is the main setup page */
 
+static const char* results_markup = X_("<span weight=\"bold\" size=\"larger\">%1</span>");
+
 EngineControl::EngineControl ()
        : ArdourDialog (_("Audio/MIDI Setup"))
-       , basic_packer (9, 3)
+       , engine_status ("")
+       , basic_packer (9, 4)
        , input_latency_adjustment (0, 0, 99999, 1)
        , input_latency (input_latency_adjustment)
        , output_latency_adjustment (0, 0, 99999, 1)
@@ -75,26 +84,35 @@ EngineControl::EngineControl ()
        , ports_adjustment (128, 8, 1024, 1, 16)
        , ports_spinner (ports_adjustment)
        , control_app_button (_("Device Control Panel"))
-       , lm_start_stop_label (_("Measure latency"))
+       , midi_devices_button (_("Midi Device Setup"))
+       , start_stop_button (_("Stop"))
+       , update_devices_button (_("Refresh Devices"))
+       , use_buffered_io_button (_("Use Buffered I/O"), ArdourButton::led_default_elements)
+       , lm_measure_label (_("Measure"))
        , lm_use_button (_("Use results"))
-       , lm_table (5, 2)
+       , lm_back_button (_("Back to settings ... (ignore results)"))
+       , lm_button_audio (_("Calibrate Audio"))
+       , lm_table (12, 3)
        , have_lm_results (false)
-       , midi_refresh_button (_("Refresh list"))
+       , lm_running (false)
+       , midi_back_button (_("Back to settings"))
        , ignore_changes (0)
+       , ignore_device_changes (0)
        , _desired_sample_rate (0)
-       , no_push (true)
        , started_at_least_once (false)
+       , queue_device_changed (false)
+       , _have_control (true)
+       , block_signals(0)
 {
        using namespace Notebook_Helpers;
-       vector<string> strings;
+       vector<string> backend_names;
        Label* label;
        AttachOptions xopt = AttachOptions (FILL|EXPAND);
        int row;
 
        set_name (X_("AudioMIDISetup"));
 
-       /* the backend combo is the one thing that is ALWAYS visible 
-        */
+       /* the backend combo is the one thing that is ALWAYS visible */
 
        vector<const ARDOUR::AudioBackendInfo*> backends = ARDOUR::AudioEngine::instance()->available_backends();
 
@@ -105,12 +123,10 @@ EngineControl::EngineControl ()
        }
 
        for (vector<const ARDOUR::AudioBackendInfo*>::const_iterator b = backends.begin(); b != backends.end(); ++b) {
-               strings.push_back ((*b)->name);
+               backend_names.push_back ((*b)->name);
        }
 
-       set_popdown_strings (backend_combo, strings);
-       backend_combo.set_active_text (strings.front());
-       backend_combo.signal_changed().connect (sigc::mem_fun (*this, &EngineControl::backend_changed));
+       set_popdown_strings (backend_combo, backend_names);
 
        /* setup basic packing characteristics for the table used on the main
         * tab of the notebook
@@ -118,40 +134,38 @@ EngineControl::EngineControl ()
 
        basic_packer.set_spacings (6);
        basic_packer.set_border_width (12);
-       basic_packer.set_homogeneous (true);
+       basic_packer.set_homogeneous (false);
 
        /* pack it in */
 
        basic_hbox.pack_start (basic_packer, false, false);
 
-       /* latency tab */
-
        /* latency measurement tab */
-       
+
        lm_title.set_markup (string_compose ("<span size=\"large\" weight=\"bold\">%1</span>", _("Latency Measurement Tool")));
-       
+
        row = 0;
        lm_table.set_row_spacings (12);
+       lm_table.set_col_spacings (6);
+       lm_table.set_homogeneous (false);
 
-       lm_table.attach (lm_title, 0, 2, row, row+1, xopt, (AttachOptions) 0);
+       lm_table.attach (lm_title, 0, 3, row, row+1, xopt, (AttachOptions) 0);
        row++;
 
-       Gtk::Label* preamble;
-
-       preamble = manage (new Label);
-       preamble->set_width_chars (60);
-       preamble->set_line_wrap (true);
-       preamble->set_markup (_("<span weight=\"bold\">Turn down the volume on your hardware to a very low level.</span>"));
+       lm_preamble.set_width_chars (60);
+       lm_preamble.set_line_wrap (true);
+       lm_preamble.set_markup (_("<span weight=\"bold\">Turn down the volume on your audio equipment to a very low level.</span>"));
 
-       lm_table.attach (*preamble, 0, 2, row, row+1, AttachOptions(FILL|EXPAND), (AttachOptions) 0);
+       lm_table.attach (lm_preamble, 0, 3, row, row+1, AttachOptions(FILL|EXPAND), (AttachOptions) 0);
        row++;
 
+       Gtk::Label* preamble;
        preamble = manage (new Label);
        preamble->set_width_chars (60);
        preamble->set_line_wrap (true);
-       preamble->set_markup (_("Select two channels below and connect them using a cable or (less ideally) a speaker and microphone."));
+       preamble->set_markup (_("Select two channels below and connect them using a cable."));
 
-       lm_table.attach (*preamble, 0, 2, row, row+1, AttachOptions(FILL|EXPAND), (AttachOptions) 0);
+       lm_table.attach (*preamble, 0, 3, row, row+1, AttachOptions(FILL|EXPAND), (AttachOptions) 0);
        row++;
 
        label = manage (new Label (_("Output channel")));
@@ -159,7 +173,7 @@ EngineControl::EngineControl ()
 
        Gtk::Alignment* misc_align = manage (new Alignment (0.0, 0.5));
        misc_align->add (lm_output_channel_combo);
-       lm_table.attach (*misc_align, 1, 2, row, row+1, xopt, (AttachOptions) 0);
+       lm_table.attach (*misc_align, 1, 3, row, row+1, xopt, (AttachOptions) 0);
        ++row;
 
        label = manage (new Label (_("Input channel")));
@@ -167,53 +181,72 @@ EngineControl::EngineControl ()
 
        misc_align = manage (new Alignment (0.0, 0.5));
        misc_align->add (lm_input_channel_combo);
-       lm_table.attach (*misc_align, 1, 2, row, row+1, FILL, (AttachOptions) 0);
+       lm_table.attach (*misc_align, 1, 3, row, row+1, FILL, (AttachOptions) 0);
        ++row;
 
-       xopt = AttachOptions(0);
-
-       lm_measure_button.add (lm_start_stop_label);
-       
-       lm_measure_button.signal_toggled().connect (sigc::mem_fun (*this, &EngineControl::latency_button_toggled));
+       lm_measure_label.set_padding (10, 10);
+       lm_measure_button.add (lm_measure_label);
+       lm_measure_button.signal_clicked().connect (sigc::mem_fun (*this, &EngineControl::latency_button_clicked));
        lm_use_button.signal_clicked().connect (sigc::mem_fun (*this, &EngineControl::use_latency_button_clicked));
+       lm_back_button_signal = lm_back_button.signal_clicked().connect(
+           sigc::mem_fun(*this, &EngineControl::latency_back_button_clicked));
+
        lm_use_button.set_sensitive (false);
 
+       /* Increase the default spacing around the labels of these three
+        * buttons
+        */
+
+       Gtk::Misc* l;
+
+       if ((l = dynamic_cast<Gtk::Misc*>(lm_use_button.get_child())) != 0) {
+               l->set_padding (10, 10);
+       }
+
+       if ((l = dynamic_cast<Gtk::Misc*>(lm_back_button.get_child())) != 0) {
+               l->set_padding (10, 10);
+       }
+
        preamble = manage (new Label);
        preamble->set_width_chars (60);
        preamble->set_line_wrap (true);
-       preamble->set_markup (_("Once the channels are connected, click the \"Measure latency\" button."));
-       lm_table.attach (*preamble, 0, 2, row, row+1, AttachOptions(FILL|EXPAND), (AttachOptions) 0);
+       preamble->set_markup (_("Once the channels are connected, click the \"Measure\" button."));
+       lm_table.attach (*preamble, 0, 3, row, row+1, AttachOptions(FILL|EXPAND), (AttachOptions) 0);
        row++;
 
-       lm_table.attach (lm_measure_button, 0, 2, row, row+1, xopt, (AttachOptions) 0);
-       ++row;
-       lm_table.attach (lm_results, 0, 2, row, row+1, AttachOptions(FILL|EXPAND), (AttachOptions) 0);
-       ++row;
-
-
        preamble = manage (new Label);
        preamble->set_width_chars (60);
        preamble->set_line_wrap (true);
        preamble->set_markup (_("When satisfied with the results, click the \"Use results\" button."));
-       lm_table.attach (*preamble, 0, 2, row, row+1, AttachOptions(FILL|EXPAND), (AttachOptions) 0);
-       row++;
+       lm_table.attach (*preamble, 0, 3, row, row+1, AttachOptions(FILL|EXPAND), (AttachOptions) 0);
 
-       lm_table.attach (lm_use_button, 0, 2, row, row+1, xopt, (AttachOptions) 0);
-       ++row;
+       ++row; // skip a row in the table
+       ++row; // skip a row in the table
 
-       lm_results.set_markup ("<i>No measurement results yet</i>");
+       lm_table.attach (lm_results, 0, 3, row, row+1, AttachOptions(FILL|EXPAND), (AttachOptions) 0);
+
+       ++row; // skip a row in the table
+       ++row; // skip a row in the table
+
+       lm_table.attach (lm_measure_button, 0, 1, row, row+1, AttachOptions(FILL|EXPAND), (AttachOptions) 0);
+       lm_table.attach (lm_use_button, 1, 2, row, row+1, AttachOptions(FILL|EXPAND), (AttachOptions) 0);
+       lm_table.attach (lm_back_button, 2, 3, row, row+1, AttachOptions(FILL|EXPAND), (AttachOptions) 0);
+
+       lm_results.set_markup (string_compose (results_markup, _("No measurement results yet")));
 
        lm_vbox.set_border_width (12);
        lm_vbox.pack_start (lm_table, false, false);
 
+       midi_back_button.signal_clicked().connect (sigc::bind (sigc::mem_fun (notebook, &Gtk::Notebook::set_current_page), 0));
+
        /* pack it all up */
 
        notebook.pages().push_back (TabElem (basic_vbox, _("Audio")));
-       // notebook.pages().push_back (TabElem (midi_vbox, _("MIDI")));
        notebook.pages().push_back (TabElem (lm_vbox, _("Latency")));
+       notebook.pages().push_back (TabElem (midi_vbox, _("MIDI")));
        notebook.set_border_width (12);
 
-       notebook.set_tab_pos (POS_RIGHT);
+       notebook.set_show_tabs (false);
        notebook.show_all ();
 
        notebook.set_name ("SettingsNotebook");
@@ -230,43 +263,200 @@ EngineControl::EngineControl ()
        input_channels.signal_output().connect (sigc::bind (sigc::ptr_fun (&EngineControl::print_channel_count), &input_channels));
        output_channels.signal_output().connect (sigc::bind (sigc::ptr_fun (&EngineControl::print_channel_count), &output_channels));
 
-       control_app_button.signal_clicked().connect (mem_fun (*this, &EngineControl::control_app_button_clicked));
+       midi_devices_button.signal_clicked.connect (mem_fun (*this, &EngineControl::configure_midi_devices));
+       midi_devices_button.set_name ("generic button");
+       midi_devices_button.set_can_focus(true);
+
+       control_app_button.signal_clicked.connect (mem_fun (*this, &EngineControl::control_app_button_clicked));
+       control_app_button.set_name ("generic button");
+       control_app_button.set_can_focus(true);
        manage_control_app_sensitivity ();
 
-       cancel_button = add_button (Gtk::Stock::CANCEL, Gtk::RESPONSE_CANCEL);
+       start_stop_button.signal_clicked.connect (mem_fun (*this, &EngineControl::start_stop_button_clicked));
+       start_stop_button.set_sensitive (false);
+       start_stop_button.set_name ("generic button");
+       start_stop_button.set_can_focus(true);
+
+       update_devices_button.signal_clicked.connect (mem_fun (*this, &EngineControl::update_devices_button_clicked));
+       update_devices_button.set_sensitive (false);
+       update_devices_button.set_name ("generic button");
+       update_devices_button.set_can_focus(true);
+
+       use_buffered_io_button.signal_clicked.connect (mem_fun (*this, &EngineControl::use_buffered_io_button_clicked));
+       use_buffered_io_button.set_sensitive (false);
+       use_buffered_io_button.set_name ("generic button");
+       use_buffered_io_button.set_can_focus(true);
+
+       cancel_button = add_button (Gtk::Stock::CLOSE, Gtk::RESPONSE_CANCEL);
        ok_button = add_button (Gtk::Stock::OK, Gtk::RESPONSE_OK);
-       apply_button = add_button (Gtk::Stock::APPLY, Gtk::RESPONSE_APPLY);
 
        /* Pick up any existing audio setup configuration, if appropriate */
 
        XMLNode* audio_setup = ARDOUR::Config->extra_xml ("AudioMIDISetup");
-       
+
        ARDOUR::AudioEngine::instance()->Running.connect (running_connection, MISSING_INVALIDATOR, boost::bind (&EngineControl::engine_running, this), gui_context());
        ARDOUR::AudioEngine::instance()->Stopped.connect (stopped_connection, MISSING_INVALIDATOR, boost::bind (&EngineControl::engine_stopped, this), gui_context());
        ARDOUR::AudioEngine::instance()->Halted.connect (stopped_connection, MISSING_INVALIDATOR, boost::bind (&EngineControl::engine_stopped, this), gui_context());
-
-       backend_changed ();
+       ARDOUR::AudioEngine::instance()->DeviceListChanged.connect (devicelist_connection, MISSING_INVALIDATOR, boost::bind (&EngineControl::device_list_changed, this), gui_context());
 
        if (audio_setup) {
-               set_state (*audio_setup);
+               if (!set_state (*audio_setup)) {
+                       set_default_state ();
+               }
+       } else {
+               set_default_state ();
        }
 
-       /* Connect to signals */
+       update_sensitivity ();
+       connect_changed_signals ();
 
-       driver_combo.signal_changed().connect (sigc::mem_fun (*this, &EngineControl::driver_changed));
-       sample_rate_combo.signal_changed().connect (sigc::mem_fun (*this, &EngineControl::sample_rate_changed));
-       buffer_size_combo.signal_changed().connect (sigc::mem_fun (*this, &EngineControl::buffer_size_changed));
-       device_combo.signal_changed().connect (sigc::mem_fun (*this, &EngineControl::device_changed));
-       midi_option_combo.signal_changed().connect (sigc::mem_fun (*this, &EngineControl::midi_option_changed));
+       notebook.signal_switch_page().connect (sigc::mem_fun (*this, &EngineControl::on_switch_page));
 
-       input_latency.signal_changed().connect (sigc::mem_fun (*this, &EngineControl::parameter_changed));
-       output_latency.signal_changed().connect (sigc::mem_fun (*this, &EngineControl::parameter_changed));
-       input_channels.signal_changed().connect (sigc::mem_fun (*this, &EngineControl::parameter_changed));
-       output_channels.signal_changed().connect (sigc::mem_fun (*this, &EngineControl::parameter_changed));
+       connect_disconnect_button.signal_clicked().connect (sigc::mem_fun (*this, &EngineControl::connect_disconnect_click));
 
