Support LV2 log trace messages
[ardour.git] / libs / ardour / session_transport.cc
index 55c09f7ed84f8766e43f21030e0d4412317dfd88..8771af46aa7138df63c17c386571d89a52cb982e 100644 (file)
 
 */
 
+#ifdef WAF_BUILD
+#include "libardour-config.h"
+#endif
+
 #include <cmath>
 #include <cerrno>
 #include <unistd.h>
 
-#include <sigc++/bind.h>
-#include <sigc++/retype.h>
-
 #include "pbd/undo.h"
 #include "pbd/error.h"
-#include <glibmm/thread.h>
+#include "pbd/enumwriter.h"
 #include "pbd/pthread_utils.h"
 #include "pbd/memento_command.h"
 #include "pbd/stacktrace.h"
 #include "midi++/mmc.h"
 #include "midi++/port.h"
 
-#include "ardour/ardour.h"
 #include "ardour/audioengine.h"
-#include "ardour/session.h"
-#include "ardour/audio_diskstream.h"
 #include "ardour/auditioner.h"
-#include "ardour/slave.h"
+#include "ardour/butler.h"
+#include "ardour/click.h"
+#include "ardour/debug.h"
 #include "ardour/location.h"
+#include "ardour/profile.h"
+#include "ardour/scene_changer.h"
+#include "ardour/session.h"
+#include "ardour/slave.h"
+#include "ardour/operations.h"
 
-#include "i18n.h"
+#include "pbd/i18n.h"
 
 using namespace std;
 using namespace ARDOUR;
-using namespace sigc;
 using namespace PBD;
 
+void
+Session::add_post_transport_work (PostTransportWork ptw)
+{
+       PostTransportWork oldval;
+       PostTransportWork newval;
+       int tries = 0;
+
+       while (tries < 8) {
+               oldval = (PostTransportWork) g_atomic_int_get (&_post_transport_work);
+               newval = PostTransportWork (oldval | ptw);
+               if (g_atomic_int_compare_and_exchange (&_post_transport_work, oldval, newval)) {
+                       /* success */
+                       return;
+               }
+       }
+
+       error << "Could not set post transport work! Crazy thread madness, call the programmers" << endmsg;
+}
+
 void
 Session::request_input_change_handling ()
 {
        if (!(_state_of_the_state & (InitialConnecting|Deletion))) {
-               Event* ev = new Event (Event::InputConfigurationChange, Event::Add, Event::Immediate, 0, 0.0);
+               SessionEvent* ev = new SessionEvent (SessionEvent::InputConfigurationChange, SessionEvent::Add, SessionEvent::Immediate, 0, 0.0);
                queue_event (ev);
        }
 }
 
 void
-Session::request_slave_source (SlaveSource src)
+Session::request_sync_source (Slave* new_slave)
 {
-       Event* ev = new Event (Event::SetSlaveSource, Event::Add, Event::Immediate, 0, 0.0);
+       SessionEvent* ev = new SessionEvent (SessionEvent::SetSyncSource, SessionEvent::Add, SessionEvent::Immediate, 0, 0.0);
+       bool seamless;
 
-       if (src == JACK) {
-               /* could set_seamless_loop() be disposed of entirely?*/
+       seamless = Config->get_seamless_loop ();
+
+       if (dynamic_cast<Engine_Slave*>(new_slave)) {
+               /* JACK cannot support seamless looping at present */
                Config->set_seamless_loop (false);
        } else {
-               Config->set_seamless_loop (true);
+               /* reset to whatever the value was before we last switched slaves */
+               Config->set_seamless_loop (_was_seamless);
        }
-       ev->slave = src;
+
+       /* save value of seamless from before the switch */
+       _was_seamless = seamless;
+
+       ev->slave = new_slave;
+       DEBUG_TRACE (DEBUG::Slave, "sent request for new slave\n");
        queue_event (ev);
 }
 
 void
-Session::request_transport_speed (double speed)
+Session::request_transport_speed (double speed, bool as_default)
 {
-       Event* ev = new Event (Event::SetTransportSpeed, Event::Add, Event::Immediate, 0, speed);
+       SessionEvent* ev = new SessionEvent (SessionEvent::SetTransportSpeed, SessionEvent::Add, SessionEvent::Immediate, 0, speed);
+       ev->third_yes_or_no = as_default; // as_default
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("Request transport speed = %1 as default = %2\n", speed, as_default));
        queue_event (ev);
 }
 
