bump default silent-after-seconds duration to 10 minutes
[ardour.git] / libs / ardour / audioengine.cc
index f79c90feeadd691209fe79985432339c593b5766..3a7b4f910aef7a57697a283f0057f9c4a13bf11a 100644 (file)
@@ -23,6 +23,7 @@
 #include <exception>
 #include <stdexcept>
 #include <sstream>
+#include <cmath>
 
 #include <glibmm/timer.h>
 #include <glibmm/pattern.h>
@@ -34,8 +35,6 @@
 #include "pbd/stacktrace.h"
 #include "pbd/unknown_type.h"
 
-#include <jack/weakjack.h>
-
 #include "midi++/port.h"
 #include "midi++/mmc.h"
 
 #include "ardour/audio_port.h"
 #include "ardour/audio_backend.h"
 #include "ardour/audioengine.h"
-#include "ardour/backend_search_path.h"
+#include "ardour/search_paths.h"
 #include "ardour/buffer.h"
 #include "ardour/cycle_timer.h"
 #include "ardour/internal_send.h"
 #include "ardour/meter.h"
 #include "ardour/midi_port.h"
 #include "ardour/midiport_manager.h"
+#include "ardour/mididm.h"
 #include "ardour/mtdm.h"
 #include "ardour/port.h"
 #include "ardour/process_thread.h"
@@ -64,6 +64,10 @@ using namespace PBD;
 gint AudioEngine::m_meter_exit;
 AudioEngine* AudioEngine::_instance = 0;
 
+#ifdef SILENCE_AFTER
+#define SILENCE_AFTER_SECONDS 600
+#endif
+
 AudioEngine::AudioEngine ()
        : session_remove_pending (false)
        , session_removal_countdown (-1)
@@ -75,15 +79,29 @@ AudioEngine::AudioEngine ()
        , m_meter_thread (0)
        , _main_thread (0)
        , _mtdm (0)
-       , _measuring_latency (false)
+       , _mididm (0)
+       , _measuring_latency (MeasureNone)
        , _latency_input_port (0)
        , _latency_output_port (0)
        , _latency_flush_frames (0)
        , _latency_signal_latency (0)
+       , _stopped_for_latency (false)
        , _started_for_latency (false)
        , _in_destructor (false)
+    , _hw_reset_event_thread(0)
+    , _hw_reset_request_count(0)
+    , _stop_hw_reset_processing(0)
+    , _hw_devicelist_update_thread(0)
+    , _hw_devicelist_update_count(0)
+    , _stop_hw_devicelist_processing(0)
+#ifdef SILENCE_AFTER_SECONDS
+       , _silence_countdown (0)
+       , _silence_hit_cnt (0)
+#endif
 {
        g_atomic_int_set (&m_meter_exit, 0);
+       reset_silence_countdown ();
+       start_hw_event_processing();
        discover_backends ();
 }
 
@@ -91,7 +109,11 @@ AudioEngine::~AudioEngine ()
 {
        _in_destructor = true;
        stop_metering_thread ();
+       stop_hw_event_processing();
        drop_backend ();
+       for (BackendMap::const_iterator i = _backends.begin(); i != _backends.end(); ++i) {
+               i->second->deinstantiate();
+       }
 }
 
 AudioEngine*
@@ -106,23 +128,6 @@ AudioEngine::create ()
        return _instance;
 }
 
-void
-_thread_init_callback (void * /*arg*/)
-{
-       /* make sure that anybody who needs to know about this thread
-          knows about it.
-       */
-
-       pthread_set_name (X_("audioengine"));
-
-       PBD::notify_gui_about_thread_creation ("gui", pthread_self(), X_("Audioengine"), 4096);
-       PBD::notify_gui_about_thread_creation ("midiui", pthread_self(), X_("Audioengine"), 128);
-
-       SessionEvent::create_per_thread_pool (X_("Audioengine"), 512);
-
-       AsyncMIDIPort::set_process_thread (pthread_self());
-}
-
 void
 AudioEngine::split_cycle (pframes_t offset)
 {
@@ -153,6 +158,10 @@ AudioEngine::sample_rate_change (pframes_t nframes)
 