-       notebook.signal_switch_page().connect (sigc::mem_fun (*this, &EngineControl::on_switch_page));
+       connect_disconnect_button.set_no_show_all();
+       use_buffered_io_button.set_no_show_all();
+       update_devices_button.set_no_show_all();
+       start_stop_button.set_no_show_all();
+       midi_devices_button.set_no_show_all();
+}
+
+void
+EngineControl::connect_changed_signals ()
+{
+       backend_combo_connection = backend_combo.signal_changed ().connect (
+           sigc::mem_fun (*this, &EngineControl::backend_changed));
+       driver_combo_connection = driver_combo.signal_changed ().connect (
+           sigc::mem_fun (*this, &EngineControl::driver_changed));
+       sample_rate_combo_connection = sample_rate_combo.signal_changed ().connect (
+           sigc::mem_fun (*this, &EngineControl::sample_rate_changed));
+       buffer_size_combo_connection = buffer_size_combo.signal_changed ().connect (
+           sigc::mem_fun (*this, &EngineControl::buffer_size_changed));
+       nperiods_combo_connection = nperiods_combo.signal_changed ().connect (
+           sigc::mem_fun (*this, &EngineControl::nperiods_changed));
+       device_combo_connection = device_combo.signal_changed ().connect (
+           sigc::mem_fun (*this, &EngineControl::device_changed));
+       midi_option_combo_connection = midi_option_combo.signal_changed ().connect (
+           sigc::mem_fun (*this, &EngineControl::midi_option_changed));
+
+       input_device_combo_connection = input_device_combo.signal_changed ().connect (
+           sigc::mem_fun (*this, &EngineControl::input_device_changed));
+       output_device_combo_connection = output_device_combo.signal_changed ().connect (
+           sigc::mem_fun (*this, &EngineControl::output_device_changed));
+
+       input_latency_connection = input_latency.signal_changed ().connect (
+           sigc::mem_fun (*this, &EngineControl::parameter_changed));
+       output_latency_connection = output_latency.signal_changed ().connect (
+           sigc::mem_fun (*this, &EngineControl::parameter_changed));
+       input_channels_connection = input_channels.signal_changed ().connect (
+           sigc::mem_fun (*this, &EngineControl::parameter_changed));
+       output_channels_connection = output_channels.signal_changed ().connect (
+           sigc::mem_fun (*this, &EngineControl::parameter_changed));
+}
+
+void
+EngineControl::block_changed_signals ()
+{
+       if (block_signals++ == 0) {
+               DEBUG_ECONTROL ("Blocking changed signals");
+               backend_combo_connection.block ();
+               driver_combo_connection.block ();
+               sample_rate_combo_connection.block ();
+               buffer_size_combo_connection.block ();
+               nperiods_combo_connection.block ();
+               device_combo_connection.block ();
+               input_device_combo_connection.block ();
+               output_device_combo_connection.block ();
+               midi_option_combo_connection.block ();
+               input_latency_connection.block ();
+               output_latency_connection.block ();
+               input_channels_connection.block ();
+               output_channels_connection.block ();
+       }
+}
+
+void
+EngineControl::unblock_changed_signals ()
+{
+       if (--block_signals == 0) {
+               DEBUG_ECONTROL ("Unblocking changed signals");
+               backend_combo_connection.unblock ();
+               driver_combo_connection.unblock ();
+               sample_rate_combo_connection.unblock ();
+               buffer_size_combo_connection.unblock ();
+               nperiods_combo_connection.unblock ();
+               device_combo_connection.unblock ();
+               input_device_combo_connection.unblock ();
+               output_device_combo_connection.unblock ();
+               midi_option_combo_connection.unblock ();
+               input_latency_connection.unblock ();
+               output_latency_connection.unblock ();
+               input_channels_connection.unblock ();
+               output_channels_connection.unblock ();
+       }
+}
+
+EngineControl::SignalBlocker::SignalBlocker (EngineControl& engine_control,
+                                             const std::string& reason)
+    : ec (engine_control)
+    , m_reason (reason)
+{
+       DEBUG_ECONTROL (string_compose ("SignalBlocker: %1", m_reason));
+       ec.block_changed_signals ();
+}
+
+EngineControl::SignalBlocker::~SignalBlocker ()
+{
+       DEBUG_ECONTROL (string_compose ("~SignalBlocker: %1", m_reason));
+       ec.unblock_changed_signals ();
+}
+
+void
+EngineControl::on_show ()
+{
+       ArdourDialog::on_show ();
+       if (!ARDOUR::AudioEngine::instance()->current_backend() || !ARDOUR::AudioEngine::instance()->running()) {
+               // re-check _have_control (jackd running) see #6041
+               backend_changed ();
+       }
+       device_changed ();
+       ok_button->grab_focus();
+}
+
+bool
+EngineControl::try_autostart ()
+{
+       if (!start_stop_button.get_sensitive()) {
+               return false;
+       }
+       if (ARDOUR::AudioEngine::instance()->running()) {
+               return true;
+       }
+       return start_engine ();
+}
+
+bool
+EngineControl::start_engine ()
+{
+       if (push_state_to_backend(true) != 0) {
+               MessageDialog msg(*this,
+                                 ARDOUR::AudioEngine::instance()->get_last_backend_error());
+               msg.run();
+               return false;
+       }
+       return true;
+}
 
-       no_push = false;
+bool
+EngineControl::stop_engine (bool for_latency)
+{
+       if (ARDOUR::AudioEngine::instance()->stop(for_latency)) {
+               MessageDialog msg(*this,
+                                 ARDOUR::AudioEngine::instance()->get_last_backend_error());
+               msg.run();
+               return false;
+       }
+       return true;
 }
 
 void
@@ -275,22 +465,40 @@ EngineControl::on_response (int response_id)
        ArdourDialog::on_response (response_id);
 
        switch (response_id) {
-       case RESPONSE_APPLY:
-               push_state_to_backend (true);
-               break;
        case RESPONSE_OK:
-               push_state_to_backend (true);
-               hide ();
+               if (!start_engine()) {
+                       return;
+               } else {
+                       hide();
+               }
+#ifdef PLATFORM_WINDOWS
+
+               // But if there's no session open, this can produce
+               // a long gap when nothing appears to be happening.
+               // Let's show the splash image while we're waiting.
+               if (!ARDOUR_COMMAND_LINE::no_splash) {
+                       if (ARDOUR_UI::instance()) {
+                               if (!ARDOUR_UI::instance()->session_loaded) {
+                                       ARDOUR_UI::instance()->show_splash();
+                               }
+                       }
+               }
+#endif
                break;
        case RESPONSE_DELETE_EVENT: {
                GdkEventButton ev;
                ev.type = GDK_BUTTON_PRESS;
                ev.button = 1;
-               on_delete_event ((GdkEventAny*) &ev);
+               on_delete_event((GdkEventAny*)&ev);
                break;
        }
+       case RESPONSE_CANCEL:
+               if (ARDOUR_UI::instance() && ARDOUR_UI::instance()->session_loaded) {
+                       ARDOUR_UI::instance()->check_audioengine(*this);
+               }
+       // fall through
        default:
-               hide ();
+               hide();
        }
 }
 
@@ -305,10 +513,25 @@ EngineControl::build_notebook ()
        Gtkmm2ext::container_clear (basic_vbox);
        Gtkmm2ext::container_clear (basic_packer);
 
+       if (control_app_button.get_parent()) {
+               control_app_button.get_parent()->remove (control_app_button);
+       }
+
        label = manage (left_aligned_label (_("Audio System:")));
        basic_packer.attach (*label, 0, 1, 0, 1, xopt, (AttachOptions) 0);
        basic_packer.attach (backend_combo, 1, 2, 0, 1, xopt, (AttachOptions) 0);
-       
+
+       basic_packer.attach (engine_status, 2, 3, 0, 1, xopt, (AttachOptions) 0);
+       engine_status.show();
+
+       basic_packer.attach (start_stop_button, 3, 4, 0, 1, xopt, xopt);
+       basic_packer.attach (update_devices_button, 3, 4, 1, 2, xopt, xopt);
+       basic_packer.attach (use_buffered_io_button, 3, 4, 2, 3, xopt, xopt);
+
+       lm_button_audio.signal_clicked.connect (sigc::mem_fun (*this, &EngineControl::calibrate_audio_latency));
+       lm_button_audio.set_name ("generic button");
+       lm_button_audio.set_can_focus(true);
+
        if (_have_control) {
                build_full_control_notebook ();
        } else {
@@ -317,16 +540,10 @@ EngineControl::build_notebook ()
 
        basic_vbox.pack_start (basic_hbox, false, false);
 
-       if (_have_control) {
-               Gtk::HBox* hpacker = manage (new HBox);
-               hpacker->set_border_width (12);
-               hpacker->pack_start (control_app_button, false, false);
-               hpacker->show ();
-               control_app_button.show();
-               basic_vbox.pack_start (*hpacker);
+       {
+               PBD::Unwinder<uint32_t> protect_ignore_changes (ignore_changes, ignore_changes + 1);
+               basic_vbox.show_all ();
        }
-
-       basic_vbox.show_all ();
 }
 
 void
@@ -350,10 +567,26 @@ EngineControl::build_full_control_notebook ()
                row++;
        }
 
-       label = manage (left_aligned_label (_("Device:")));
-       basic_packer.attach (*label, 0, 1, row, row + 1, xopt, (AttachOptions) 0);
-       basic_packer.attach (device_combo, 1, 2, row, row + 1, xopt, (AttachOptions) 0);
-       row++;
+       if (backend->use_separate_input_and_output_devices()) {
+               label = manage (left_aligned_label (_("Input Device:")));
+               basic_packer.attach (*label, 0, 1, row, row + 1, xopt, (AttachOptions) 0);
+               basic_packer.attach (input_device_combo, 1, 2, row, row + 1, xopt, (AttachOptions) 0);
+               row++;
+               label = manage (left_aligned_label (_("Output Device:")));
+               basic_packer.attach (*label, 0, 1, row, row + 1, xopt, (AttachOptions) 0);
+               basic_packer.attach (output_device_combo, 1, 2, row, row + 1, xopt, (AttachOptions) 0);
+               row++;
+               // reset so it isn't used in state comparisons
+               device_combo.set_active_text ("");
+       } else {
+               label = manage (left_aligned_label (_("Device:")));
+               basic_packer.attach (*label, 0, 1, row, row + 1, xopt, (AttachOptions) 0);
+               basic_packer.attach (device_combo, 1, 2, row, row + 1, xopt, (AttachOptions) 0);
+               row++;
+               // reset these so they don't get used in state comparisons
+               input_device_combo.set_active_text ("");
+               output_device_combo.set_active_text ("");
+       }
 
        label = manage (left_aligned_label (_("Sample rate:")));
        basic_packer.attach (*label, 0, 1, row, row + 1, xopt, (AttachOptions) 0);
@@ -365,60 +598,82 @@ EngineControl::build_full_control_notebook ()
        basic_packer.attach (*label, 0, 1, row, row + 1, xopt, (AttachOptions) 0);
        basic_packer.attach (buffer_size_combo, 1, 2, row, row + 1, xopt, (AttachOptions) 0);
        buffer_size_duration_label.set_alignment (0.0); /* left-align */
-       basic_packer.attach (buffer_size_duration_label, 2, 3, row, row+1, xopt, (AttachOptions) 0);
+       basic_packer.attach (buffer_size_duration_label, 2, 3, row, row+1, SHRINK, (AttachOptions) 0);
+
+       int ctrl_btn_span = 1;
+       if (backend->can_set_period_size ()) {
+               row++;
+               label = manage (left_aligned_label (_("Periods:")));
+               basic_packer.attach (*label, 0, 1, row, row + 1, xopt, (AttachOptions) 0);
+               basic_packer.attach (nperiods_combo, 1, 2, row, row + 1, xopt, (AttachOptions) 0);
+               ++ctrl_btn_span;
+       }
+
+       /* button spans 2 or 3 rows */
+
+       basic_packer.attach (control_app_button, 3, 4, row - ctrl_btn_span, row + 1, xopt, xopt);
        row++;
 
        input_channels.set_name ("InputChannels");
-       input_channels.set_flags(Gtk::CAN_FOCUS);
-       input_channels.set_digits(0);
-       input_channels.set_wrap(false);
+       input_channels.set_flags (Gtk::CAN_FOCUS);
+       input_channels.set_digits (0);
+       input_channels.set_wrap (false);
        output_channels.set_editable (true);
 
-       label = manage (left_aligned_label (_("Input Channels:")));
-       basic_packer.attach (*label, 0, 1, row, row+1, xopt, (AttachOptions) 0);
-       basic_packer.attach (input_channels, 1, 2, row, row+1, xopt, (AttachOptions) 0);
-       ++row;
+       if (!ARDOUR::Profile->get_mixbus()) {
+               label = manage (left_aligned_label (_("Input Channels:")));
+               basic_packer.attach (*label, 0, 1, row, row+1, xopt, (AttachOptions) 0);
+               basic_packer.attach (input_channels, 1, 2, row, row+1, xopt, (AttachOptions) 0);
+               ++row;
+       }
 
        output_channels.set_name ("OutputChannels");
-       output_channels.set_flags(Gtk::CAN_FOCUS);
-       output_channels.set_digits(0);
-       output_channels.set_wrap(false);
+       output_channels.set_flags (Gtk::CAN_FOCUS);
+       output_channels.set_digits (0);
+       output_channels.set_wrap (false);
        output_channels.set_editable (true);
 
-       label = manage (left_aligned_label (_("Output Channels:")));
-       basic_packer.attach (*label, 0, 1, row, row+1, xopt, (AttachOptions) 0);
-       basic_packer.attach (output_channels, 1, 2, row, row+1, xopt, (AttachOptions) 0);
-       ++row;
+       if (!ARDOUR::Profile->get_mixbus()) {
+               label = manage (left_aligned_label (_("Output Channels:")));
+               basic_packer.attach (*label, 0, 1, row, row+1, xopt, (AttachOptions) 0);
+               basic_packer.attach (output_channels, 1, 2, row, row+1, xopt, (AttachOptions) 0);
+               ++row;
+       }
 
        input_latency.set_name ("InputLatency");
-       input_latency.set_flags(Gtk::CAN_FOCUS);
-       input_latency.set_digits(0);
-       input_latency.set_wrap(false);
+       input_latency.set_flags (Gtk::CAN_FOCUS);
+       input_latency.set_digits (0);
+       input_latency.set_wrap (false);
        input_latency.set_editable (true);
 
        label = manage (left_aligned_label (_("Hardware input latency:")));
        basic_packer.attach (*label, 0, 1, row, row+1, xopt, (AttachOptions) 0);
        basic_packer.attach (input_latency, 1, 2, row, row+1, xopt, (AttachOptions) 0);
        label = manage (left_aligned_label (_("samples")));
-       basic_packer.attach (*label, 2, 3, row, row+1, xopt, (AttachOptions) 0);
+       basic_packer.attach (*label, 2, 3, row, row+1, SHRINK, (AttachOptions) 0);
        ++row;
 
        output_latency.set_name ("OutputLatency");
-       output_latency.set_flags(Gtk::CAN_FOCUS);
-       output_latency.set_digits(0);
-       output_latency.set_wrap(false);
+       output_latency.set_flags (Gtk::CAN_FOCUS);
+       output_latency.set_digits (0);
+       output_latency.set_wrap (false);
        output_latency.set_editable (true);
 
        label = manage (left_aligned_label (_("Hardware output latency:")));
        basic_packer.attach (*label, 0, 1, row, row+1, xopt, (AttachOptions) 0);
        basic_packer.attach (output_latency, 1, 2, row, row+1, xopt, (AttachOptions) 0);
        label = manage (left_aligned_label (_("samples")));
-       basic_packer.attach (*label, 2, 3, row, row+1, xopt, (AttachOptions) 0);
+       basic_packer.attach (*label, 2, 3, row, row+1, SHRINK, (AttachOptions) 0);
+
+       /* button spans 2 rows */
+
+       basic_packer.attach (lm_button_audio, 3, 4, row-1, row+1, xopt, xopt);
        ++row;
 