+/** Request a new transport speed, but if the speed parameter is exactly zero then use
+ *  a very small +ve value to prevent the transport actually stopping.  This method should
+ *  be used by callers who are varying transport speed but don't ever want to stop it.
+ */
 void
-Session::request_diskstream_speed (Diskstream& ds, double speed)
+Session::request_transport_speed_nonzero (double speed, bool as_default)
 {
-       Event* ev = new Event (Event::SetDiskstreamSpeed, Event::Add, Event::Immediate, 0, speed);
-       ev->set_ptr (&ds);
+       if (speed == 0) {
+               speed = DBL_EPSILON;
+       }
+
+       request_transport_speed (speed, as_default);
+}
+
+void
+Session::request_track_speed (Track* tr, double speed)
+{
+       SessionEvent* ev = new SessionEvent (SessionEvent::SetTrackSpeed, SessionEvent::Add, SessionEvent::Immediate, 0, speed);
+       ev->set_ptr (tr);
        queue_event (ev);
 }
 
 void
-Session::request_stop (bool abort)
+Session::request_stop (bool abort, bool clear_state)
 {
-       Event* ev = new Event (Event::SetTransportSpeed, Event::Add, Event::Immediate, 0, 0.0, abort);
+       SessionEvent* ev = new SessionEvent (SessionEvent::SetTransportSpeed, SessionEvent::Add, SessionEvent::Immediate, audible_frame(), 0.0, abort, clear_state);
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("Request transport stop, audible %3 transport %4 abort = %1, clear state = %2\n", abort, clear_state, audible_frame(), _transport_frame));
        queue_event (ev);
 }
 
 void
-Session::request_locate (nframes_t target_frame, bool with_roll)
+Session::request_locate (framepos_t target_frame, bool with_roll)
 {
-       Event *ev = new Event (with_roll ? Event::LocateRoll : Event::Locate, Event::Add, Event::Immediate, target_frame, 0, false);
+       SessionEvent *ev = new SessionEvent (with_roll ? SessionEvent::LocateRoll : SessionEvent::Locate, SessionEvent::Add, SessionEvent::Immediate, target_frame, 0, false);
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("Request locate to %1\n", target_frame));
        queue_event (ev);
 }
 
 void
-Session::force_locate (nframes_t target_frame, bool with_roll)
+Session::force_locate (framepos_t target_frame, bool with_roll)
 {
-       Event *ev = new Event (with_roll ? Event::LocateRoll : Event::Locate, Event::Add, Event::Immediate, target_frame, 0, true);
+       SessionEvent *ev = new SessionEvent (with_roll ? SessionEvent::LocateRoll : SessionEvent::Locate, SessionEvent::Add, SessionEvent::Immediate, target_frame, 0, true);
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("Request forced locate to %1\n", target_frame));
        queue_event (ev);
 }
 
 void
-Session::request_play_loop (bool yn)
+Session::request_play_loop (bool yn, bool change_transport_roll)
 {
-       Event* ev;
-       Location *location = _locations.auto_loop_location();
+       if (_slave && yn) {
+               // don't attempt to loop when not using Internal Transport
+               // see also gtk2_ardour/ardour_ui_options.cc parameter_changed()
+               return;
+       }
+
+       SessionEvent* ev;
+       Location *location = _locations->auto_loop_location();
+       double target_speed;
 
        if (location == 0 && yn) {
                error << _("Cannot loop - no loop range defined")
@@ -121,169 +179,320 @@ Session::request_play_loop (bool yn)
                return;
        }
 
-       ev = new Event (Event::SetLoop, Event::Add, Event::Immediate, 0, 0.0, yn);
+       if (change_transport_roll) {
+               if (transport_rolling()) {
+                       /* start looping at current speed */
+                       target_speed = transport_speed ();
+               } else {
+                       /* currently stopped */
+                       if (yn) {
+                               /* start looping at normal speed */
+                               target_speed = 1.0;
+                       } else {
+                               target_speed = 0.0;
+                       }
+               }
+       } else {
+               /* leave the speed alone */
+               target_speed = transport_speed ();
+       }
+
+       ev = new SessionEvent (SessionEvent::SetLoop, SessionEvent::Add, SessionEvent::Immediate, 0, target_speed, yn);
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("Request set loop = %1, change roll state ? %2\n", yn, change_transport_roll));
        queue_event (ev);
 