        SampleRateChanged (nframes); /* EMIT SIGNAL */
 
+#ifdef SILENCE_AFTER_SECONDS
+       _silence_countdown = nframes * SILENCE_AFTER_SECONDS;
+#endif
+       
        return 0;
 }
 
@@ -164,12 +173,17 @@ AudioEngine::buffer_size_change (pframes_t bufsiz)
                last_monitor_check = 0;
        }
 
+       BufferSizeChanged (bufsiz); /* EMIT SIGNAL */
+
        return 0;
 }
 
 /** Method called by our ::process_thread when there is work to be done.
  *  @param nframes Number of frames to process.
  */
+#ifdef __clang__
+__attribute__((annotate("realtime")))
+#endif
 int
 AudioEngine::process_callback (pframes_t nframes)
 {
@@ -197,7 +211,7 @@ AudioEngine::process_callback (pframes_t nframes)
 
        bool return_after_remove_check = false;
 
-       if (_measuring_latency && _mtdm) {
+       if (_measuring_latency == MeasureAudio && _mtdm) {
                /* run a normal cycle from the perspective of the PortManager
                   so that we get silence on all registered ports.
                   
@@ -220,6 +234,28 @@ AudioEngine::process_callback (pframes_t nframes)
                PortManager::cycle_end (nframes);
                return_after_remove_check = true;
 
+       } else if (_measuring_latency == MeasureMIDI && _mididm) {
+               /* run a normal cycle from the perspective of the PortManager
+                  so that we get silence on all registered ports.
+
+                  we overwrite the silence on the two ports used for latency
+                  measurement.
+               */
+
+               PortManager::cycle_start (nframes);
+               PortManager::silence (nframes);
+
+               if (_latency_input_port && _latency_output_port) {
+                       PortEngine& pe (port_engine());
+
+                       _mididm->process (nframes, pe,
+                                       pe.get_buffer (_latency_input_port, nframes),
+                                       pe.get_buffer (_latency_output_port, nframes));
+               }
+
+               PortManager::cycle_end (nframes);
+               return_after_remove_check = true;
+
        } else if (_latency_flush_frames) {
                
                /* wait for the appropriate duration for the MTDM signal to
@@ -305,18 +341,18 @@ AudioEngine::process_callback (pframes_t nframes)
        */
 
        if (_freewheeling && !Freewheel.empty()) {
-                Freewheel (nframes);
+               Freewheel (nframes);
        } else {
-               if (_session) {
-                       _session->process (nframes);
-               }
+               _session->process (nframes);
        }
 
        if (_freewheeling) {
+               PortManager::cycle_end (nframes);
                return 0;
        }
 
        if (!_running) {
+               PortManager::cycle_end (nframes);
                _processed_frames = next_processed_frames;
                return 0;
        }
@@ -327,10 +363,31 @@ AudioEngine::process_callback (pframes_t nframes)
                last_monitor_check = next_processed_frames;
        }
 
+#ifdef SILENCE_AFTER_SECONDS
+
+       bool was_silent = (_silence_countdown == 0);
+       
+       if (_silence_countdown >= nframes) {
+               _silence_countdown -= nframes;
+       } else {
+               _silence_countdown = 0;
+       }
+
+       if (!was_silent && _silence_countdown == 0) {
+               _silence_hit_cnt++;
+               BecameSilent (); /* EMIT SIGNAL */
+       }
+
+       if (_silence_countdown == 0 || _session->silent()) {
+               PortManager::silence (nframes);
+       }
+       
+#else  
        if (_session->silent()) {
                PortManager::silence (nframes);
        }
-
+#endif
+       
        if (session_remove_pending && session_removal_countdown) {
 
                PortManager::fade_out (session_removal_gain, session_removal_gain_step, nframes);
@@ -353,6 +410,165 @@ AudioEngine::process_callback (pframes_t nframes)
        return 0;
 }
 