-       label = manage (left_aligned_label (_("MIDI System")));
+       label = manage (left_aligned_label (_("MIDI System:")));
        basic_packer.attach (*label, 0, 1, row, row + 1, xopt, (AttachOptions) 0);
-       basic_packer.attach (midi_option_combo, 1, 2, row, row + 1, xopt, (AttachOptions) 0);
+       basic_packer.attach (midi_option_combo, 1, 2, row, row + 1, SHRINK, (AttachOptions) 0);
+       basic_packer.attach (midi_devices_button, 3, 4, row, row+1, xopt, xopt);
        row++;
 }
 
@@ -433,7 +688,7 @@ EngineControl::build_no_control_notebook ()
        vector<string> strings;
        AttachOptions xopt = AttachOptions (FILL|EXPAND);
        int row = 1; // row zero == backend combo
-       const string msg = string_compose (_("The %1 audio backend was configured and started externally.\nThis limits your control over it."), backend->name());
+       const string msg = string_compose (_("%1 is already running. %2 will connect to it and use the existing settings."), backend->name(), PROGRAM_NAME);
 
        label = manage (new Label);
        label->set_markup (string_compose ("<span weight=\"bold\" foreground=\"red\">%1</span>", msg));
@@ -456,15 +711,13 @@ EngineControl::build_no_control_notebook ()
                row++;
        }
 
-       connect_disconnect_button.signal_clicked().connect (sigc::mem_fun (*this, &EngineControl::connect_disconnect_click));
-
        basic_packer.attach (connect_disconnect_button, 0, 2, row, row+1, FILL, AttachOptions (0));
        row++;
 }
 
 EngineControl::~EngineControl ()
 {
-
+       ignore_changes = true;
 }
 
 void
@@ -481,14 +734,42 @@ void
 EngineControl::enable_latency_tab ()
 {
        vector<string> outputs;
-       ARDOUR::AudioEngine::instance()->get_physical_outputs (ARDOUR::DataType::AUDIO, outputs);
+       vector<string> inputs;
+
+       ARDOUR::DataType const type = _measure_midi ? ARDOUR::DataType::MIDI : ARDOUR::DataType::AUDIO;
+       ARDOUR::AudioEngine::instance()->get_physical_outputs (type, outputs);
+       ARDOUR::AudioEngine::instance()->get_physical_inputs (type, inputs);
+
+       if (!ARDOUR::AudioEngine::instance()->running()) {
+               MessageDialog msg (_("Failed to start or connect to audio-engine.\n\nLatency calibration requires a working audio interface."));
+               notebook.set_current_page (0);
+               msg.run ();
+               return;
+       }
+       else if (inputs.empty() || outputs.empty()) {
+               MessageDialog msg (_("Your selected audio configuration is playback- or capture-only.\n\nLatency calibration requires playback and capture"));
+               notebook.set_current_page (0);
+               msg.run ();
+               return;
+       }
+
+       lm_back_button_signal.disconnect();
+       if (_measure_midi) {
+               lm_back_button_signal = lm_back_button.signal_clicked().connect (sigc::bind (sigc::mem_fun (notebook, &Gtk::Notebook::set_current_page), midi_tab));
+               lm_preamble.hide ();
+       } else {
+               lm_back_button_signal = lm_back_button.signal_clicked().connect(
+                   sigc::mem_fun(*this, &EngineControl::latency_back_button_clicked));
+               lm_preamble.show ();
+       }
+
        set_popdown_strings (lm_output_channel_combo, outputs);
        lm_output_channel_combo.set_active_text (outputs.front());
+       lm_output_channel_combo.set_sensitive (true);
 
-       vector<string> inputs;
-       ARDOUR::AudioEngine::instance()->get_physical_inputs (ARDOUR::DataType::AUDIO, inputs);
        set_popdown_strings (lm_input_channel_combo, inputs);
        lm_input_channel_combo.set_active_text (inputs.front());
+       lm_input_channel_combo.set_sensitive (true);
 
        lm_measure_button.set_sensitive (true);
 }
@@ -508,138 +789,335 @@ EngineControl::setup_midi_tab_for_backend ()
        }
 
        midi_vbox.pack_start (midi_device_table, true, true);
-       midi_vbox.pack_start (midi_refresh_button, false, false);
+       midi_vbox.pack_start (midi_back_button, false, false);
        midi_vbox.show_all ();
+}
+
+void
+EngineControl::update_sensitivity ()
+{
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+       if (!backend) {
+               ok_button->set_sensitive (false);
+               start_stop_button.set_sensitive (false);
+               return;
+       }
+
+       bool valid = true;
+       size_t devices_available = 0;
+
+       if (backend->use_separate_input_and_output_devices ()) {
+               devices_available += get_popdown_string_count (input_device_combo);
+               devices_available += get_popdown_string_count (output_device_combo);
+       } else {
+               devices_available += get_popdown_string_count (device_combo);
+       }
+
+       if (devices_available == 0) {
+               valid = false;
+               input_latency.set_sensitive (false);
+               output_latency.set_sensitive (false);
+               input_channels.set_sensitive (false);
+               output_channels.set_sensitive (false);
+       } else {
+               input_latency.set_sensitive (true);
+               output_latency.set_sensitive (true);
+               input_channels.set_sensitive (true);
+               output_channels.set_sensitive (true);
+       }
+
+       if (get_popdown_string_count (buffer_size_combo) > 0) {
+               if (!ARDOUR::AudioEngine::instance()->running()) {
+                       buffer_size_combo.set_sensitive (valid);
+               } else if (backend->can_change_sample_rate_when_running()) {
+                       buffer_size_combo.set_sensitive (valid || !_have_control);
+               } else {
+#if 1
+                       /* TODO
+                        * Currently there is no way to manually stop the
+                        * engine in order to re-configure it.
+                        * This needs to remain sensitive for now.
+                        *
+                        * (it's also handy to implicily
+                        * re-start the engine)
+                        */
+                       buffer_size_combo.set_sensitive (true);
+#else
+                       buffer_size_combo.set_sensitive (false);
+#endif
+               }
+       } else {
+               buffer_size_combo.set_sensitive (false);
+               valid = false;
+       }
+
+       if (get_popdown_string_count (sample_rate_combo) > 0) {
+               bool allow_to_set_rate = false;
+               if (!ARDOUR::AudioEngine::instance()->running()) {
+                       if (!ARDOUR_UI::instance()->session_loaded) {
+                               // engine is not running, no session loaded -> anything goes.
+                               allow_to_set_rate = true;
+                       } else if (_desired_sample_rate > 0 && get_rate () != _desired_sample_rate) {
+                               // only allow to change if the current setting is not the native session rate.
+                               allow_to_set_rate = true;
+                       }
+               }
+               sample_rate_combo.set_sensitive (allow_to_set_rate);
+       } else {
+               sample_rate_combo.set_sensitive (false);
+               valid = false;
+       }
+
+       if (get_popdown_string_count (nperiods_combo) > 0) {
+               if (!ARDOUR::AudioEngine::instance()->running()) {
+                       nperiods_combo.set_sensitive (true);
+               } else {
+                       nperiods_combo.set_sensitive (false);
+               }
+       } else {
+               nperiods_combo.set_sensitive (false);
+       }
 
-       midi_refresh_button.signal_clicked().connect (sigc::mem_fun (*this, &EngineControl::refresh_midi_display));
+       if (_have_control) {
+               start_stop_button.set_sensitive(true);
+               start_stop_button.show();
+               if (ARDOUR::AudioEngine::instance()->running()) {
+                       start_stop_button.set_text("Stop");
+                       update_devices_button.set_sensitive(false);
+                       use_buffered_io_button.set_sensitive(false);
+               } else {
+                       if (backend->can_request_update_devices()) {
+                               update_devices_button.show();
+                       } else {
+                               update_devices_button.hide();
+                       }
+                       if (backend->can_use_buffered_io()) {
+                               use_buffered_io_button.show();
+                       } else {
+                               use_buffered_io_button.hide();
+                       }
+                       start_stop_button.set_text("Start");
+                       update_devices_button.set_sensitive(true);
+                       use_buffered_io_button.set_sensitive(true);
+               }
+       } else {
+               update_devices_button.set_sensitive(false);
+               update_devices_button.hide();
+               use_buffered_io_button.set_sensitive(false);
+               use_buffered_io_button.hide();
+               start_stop_button.set_sensitive(false);
+               start_stop_button.hide();
+       }
+
+       if (ARDOUR::AudioEngine::instance()->running() && _have_control) {
+               input_device_combo.set_sensitive (false);
+               output_device_combo.set_sensitive (false);
+               device_combo.set_sensitive (false);
+               driver_combo.set_sensitive (false);
+       } else {
+               input_device_combo.set_sensitive (true);
+               output_device_combo.set_sensitive (true);
+               device_combo.set_sensitive (true);
+               if (backend->requires_driver_selection() && get_popdown_string_count(driver_combo) > 0) {
+                       driver_combo.set_sensitive (true);
+               } else {
+                       driver_combo.set_sensitive (false);
+               }
+       }
+
+       if (valid || !_have_control) {
+               ok_button->set_sensitive (true);
+       } else {
+               ok_button->set_sensitive (false);
+       }
 }
 
 void
 EngineControl::setup_midi_tab_for_jack ()
 {
-}      
+}
+
+void
+EngineControl::midi_latency_adjustment_changed (Gtk::Adjustment *a, MidiDeviceSettings device, bool for_input) {
+       if (for_input) {
+               device->input_latency = a->get_value();
+       } else {
+               device->output_latency = a->get_value();
+       }
+}
 
 void
-EngineControl::refresh_midi_display ()
+EngineControl::midi_device_enabled_toggled (ArdourButton *b, MidiDeviceSettings device) {
+       b->set_active (!b->get_active());
+       device->enabled = b->get_active();
+       refresh_midi_display(device->name);
+}
+
+void
+EngineControl::refresh_midi_display (std::string focus)
 {
        boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
        assert (backend);
 
-       vector<string> midi_inputs;
-       vector<string> midi_outputs;
        int row  = 0;
        AttachOptions xopt = AttachOptions (FILL|EXPAND);
        Gtk::Label* l;
 
        Gtkmm2ext::container_clear (midi_device_table);
 
-       backend->get_physical_inputs (ARDOUR::DataType::MIDI, midi_inputs);
-       backend->get_physical_outputs (ARDOUR::DataType::MIDI, midi_outputs);
-
        midi_device_table.set_spacings (6);
-       midi_device_table.set_homogeneous (true);
-       midi_device_table.resize (midi_inputs.size() + midi_outputs.size() + 3, 1);
 
        l = manage (new Label);
-       l->set_markup (string_compose ("<span size=\"large\" weight=\"bold\">%1</span>", _("MIDI Inputs")));
-       midi_device_table.attach (*l, 0, 1, row, row + 1, xopt, AttachOptions (0));
-       l->set_alignment (0, 0.5);
+       l->set_markup (string_compose ("<span size=\"large\" weight=\"bold\">%1</span>", _("MIDI Devices")));
+       midi_device_table.attach (*l, 0, 4, row, row + 1, xopt, AttachOptions (0));
+       l->set_alignment (0.5, 0.5);
        row++;
        l->show ();
-       
-       for (vector<string>::iterator p = midi_inputs.begin(); p != midi_inputs.end(); ++p) {
-               l = manage (new Label ((*p).substr ((*p).find_last_of (':') + 1)));
-               l->set_alignment (0, 0.5);
-               midi_device_table.attach (*l, 0, 1, row, row + 1, xopt, AttachOptions (0));
-               l->show ();
-               row++;
-       }
 
-       row++; // extra row of spacing
-
-       l = manage (new Label);
-       l->set_markup (string_compose ("<span size=\"large\" weight=\"bold\">%1</span>", _("MIDI Outputs")));
-       midi_device_table.attach (*l, 0, 1, row, row + 1, xopt, AttachOptions (0));
-       l->set_alignment (0, 0.5);
+       l = manage (new Label (_("Device"))); l->show (); l->set_alignment (0.5, 0.5);
+       midi_device_table.attach (*l, 0, 1, row, row + 2, xopt, AttachOptions (0));
+       l = manage (new Label (_("Hardware Latencies"))); l->show (); l->set_alignment (0.5, 0.5);
+       midi_device_table.attach (*l, 1, 3, row, row + 1, xopt, AttachOptions (0));
        row++;
-       l->show ();
+       l = manage (new Label (_("Input"))); l->show (); l->set_alignment (0.5, 0.5);
+       midi_device_table.attach (*l, 1, 2, row, row + 1, xopt, AttachOptions (0));
+       l = manage (new Label (_("Output"))); l->show (); l->set_alignment (0.5, 0.5);
+       midi_device_table.attach (*l, 2, 3, row, row + 1, xopt, AttachOptions (0));
+       row++;
+
+       for (vector<MidiDeviceSettings>::const_iterator p = _midi_devices.begin(); p != _midi_devices.end(); ++p) {
+               ArdourButton *m;
+               Gtk::Button* b;
+               Gtk::Adjustment *a;
+               Gtk::SpinButton *s;
+               bool enabled = (*p)->enabled;
+
+               m = manage (new ArdourButton ((*p)->name, ArdourButton::led_default_elements));
+               m->set_name ("midi device");
+               m->set_can_focus (Gtk::CAN_FOCUS);
+               m->add_events (Gdk::BUTTON_RELEASE_MASK);
+               m->set_active (enabled);
+               m->signal_clicked.connect (sigc::bind (sigc::mem_fun (*this, &EngineControl::midi_device_enabled_toggled), m, *p));
+               midi_device_table.attach (*m, 0, 1, row, row + 1, xopt, AttachOptions (0)); m->show ();
+               if ((*p)->name == focus) {
+                       m->grab_focus();
+               }
+
+               a = manage (new Gtk::Adjustment (0, 0, 99999, 1));
+               s = manage (new Gtk::SpinButton (*a));
+               a->set_value ((*p)->input_latency);
+               s->signal_value_changed().connect (sigc::bind (sigc::mem_fun (*this, &EngineControl::midi_latency_adjustment_changed), a, *p, true));
+               s->set_sensitive (_can_set_midi_latencies && enabled);
+               midi_device_table.attach (*s, 1, 2, row, row + 1, xopt, AttachOptions (0)); s->show ();
+
+               a = manage (new Gtk::Adjustment (0, 0, 99999, 1));
+               s = manage (new Gtk::SpinButton (*a));
+               a->set_value ((*p)->output_latency);
+               s->signal_value_changed().connect (sigc::bind (sigc::mem_fun (*this, &EngineControl::midi_latency_adjustment_changed), a, *p, false));
+               s->set_sensitive (_can_set_midi_latencies && enabled);
+               midi_device_table.attach (*s, 2, 3, row, row + 1, xopt, AttachOptions (0)); s->show ();
+
+               b = manage (new Button (_("Calibrate")));
+               b->signal_clicked().connect (sigc::bind (sigc::mem_fun (*this, &EngineControl::calibrate_midi_latency), *p));
+               b->set_sensitive (_can_set_midi_latencies && enabled);
+               midi_device_table.attach (*b, 3, 4, row, row + 1, xopt, AttachOptions (0)); b->show ();
 
-       for (vector<string>::iterator p = midi_outputs.begin(); p != midi_outputs.end(); ++p) {
-               l = manage (new Label ((*p).substr ((*p).find_last_of (':') + 1)));
-               l->set_alignment (0, 0.5);
-               midi_device_table.attach (*l, 0, 1, row, row + 1, xopt, AttachOptions (0));
-               l->show ();
                row++;
        }
 }
 
-void
-EngineControl::update_sensitivity ()
-{
-}
-
 void
 EngineControl::backend_changed ()
 {
-       if (ignore_changes) {
-               return;
-       }
-
+       SignalBlocker blocker (*this, "backend_changed");
        string backend_name = backend_combo.get_active_text();
        boost::shared_ptr<ARDOUR::AudioBackend> backend;
 