-       if (!yn && Config->get_seamless_loop() && transport_rolling()) {
-               // request an immediate locate to refresh the diskstreams
-               // after disabling looping
-               request_locate (_transport_frame-1, false);
+       if (yn) {
+               if (!change_transport_roll) {
+                       if (!transport_rolling()) {
+                               /* we're not changing transport state, but we do want
+                                  to set up position for the new loop. Don't
+                                  do this if we're rolling already.
+                               */
+                               request_locate (location->start(), false);
+                       }
+               }
+       } else {
+               if (!change_transport_roll && Config->get_seamless_loop() && transport_rolling()) {
+                       // request an immediate locate to refresh the tracks
+                       // after disabling looping
+                       request_locate (_transport_frame-1, false);
+               }
        }
 }
 
 void
-Session::realtime_stop (bool abort)
+Session::request_play_range (list<AudioRange>* range, bool leave_rolling)
 {
-       /* assume that when we start, we'll be moving forwards */
+       SessionEvent* ev = new SessionEvent (SessionEvent::SetPlayAudioRange, SessionEvent::Add, SessionEvent::Immediate, 0, (leave_rolling ? 1.0 : 0.0));
+       if (range) {
+               ev->audio_range = *range;
+       } else {
+               ev->audio_range.clear ();
+       }
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("Request play range, leave rolling ? %1\n", leave_rolling));
+       queue_event (ev);
+}
+
+void
+Session::request_cancel_play_range ()
+{
+       SessionEvent* ev = new SessionEvent (SessionEvent::CancelPlayAudioRange, SessionEvent::Add, SessionEvent::Immediate, 0, 0);
+       queue_event (ev);
+}
 
-       // FIXME: where should this really be? [DR]
-       //send_full_time_code();
-       deliver_mmc (MIDI::MachineControl::cmdStop, 0);
-       deliver_mmc (MIDI::MachineControl::cmdLocate, _transport_frame);
+
+void
+Session::realtime_stop (bool abort, bool clear_state)
+{
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("realtime stop @ %1\n", _transport_frame));
+       PostTransportWork todo = PostTransportWork (0);
+
+       /* assume that when we start, we'll be moving forwards */
 
        if (_transport_speed < 0.0f) {
-               post_transport_work = PostTransportWork (post_transport_work | PostTransportStop | PostTransportReverse);
+               todo = (PostTransportWork (todo | PostTransportStop | PostTransportReverse));
+               _default_transport_speed = 1.0;
        } else {
-               post_transport_work = PostTransportWork (post_transport_work | PostTransportStop);
+               todo = PostTransportWork (todo | PostTransportStop);
        }
 
-       if (actively_recording()) {
+       /* call routes */
 
-               /* move the transport position back to where the
-                  request for a stop was noticed. we rolled
-                  past that point to pick up delayed input.
-               */
+       boost::shared_ptr<RouteList> r = routes.reader ();
 
-#ifndef LEAVE_TRANSPORT_UNADJUSTED
-               decrement_transport_position (_worst_output_latency);
-#endif
+       for (RouteList::iterator i = r->begin (); i != r->end(); ++i) {
+               (*i)->realtime_handle_transport_stopped ();
+       }
 
-               /* the duration change is not guaranteed to have happened, but is likely */
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("stop complete, auto-return scheduled for return to %1\n", _requested_return_frame));
 
-               post_transport_work = PostTransportWork (post_transport_work | PostTransportDuration);
-       }
+       /* the duration change is not guaranteed to have happened, but is likely */
+
+       todo = PostTransportWork (todo | PostTransportDuration);
 
        if (abort) {
-               post_transport_work = PostTransportWork (post_transport_work | PostTransportAbort);
+               todo = PostTransportWork (todo | PostTransportAbort);
+       }
+
+       if (clear_state) {
+               todo = PostTransportWork (todo | PostTransportClearSubstate);
+       }
+
+       if (todo) {
+               add_post_transport_work (todo);
        }
 
-       _clear_event_type (Event::StopOnce);
-       _clear_event_type (Event::RangeStop);
-       _clear_event_type (Event::RangeLocate);
+       _clear_event_type (SessionEvent::StopOnce);
+       _clear_event_type (SessionEvent::RangeStop);
+       _clear_event_type (SessionEvent::RangeLocate);
+
+       /* if we're going to clear loop state, then force disabling record BUT only if we're not doing latched rec-enable */
+       disable_record (true, (!Config->get_latched_record_enable() && clear_state));
 