+void
+AudioEngine::reset_silence_countdown ()
+{
+#ifdef SILENCE_AFTER_SECONDS
+       double sr = 48000; /* default in case there is no backend */
+
+       sr = sample_rate();
+
+       _silence_countdown = max (60 * sr, /* 60 seconds */
+                                 sr * (SILENCE_AFTER_SECONDS / pow (2, _silence_hit_cnt)));
+
+#endif
+}
+
+void
+AudioEngine::launch_device_control_app()
+{
+       if (_state_lock.trylock () ) {
+               _backend->launch_control_app ();
+               _state_lock.unlock ();
+       }
+}
+
+
+void
+AudioEngine::request_backend_reset()
+{
+    Glib::Threads::Mutex::Lock guard (_reset_request_lock);
+    g_atomic_int_inc (&_hw_reset_request_count);
+    _hw_reset_condition.signal ();
+}
+
+int
+AudioEngine::backend_reset_requested()
+{
+       return g_atomic_int_get (&_hw_reset_request_count);
+}
+
+void
+AudioEngine::do_reset_backend()
+{
+       SessionEvent::create_per_thread_pool (X_("Backend reset processing thread"), 512);
+    
+       Glib::Threads::Mutex::Lock guard (_reset_request_lock);
+    
+       while (!_stop_hw_reset_processing) {
+        
+               if (g_atomic_int_get (&_hw_reset_request_count) != 0 && _backend) {
+               
+                       _reset_request_lock.unlock();
+               
+                       Glib::Threads::RecMutex::Lock pl (_state_lock);
+                       g_atomic_int_dec_and_test (&_hw_reset_request_count);
+               
+                       std::cout << "AudioEngine::RESET::Reset request processing. Requests left: " << _hw_reset_request_count << std::endl;
+                       DeviceResetStarted(); // notify about device reset to be started
+               
+                       // backup the device name
+                       std::string name = _backend->device_name ();
+               
+                       std::cout << "AudioEngine::RESET::Stoping engine..." << std::endl;
+                       stop();
+               
+                       std::cout << "AudioEngine::RESET::Reseting device..." << std::endl;
+                       if ( 0 == _backend->reset_device () ) {
+                       
+                               std::cout << "AudioEngine::RESET::Starting engine..." << std::endl;
+                               start ();
+                       
+                               // inform about possible changes
+                               BufferSizeChanged (_backend->buffer_size() );
+                       } else {
+                               DeviceError();
+                       }
+                       
+                       std::cout << "AudioEngine::RESET::Done." << std::endl;
+
+                       _reset_request_lock.lock();
+            
+               } else {
+            
+                       _hw_reset_condition.wait (_reset_request_lock);
+            
+               }
+       }
+}
+void
+AudioEngine::request_device_list_update()
+{
+    Glib::Threads::Mutex::Lock guard (_devicelist_update_lock);
+    g_atomic_int_inc (&_hw_devicelist_update_count);
+    _hw_devicelist_update_condition.signal ();
+}
+
+
+void
+AudioEngine::do_devicelist_update()
+{
+    SessionEvent::create_per_thread_pool (X_("Device list update processing thread"), 512);
+    
+    Glib::Threads::Mutex::Lock guard (_devicelist_update_lock);
+    
+    while (!_stop_hw_devicelist_processing) {
+        
+        if (_hw_devicelist_update_count) {
+
+            _devicelist_update_lock.unlock();
+            
+            g_atomic_int_dec_and_test (&_hw_devicelist_update_count);
+            DeviceListChanged (); /* EMIT SIGNAL */
+        
+            _devicelist_update_lock.lock();
+            
+        } else {
+            _hw_devicelist_update_condition.wait (_devicelist_update_lock);
+        }
+    }
+}
+
+
+void
+AudioEngine::start_hw_event_processing()
+{   
+    if (_hw_reset_event_thread == 0) {
+        g_atomic_int_set(&_hw_reset_request_count, 0);
+        g_atomic_int_set(&_stop_hw_reset_processing, 0);
+        _hw_reset_event_thread = Glib::Threads::Thread::create (boost::bind (&AudioEngine::do_reset_backend, this));
+    }
+    
+    if (_hw_devicelist_update_thread == 0) {
+        g_atomic_int_set(&_hw_devicelist_update_count, 0);
+        g_atomic_int_set(&_stop_hw_devicelist_processing, 0);
+        _hw_devicelist_update_thread = Glib::Threads::Thread::create (boost::bind (&AudioEngine::do_devicelist_update, this));
+    }
+}
+
+
+void
+AudioEngine::stop_hw_event_processing()
+{
+    if (_hw_reset_event_thread) {
+        g_atomic_int_set(&_stop_hw_reset_processing, 1);
+        g_atomic_int_set(&_hw_reset_request_count, 0);
+        _hw_reset_condition.signal ();
+        _hw_reset_event_thread->join ();
+        _hw_reset_event_thread = 0;
+    }
+    
+    if (_hw_devicelist_update_thread) {
+        g_atomic_int_set(&_stop_hw_devicelist_processing, 1);
+        g_atomic_int_set(&_hw_devicelist_update_count, 0);
+        _hw_devicelist_update_condition.signal ();
+        _hw_devicelist_update_thread->join ();
+        _hw_devicelist_update_thread = 0;
+    }
+       
+}
+
+
 