-       if (!(backend = ARDOUR::AudioEngine::instance()->set_backend (backend_name, "ardour", ""))) {
+       if (!(backend = ARDOUR::AudioEngine::instance()->set_backend (backend_name, downcase (std::string(PROGRAM_NAME)), ""))) {
                /* eh? setting the backend failed... how ? */
+               /* A: stale config contains a backend that does not exist in current build */
                return;
        }
 
+       DEBUG_ECONTROL (string_compose ("Backend name: %1", backend_name));
+
        _have_control = ARDOUR::AudioEngine::instance()->setup_required ();
 
        build_notebook ();
        setup_midi_tab_for_backend ();
+       _midi_devices.clear();
 
        if (backend->requires_driver_selection()) {
-               vector<string> drivers = backend->enumerate_drivers();
-               
-               if (!drivers.empty()) {
-                       {
-                               PBD::Unwinder<uint32_t> protect_ignore_changes (ignore_changes, ignore_changes + 1);
-                               set_popdown_strings (driver_combo, drivers);
-                               driver_combo.set_active_text (drivers.front());
-                       }
-
+               if (set_driver_popdown_strings ()) {
                        driver_changed ();
                }
-               
        } else {
-               driver_combo.set_sensitive (false);
                /* this will change the device text which will cause a call to
                 * device changed which will set up parameters
                 */
                list_devices ();
        }
 
-       vector<string> midi_options = backend->enumerate_midi_options();
+       update_midi_options ();
 
-       if (midi_options.size() == 1) {
-               /* only contains the "none" option */
-               midi_option_combo.set_sensitive (false);
-       } else {
-               if (_have_control) {
-                       set_popdown_strings (midi_option_combo, midi_options);
-                       midi_option_combo.set_active_text (midi_options.front());
-                       midi_option_combo.set_sensitive (true);
-               } else {
-                       midi_option_combo.set_sensitive (false);
-               }
-       }
+       connect_disconnect_button.hide();
 
-       maybe_display_saved_state ();
-}
+       midi_option_changed();
 
-bool
+       started_at_least_once = false;
+
+       /* changing the backend implies stopping the engine
+        * ARDOUR::AudioEngine() may or may not emit this signal
+        * depending on previous engine state
+        */
+       engine_stopped (); // set "active/inactive"
+
+       if (!_have_control) {
+               // set settings from backend that we do have control over
+               set_active_text_if_present (buffer_size_combo, bufsize_as_string (backend->buffer_size()));
+       }
+
+       if (_have_control && !ignore_changes) {
+               // set driver & devices
+               State state = get_matching_state (backend_combo.get_active_text());
+               if (state) {
+                       PBD::Unwinder<uint32_t> protect_ignore_changes (ignore_changes, ignore_changes + 1);
+                       set_current_state (state);
+               }
+       }
+
+       if (!ignore_changes) {
+               maybe_display_saved_state ();
+       }
+}
+
+void
+EngineControl::update_midi_options ()
+{
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+       vector<string> midi_options = backend->enumerate_midi_options();
+
+       if (midi_options.size() == 1) {
+               /* only contains the "none" option */
+               midi_option_combo.set_sensitive (false);
+       } else {
+               if (_have_control) {
+                       set_popdown_strings (midi_option_combo, midi_options);
+                       midi_option_combo.set_active_text (midi_options.front());
+                       midi_option_combo.set_sensitive (true);
+               } else {
+                       midi_option_combo.set_sensitive (false);
+               }
+       }
+}
+
+bool
 EngineControl::print_channel_count (Gtk::SpinButton* sb)
 {
+       if (ARDOUR::Profile->get_mixbus()) {
+               return true;
+       }
+
        uint32_t cnt = (uint32_t) sb->get_value();
        if (cnt == 0) {
                sb->set_text (_("all available channels"));
@@ -651,16 +1129,84 @@ EngineControl::print_channel_count (Gtk::SpinButton* sb)
        return true;
 }
 
-void
-EngineControl::list_devices ()
+// @return true if there are drivers available
+bool
+EngineControl::set_driver_popdown_strings ()
 {
+       DEBUG_ECONTROL ("set_driver_popdown_strings");
        boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
-       assert (backend);
+       vector<string> drivers = backend->enumerate_drivers();
 
-       /* now fill out devices, mark sample rates, buffer sizes insensitive */
-           
+       if (drivers.empty ()) {
+               // This is an error...?
+               return false;
+       }
+
+       string current_driver = backend->driver_name ();
+
+       DEBUG_ECONTROL (string_compose ("backend->driver_name: %1", current_driver));
+
+       if (std::find (drivers.begin (), drivers.end (), current_driver) ==
+           drivers.end ()) {
+
+               current_driver = drivers.front ();
+       }
+
+       set_popdown_strings (driver_combo, drivers);
+       DEBUG_ECONTROL (
+           string_compose ("driver_combo.set_active_text: %1", current_driver));
+       driver_combo.set_active_text (current_driver);
+       return true;
+}
+
+std::string
+EngineControl::get_default_device(const string& current_device_name,
+                                  const vector<string>& available_devices)
+{
+       // If the current device is available, use it as default
+       if (std::find (available_devices.begin (),
+                      available_devices.end (),
+                      current_device_name) != available_devices.end ()) {
+
+               return current_device_name;
+       }
+
+       using namespace ARDOUR;
+
+       string default_device_name =
+           AudioBackend::get_standard_device_name(AudioBackend::DeviceDefault);
+
+       vector<string>::const_iterator i;
+
+       // If there is a "Default" device available, use it
+       for (i = available_devices.begin(); i != available_devices.end(); ++i) {
+               if (*i == default_device_name) {
+                       return *i;
+               }
+       }
+
+       string none_device_name =
+           AudioBackend::get_standard_device_name(AudioBackend::DeviceNone);
+
+       // Use the first device that isn't "None"
+       for (i = available_devices.begin(); i != available_devices.end(); ++i) {
+               if (*i != none_device_name) {
+                       return *i;
+               }
+       }
+
+       // Use "None" if there are no other available
+       return available_devices.front();
+}
+
+// @return true if there are devices available
+bool
+EngineControl::set_device_popdown_strings ()
+{
+       DEBUG_ECONTROL ("set_device_popdown_strings");
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
        vector<ARDOUR::AudioBackend::DeviceStatus> all_devices = backend->enumerate_devices ();
-       
+
        /* NOTE: Ardour currently does not display the "available" field of the
         * returned devices.
         *
@@ -676,201 +1222,431 @@ EngineControl::list_devices ()
                available_devices.push_back (i->name);
        }
 
-       if (!available_devices.empty()) {
+       if (available_devices.empty ()) {
+               return false;
+       }
 
-               update_sensitivity ();
-                                               
-               {
-                       PBD::Unwinder<uint32_t> protect_ignore_changes (ignore_changes, ignore_changes + 1);
-                       set_popdown_strings (device_combo, available_devices);
-                       device_combo.set_active_text (available_devices.front());
-               }
+       set_popdown_strings (device_combo, available_devices);
 
-               device_changed ();
+       std::string default_device =
+           get_default_device(backend->device_name(), available_devices);
 
-               ok_button->set_sensitive (true);
-               apply_button->set_sensitive (true);
+       DEBUG_ECONTROL (
+           string_compose ("set device_combo active text: %1", default_device));
 
-       } else {
-               sample_rate_combo.set_sensitive (false);
-               buffer_size_combo.set_sensitive (false);
-               input_latency.set_sensitive (false);
-               output_latency.set_sensitive (false);
-               input_channels.set_sensitive (false);
-               output_channels.set_sensitive (false);
-               ok_button->set_sensitive (false);
-               apply_button->set_sensitive (false);
+       device_combo.set_active_text(default_device);
+       return true;
+}
+
+// @return true if there are input devices available
+bool
+EngineControl::set_input_device_popdown_strings ()
+{
+       DEBUG_ECONTROL ("set_input_device_popdown_strings");
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+       vector<ARDOUR::AudioBackend::DeviceStatus> all_devices = backend->enumerate_input_devices ();
+
+       vector<string> available_devices;
+
+       for (vector<ARDOUR::AudioBackend::DeviceStatus>::const_iterator i = all_devices.begin(); i != all_devices.end(); ++i) {
+               available_devices.push_back (i->name);
+       }
+
+       if (available_devices.empty()) {
+               return false;
        }
+
+       set_popdown_strings (input_device_combo, available_devices);
+
+       std::string default_device =
+           get_default_device(backend->input_device_name(), available_devices);
+
+       DEBUG_ECONTROL (
+           string_compose ("set input_device_combo active text: %1", default_device));
+       input_device_combo.set_active_text(default_device);
+       return true;
+}
+
+// @return true if there are output devices available
+bool
+EngineControl::set_output_device_popdown_strings ()
+{
+       DEBUG_ECONTROL ("set_output_device_popdown_strings");
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+       vector<ARDOUR::AudioBackend::DeviceStatus> all_devices = backend->enumerate_output_devices ();
+
+       vector<string> available_devices;
+
+       for (vector<ARDOUR::AudioBackend::DeviceStatus>::const_iterator i = all_devices.begin(); i != all_devices.end(); ++i) {
+               available_devices.push_back (i->name);
+       }
+
+       if (available_devices.empty()) {
+               return false;
+       }
+
+       set_popdown_strings (output_device_combo, available_devices);
+
+       std::string default_device =
+           get_default_device(backend->output_device_name(), available_devices);
+
+       DEBUG_ECONTROL (
+           string_compose ("set output_device_combo active text: %1", default_device));
+       output_device_combo.set_active_text(default_device);
+       return true;
 }
 
 void
-EngineControl::driver_changed ()
+EngineControl::list_devices ()
 {
-       if (ignore_changes) {
-               return;
+       DEBUG_ECONTROL ("list_devices");
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+       assert (backend);
+
+       /* now fill out devices, mark sample rates, buffer sizes insensitive */
+
+       bool devices_available = false;
+
+       if (backend->use_separate_input_and_output_devices ()) {
+               bool input_devices_available = set_input_device_popdown_strings ();
+               bool output_devices_available = set_output_device_popdown_strings ();
+               devices_available = input_devices_available || output_devices_available;
+       } else {
+               devices_available = set_device_popdown_strings ();
+       }
+
+       if (devices_available) {
+               device_changed ();
+       } else {
+               device_combo.clear();
+               input_device_combo.clear();
+               output_device_combo.clear();
        }
+       update_sensitivity ();
+}
 
+void
+EngineControl::driver_changed ()
+{
+       SignalBlocker blocker (*this, "driver_changed");
        boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
        assert (backend);
 
        backend->set_driver (driver_combo.get_active_text());
        list_devices ();
 
-       maybe_display_saved_state ();
+       // TODO load LRU device(s) for backend + driver combo
+
+       if (!ignore_changes) {
+               maybe_display_saved_state ();
+       }
 }
 
-void
-EngineControl::device_changed ()
+vector<float>
+EngineControl::get_sample_rates_for_all_devices ()
 {
-       if (ignore_changes) {
-               return;
+       boost::shared_ptr<ARDOUR::AudioBackend> backend =
+           ARDOUR::AudioEngine::instance ()->current_backend ();
+       vector<float> all_rates;
+
+       if (backend->use_separate_input_and_output_devices ()) {
+               all_rates = backend->available_sample_rates2 (get_input_device_name (), get_output_device_name ());
+       } else {
+               all_rates = backend->available_sample_rates (get_device_name ());
        }
+       return all_rates;
+}
 
+vector<float>
+EngineControl::get_default_sample_rates ()
+{
+       vector<float> rates;
+       rates.push_back (8000.0f);
+       rates.push_back (16000.0f);
+       rates.push_back (32000.0f);
+       rates.push_back (44100.0f);
+       rates.push_back (48000.0f);
+       rates.push_back (88200.0f);
+       rates.push_back (96000.0f);
+       rates.push_back (192000.0f);
+       rates.push_back (384000.0f);
+       return rates;
+}
+
+void
+EngineControl::set_samplerate_popdown_strings ()
+{
+       DEBUG_ECONTROL ("set_samplerate_popdown_strings");
        boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
-       assert (backend);
-       string device_name = device_combo.get_active_text ();
+       string desired;
+       vector<float> sr;
        vector<string> s;
 
-       {
-               PBD::Unwinder<uint32_t> protect_ignore_changes (ignore_changes, ignore_changes + 1);
+       if (_have_control) {
+               sr = get_sample_rates_for_all_devices ();
+       } else {
+               sr = get_default_sample_rates ();
+       }
 
-               /* don't allow programmatic change to combos to cause a
-                  recursive call to this method.
-               */
-               
-               /* sample rates */
-               
-               string desired;
-               
-               vector<float> sr;
+       for (vector<float>::const_iterator x = sr.begin(); x != sr.end(); ++x) {
+               s.push_back (rate_as_string (*x));
+               if (*x == _desired_sample_rate) {
+                       desired = s.back();
+               }
+       }
 
-               if (_have_control) {
-                       sr = backend->available_sample_rates (device_name);
-               } else {
+       set_popdown_strings (sample_rate_combo, s);
 
-                       sr.push_back (8000.0f);
-                       sr.push_back (16000.0f);
-                       sr.push_back (32000.0f);
-                       sr.push_back (44100.0f);
-                       sr.push_back (48000.0f);
-                       sr.push_back (88200.0f);
-                       sr.push_back (96000.0f);
-                       sr.push_back (192000.0f);
-                       sr.push_back (384000.0f);
-               }
-
-               for (vector<float>::const_iterator x = sr.begin(); x != sr.end(); ++x) {
-                       s.push_back (rate_as_string (*x));
-                       if (*x == _desired_sample_rate) {
-                               desired = s.back();
-                       }
+       if (!s.empty()) {
+               if (ARDOUR::AudioEngine::instance()->running()) {
+                       sample_rate_combo.set_active_text (rate_as_string (backend->sample_rate()));
                }
-               
-               if (!s.empty()) {
-                       sample_rate_combo.set_sensitive (true);
-                       set_popdown_strings (sample_rate_combo, s);
+               else if (desired.empty ()) {
+                       float new_active_sr = backend->default_sample_rate ();
 
-                       if (desired.empty()) {
-                               sample_rate_combo.set_active_text (s.front());
-                       } else {
-                               sample_rate_combo.set_active_text (desired);
+                       if (std::find (sr.begin (), sr.end (), new_active_sr) == sr.end ()) {
+                               new_active_sr = sr.front ();
                        }
 
+                       sample_rate_combo.set_active_text (rate_as_string (new_active_sr));
                } else {
-                       sample_rate_combo.set_sensitive (false);
+                       sample_rate_combo.set_active_text (desired);
                }
 