-       disable_record (true);
+       if (clear_state && !Config->get_loop_is_mode()) {
+               unset_play_loop ();
+       }
 
        reset_slave_state ();
 
        _transport_speed = 0;
-       phi = 0;
-       target_phi = 0;
-       phase = 0;
+       _target_transport_speed = 0;
 
-       if (Config->get_use_video_sync()) {
+       g_atomic_int_set (&_playback_load, 100);
+       g_atomic_int_set (&_capture_load, 100);
+
+       if (config.get_use_video_sync()) {
                waiting_for_sync_offset = true;
        }
 
-       transport_sub_state = ((Config->get_slave_source() == None && Config->get_auto_return()) ? AutoReturning : 0);
+       transport_sub_state = 0;
+}
+
+void
+Session::realtime_locate ()
+{
+       boost::shared_ptr<RouteList> r = routes.reader ();
+       for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+               (*i)->realtime_locate ();
+       }
 }
 
 void
 Session::butler_transport_work ()
 {
+       /* Note: this function executes in the butler thread context */
+
   restart:
        bool finished;
+       PostTransportWork ptw;
        boost::shared_ptr<RouteList> r = routes.reader ();
-       boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+       uint64_t before;
 
-       int on_entry = g_atomic_int_get (&butler_should_do_transport_work);
+       int on_entry = g_atomic_int_get (&_butler->should_do_transport_work);
        finished = true;
+       ptw = post_transport_work();
+
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("Butler transport work, todo = %1 at %2\n", enum_2_string (ptw), (before = g_get_monotonic_time())));
 
-       if (post_transport_work & PostTransportCurveRealloc) {
+
+       if (ptw & PostTransportLocate) {
+
+               if (get_play_loop() && !Config->get_seamless_loop()) {
+
+                       DEBUG_TRACE (DEBUG::Butler, "flush loop recording fragment to disk\n");
+
+                       /* this locate might be happening while we are
+                        * loop recording.
+                        *
+                        * Non-seamless looping will require a locate (below) that
+                        * will reset capture buffers and throw away data.
+                        *
+                        * Rather than first find all tracks and see if they
+                        * have outstanding data, just do a flush anyway. It
+                        * may be cheaper this way anyway, and is certainly
+                        * more accurate.
+                        */
+
+                       bool more_disk_io_to_do = false;
+                       uint32_t errors = 0;
+
+                       do {
+                               more_disk_io_to_do = _butler->flush_tracks_to_disk_after_locate (r, errors);
+
+                               if (errors) {
+                                       break;
+                               }
+
+                               if (more_disk_io_to_do) {
+                                       continue;
+                               }
+
+                       } while (false);
+
+               }
+       }
+
+       if (ptw & PostTransportAdjustPlaybackBuffering) {
+               /* non_realtime_locate() calls Automatable::transport_located()
+                * for every route. This eventually calls
+                * ARDOUR::AutomationList::state () which has a LocaleGuard,
+                * and would switch locales forth/back every time.
+                */
+               LocaleGuard lg;
+               for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+                       boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+                       if (tr) {
+                               tr->adjust_playback_buffering ();
+                               /* and refill those buffers ... */
+                       }
+                       (*i)->non_realtime_locate (_transport_frame);
+               }
+
+       }
+
+       if (ptw & PostTransportAdjustCaptureBuffering) {
+               for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+                       boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+                       if (tr) {
+                               tr->adjust_capture_buffering ();
+                       }
+               }
+       }
+
+       if (ptw & PostTransportCurveRealloc) {
                for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
                        (*i)->curve_reallocate();
                }
        }
 
-       if (post_transport_work & PostTransportInputChange) {
-               for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-                       (*i)->non_realtime_input_change ();
+       if (ptw & PostTransportInputChange) {
+               for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+                       boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+                       if (tr) {
+                               tr->non_realtime_input_change ();
+                       }
                }
        }
 
-       if (post_transport_work & PostTransportSpeed) {
+       if (ptw & PostTransportSpeed) {
                non_realtime_set_speed ();
        }
 
-       if (post_transport_work & PostTransportReverse) {
-               
+       if (ptw & PostTransportReverse) {
+
                clear_clicks();
                cumulative_rf_motion = 0;
                reset_rf_scale (0);
 
                /* don't seek if locate will take care of that in non_realtime_stop() */
 
-               if (!(post_transport_work & PostTransportLocate)) {
+               if (!(ptw & PostTransportLocate)) {
+                       LocaleGuard lg; // see note for non_realtime_locate() above
+                       for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+                               (*i)->non_realtime_locate (_transport_frame);
 