 void
 AudioEngine::stop_metering_thread ()
@@ -434,6 +650,15 @@ AudioEngine::remove_session ()
 }
 
 
+void
+AudioEngine::reconnect_session_routes (bool reconnect_inputs, bool reconnect_outputs)
+{
+    if (_session) {
+        _session->reconnect_existing_routes(true, true, reconnect_inputs, reconnect_outputs);
+    }
+}
+
+
 void
 AudioEngine::died ()
 {
@@ -441,7 +666,7 @@ AudioEngine::died ()
 
        stop_metering_thread ();
 
-        _running = false;
+    _running = false;
 }
 
 int
@@ -474,35 +699,56 @@ AudioEngine::discover_backends ()
 
        Glib::PatternSpec so_extension_pattern("*backend.so");
        Glib::PatternSpec dylib_extension_pattern("*backend.dylib");
+
+#if defined(PLATFORM_WINDOWS) && defined(DEBUGGABLE_BACKENDS)
+       #if defined(DEBUG) || defined(_DEBUG)
+               Glib::PatternSpec dll_extension_pattern("*backendD.dll");
+       #else
+               Glib::PatternSpec dll_extension_pattern("*backendRDC.dll");
+       #endif
+#else
        Glib::PatternSpec dll_extension_pattern("*backend.dll");
+#endif
 
-       find_matching_files_in_search_path (backend_search_path (),
-                                           so_extension_pattern, backend_modules);
+       find_files_matching_pattern (backend_modules, backend_search_path (),
+                                    so_extension_pattern);
 
-       find_matching_files_in_search_path (backend_search_path (),
-                                           dylib_extension_pattern, backend_modules);
+       find_files_matching_pattern (backend_modules, backend_search_path (),
+                                    dylib_extension_pattern);
 
-       find_matching_files_in_search_path (backend_search_path (),
-                                           dll_extension_pattern, backend_modules);
+       find_files_matching_pattern (backend_modules, backend_search_path (),
+                                    dll_extension_pattern);
 
-       DEBUG_TRACE (DEBUG::Panning, string_compose (_("looking for backends in %1\n"), backend_search_path().to_string()));
+       DEBUG_TRACE (DEBUG::AudioEngine, string_compose ("looking for backends in %1\n", backend_search_path().to_string()));
 
        for (vector<std::string>::iterator i = backend_modules.begin(); i != backend_modules.end(); ++i) {
 
                AudioBackendInfo* info;
 
+               DEBUG_TRACE (DEBUG::AudioEngine, string_compose ("Checking possible backend in %1\n", *i));
+
                if ((info = backend_discover (*i)) != 0) {
                        _backends.insert (make_pair (info->name, info));
                }
        }
 
+       DEBUG_TRACE (DEBUG::AudioEngine, string_compose ("Found %1 backends\n", _backends.size()));
+
        return _backends.size();
 }
 