-               /* buffer sizes */
-               
-               vector<uint32_t> bs;
-               
-               if (_have_control) {
-                       bs = backend->available_buffer_sizes(device_name);
-               } else if (backend->can_change_buffer_size_when_running()) {
-                       bs.push_back (8);
-                       bs.push_back (16);
-                       bs.push_back (32);
-                       bs.push_back (64);
-                       bs.push_back (128);
-                       bs.push_back (256);
-                       bs.push_back (512);
-                       bs.push_back (1024);
-                       bs.push_back (2048);
-                       bs.push_back (4096);
-                       bs.push_back (8192);
-               }
-               s.clear ();
-               for (vector<uint32_t>::const_iterator x = bs.begin(); x != bs.end(); ++x) {
-                       s.push_back (bufsize_as_string (*x));
-               }
-               
-               if (!s.empty()) {
-                       buffer_size_combo.set_sensitive (true);
-                       set_popdown_strings (buffer_size_combo, s);
-                       
-                       buffer_size_combo.set_active_text (s.front());
-                       show_buffer_duration ();
+       }
+       update_sensitivity ();
+}
+
+vector<uint32_t>
+EngineControl::get_buffer_sizes_for_all_devices ()
+{
+       boost::shared_ptr<ARDOUR::AudioBackend> backend =
+           ARDOUR::AudioEngine::instance ()->current_backend ();
+       vector<uint32_t> all_sizes;
+
+       if (backend->use_separate_input_and_output_devices ()) {
+               all_sizes = backend->available_buffer_sizes2 (get_input_device_name (), get_output_device_name ());
+       } else {
+               all_sizes = backend->available_buffer_sizes (get_device_name ());
+       }
+       return all_sizes;
+}
+
+vector<uint32_t>
+EngineControl::get_default_buffer_sizes ()
+{
+       vector<uint32_t> sizes;
+       sizes.push_back (8);
+       sizes.push_back (16);
+       sizes.push_back (32);
+       sizes.push_back (64);
+       sizes.push_back (128);
+       sizes.push_back (256);
+       sizes.push_back (512);
+       sizes.push_back (1024);
+       sizes.push_back (2048);
+       sizes.push_back (4096);
+       sizes.push_back (8192);
+       return sizes;
+}
+
+void
+EngineControl::set_buffersize_popdown_strings ()
+{
+       DEBUG_ECONTROL ("set_buffersize_popdown_strings");
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+       vector<uint32_t> bs;
+       vector<string> s;
+
+       if (_have_control) {
+               bs = get_buffer_sizes_for_all_devices ();
+       } else if (backend->can_change_buffer_size_when_running()) {
+               bs = get_default_buffer_sizes ();
+       }
+
+       for (vector<uint32_t>::const_iterator x = bs.begin(); x != bs.end(); ++x) {
+               s.push_back (bufsize_as_string (*x));
+       }
+
+       uint32_t previous_size = 0;
+       if (!buffer_size_combo.get_active_text().empty()) {
+               previous_size = get_buffer_size ();
+       }
+
+       set_popdown_strings (buffer_size_combo, s);
+
+       if (!s.empty()) {
+
+               if (std::find(bs.begin(), bs.end(), previous_size) != bs.end()) {
+                       buffer_size_combo.set_active_text(bufsize_as_string(previous_size));
                } else {
-                       buffer_size_combo.set_sensitive (false);
+
+                       buffer_size_combo.set_active_text(s.front());
+
+                       uint32_t period = backend->buffer_size();
+                       if (0 == period && backend->use_separate_input_and_output_devices()) {
+                               period = backend->default_buffer_size(get_input_device_name());
+                       }
+                       if (0 == period && backend->use_separate_input_and_output_devices()) {
+                               period = backend->default_buffer_size(get_output_device_name());
+                       }
+                       if (0 == period && !backend->use_separate_input_and_output_devices()) {
+                               period = backend->default_buffer_size(get_device_name());
+                       }
+
+                       set_active_text_if_present(buffer_size_combo, bufsize_as_string(period));
                }
+               show_buffer_duration ();
+       }
+       update_sensitivity ();
+}
+
+void
+EngineControl::set_nperiods_popdown_strings ()
+{
+       DEBUG_ECONTROL ("set_nperiods_popdown_strings");
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+       vector<uint32_t> np;
+       vector<string> s;
 
-               /* XXX theoretically need to set min + max channel counts here
+       if (backend->can_set_period_size()) {
+               np = backend->available_period_sizes (get_driver());
+       }
+
+       for (vector<uint32_t>::const_iterator x = np.begin(); x != np.end(); ++x) {
+               s.push_back (nperiods_as_string (*x));
+       }
+
+       set_popdown_strings (nperiods_combo, s);
+
+       if (!s.empty()) {
+               set_active_text_if_present (nperiods_combo, nperiods_as_string (backend->period_size())); // XXX 
+       }
+
+       update_sensitivity ();
+}
+
+void
+EngineControl::device_changed ()
+{
+       SignalBlocker blocker (*this, "device_changed");
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+       assert (backend);
+
+       string device_name_in;
+       string device_name_out; // only used if backend support separate I/O devices
+
+       if (backend->use_separate_input_and_output_devices()) {
+               device_name_in  = get_input_device_name ();
+               device_name_out = get_output_device_name ();
+       } else {
+               device_name_in = get_device_name ();
+       }
+
+       /* we set the backend-device to query various device related intormation.
+        * This has the side effect that backend->device_name() will match
+        * the device_name and  'change_device' will never be true.
+        * so work around this by setting...
+        */
+       if (backend->use_separate_input_and_output_devices()) {
+               if (device_name_in != backend->input_device_name() || device_name_out != backend->output_device_name ()) {
+                       queue_device_changed = true;
+               }
+       } else {
+               if (device_name_in != backend->device_name()) {
+                       queue_device_changed = true;
+               }
+       }
+
+       //the device name must be set FIRST so ASIO can populate buffersizes and the control panel button
+       if (backend->use_separate_input_and_output_devices()) {
+               backend->set_input_device_name (device_name_in);
+               backend->set_output_device_name (device_name_out);
+       } else {
+               backend->set_device_name(device_name_in);
+       }
+
+       {
+               /* don't allow programmatic change to combos to cause a
+                  recursive call to this method.
                 */
-               
+               PBD::Unwinder<uint32_t> protect_ignore_changes (ignore_changes, ignore_changes + 1);
+
+               set_samplerate_popdown_strings ();
+               set_buffersize_popdown_strings ();
+               set_nperiods_popdown_strings ();
+
+               /* TODO set min + max channel counts here */
+
                manage_control_app_sensitivity ();
        }
 
        /* pick up any saved state for this device */
 
-       maybe_display_saved_state ();
+       if (!ignore_changes) {
+               maybe_display_saved_state ();
+       }
+}
 
-       /* and push it to the backend */
+void
+EngineControl::input_device_changed ()
+{
+       DEBUG_ECONTROL ("input_device_changed");
+       device_changed ();
+}
 
-       push_state_to_backend (false);
-}      
+void
+EngineControl::output_device_changed ()
+{
+       DEBUG_ECONTROL ("output_device_changed");
+       device_changed ();
+}
 
 string
 EngineControl::bufsize_as_string (uint32_t sz)
 {
-       /* Translators: "samples" is always plural here, so no
-          need for plural+singular forms.
-       */
-       char buf[32];
-       snprintf (buf, sizeof (buf), _("%u samples"), sz);
+       return string_compose (P_("%1 sample", "%1 samples", sz), sz);
+}
+
+string
+EngineControl::nperiods_as_string (uint32_t np)
+{
+       char buf[8];
+       snprintf (buf, sizeof (buf), "%u", np);
        return buf;
 }
 
-void 
+
+void
 EngineControl::sample_rate_changed ()
 {
-       if (ignore_changes) {
-               return;
-       }
-
+       DEBUG_ECONTROL ("sample_rate_changed");
        /* reset the strings for buffer size to show the correct msec value
           (reflecting the new sample rate).
-       */
+        */
 
        show_buffer_duration ();
-       save_state ();
 
 }
 
-void 
+void
 EngineControl::buffer_size_changed ()
 {
-       if (ignore_changes) {
-               return;
-       }
+       DEBUG_ECONTROL ("buffer_size_changed");
+       show_buffer_duration ();
+}
 
+void
+EngineControl::nperiods_changed ()
+{
+       DEBUG_ECONTROL ("nperiods_changed");
        show_buffer_duration ();
-       save_state ();
 }
 
 void
 EngineControl::show_buffer_duration ()
 {
-
+       DEBUG_ECONTROL ("show_buffer_duration");
        /* buffer sizes  - convert from just samples to samples + msecs for
         * the displayed string
         */
@@ -879,103 +1655,213 @@ EngineControl::show_buffer_duration ()
        uint32_t samples = atoi (bs_text); /* will ignore trailing text */
        uint32_t rate = get_rate();
 
-       /* Translators: "msecs" is ALWAYS plural here, so we do not
-          need singular form as well.
-       */
-       /* Developers: note the hard-coding of a double buffered model
-          in the (2 * samples) computation of latency. we always start
-          the audiobackend in this configuration.
-       */
+       /* Except for ALSA and Dummy backends, we don't know the number of periods
+        * per cycle and settings.
+        *
+        * jack1 vs jack2 have different default latencies since jack2 start
+        * in async-mode unless --sync is given which adds an extra cycle
+        * of latency. The value is not known if jackd is started externally..
+        *
+        * So just display the period size, that's also what
+        * ARDOUR_UI::update_sample_rate() does for the status bar.
+        * (the statusbar calls AudioEngine::instance()->usecs_per_cycle()
+        * but still, that's the buffer period, not [round-trip] latency)
+        */
        char buf[32];
-       snprintf (buf, sizeof (buf), _("(%.1f msecs)"), (2 * samples) / (rate/1000.0));
+       snprintf (buf, sizeof (buf), _("(%.1f ms)"), (samples / (rate/1000.0f)));
        buffer_size_duration_label.set_text (buf);
 }
 
 void
 EngineControl::midi_option_changed ()
 {
-       if (!ignore_changes) {
-               save_state ();
+       DEBUG_ECONTROL ("midi_option_changed");
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+       assert (backend);
+
+       backend->set_midi_option (get_midi_option());
+
+       vector<ARDOUR::AudioBackend::DeviceStatus> midi_devices = backend->enumerate_midi_devices();
+
+       //_midi_devices.clear(); // TODO merge with state-saved settings..
+       _can_set_midi_latencies = backend->can_set_systemic_midi_latencies();
+       std::vector<MidiDeviceSettings> new_devices;
+
+       for (vector<ARDOUR::AudioBackend::DeviceStatus>::const_iterator i = midi_devices.begin(); i != midi_devices.end(); ++i) {
+               MidiDeviceSettings mds = find_midi_device (i->name);
+               if (i->available && !mds) {
+                       uint32_t input_latency = 0;
+                       uint32_t output_latency = 0;
+                       if (_can_set_midi_latencies) {
+                               input_latency = backend->systemic_midi_input_latency (i->name);
+                               output_latency = backend->systemic_midi_output_latency (i->name);
+                       }
+                       bool enabled = backend->midi_device_enabled (i->name);
+                       MidiDeviceSettings ptr (new MidiDeviceSetting (i->name, enabled, input_latency, output_latency));
+                       new_devices.push_back (ptr);
+               } else if (i->available) {
+                       new_devices.push_back (mds);
+               }
+       }
+       _midi_devices = new_devices;
+
+       if (_midi_devices.empty()) {
+               midi_devices_button.hide ();
+       } else {
+               midi_devices_button.show ();
        }
 }
 
 void
 EngineControl::parameter_changed ()
 {
-       if (!ignore_changes) {
-               save_state ();
+}
+
+EngineControl::State
+EngineControl::get_matching_state (const string& backend)
+{
+       for (StateList::iterator i = states.begin(); i != states.end(); ++i) {
+               if ((*i)->backend == backend) {
+                       return (*i);
+               }
        }
+       return State();
 }
 
-EngineControl::State*
-EngineControl::get_matching_state (const string& backend,
-                                  const string& driver,
-                                  const string& device)
+EngineControl::State
+EngineControl::get_matching_state (
+               const string& backend,
+               const string& driver,
+               const string& device)
 {
        for (StateList::iterator i = states.begin(); i != states.end(); ++i) {
-               if ((*i).backend == backend &&
-                   (*i).driver == driver &&
-                   (*i).device == device) {
-                       return &(*i);
+               if ((*i)->backend == backend &&
+                               (!_have_control || ((*i)->driver == driver && (*i)->device == device)))
+               {
+                       return (*i);
                }
        }
-       return 0;
+       return State();
+}
+
+EngineControl::State
+EngineControl::get_matching_state (
+               const string& backend,
+               const string& driver,
+               const string& input_device,
+               const string& output_device)
+{
+       for (StateList::iterator i = states.begin(); i != states.end(); ++i) {
+               if ((*i)->backend == backend &&
+                               (!_have_control || ((*i)->driver == driver && ((*i)->input_device == input_device) && (*i)->output_device == output_device)))
+               {
+                       return (*i);
+               }
+       }
+       return State();
 }
 
-EngineControl::State*
+EngineControl::State
 EngineControl::get_saved_state_for_currently_displayed_backend_and_device ()
 {
        boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
 
        if (backend) {
-               return get_matching_state (backend_combo.get_active_text(),
-                                          (backend->requires_driver_selection() ? (std::string) driver_combo.get_active_text() : string()),
-                                          device_combo.get_active_text());
+               if (backend->use_separate_input_and_output_devices ()) {
+                       return get_matching_state (backend_combo.get_active_text(),
+                                       (backend->requires_driver_selection() ? (std::string) driver_combo.get_active_text() : string()),
+                                       input_device_combo.get_active_text(),
+                                       output_device_combo.get_active_text());
+               } else {
+                       return get_matching_state (backend_combo.get_active_text(),
+                                       (backend->requires_driver_selection() ? (std::string) driver_combo.get_active_text() : string()),
+                                       device_combo.get_active_text());
+               }
        }
 
-
        return get_matching_state (backend_combo.get_active_text(),
-                                  string(),
-                                  device_combo.get_active_text());
+                       string(),
+                       device_combo.get_active_text());
 }
 
-EngineControl::State*
-EngineControl::save_state ()
+bool EngineControl::equivalent_states (const EngineControl::State& state1,
+                                       const EngineControl::State& state2)
 {
-       if (!_have_control) {
-               return 0;
+       if (state1->backend == state2->backend &&
+                       state1->driver == state2->driver &&
+                       state1->device == state2->device &&
+                       state1->input_device == state2->input_device &&
+                       state1->output_device == state2->output_device) {
+               return true;
+       }
+       return false;
+}
+
+bool
+EngineControl::state_sort_cmp (const State &a, const State &b) {
+       if (a->active) {
+               return true;
        }
+       else if (b->active) {
+               return false;
+       }
+       else {
+               return a->lru < b->lru;
+       }
+}
 
-       bool existing = true;
-       State* state = get_saved_state_for_currently_displayed_backend_and_device ();
+EngineControl::State
+EngineControl::save_state ()
+{
+       State state;
 
-       if (!state) {
-               existing = false;
-               state = new State;
+       if (!_have_control) {
+               state = get_matching_state (backend_combo.get_active_text(), string(), string());
+               if (state) {
+                       state->lru = time (NULL) ;
+                       return state;
+               }
+               state.reset(new StateStruct);
+               state->backend = get_backend ();
+       } else {
+               state.reset(new StateStruct);
+               store_state (state);
        }
-       
-       store_state (*state);
 
-       if (!existing) {
-               states.push_back (*state);
+       for (StateList::iterator i = states.begin(); i != states.end();) {
+               if (equivalent_states (*i, state)) {
+                       i =  states.erase(i);
+               } else {
+                       ++i;
+               }
        }
 
+       states.push_back (state);
+
+       states.sort (state_sort_cmp);
+
        return state;
 }
 
 void
-EngineControl::store_state (State& state)
+EngineControl::store_state (State state)
 {
-       state.backend = get_backend ();
-       state.driver = get_driver ();
-       state.device = get_device_name ();
-       state.sample_rate = get_rate ();
-       state.buffer_size = get_buffer_size ();
-       state.input_latency = get_input_latency ();
-       state.output_latency = get_output_latency ();
-       state.input_channels = get_input_channels ();
-       state.output_channels = get_output_channels ();
-       state.midi_option = get_midi_option ();
+       state->backend = get_backend ();
+       state->driver = get_driver ();
+       state->device = get_device_name ();
+       state->input_device = get_input_device_name ();
+       state->output_device = get_output_device_name ();
+       state->sample_rate = get_rate ();
+       state->buffer_size = get_buffer_size ();
+       state->n_periods = get_nperiods ();
+       state->input_latency = get_input_latency ();
+       state->output_latency = get_output_latency ();
+       state->input_channels = get_input_channels ();
+       state->output_channels = get_output_channels ();
+       state->midi_option = get_midi_option ();
+       state->midi_devices = _midi_devices;
+       state->use_buffered_io = get_use_buffered_io ();
+       state->lru = time (NULL) ;
 }
 
 void
@@ -985,56 +1871,82 @@ EngineControl::maybe_display_saved_state ()
                return;
        }
 