-                       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-                               if (!(*i)->hidden()) {
-                                       (*i)->non_realtime_locate (_transport_frame);
-                               }
-                               if (on_entry != g_atomic_int_get (&butler_should_do_transport_work)) {
+                               if (on_entry != g_atomic_int_get (&_butler->should_do_transport_work)) {
                                        /* new request, stop seeking, and start again */
-                                       g_atomic_int_dec_and_test (&butler_should_do_transport_work);
+                                       g_atomic_int_dec_and_test (&_butler->should_do_transport_work);
                                        goto restart;
                                }
                        }
                }
        }
 
-       if (post_transport_work & PostTransportLocate) {
+       if (ptw & PostTransportLocate) {
+               DEBUG_TRACE (DEBUG::Transport, "nonrealtime locate invoked from BTW\n");
                non_realtime_locate ();
        }
 
-       if (post_transport_work & PostTransportStop) {
-               non_realtime_stop (post_transport_work & PostTransportAbort, on_entry, finished);
+       if (ptw & PostTransportStop) {
+               non_realtime_stop (ptw & PostTransportAbort, on_entry, finished);
                if (!finished) {
-                       g_atomic_int_dec_and_test (&butler_should_do_transport_work);
+                       g_atomic_int_dec_and_test (&_butler->should_do_transport_work);
                        goto restart;
                }
        }
 
-       if (post_transport_work & PostTransportOverWrite) {
+       if (ptw & PostTransportOverWrite) {
                non_realtime_overwrite (on_entry, finished);
                if (!finished) {
-                       g_atomic_int_dec_and_test (&butler_should_do_transport_work);
+                       g_atomic_int_dec_and_test (&_butler->should_do_transport_work);
                        goto restart;
                }
        }
 
-       if (post_transport_work & PostTransportAudition) {
+       if (ptw & PostTransportAudition) {
                non_realtime_set_audition ();
        }
 
-       g_atomic_int_dec_and_test (&butler_should_do_transport_work);
+       g_atomic_int_dec_and_test (&_butler->should_do_transport_work);
+
+       DEBUG_TRACE (DEBUG::Transport, string_compose (X_("Butler transport work all done after %1 usecs\n"), g_get_monotonic_time() - before));
+       DEBUG_TRACE (DEBUG::Transport, X_(string_compose ("Frame %1\n", _transport_frame)));
 }
 
 void
 Session::non_realtime_set_speed ()
 {
-       boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
-
-       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-               (*i)->non_realtime_set_speed ();
+       boost::shared_ptr<RouteList> rl = routes.reader();
+       for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
+               boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+               if (tr) {
+                       tr->non_realtime_set_speed ();
+               }
        }
 }
 
 void
 Session::non_realtime_overwrite (int on_entry, bool& finished)
 {
-       boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
-
-       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-               if ((*i)->pending_overwrite) {
-                       (*i)->overwrite_existing_buffers ();
+       boost::shared_ptr<RouteList> rl = routes.reader();
+       for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
+               boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+               if (tr && tr->pending_overwrite ()) {
+                       tr->overwrite_existing_buffers ();
                }
-               if (on_entry != g_atomic_int_get (&butler_should_do_transport_work)) {
+               if (on_entry != g_atomic_int_get (&_butler->should_do_transport_work)) {
                        finished = false;
                        return;
                }
@@ -294,13 +503,155 @@ Session::non_realtime_overwrite (int on_entry, bool& finished)
 void
 Session::non_realtime_locate ()
 {
-       boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("locate tracks to %1\n", _transport_frame));
+
+       if (Config->get_loop_is_mode() && get_play_loop()) {
 