 AudioBackendInfo*
 AudioEngine::backend_discover (const string& path)
 {
+#ifdef PLATFORM_WINDOWS
+       // do not show popup dialog (e.g. missing libjack.dll)
+       // win7+ should use SetThreadErrorMode()
+       SetErrorMode(SEM_FAILCRITICALERRORS);
+#endif
        Glib::Module module (path);
+#ifdef PLATFORM_WINDOWS
+       SetErrorMode(0); // reset to system default
+#endif
        AudioBackendInfo* info;
        AudioBackendInfo* (*dfunc)(void);
        void* func = 0;
@@ -518,11 +764,14 @@ AudioEngine::backend_discover (const string& path)
                error << Glib::Module::get_last_error() << endmsg;
                return 0;
        }
-
-       module.make_resident ();
        
        dfunc = (AudioBackendInfo* (*)(void))func;
        info = dfunc();
+       if (!info->available()) {
+               return 0;
+       }
+
+       module.make_resident ();
        
        return info;
 }
@@ -552,9 +801,21 @@ void
 AudioEngine::drop_backend ()
 {
        if (_backend) {
-               _backend->stop ();
+               stop(false);
+               _backend->drop_device ();
                _backend.reset ();
+               _running = false;
+       }
+}
+
+boost::shared_ptr<AudioBackend>
+AudioEngine::set_default_backend ()
+{
+       if (_backends.empty()) {
+               return boost::shared_ptr<AudioBackend>();
        }
+
+       return set_backend (_backends.begin()->first, "", "");
 }
 
 boost::shared_ptr<AudioBackend>
@@ -572,7 +833,7 @@ AudioEngine::set_backend (const std::string& name, const std::string& arg1, cons
                if (b->second->instantiate (arg1, arg2)) {
                        throw failed_constructor ();
                }
-
+               
                _backend = b->second->factory (*this);
 
        } catch (exception& e) {
@@ -586,7 +847,7 @@ AudioEngine::set_backend (const std::string& name, const std::string& arg1, cons
 /* BACKEND PROXY WRAPPERS */
 
 int
-AudioEngine::start ()
+AudioEngine::start (bool for_latency)
 {
        if (!_backend) {
                return -1;
@@ -599,7 +860,7 @@ AudioEngine::start ()
        _processed_frames = 0;
        last_monitor_check = 0;
        
-       if (_backend->start()) {
+       if (_backend->start (for_latency)) {
                return -1;
        }
 
@@ -611,11 +872,12 @@ AudioEngine::start ()
                if (_session->config.get_jack_time_master()) {
                        _backend->set_time_master (true);
                }
+
        }
        
        start_metering_thread ();
        
-       if (!_started_for_latency) {
+       if (!for_latency) {
                Running(); /* EMIT SIGNAL */
        }
        
@@ -623,12 +885,18 @@ AudioEngine::start ()
 }
 
 int
-AudioEngine::stop ()
+AudioEngine::stop (bool for_latency)
 {
        if (!_backend) {
                return 0;
        }
 
+       if (_session && _running) {
+               // it's not a halt, but should be handled the same way:
+               // disable record, stop transport and I/O processign but save the data.
+               _session->engine_halted ();
+       }
+
        Glib::Threads::Mutex::Lock lm (_process_lock);
 
        if (_backend->stop ()) {
@@ -637,32 +905,18 @@ AudioEngine::stop ()
        
        _running = false;
        _processed_frames = 0;
-       _measuring_latency = false;
+       _measuring_latency = MeasureNone;
        _latency_output_port = 0;
        _latency_input_port = 0;
        _started_for_latency = false;
        stop_metering_thread ();
        
        Port::PortDrop ();
-       Stopped (); /* EMIT SIGNAL */
-       
-       return 0;
-}
 
-int
-AudioEngine::pause ()
-{
-       if (!_backend) {
-               return 0;
+       if (!for_latency) {
+               Stopped (); /* EMIT SIGNAL */
        }
        
-       if (_backend->pause ()) {
-               return -1;
-       }
-
-       _running = false;
-       
-       Stopped(); /* EMIT SIGNAL */
        return 0;
 }
 
@@ -679,12 +933,12 @@ AudioEngine::freewheel (bool start_stop)
 }
 
 float
-AudioEngine::get_cpu_load() const 
+AudioEngine::get_dsp_load() const 
 {
        if (!_backend) {
                return 0.0;
        }
-       return _backend->cpu_load ();
+       return _backend->dsp_load ();
 }
 
 bool
@@ -788,7 +1042,7 @@ AudioEngine::raw_buffer_size (DataType t)
        return _backend->raw_buffer_size (t);
 }
 