-       State* state = get_saved_state_for_currently_displayed_backend_and_device ();
+       State state = get_saved_state_for_currently_displayed_backend_and_device ();
 
        if (state) {
+               DEBUG_ECONTROL ("Restoring saved state");
                PBD::Unwinder<uint32_t> protect_ignore_changes (ignore_changes, ignore_changes + 1);
 
                if (!_desired_sample_rate) {
                        sample_rate_combo.set_active_text (rate_as_string (state->sample_rate));
                }
-               buffer_size_combo.set_active_text (bufsize_as_string (state->buffer_size));
+               set_active_text_if_present (buffer_size_combo, bufsize_as_string (state->buffer_size));
+
+               set_active_text_if_present (nperiods_combo, nperiods_as_string (state->n_periods));
                /* call this explicitly because we're ignoring changes to
                   the controls at this point.
-               */
+                */
                show_buffer_duration ();
                input_latency.set_value (state->input_latency);
                output_latency.set_value (state->output_latency);
 
+               use_buffered_io_button.set_active (state->use_buffered_io);
+
                if (!state->midi_option.empty()) {
                        midi_option_combo.set_active_text (state->midi_option);
+                       _midi_devices = state->midi_devices;
                }
+       } else {
+               DEBUG_ECONTROL ("Unable to find saved state for backend and devices");
        }
 }
-       
+
 XMLNode&
 EngineControl::get_state ()
 {
+       LocaleGuard lg;
+
        XMLNode* root = new XMLNode ("AudioMIDISetup");
        std::string path;
 
        if (!states.empty()) {
                XMLNode* state_nodes = new XMLNode ("EngineStates");
-               
+
                for (StateList::const_iterator i = states.begin(); i != states.end(); ++i) {
-                       
+
                        XMLNode* node = new XMLNode ("State");
-                       
-                       node->add_property ("backend", (*i).backend);
-                       node->add_property ("driver", (*i).driver);
-                       node->add_property ("device", (*i).device);
-                       node->add_property ("sample-rate", (*i).sample_rate);
-                       node->add_property ("buffer-size", (*i).buffer_size);
-                       node->add_property ("input-latency", (*i).input_latency);
-                       node->add_property ("output-latency", (*i).output_latency);
-                       node->add_property ("input-channels", (*i).input_channels);
-                       node->add_property ("output-channels", (*i).output_channels);
-                       node->add_property ("active", (*i).active ? "yes" : "no");
-                       node->add_property ("midi-option", (*i).midi_option);
-                       
+
+                       node->add_property ("backend", (*i)->backend);
+                       node->add_property ("driver", (*i)->driver);
+                       node->add_property ("device", (*i)->device);
+                       node->add_property ("input-device", (*i)->input_device);
+                       node->add_property ("output-device", (*i)->output_device);
+                       node->add_property ("sample-rate", (*i)->sample_rate);
+                       node->add_property ("buffer-size", (*i)->buffer_size);
+                       node->add_property ("n-periods", (*i)->n_periods);
+                       node->add_property ("input-latency", (*i)->input_latency);
+                       node->add_property ("output-latency", (*i)->output_latency);
+                       node->add_property ("input-channels", (*i)->input_channels);
+                       node->add_property ("output-channels", (*i)->output_channels);
+                       node->add_property ("active", (*i)->active ? "yes" : "no");
+                       node->add_property ("use-buffered-io", (*i)->use_buffered_io ? "yes" : "no");
+                       node->add_property ("midi-option", (*i)->midi_option);
+                       node->add_property ("lru", (*i)->active ? time (NULL) : (*i)->lru);
+
+                       XMLNode* midi_devices = new XMLNode ("MIDIDevices");
+                       for (std::vector<MidiDeviceSettings>::const_iterator p = (*i)->midi_devices.begin(); p != (*i)->midi_devices.end(); ++p) {
+                               XMLNode* midi_device_stuff = new XMLNode ("MIDIDevice");
+                               midi_device_stuff->add_property (X_("name"), (*p)->name);
+                               midi_device_stuff->add_property (X_("enabled"), (*p)->enabled);
+                               midi_device_stuff->add_property (X_("input-latency"), (*p)->input_latency);
+                               midi_device_stuff->add_property (X_("output-latency"), (*p)->output_latency);
+                               midi_devices->add_child_nocopy (*midi_device_stuff);
+                       }
+                       node->add_child_nocopy (*midi_devices);
+
                        state_nodes->add_child_nocopy (*node);
                }
-               
+
                root->add_child_nocopy (*state_nodes);
        }
 
@@ -1042,16 +1954,32 @@ EngineControl::get_state ()
 }
 
 void
+EngineControl::set_default_state ()
+{
+       vector<string> backend_names;
+       vector<const ARDOUR::AudioBackendInfo*> backends = ARDOUR::AudioEngine::instance()->available_backends();
+
+       for (vector<const ARDOUR::AudioBackendInfo*>::const_iterator b = backends.begin(); b != backends.end(); ++b) {
+               backend_names.push_back ((*b)->name);
+       }
+       backend_combo.set_active_text (backend_names.front());
+
+       // We could set default backends per platform etc here
+
+       backend_changed ();
+}
+
+bool
 EngineControl::set_state (const XMLNode& root)
 {
        XMLNodeList          clist, cclist;
        XMLNodeConstIterator citer, cciter;
-       XMLNode* child;
-       XMLNode* grandchild;
-       XMLProperty* prop = NULL;
+       XMLNode const * child;
+       XMLNode const * grandchild;
+       XMLProperty const * prop = NULL;
 
        if (root.name() != "AudioMIDISetup") {
-               return;
+               return false;
        }
 
        clist = root.children();
@@ -1061,7 +1989,7 @@ EngineControl::set_state (const XMLNode& root)
        for (citer = clist.begin(); citer != clist.end(); ++citer) {
 
                child = *citer;
-               
+
                if (child->name() != "EngineStates") {
                        continue;
                }
@@ -1069,107 +1997,276 @@ EngineControl::set_state (const XMLNode& root)
                cclist = child->children();
 
                for (cciter = cclist.begin(); cciter != cclist.end(); ++cciter) {
-                       State state;
-                       
+                       State state (new StateStruct);
+
                        grandchild = *cciter;
 
                        if (grandchild->name() != "State") {
                                continue;
                        }
-                       
+
                        if ((prop = grandchild->property ("backend")) == 0) {
                                continue;
                        }
-                       state.backend = prop->value ();
-                       
+                       state->backend = prop->value ();
+
                        if ((prop = grandchild->property ("driver")) == 0) {
                                continue;
                        }
-                       state.driver = prop->value ();
-                       
+                       state->driver = prop->value ();
+
                        if ((prop = grandchild->property ("device")) == 0) {
                                continue;
                        }
-                       state.device = prop->value ();
-                       
+                       state->device = prop->value ();
+
+                       if ((prop = grandchild->property ("input-device")) == 0) {
+                               continue;
+                       }
+                       state->input_device = prop->value ();
+
+                       if ((prop = grandchild->property ("output-device")) == 0) {
+                               continue;
+                       }
+                       state->output_device = prop->value ();
+
                        if ((prop = grandchild->property ("sample-rate")) == 0) {
                                continue;
                        }
-                       state.sample_rate = atof (prop->value ());
-                       
+                       state->sample_rate = atof (prop->value ());
+
                        if ((prop = grandchild->property ("buffer-size")) == 0) {
                                continue;
                        }
-                       state.buffer_size = atoi (prop->value ());
-                       
+                       state->buffer_size = atoi (prop->value ());
+
+                       if ((prop = grandchild->property ("n-periods")) == 0) {
+                               // optional (new value in 4.5)
+                               state->n_periods = 0;
+                       } else {
+                               state->n_periods = atoi (prop->value ());
+                       }
+
                        if ((prop = grandchild->property ("input-latency")) == 0) {
                                continue;
                        }
-                       state.input_latency = atoi (prop->value ());
-                       
+                       state->input_latency = atoi (prop->value ());
+
                        if ((prop = grandchild->property ("output-latency")) == 0) {
                                continue;
                        }
-                       state.output_latency = atoi (prop->value ());
-                       
+                       state->output_latency = atoi (prop->value ());
+
                        if ((prop = grandchild->property ("input-channels")) == 0) {
                                continue;
                        }
-                       state.input_channels = atoi (prop->value ());
-                       
+                       state->input_channels = atoi (prop->value ());
+
                        if ((prop = grandchild->property ("output-channels")) == 0) {
                                continue;
                        }
-                       state.output_channels = atoi (prop->value ());
+                       state->output_channels = atoi (prop->value ());
 
                        if ((prop = grandchild->property ("active")) == 0) {
                                continue;
                        }
-                       state.active = string_is_affirmative (prop->value ());
-                       
+                       state->active = string_is_affirmative (prop->value ());
+
+                       if ((prop = grandchild->property ("use-buffered-io")) == 0) {
+                               continue;
+                       }
+                       state->use_buffered_io = string_is_affirmative (prop->value ());
+
                        if ((prop = grandchild->property ("midi-option")) == 0) {
                                continue;
                        }
-                       state.midi_option = prop->value ();
+                       state->midi_option = prop->value ();
+
+                       state->midi_devices.clear();
+                       XMLNode* midinode;
+                       if ((midinode = ARDOUR::find_named_node (*grandchild, "MIDIDevices")) != 0) {
+                               const XMLNodeList mnc = midinode->children();
+                               for (XMLNodeList::const_iterator n = mnc.begin(); n != mnc.end(); ++n) {
+                                       if ((*n)->property (X_("name")) == 0
+                                                       || (*n)->property (X_("enabled")) == 0
+                                                       || (*n)->property (X_("input-latency")) == 0
+                                                       || (*n)->property (X_("output-latency")) == 0
+                                                ) {
+                                               continue;
+                                       }
+
+                                       MidiDeviceSettings ptr (new MidiDeviceSetting(
+                                                               (*n)->property (X_("name"))->value (),
+                                                               string_is_affirmative ((*n)->property (X_("enabled"))->value ()),
+                                                               atoi ((*n)->property (X_("input-latency"))->value ()),
+                                                               atoi ((*n)->property (X_("output-latency"))->value ())
+                                                               ));
+                                       state->midi_devices.push_back (ptr);
+                               }
+                       }
+
+                       if ((prop = grandchild->property ("lru"))) {
+                               state->lru = atoi (prop->value ());
+                       }
+
+#if 1
+                       /* remove accumulated duplicates (due to bug in ealier version)
+                        * this can be removed again before release
+                        */
+                       for (StateList::iterator i = states.begin(); i != states.end();) {
+                               if ((*i)->backend == state->backend &&
+                                               (*i)->driver == state->driver &&
+                                               (*i)->device == state->device) {
+                                       i =  states.erase(i);
+                               } else {
+                                       ++i;
+                               }
+                       }
+#endif
 
                        states.push_back (state);
                }
-       }
+       }
+
+       /* now see if there was an active state and switch the setup to it */
+
+       // purge states of backend that are not available in this built
+       vector<const ARDOUR::AudioBackendInfo*> backends = ARDOUR::AudioEngine::instance()->available_backends();
+       vector<std::string> backend_names;
+
+       for (vector<const ARDOUR::AudioBackendInfo*>::const_iterator i = backends.begin(); i != backends.end(); ++i) {
+               backend_names.push_back((*i)->name);
+       }
+       for (StateList::iterator i = states.begin(); i != states.end();) {
+               if (std::find(backend_names.begin(), backend_names.end(), (*i)->backend) == backend_names.end()) {
+                       i = states.erase(i);
+               } else {
+                       ++i;
+               }
+       }
+
+       states.sort (state_sort_cmp);
+
+       for (StateList::const_iterator i = states.begin(); i != states.end(); ++i) {
+
+               if ((*i)->active) {
+                       return set_current_state (*i);
+               }
+       }
+       return false;
+}
+
+bool
+EngineControl::set_current_state (const State& state)
+{
+       DEBUG_ECONTROL ("set_current_state");
+
+       boost::shared_ptr<ARDOUR::AudioBackend> backend;
+
+       if (!(backend = ARDOUR::AudioEngine::instance ()->set_backend (
+                 state->backend, downcase (std::string(PROGRAM_NAME)), ""))) {
+               DEBUG_ECONTROL (string_compose ("Unable to set backend to %1", state->backend));
+               // this shouldn't happen as the invalid backend names should have been
+               // removed from the list of states.
+               return false;
+       }
+
+       // now reflect the change in the backend in the GUI so backend_changed will
+       // do the right thing
+       backend_combo.set_active_text (state->backend);
+
+       if (!ARDOUR::AudioEngine::instance()->setup_required ()) {
+               backend_changed ();
+               // we don't have control don't restore state
+               return true;
+       }
+
+
+       if (!state->driver.empty ()) {
+               if (!backend->requires_driver_selection ()) {
+                       DEBUG_ECONTROL ("Backend should require driver selection");
+                       // A backend has changed from having driver selection to not having
+                       // it or someone has been manually editing a config file and messed
+                       // it up
+                       return false;
+               }
+
+               if (backend->set_driver (state->driver) != 0) {
+                       DEBUG_ECONTROL (string_compose ("Unable to set driver %1", state->driver));
+                       // Driver names for a backend have changed and the name in the
+                       // config file is now invalid or support for driver is no longer
+                       // included in the backend
+                       return false;
+               }
+               // no need to set the driver_combo as backend_changed will use
+               // backend->driver_name to set the active driver
+       }
+
+       if (!state->device.empty ()) {
+               if (backend->set_device_name (state->device) != 0) {
+                       DEBUG_ECONTROL (
+                           string_compose ("Unable to set device name %1", state->device));
+                       // device is no longer available on the system
+                       return false;
+               }
+               // no need to set active device as it will be picked up in
+               // via backend_changed ()/set_device_popdown_strings
 
-       /* now see if there was an active state and switch the setup to it */
-       
-       for (StateList::const_iterator i = states.begin(); i != states.end(); ++i) {
+       } else {
+               // backend supports separate input/output devices
+               if (backend->set_input_device_name (state->input_device) != 0) {
+                       DEBUG_ECONTROL (string_compose ("Unable to set input device name %1",
+                                                       state->input_device));
+                       // input device is no longer available on the system
+                       return false;
+               }
 
-               if ((*i).active) {
-                       ignore_changes++;
-                       backend_combo.set_active_text ((*i).backend);
-                       driver_combo.set_active_text ((*i).driver);
-                       device_combo.set_active_text ((*i).device);
-                       sample_rate_combo.set_active_text (rate_as_string ((*i).sample_rate));
-                       buffer_size_combo.set_active_text (bufsize_as_string ((*i).buffer_size));
-                       input_latency.set_value ((*i).input_latency);
-                       output_latency.set_value ((*i).output_latency);
-                       midi_option_combo.set_active_text ((*i).midi_option);
-                       ignore_changes--;
-                       break;
+               if (backend->set_output_device_name (state->output_device) != 0) {
+                       DEBUG_ECONTROL (string_compose ("Unable to set output device name %1",
+                                                       state->input_device));
+                       // output device is no longer available on the system
+                       return false;
                }
+               // no need to set active devices as it will be picked up in via
+               // backend_changed ()/set_*_device_popdown_strings
        }
-}
 