-       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-               (*i)->non_realtime_locate (_transport_frame);
+               Location *loc  = _locations->auto_loop_location();
+
+               if (!loc || (_transport_frame < loc->start() || _transport_frame >= loc->end())) {
+                       /* jumped out of loop range: stop tracks from looping,
+                          but leave loop (mode) enabled.
+                        */
+                       set_track_loop (false);
+
+               } else if (loc && Config->get_seamless_loop() &&
+                   ((loc->start() <= _transport_frame) ||
+                   (loc->end() > _transport_frame) ) ) {
+
+                       /* jumping to start of loop. This  might have been done before but it is
+                        * idempotent and cheap. Doing it here ensures that when we start playback
+                        * outside the loop we still flip tracks into the magic seamless mode
+                        * when needed.
+                        */
+                       set_track_loop (true);
+
+               } else if (loc) {
+                       set_track_loop (false);
+               }
+
+       } else {
+
+               /* no more looping .. should have been noticed elsewhere */
        }
+
+
+       {
+               LocaleGuard lg; // see note for non_realtime_locate() above
+               boost::shared_ptr<RouteList> rl = routes.reader();
+               for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
+                       (*i)->non_realtime_locate (_transport_frame);
+               }
+       }
+
+       _scene_changer->locate (_transport_frame);
+
+       /* XXX: it would be nice to generate the new clicks here (in the non-RT thread)
+          rather than clearing them so that the RT thread has to spend time constructing
+          them (in Session::click).
+        */
+       clear_clicks ();
 }
 
+#ifdef USE_TRACKS_CODE_FEATURES
+bool
+Session::select_playhead_priority_target (framepos_t& jump_to)
+{
+       jump_to = -1;
+
+       AutoReturnTarget autoreturn = Config->get_auto_return_target_list ();
+
+       if (!autoreturn) {
+               return false;
+       }
+
+       if (Profile->get_trx() && transport_rolling() ) {
+               // We're playing, so do nothing.
+               // Next stop will put us where we need to be.
+               return false;
+       }
+
+       /* Note that the order of checking each AutoReturnTarget flag defines
+          the priority each flag.
+
+          Ardour/Mixbus: Last Locate
+                         Range Selection
+                         Loop Range
+                         Region Selection
+
+          Tracks:        Range Selection
+                          Loop Range
+                          Region Selection
+                          Last Locate
+       */
+
+       if (autoreturn & RangeSelectionStart) {
+               if (!_range_selection.empty()) {
+                       jump_to = _range_selection.from;
+               } else {
+                       if (transport_rolling ()) {
+                               /* Range selection no longer exists, but we're playing,
+                                  so do nothing. Next stop will put us where
+                                  we need to be.
+                               */
+                               return false;
+                       }
+               }
+       }
+
+       if (jump_to < 0 && (autoreturn & Loop) && get_play_loop()) {
+               /* don't try to handle loop play when synced to JACK */
+
+               if (!synced_to_engine()) {
+                       Location *location = _locations->auto_loop_location();
+
+                       if (location) {
+                               jump_to = location->start();
+
+                               if (Config->get_seamless_loop()) {
+                                       /* need to get track buffers reloaded */
+                                       set_track_loop (true);
+                               }
+                       }
+               }
+       }
+
+       if (jump_to < 0 && (autoreturn & RegionSelectionStart)) {
+               if (!_object_selection.empty()) {
+                       jump_to = _object_selection.from;
+               }
+       }
+
+       if (jump_to < 0 && (autoreturn & LastLocate)) {
+               jump_to = _last_roll_location;
+       }
+
+       return jump_to >= 0;
+}
+#else
+
+bool
+Session::select_playhead_priority_target (framepos_t& jump_to)
+{
+       if (config.get_external_sync() || !config.get_auto_return()) {
+               return false;
+       }
+
+       jump_to = _last_roll_location;
+       return jump_to >= 0;
+}
+
+#endif
+
+void
+Session::follow_playhead_priority ()
+{
+       framepos_t target;
+
+       if (select_playhead_priority_target (target)) {
+               request_locate (target);
+       }
+}
 
 void
 Session::non_realtime_stop (bool abort, int on_entry, bool& finished)
@@ -309,14 +660,15 @@ Session::non_realtime_stop (bool abort, int on_entry, bool& finished)
        time_t     xnow;
        bool       did_record;
        bool       saved;
+       PostTransportWork ptw = post_transport_work();
 
        did_record = false;
        saved = false;
 
-       boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
-
-       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-               if ((*i)->get_captured_frames () != 0) {
+       boost::shared_ptr<RouteList> rl = routes.reader();
+       for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
+               boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+               if (tr && tr->get_captured_frames () != 0) {
                        did_record = true;
                        break;
                }
@@ -331,180 +683,205 @@ Session::non_realtime_stop (bool abort, int on_entry, bool& finished)
                auditioner->cancel_audition ();
        }
 