-pframes_t
+framepos_t
 AudioEngine::sample_time ()
 {
        if (!_backend) {
@@ -797,7 +1051,7 @@ AudioEngine::sample_time ()
        return _backend->sample_time ();
 }
 
-pframes_t
+framepos_t
 AudioEngine::sample_time_at_cycle_start ()
 {
        if (!_backend) {
@@ -875,6 +1129,7 @@ AudioEngine::set_sample_rate (float sr)
        if (!_backend) {
                return -1;
        }
+
        return _backend->set_sample_rate  (sr);
 }
 
@@ -887,15 +1142,6 @@ AudioEngine::set_buffer_size (uint32_t bufsiz)
        return _backend->set_buffer_size  (bufsiz);
 }
 
-int
-AudioEngine::set_sample_format (SampleFormat sf)
-{
-       if (!_backend) {
-               return -1;
-       }
-       return _backend->set_sample_format  (sf);
-}
-
 int
 AudioEngine::set_interleaved (bool yn)
 {
@@ -952,11 +1198,11 @@ AudioEngine::thread_init_callback (void* arg)
 
        pthread_set_name (X_("audioengine"));
 
+       SessionEvent::create_per_thread_pool (X_("AudioEngine"), 512);
+
        PBD::notify_gui_about_thread_creation ("gui", pthread_self(), X_("AudioEngine"), 4096);
        PBD::notify_gui_about_thread_creation ("midiui", pthread_self(), X_("AudioEngine"), 128);
 
-       SessionEvent::create_per_thread_pool (X_("AudioEngine"), 512);
-
        AsyncMIDIPort::set_process_thread (pthread_self());
 
        if (arg) {
@@ -1004,56 +1250,54 @@ AudioEngine::halted_callback (const char* why)
                return;
        }
 
-        stop_metering_thread ();
+    stop_metering_thread ();
        _running = false;
 
        Port::PortDrop (); /* EMIT SIGNAL */
-       Halted (why);      /* EMIT SIGNAL */
+
+       if (!_started_for_latency) {
+               Halted (why);      /* EMIT SIGNAL */
+       }
 }
 
 bool
 AudioEngine::setup_required () const
 {
-       /* If there is only a single backend and it claims to be configured
-        * already there is no setup to be done.
-        *
-        * Primarily for a case where there is only a JACK backend and
-        * JACK is already running.
-        */
-        
-       if (_backends.size() == 1 && _backends.begin()->second->already_configured()) {
-               return false;
+       if (_backend) {
+               if (_backend->info().already_configured())
+                       return false;
+       } else {
+               if (_backends.size() == 1 && _backends.begin()->second->already_configured()) {
+                       return false;
+               }
        }
-
+       
        return true;
 }
 
-MTDM*
-AudioEngine::mtdm() 
-{
-       return _mtdm;
-}
-
 int
 AudioEngine::prepare_for_latency_measurement ()
 {
-       if (!running()) {
-               _started_for_latency = true;
+       if (running()) {
+               _stopped_for_latency = true;
+               stop (true);
+       }
 
-               if (start()) {
-                       _started_for_latency = false;
-                       return -1;
-               }
+       if (start (true)) {
+               _started_for_latency = true;
+               return -1;
        }
 
        return 0;
 }
 
-void
-AudioEngine::start_latency_detection ()
+int
+AudioEngine::start_latency_detection (bool for_midi)
 {
-       if (prepare_for_latency_measurement ()) {
-               return;
+       if (!running()) {
+               if (prepare_for_latency_measurement ()) {
+                       return -1;
+               }
        }
 
        PortEngine& pe (port_engine());
@@ -1061,33 +1305,75 @@ AudioEngine::start_latency_detection ()
        delete _mtdm;
        _mtdm = 0;
 
+       delete _mididm;
+       _mididm = 0;
+
        /* find the ports we will connect to */
 