+       backend_changed ();
+
+       // Now restore the state of the rest of the controls
+
+       // We don't use a SignalBlocker as set_current_state is currently only
+       // called from set_state before any signals are connected. If at some point
+       // a more general named state mechanism is implemented and
+       // set_current_state is called while signals are connected then a
+       // SignalBlocker will need to be instantiated before setting these.
+
+       device_combo.set_active_text (state->device);
+       input_device_combo.set_active_text (state->input_device);
+       output_device_combo.set_active_text (state->output_device);
+       if (!_desired_sample_rate) {
+               sample_rate_combo.set_active_text (rate_as_string (state->sample_rate));
+       }
+       set_active_text_if_present (buffer_size_combo, bufsize_as_string (state->buffer_size));
+       set_active_text_if_present (nperiods_combo, nperiods_as_string (state->n_periods));
+       input_latency.set_value (state->input_latency);
+       output_latency.set_value (state->output_latency);
+       midi_option_combo.set_active_text (state->midi_option);
+       use_buffered_io_button.set_active (state->use_buffered_io);
+       return true;
+}
 
 int
 EngineControl::push_state_to_backend (bool start)
 {
-       if (no_push) {
-               return 0;
-       }
-
+       DEBUG_ECONTROL ("push_state_to_backend");
        boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+       PBD::Unwinder<uint32_t> protect_ignore_device_changes (ignore_device_changes, ignore_device_changes + 1);
 
        if (!backend) {
                return 0;
        }
-       
+
        /* figure out what is going to change */
 
        bool restart_required = false;
@@ -1178,9 +2275,11 @@ EngineControl::push_state_to_backend (bool start)
        bool change_device = false;
        bool change_rate = false;
        bool change_bufsize = false;
+       bool change_nperiods = false;
        bool change_latency = false;
        bool change_channels = false;
        bool change_midi = false;
+       bool change_buffered_io = false;
 
        uint32_t ochan = get_output_channels ();
        uint32_t ichan = get_input_channels ();
@@ -1188,64 +2287,93 @@ EngineControl::push_state_to_backend (bool start)
        if (_have_control) {
 
                if (started_at_least_once) {
-                       
+
                        /* we can control the backend */
-                       
+
                        if (backend->requires_driver_selection()) {
                                if (get_driver() != backend->driver_name()) {
                                        change_driver = true;
                                }
                        }
-                       
-                       if (get_device_name() != backend->device_name()) {
+
+                       if (backend->use_separate_input_and_output_devices()) {
+                               if (get_input_device_name() != backend->input_device_name()) {
+                                       change_device = true;
+                               }
+                               if (get_output_device_name() != backend->output_device_name()) {
+                                       change_device = true;
+                               }
+                       } else {
+                               if (get_device_name() != backend->device_name()) {
+                                       change_device = true;
+                               }
+                       }
+
+                       if (queue_device_changed) {
                                change_device = true;
                        }
-                       
+
                        if (get_rate() != backend->sample_rate()) {
                                change_rate = true;
                        }
-                       
+
                        if (get_buffer_size() != backend->buffer_size()) {
                                change_bufsize = true;
                        }
 
+                       if (backend->can_set_period_size() && get_popdown_string_count (nperiods_combo) > 0
+                                       && get_nperiods() != backend->period_size()) {
+                               change_nperiods = true;
+                       }
+
                        if (get_midi_option() != backend->midi_option()) {
                                change_midi = true;
                        }
-                       
+
+                       if (backend->can_use_buffered_io()) {
+                               if (get_use_buffered_io() != backend->get_use_buffered_io()) {
+                                       change_buffered_io = true;
+                               }
+                       }
+
                        /* zero-requested channels means "all available" */
 
                        if (ichan == 0) {
                                ichan = backend->input_channels();
                        }
-                       
+
                        if (ochan == 0) {
                                ochan = backend->output_channels();
                        }
-                       
+
                        if (ichan != backend->input_channels()) {
                                change_channels = true;
                        }
-                       
+
                        if (ochan != backend->output_channels()) {
                                change_channels = true;
                        }
 
                        if (get_input_latency() != backend->systemic_input_latency() ||
-                           get_output_latency() != backend->systemic_output_latency()) {
+                                       get_output_latency() != backend->systemic_output_latency()) {
                                change_latency = true;
                        }
                } else {
                        /* backend never started, so we have to force a group
                           of settings.
-                       */
-                       change_driver = true;
+                        */
                        change_device = true;
+                       if (backend->requires_driver_selection()) {
+                               change_driver = true;
+                       }
                        change_rate = true;
                        change_bufsize = true;
                        change_channels = true;
                        change_latency = true;
                        change_midi = true;
+                       change_buffered_io = backend->can_use_buffered_io();
+                       change_channels = true;
+                       change_nperiods = backend->can_set_period_size() && get_popdown_string_count (nperiods_combo) > 0;
                }
 
        } else {
@@ -1264,6 +2392,8 @@ EngineControl::push_state_to_backend (bool start)
                }
        }
 
+       queue_device_changed = false;
+
        if (!_have_control) {
 
                /* We do not have control over the backend, so the best we can
@@ -1278,67 +2408,66 @@ EngineControl::push_state_to_backend (bool start)
                if (change_bufsize && !backend->can_change_buffer_size_when_running()) {
                        return 1;
                }
-               
+
                if (change_rate) {
                        backend->set_sample_rate (get_rate());
                }
-               
+
                if (change_bufsize) {
                        backend->set_buffer_size (get_buffer_size());
                }
 
+               if (start) {
+                       if (ARDOUR::AudioEngine::instance()->start ()) {
+                               error << string_compose (_("Could not start backend engine %1"), backend->name()) << endmsg;
+                               return -1;
+                       }
+               }
+
                post_push ();
 
                return 0;
-       } 
+       }
 
        /* determine if we need to stop the backend before changing parameters */
 
-       if (change_driver || change_device || change_channels || change_latency ||
-           (change_rate && !backend->can_change_sample_rate_when_running()) ||
-           change_midi ||
-           (change_bufsize && !backend->can_change_buffer_size_when_running())) {
+       if (change_driver || change_device || change_channels || change_nperiods ||
+                       (change_latency && !backend->can_change_systemic_latency_when_running ()) ||
+                       (change_rate && !backend->can_change_sample_rate_when_running()) ||
+                       change_midi || change_buffered_io ||
+                       (change_bufsize && !backend->can_change_buffer_size_when_running())) {
                restart_required = true;
        } else {
                restart_required = false;
        }
 
-       if (was_running) {
-
-               if (!change_driver && !change_device && !change_channels && !change_latency && !change_midi) {
-                       /* no changes in any parameters that absolutely require a
-                        * restart, so check those that might be changeable without a
-                        * restart
-                        */
-                       
-                       if (change_rate && !backend->can_change_sample_rate_when_running()) {
-                               /* can't do this while running ... */
-                               restart_required = true;
-                       }
-
-                       if (change_bufsize && !backend->can_change_buffer_size_when_running()) {
-                               /* can't do this while running ... */
-                               restart_required = true;
-                       }
-               }
-       }
 
        if (was_running) {
                if (restart_required) {
-                       if (ARDOUR_UI::instance()->disconnect_from_engine ()) {
+                       if (ARDOUR::AudioEngine::instance()->stop()) {
                                return -1;
                        }
                }
        }
-               
 
        if (change_driver && backend->set_driver (get_driver())) {
                error << string_compose (_("Cannot set driver to %1"), get_driver()) << endmsg;
                return -1;
        }
-       if (change_device && backend->set_device_name (get_device_name())) {
-               error << string_compose (_("Cannot set device name to %1"), get_device_name()) << endmsg;
-               return -1;
+       if (backend->use_separate_input_and_output_devices()) {
+               if (change_device && backend->set_input_device_name (get_input_device_name())) {
+                       error << string_compose (_("Cannot set input device name to %1"), get_input_device_name()) << endmsg;
+                       return -1;
+               }
+               if (change_device && backend->set_output_device_name (get_output_device_name())) {
+                       error << string_compose (_("Cannot set output device name to %1"), get_output_device_name()) << endmsg;
+                       return -1;
+               }
+       } else {
+               if (change_device && backend->set_device_name (get_device_name())) {
+                       error << string_compose (_("Cannot set device name to %1"), get_device_name()) << endmsg;
+                       return -1;
+               }
        }
        if (change_rate && backend->set_sample_rate (get_rate())) {
                error << string_compose (_("Cannot set sample rate to %1"), get_rate()) << endmsg;
@@ -1348,6 +2477,10 @@ EngineControl::push_state_to_backend (bool start)
                error << string_compose (_("Cannot set buffer size to %1"), get_buffer_size()) << endmsg;
                return -1;
        }
+       if (change_nperiods && backend->set_peridod_size (get_nperiods())) {
+               error << string_compose (_("Cannot set periods to %1"), get_nperiods()) << endmsg;
+               return -1;
+       }
 
        if (change_channels || get_input_channels() == 0 || get_output_channels() == 0) {
                if (backend->set_input_channels (get_input_channels())) {
@@ -1373,13 +2506,39 @@ EngineControl::push_state_to_backend (bool start)
        if (change_midi) {
                backend->set_midi_option (get_midi_option());
        }
-                       
+
+       if (change_buffered_io) {
+               backend->set_use_buffered_io (use_buffered_io_button.get_active());
+       }
+
+       if (1 /* TODO */) {
+               for (vector<MidiDeviceSettings>::const_iterator p = _midi_devices.begin(); p != _midi_devices.end(); ++p) {
+                       if (_measure_midi) {
+                               if (*p == _measure_midi) {
+                                       backend->set_midi_device_enabled ((*p)->name, true);
+                               } else {
+                                       backend->set_midi_device_enabled ((*p)->name, false);
+                               }
+                               if (backend->can_change_systemic_latency_when_running ()) {
+                                       backend->set_systemic_midi_input_latency ((*p)->name, 0);
+                                       backend->set_systemic_midi_output_latency ((*p)->name, 0);
+                               }
+                               continue;
+                       }
+                       backend->set_midi_device_enabled ((*p)->name, (*p)->enabled);
+                       if (backend->can_set_systemic_midi_latencies()) {
+                               backend->set_systemic_midi_input_latency ((*p)->name, (*p)->input_latency);
+                               backend->set_systemic_midi_output_latency ((*p)->name, (*p)->output_latency);
+                       }
+               }
+       }
+
        if (start || (was_running && restart_required)) {
-               if (ARDOUR_UI::instance()->reconnect_to_engine()) {
+               if (ARDOUR::AudioEngine::instance()->start()) {
                        return -1;
                }
        }
-       
+
        post_push ();
 
        return 0;
@@ -1391,33 +2550,36 @@ EngineControl::post_push ()
        /* get a pointer to the current state object, creating one if
         * necessary
         */
-       
-       if (_have_control) {
-               State* state = get_saved_state_for_currently_displayed_backend_and_device ();
-               
-               if (!state) {
-                       state = save_state ();
-                       assert (state);
-               }
-               
-               /* all off */
-               
-               for (StateList::iterator i = states.begin(); i != states.end(); ++i) {
-                       (*i).active = false;
-               }
-               
-               /* mark this one active (to be used next time the dialog is
-                * shown)
-                */
-               
-               state->active = true;
-               
+
+       State state = get_saved_state_for_currently_displayed_backend_and_device ();
+
+       if (!state) {
+               state = save_state ();
+               assert (state);
+       } else {
+               store_state(state);
+       }
+
+       states.sort (state_sort_cmp);
+
+       /* all off */
+
+       for (StateList::iterator i = states.begin(); i != states.end(); ++i) {
+               (*i)->active = false;
+       }
+
+       /* mark this one active (to be used next time the dialog is
+        * shown)
+        */
+
+       state->active = true;
+
+       if (_have_control) { // XXX
                manage_control_app_sensitivity ();
        }
 
        /* schedule a redisplay of MIDI ports */
-       
-       Glib::signal_timeout().connect (sigc::bind_return (sigc::mem_fun (*this, &EngineControl::refresh_midi_display), false), 1000);
+       //Glib::signal_timeout().connect (sigc::bind_return (sigc::mem_fun (*this, &EngineControl::refresh_midi_display), false), 1000);
 }
 
 
@@ -1433,7 +2595,7 @@ EngineControl::get_rate () const
        }
        return r;
 }
-       
+
 
 uint32_t
 EngineControl::get_buffer_size () const
@@ -1442,27 +2604,52 @@ EngineControl::get_buffer_size () const
        uint32_t samples;
 
        if (sscanf (txt.c_str(), "%d", &samples) != 1) {
+               fprintf(stderr, "Find a trout and repeatedly slap the nearest C++ who throws exceptions without catching them.\n");
+               fprintf(stderr, "Ardour will likely crash now, giving you time to get the trout.\n");
                throw exception ();
        }
 
        return samples;
 }
 
+uint32_t
+EngineControl::get_nperiods () const
+{
+       string txt = nperiods_combo.get_active_text ();
+       return atoi (txt.c_str());
+}
+
 string
 EngineControl::get_midi_option () const
 {
        return midi_option_combo.get_active_text();
 }
 
+bool
+EngineControl::get_use_buffered_io () const
+{
+       return use_buffered_io_button.get_active();
+}
+
 uint32_t
 EngineControl::get_input_channels() const
 {
+       if (ARDOUR::Profile->get_mixbus()) {
+               boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+               if (!backend) return 0;
+               return backend->input_channels();
+       }
        return (uint32_t) input_channels_adjustment.get_value();
 }
 
 uint32_t
 EngineControl::get_output_channels() const
 {
+       if (ARDOUR::Profile->get_mixbus()) {
+               boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+               if (!backend) return 0;
+               return backend->input_channels();
+       }
        return (uint32_t) output_channels_adjustment.get_value();
 }
 
@@ -1487,7 +2674,11 @@ EngineControl::get_backend () const
 string
 EngineControl::get_driver () const
 {
-       return driver_combo.get_active_text ();
+       if (driver_combo.get_parent()) {
+               return driver_combo.get_active_text ();
+       } else {
+               return "";
+       }
 }
 
 string
@@ -1496,27 +2687,83 @@ EngineControl::get_device_name () const
        return device_combo.get_active_text ();
 }
 
+string
+EngineControl::get_input_device_name () const
+{
+       return input_device_combo.get_active_text ();
+}
+
+string
+EngineControl::get_output_device_name () const
+{
+       return output_device_combo.get_active_text ();
+}
+
 void
 EngineControl::control_app_button_clicked ()
 {
        boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
-       
+
        if (!backend) {
                return;
        }
-       
+
        backend->launch_control_app ();
 }
 
+void
+EngineControl::start_stop_button_clicked ()
+{
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+
+       if (!backend) {
+               return;
+       }
+
+       if (ARDOUR::AudioEngine::instance()->running()) {
+               ARDOUR::AudioEngine::instance()->stop ();
+       } else {
+               start_engine ();
+       }
+}
+
+void
+EngineControl::update_devices_button_clicked ()
+{
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+
+       if (!backend) {
+               return;
+       }
+
+       if (backend->update_devices()) {
+               device_list_changed ();
+       }
+}
+
+void
+EngineControl::use_buffered_io_button_clicked ()
+{
+       boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
+
+       if (!backend) {
+               return;
+       }
+
+       bool set_buffered_io = !use_buffered_io_button.get_active();
+       use_buffered_io_button.set_active (set_buffered_io);
+       backend->set_use_buffered_io (set_buffered_io);
+}
+
 void
 EngineControl::manage_control_app_sensitivity ()
 {
        boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
-       
+
        if (!backend) {
                return;
        }
-       
+
        string appname = backend->control_app_name();
 
        if (appname.empty()) {
@@ -1530,6 +2777,10 @@ void
 EngineControl::set_desired_sample_rate (uint32_t sr)
 {
        _desired_sample_rate = sr;
+       if (ARDOUR::AudioEngine::instance ()->running ()
+                       && ARDOUR::AudioEngine::instance ()->sample_rate () != sr) {
+               stop_engine ();
+       }
        device_changed ();
 }
 