-       clear_clicks();
        cumulative_rf_motion = 0;
        reset_rf_scale (0);
 
        if (did_record) {
-               begin_reversible_command ("capture");
-
-               Location* loc = _locations.end_location();
-               bool change_end = false;
-
-               if (_transport_frame < loc->end()) {
-
-                       /* stopped recording before current end */
-
-                       if (_end_location_is_free) {
-
-                               /* first capture for this session, move end back to where we are */
-
-                               change_end = true;
-                       }
-
-               } else if (_transport_frame > loc->end()) {
+               begin_reversible_command (Operations::capture);
+               _have_captured = true;
+       }
 
-                       /* stopped recording after the current end, extend it */
+       DEBUG_TRACE (DEBUG::Transport, X_("Butler PTW: DS stop\n"));
 
-                       change_end = true;
-               }
+       if (abort && did_record) {
+               /* no reason to save the session file when we remove sources
+                */
+               _state_of_the_state = StateOfTheState (_state_of_the_state|InCleanup);
+       }
 
-               if (change_end) {
-                        XMLNode &before = loc->get_state();
-                        loc->set_end(_transport_frame);
-                        XMLNode &after = loc->get_state();
-                        add_command (new MementoCommand<Location>(*loc, &before, &after));
+       for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
+               boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+               if (tr) {
+                       tr->transport_stopped_wallclock (*now, xnow, abort);
                }
-
-               _end_location_is_free = false;
-               _have_captured = true;
        }
 
-       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-               (*i)->transport_stopped (*now, xnow, abort);
+       if (abort && did_record) {
+               _state_of_the_state = StateOfTheState (_state_of_the_state & ~InCleanup);
        }
 
        boost::shared_ptr<RouteList> r = routes.reader ();
 
        for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
-               if (!(*i)->is_hidden()) {
+               if (!(*i)->is_auditioner()) {
                        (*i)->set_pending_declick (0);
                }
        }
 
        if (did_record) {
                commit_reversible_command ();
+               /* increase take name */
+               if (config.get_track_name_take () && !config.get_take_name ().empty()) {
+                       string newname = config.get_take_name();
+                       config.set_take_name(bump_name_number (newname));
+               }
        }
 
        if (_engine.running()) {
-               update_latency_compensation (true, abort);
+               PostTransportWork ptw = post_transport_work ();
+               for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+                       (*i)->nonrealtime_handle_transport_stopped (abort, (ptw & PostTransportLocate), (!(ptw & PostTransportLocate) || pending_locate_flush));
+               }
+               update_latency_compensation ();
        }
 
-       bool const auto_return_enabled =
-               (Config->get_slave_source() == None && Config->get_auto_return());
-       
+       bool const auto_return_enabled = (!config.get_external_sync() && (Config->get_auto_return_target_list() || abort));
+
        if (auto_return_enabled ||
-           (post_transport_work & PostTransportLocate) ||
+           (ptw & PostTransportLocate) ||
            (_requested_return_frame >= 0) ||
-           synced_to_jack()) {
+           synced_to_engine()) {
 
                if (pending_locate_flush) {
                        flush_all_inserts ();
                }
 
-               if ((auto_return_enabled || synced_to_jack() || _requested_return_frame >= 0) &&
-                   !(post_transport_work & PostTransportLocate)) {
+               if ((auto_return_enabled || synced_to_engine() || _requested_return_frame >= 0) &&
+                   !(ptw & PostTransportLocate)) {
+
+                       /* no explicit locate queued */
 
                        bool do_locate = false;
 
                        if (_requested_return_frame >= 0) {
+
+                               /* explicit return request pre-queued in event list. overrides everything else */
+
                                _transport_frame = _requested_return_frame;
-                               _requested_return_frame = -1;
                                do_locate = true;
+
                        } else {
-                               _transport_frame = _last_roll_location;
-                       }
+                               framepos_t jump_to;
 
-                       if (synced_to_jack() && !play_loop) {
-                               do_locate = true;
+                               if (select_playhead_priority_target (jump_to)) {
+
+                                       _transport_frame = jump_to;
+                                       do_locate = true;
+
+                               } else if (abort) {
+
+                                       _transport_frame = _last_roll_location;
+                                       do_locate = true;
+                               }
                        }
 
+                       _requested_return_frame = -1;
+
                        if (do_locate) {
-                               // cerr << "non-realtimestop: transport locate to " << _transport_frame << endl;
                                _engine.transport_locate (_transport_frame);
                        }
                }
 