-       PortEngine::PortHandle* out = pe.get_port_by_name (_latency_output_name);
-       PortEngine::PortHandle* in = pe.get_port_by_name (_latency_input_name);
+       PortEngine::PortHandle out = pe.get_port_by_name (_latency_output_name);
+       PortEngine::PortHandle in = pe.get_port_by_name (_latency_input_name);
 
        if (!out || !in) {
-               return;
+               stop (true);
+               return -1;
        }
 
        /* create the ports we will use to read/write data */
-       
-       if ((_latency_output_port = pe.register_port ("latency_out", DataType::AUDIO, IsOutput)) == 0) {
-               return;
-       }
-       if (pe.connect (_latency_output_port, _latency_output_name)) {
-               pe.unregister_port (_latency_output_port);
-               return;
-       }
+       if (for_midi) {
+               if ((_latency_output_port = pe.register_port ("latency_out", DataType::MIDI, IsOutput)) == 0) {
+                       stop (true);
+                       return -1;
+               }
+               if (pe.connect (_latency_output_port, _latency_output_name)) {
+                       pe.unregister_port (_latency_output_port);
+                       stop (true);
+                       return -1;
+               }
+
+               const string portname ("latency_in");
+               if ((_latency_input_port = pe.register_port (portname, DataType::MIDI, IsInput)) == 0) {
+                       pe.unregister_port (_latency_input_port);
+                       pe.unregister_port (_latency_output_port);
+                       stop (true);
+                       return -1;
+               }
+               if (pe.connect (_latency_input_name, make_port_name_non_relative (portname))) {
+                       pe.unregister_port (_latency_input_port);
+                       pe.unregister_port (_latency_output_port);
+                       stop (true);
+                       return -1;
+               }
+
+               _mididm = new MIDIDM (sample_rate());
+
+       } else {
+
+               if ((_latency_output_port = pe.register_port ("latency_out", DataType::AUDIO, IsOutput)) == 0) {
+                       stop (true);
+                       return -1;
+               }
+               if (pe.connect (_latency_output_port, _latency_output_name)) {
+                       pe.unregister_port (_latency_output_port);
+                       stop (true);
+                       return -1;
+               }
+
+               const string portname ("latency_in");
+               if ((_latency_input_port = pe.register_port (portname, DataType::AUDIO, IsInput)) == 0) {
+                       pe.unregister_port (_latency_input_port);
+                       pe.unregister_port (_latency_output_port);
+                       stop (true);
+                       return -1;
+               }
+               if (pe.connect (_latency_input_name, make_port_name_non_relative (portname))) {
+                       pe.unregister_port (_latency_input_port);
+                       pe.unregister_port (_latency_output_port);
+                       stop (true);
+                       return -1;
+               }
+
+               _mtdm = new MTDM (sample_rate());
 
-       const string portname ("latency_in");
-       if ((_latency_input_port = pe.register_port (portname, DataType::AUDIO, IsInput)) == 0) {
-               pe.unregister_port (_latency_output_port);
-               return;
-       }
-       if (pe.connect (_latency_input_name, make_port_name_non_relative (portname))) {
-               pe.unregister_port (_latency_output_port);
-               return;
        }
 
        LatencyRange lr;
@@ -1098,17 +1384,16 @@ AudioEngine::start_latency_detection ()
        _latency_signal_latency += lr.max;
 
        /* all created and connected, lets go */
+       _latency_flush_frames = samples_per_cycle();
+       _measuring_latency = for_midi ? MeasureMIDI : MeasureAudio;
 
-       _mtdm = new MTDM (sample_rate());
-       _measuring_latency = true;
-        _latency_flush_frames = samples_per_cycle();
-
+       return 0;
 }
 
 void
 AudioEngine::stop_latency_detection ()
 {
-       _measuring_latency = false;
+       _measuring_latency = MeasureNone;
 
        if (_latency_output_port) {
                port_engine().unregister_port (_latency_output_port);
@@ -1118,9 +1403,15 @@ AudioEngine::stop_latency_detection ()
                port_engine().unregister_port (_latency_input_port);
                _latency_input_port = 0;
        }
-       if (_started_for_latency) {
-               stop ();
+
+       stop (true);
+
+       if (_stopped_for_latency) {
+               start ();
        }
+
+       _stopped_for_latency = false;
+       _started_for_latency = false;
 }
 
 void