@@ -1538,12 +2789,11 @@ EngineControl::on_switch_page (GtkNotebookPage*, guint page_num)
 {
        if (page_num == 0) {
                cancel_button->set_sensitive (true);
-               ok_button->set_sensitive (true);
-               apply_button->set_sensitive (true);
+               _measure_midi.reset();
+               update_sensitivity ();
        } else {
                cancel_button->set_sensitive (false);
                ok_button->set_sensitive (false);
-               apply_button->set_sensitive (false);
        }
 
        if (page_num == midi_tab) {
@@ -1554,29 +2804,37 @@ EngineControl::on_switch_page (GtkNotebookPage*, guint page_num)
        if (page_num == latency_tab) {
                /* latency tab */
 
-               if (!ARDOUR::AudioEngine::instance()->running()) {
-                       
+               if (ARDOUR::AudioEngine::instance()->running()) {
+                       stop_engine (true);
+               }
+
+               {
                        PBD::Unwinder<uint32_t> protect_ignore_changes (ignore_changes, ignore_changes + 1);
-                       
+
                        /* save any existing latency values */
-                       
+
                        uint32_t il = (uint32_t) input_latency.get_value ();
                        uint32_t ol = (uint32_t) input_latency.get_value ();
 
-                       /* reset to zero so that our new test instance of JACK
+                       /* reset to zero so that our new test instance
                           will be clean of any existing latency measures.
+
+                          NB. this should really be done by the backend
+                          when stated for latency measurement.
                        */
-                       
+
                        input_latency.set_value (0);
                        output_latency.set_value (0);
-                       
+
+                       push_state_to_backend (false);
+
                        /* reset control */
 
                        input_latency.set_value (il);
                        output_latency.set_value (ol);
 
-               } 
-
+               }
+               // This should be done in push_state_to_backend()
                if (ARDOUR::AudioEngine::instance()->prepare_for_latency_measurement()) {
                        disable_latency_tab ();
                }
@@ -1584,63 +2842,141 @@ EngineControl::on_switch_page (GtkNotebookPage*, guint page_num)
                enable_latency_tab ();
 
        } else {
-               ARDOUR::AudioEngine::instance()->stop_latency_detection();
+               if (lm_running) {
+                       end_latency_detection ();
+                       ARDOUR::AudioEngine::instance()->stop_latency_detection();
+               }
        }
 }
 
 /* latency measurement */
 
 bool
-EngineControl::check_latency_measurement ()
+EngineControl::check_audio_latency_measurement ()
 {
-        MTDM* mtdm = ARDOUR::AudioEngine::instance()->mtdm ();
+       MTDM* mtdm = ARDOUR::AudioEngine::instance()->mtdm ();
 
-        if (mtdm->resolve () < 0) {
-               lm_results.set_markup (string_compose ("<span foreground=\"red\">%1</span>", _("No signal detected ")));
-                return true;
-        }
+       if (mtdm->resolve () < 0) {
+               lm_results.set_markup (string_compose (results_markup, _("No signal detected ")));
+               return true;
+       }
+
+       if (mtdm->get_peak () > 0.707f) {
+               // get_peak() resets the peak-hold in the detector.
+               // this GUI callback is at 10Hz and so will be fine (test-signal is at higher freq)
+               lm_results.set_markup (string_compose (results_markup, _("Input signal is > -3dBFS. Lower the signal level (output gain, input gain) on the audio-interface.")));
+               return true;
+       }
 
-        if (mtdm->err () > 0.3) {
-                mtdm->invert ();
-                mtdm->resolve ();
-        }
+       if (mtdm->err () > 0.3) {
+               mtdm->invert ();
+               mtdm->resolve ();
+       }
 
-        char buf[128];
+       char buf[256];
        ARDOUR::framecnt_t const sample_rate = ARDOUR::AudioEngine::instance()->sample_rate();
 
-        if (sample_rate == 0) {
-                lm_results.set_text (_("Disconnected from audio engine"));
+       if (sample_rate == 0) {
+               lm_results.set_markup (string_compose (results_markup, _("Disconnected from audio engine")));
                ARDOUR::AudioEngine::instance()->stop_latency_detection ();
-                return false;
-        }
+               return false;
+       }
+
+       int frames_total = mtdm->del();
+       int extra = frames_total - ARDOUR::AudioEngine::instance()->latency_signal_delay();
 
-       uint32_t frames_total = mtdm->del();
-       uint32_t extra = frames_total - ARDOUR::AudioEngine::instance()->latency_signal_delay();
+       snprintf (buf, sizeof (buf), "%s%d samples (%.3lf ms)\n%s%d samples (%.3lf ms)",
+                       _("Detected roundtrip latency: "),
+                       frames_total, frames_total * 1000.0f/sample_rate,
+                       _("Systemic latency: "),
+                       extra, extra * 1000.0f/sample_rate);
 
-        snprintf (buf, sizeof (buf), "%u samples %10.3lf ms", extra, extra * 1000.0f/sample_rate);
+       bool solid = true;
 
-        bool solid = true;
+       if (mtdm->err () > 0.2) {
+               strcat (buf, " ");
+               strcat (buf, _("(signal detection error)"));
+               solid = false;
+       }
 
-        if (mtdm->err () > 0.2) {
-                strcat (buf, " ??");
-                solid = false;
-        }
+       if (mtdm->inv ()) {
+               strcat (buf, " ");
+               strcat (buf, _("(inverted - bad wiring)"));
+               solid = false;
+       }
 
-        if (mtdm->inv ()) {
-                strcat (buf, " (Inv)");
-                solid = false;
-        }
+       lm_results.set_markup (string_compose (results_markup, buf));
 
-        if (solid) {
-                lm_measure_button.set_active (false);
+       if (solid) {
+               have_lm_results = true;
+               end_latency_detection ();
                lm_use_button.set_sensitive (true);
-                strcat (buf, " (set)");
+               return false;
+       }
+
+       return true;
+}
+
+bool
+EngineControl::check_midi_latency_measurement ()
+{
+       ARDOUR::MIDIDM* mididm = ARDOUR::AudioEngine::instance()->mididm ();
+
+       if (!mididm->have_signal () || mididm->latency () == 0) {
+               lm_results.set_markup (string_compose (results_markup, _("No signal detected ")));
+               return true;
+       }
+
+       char buf[256];
+       ARDOUR::framecnt_t const sample_rate = ARDOUR::AudioEngine::instance()->sample_rate();
+
+       if (sample_rate == 0) {
+               lm_results.set_markup (string_compose (results_markup, _("Disconnected from audio engine")));
+               ARDOUR::AudioEngine::instance()->stop_latency_detection ();
+               return false;
+       }
+
+       ARDOUR::framecnt_t frames_total = mididm->latency();
+       ARDOUR::framecnt_t extra = frames_total - ARDOUR::AudioEngine::instance()->latency_signal_delay();
+       snprintf (buf, sizeof (buf), "%s%" PRId64" samples (%.1lf ms) dev: %.2f[spl]\n%s%" PRId64" samples (%.1lf ms)",
+                       _("Detected roundtrip latency: "),
+                       frames_total, frames_total * 1000.0f / sample_rate, mididm->deviation (),
+                       _("Systemic latency: "),
+                       extra, extra * 1000.0f / sample_rate);
+
+       bool solid = true;
+
+       if (!mididm->ok ()) {
+               strcat (buf, " ");
+               strcat (buf, _("(averaging)"));
+               solid = false;
+       }
+
+       if (mididm->deviation () > 50.0) {
+               strcat (buf, " ");
+               strcat (buf, _("(too large jitter)"));
+               solid = false;
+       } else if (mididm->deviation () > 10.0) {
+               strcat (buf, " ");
+               strcat (buf, _("(large jitter)"));
+       }
+
+       if (solid) {
                have_lm_results = true;
-        }
-       
-        lm_results.set_text (buf);
+               end_latency_detection ();
+               lm_use_button.set_sensitive (true);
+               lm_results.set_markup (string_compose (results_markup, buf));
+               return false;
+       } else if (mididm->processed () > 400) {
+               have_lm_results = false;
+               end_latency_detection ();
+               lm_results.set_markup (string_compose (results_markup, _("Timeout - large MIDI jitter.")));
+               return false;
+       }
+
+       lm_results.set_markup (string_compose (results_markup, buf));
 
-        return true;
+       return true;
 }
 
 void
@@ -1648,53 +2984,84 @@ EngineControl::start_latency_detection ()
 {
        ARDOUR::AudioEngine::instance()->set_latency_input_port (lm_input_channel_combo.get_active_text());
        ARDOUR::AudioEngine::instance()->set_latency_output_port (lm_output_channel_combo.get_active_text());
-       ARDOUR::AudioEngine::instance()->start_latency_detection ();
-       lm_results.set_text (_("Detecting ..."));
-       latency_timeout = Glib::signal_timeout().connect (mem_fun (*this, &EngineControl::check_latency_measurement), 250);
-       lm_start_stop_label.set_text (_("Cancel measurement"));
-       have_lm_results = false;
-       lm_input_channel_combo.set_sensitive (false);
-       lm_output_channel_combo.set_sensitive (false);
+
+       if (ARDOUR::AudioEngine::instance()->start_latency_detection (_measure_midi ? true : false) == 0) {
+               lm_results.set_markup (string_compose (results_markup, _("Detecting ...")));
+               if (_measure_midi) {
+                       latency_timeout = Glib::signal_timeout().connect (mem_fun (*this, &EngineControl::check_midi_latency_measurement), 100);
+               } else {
+                       latency_timeout = Glib::signal_timeout().connect (mem_fun (*this, &EngineControl::check_audio_latency_measurement), 100);
+               }
+               lm_measure_label.set_text (_("Cancel"));
+               have_lm_results = false;
+               lm_use_button.set_sensitive (false);
+               lm_input_channel_combo.set_sensitive (false);
+               lm_output_channel_combo.set_sensitive (false);
+               lm_running = true;
+       }
 }
 
 void
 EngineControl::end_latency_detection ()
 {
-       ARDOUR::AudioEngine::instance()->stop_latency_detection ();
        latency_timeout.disconnect ();
-       lm_start_stop_label.set_text (_("Measure latency"));
+       ARDOUR::AudioEngine::instance()->stop_latency_detection ();
+       lm_measure_label.set_text (_("Measure"));
        if (!have_lm_results) {
-               lm_results.set_markup ("<i>No measurement results yet</i>");
+               lm_use_button.set_sensitive (false);
        }
        lm_input_channel_combo.set_sensitive (true);
        lm_output_channel_combo.set_sensitive (true);
+       lm_running = false;
 }
 
 void
-EngineControl::latency_button_toggled ()
+EngineControl::latency_button_clicked ()
 {
-        if (lm_measure_button.get_active ()) {
+       if (!lm_running) {
                start_latency_detection ();
        } else {
                end_latency_detection ();
-        }
+       }
+}
+
+void
+EngineControl::latency_back_button_clicked ()
+{
+       ARDOUR::AudioEngine::instance()->stop(true);
+       notebook.set_current_page(0);
 }
 
 void
 EngineControl::use_latency_button_clicked ()
 {
-        MTDM* mtdm = ARDOUR::AudioEngine::instance()->mtdm ();
+       if (_measure_midi) {
+               ARDOUR::MIDIDM* mididm = ARDOUR::AudioEngine::instance()->mididm ();
+               if (!mididm) {
+                       return;
+               }
+               ARDOUR::framecnt_t frames_total = mididm->latency();
+               ARDOUR::framecnt_t extra = frames_total - ARDOUR::AudioEngine::instance()->latency_signal_delay();
+               uint32_t one_way = max ((ARDOUR::framecnt_t) 0, extra / 2);
+               _measure_midi->input_latency = one_way;
+               _measure_midi->output_latency = one_way;
+               notebook.set_current_page (midi_tab);
+       } else {
+               MTDM* mtdm = ARDOUR::AudioEngine::instance()->mtdm ();
 
-       if (!mtdm) {
-               return;
-       }
+               if (!mtdm) {
+                       return;
+               }
 
-       uint32_t frames_total = mtdm->del();
-       uint32_t extra = frames_total - ARDOUR::AudioEngine::instance()->latency_signal_delay();
-       uint32_t one_way = extra/2;
+               double one_way = rint ((mtdm->del() - ARDOUR::AudioEngine::instance()->latency_signal_delay()) / 2.0);
+               one_way = std::max (0., one_way);
 
-       input_latency_adjustment.set_value (one_way);
-       output_latency_adjustment.set_value (one_way);
+               input_latency_adjustment.set_value (one_way);
+               output_latency_adjustment.set_value (one_way);
+
+               /* back to settings page */
+               notebook.set_current_page (0);
+       }
 }
 
 bool
@@ -1713,15 +3080,23 @@ EngineControl::engine_running ()
        boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
        assert (backend);
 
-       buffer_size_combo.set_active_text (bufsize_as_string (backend->buffer_size()));
+       set_active_text_if_present (buffer_size_combo, bufsize_as_string (backend->buffer_size()));
        sample_rate_combo.set_active_text (rate_as_string (backend->sample_rate()));
 
-       buffer_size_combo.set_sensitive (true);
-       sample_rate_combo.set_sensitive (true);
+       if (backend->can_set_period_size ()) {
+               set_active_text_if_present (nperiods_combo, nperiods_as_string (backend->period_size()));
+       }
 
        connect_disconnect_button.set_label (string_compose (_("Disconnect from %1"), backend->name()));
+       connect_disconnect_button.show();
 
        started_at_least_once = true;
+       if (_have_control) {
+               engine_status.set_markup(string_compose ("<span foreground=\"green\">%1</span>", _("Running")));
+       } else {
+               engine_status.set_markup(string_compose ("<span foreground=\"green\">%1</span>", _("Connected")));
+       }
+       update_sensitivity();
 }
 
 void
@@ -1730,19 +3105,61 @@ EngineControl::engine_stopped ()
        boost::shared_ptr<ARDOUR::AudioBackend> backend = ARDOUR::AudioEngine::instance()->current_backend();
        assert (backend);
 
-       buffer_size_combo.set_sensitive (false);
        connect_disconnect_button.set_label (string_compose (_("Connect to %1"), backend->name()));
+       connect_disconnect_button.show();
+
+       if (_have_control) {
+               engine_status.set_markup(string_compose ("<span foreground=\"red\">%1</span>", _("Stopped")));
+       } else {
+               engine_status.set_markup(X_(""));
+       }
 
-       sample_rate_combo.set_sensitive (true);
-       buffer_size_combo.set_sensitive (true);
+       update_sensitivity();
 }
-       
+
+void
+EngineControl::device_list_changed ()
+{
+       if (ignore_device_changes) {
+               return;
+       }
+       PBD::Unwinder<uint32_t> protect_ignore_changes (ignore_changes, ignore_changes + 1); // ??
+       list_devices ();
+       midi_option_changed();
+}
+
 void
-EngineControl::connect_disconnect_click() 
+EngineControl::connect_disconnect_click()
 {
        if (ARDOUR::AudioEngine::instance()->running()) {
-               ARDOUR_UI::instance()->disconnect_from_engine ();
+               stop_engine ();
        } else {
-               ARDOUR_UI::instance()->reconnect_to_engine ();
+               start_engine ();
        }
 }
+
+void
+EngineControl::calibrate_audio_latency ()
+{
+       _measure_midi.reset ();
+       have_lm_results = false;
+       lm_use_button.set_sensitive (false);
+       lm_results.set_markup (string_compose (results_markup, _("No measurement results yet")));
+       notebook.set_current_page (latency_tab);
+}
+
+void
+EngineControl::calibrate_midi_latency (MidiDeviceSettings s)
+{
+       _measure_midi = s;
+       have_lm_results = false;
+       lm_use_button.set_sensitive (false);
+       lm_results.set_markup (string_compose (results_markup, _("No measurement results yet")));
+       notebook.set_current_page (latency_tab);
+}
+
+void
+EngineControl::configure_midi_devices ()
+{
+       notebook.set_current_page (midi_tab);
+}