-#ifndef LEAVE_TRANSPORT_UNADJUSTED
        }
-#endif
 
-               for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-                       if (!(*i)->hidden()) {
-                               (*i)->non_realtime_locate (_transport_frame);
-                       }
-                       if (on_entry != g_atomic_int_get (&butler_should_do_transport_work)) {
+       clear_clicks();
+
+       /* do this before seeking, because otherwise the tracks will do the wrong thing in seamless loop mode.
+       */
+
+       if (ptw & PostTransportClearSubstate) {
+               unset_play_range ();
+               if (!Config->get_loop_is_mode()) {
+                       unset_play_loop ();
+               }
+       }
+
+       /* this for() block can be put inside the previous if() and has the effect of ... ??? what */
+
+       {
+               LocaleGuard lg; // see note for non_realtime_locate() above
+               DEBUG_TRACE (DEBUG::Transport, X_("Butler PTW: locate\n"));
+               for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+                       DEBUG_TRACE (DEBUG::Transport, string_compose ("Butler PTW: locate on %1\n", (*i)->name()));
+                       (*i)->non_realtime_locate (_transport_frame);
+
+                       if (on_entry != g_atomic_int_get (&_butler->should_do_transport_work)) {
                                finished = false;
                                /* we will be back */
                                return;
                        }
                }
-
-#ifdef LEAVE_TRANSPORT_UNADJUSTED
        }
-#endif
 
-        have_looped = false; 
+       have_looped = false;
 
-        send_full_time_code (0);
-       deliver_mmc (MIDI::MachineControl::cmdStop, 0);
-       deliver_mmc (MIDI::MachineControl::cmdLocate, _transport_frame);
+       /* don't bother with this stuff if we're disconnected from the engine,
+          because there will be no process callbacks to deliver stuff from
+       */
 
-       if (did_record) {
+       if (_engine.connected() && !_engine.freewheeling()) {
+               // need to queue this in the next RT cycle
+               _send_timecode_update = true;
 
-               /* XXX its a little odd that we're doing this here
-                  when realtime_stop(), which has already executed,
-                  will have done this.
-                  JLC - so let's not because it seems unnecessary and breaks loop record
-               */
-#if 0
-               if (!Config->get_latched_record_enable()) {
-                       g_atomic_int_set (&_record_status, Disabled);
-               } else {
-                       g_atomic_int_set (&_record_status, Enabled);
+               if (!dynamic_cast<MTC_Slave*>(_slave)) {
+                       send_immediate_mmc (MIDI::MachineControlCommand (MIDI::MachineControl::cmdStop));
+
+                       /* This (::non_realtime_stop()) gets called by main
+                          process thread, which will lead to confusion
+                          when calling AsyncMIDIPort::write().
+
+                          Something must be done. XXX
+                       */
+                       send_mmc_locate (_transport_frame);
                }
-               RecordStateChanged (); /* emit signal */
-#endif
        }
 
-       if ((post_transport_work & PostTransportLocate) && get_record_enabled()) {
-               /* capture start has been changed, so save pending state */
-               save_state ("", true);
-               saved = true;
+       if ((ptw & PostTransportLocate) && get_record_enabled()) {
+               /* This is scheduled by realtime_stop(), which is also done
+                * when a slave requests /locate/ for an initial sync.
+                * We can't hold up the slave for long with a save() here,
+                * without breaking its initial sync cycle.
+                *
+                * save state only if there's no slave or if it's not yet locked.
+                */
+               if (!_slave || !_slave->locked()) {
+                       DEBUG_TRACE (DEBUG::Transport, X_("Butler PTW: requests save\n"));
+                       SaveSessionRequested (_current_snapshot_name);
+                       saved = true;
+               }
        }
 
-        /* always try to get rid of this */
+       /* always try to get rid of this */
 
-        remove_pending_capture_state ();
+       remove_pending_capture_state ();
 
        /* save the current state of things if appropriate */
 
        if (did_record && !saved) {
-               save_state (_current_snapshot_name);
+               SaveSessionRequested (_current_snapshot_name);
        }
 
-       if (post_transport_work & PostTransportDuration) {
-               DurationChanged (); /* EMIT SIGNAL */
-       }
-
-       if (post_transport_work & PostTransportStop) {
-               _play_range = false;
-
-               /* do not turn off autoloop on stop */
-
+       if (ptw & PostTransportStop) {
+               unset_play_range ();
+               if (!Config->get_loop_is_mode()) {
+                       unset_play_loop ();
+               }
        }
 
-        nframes_t tf = _transport_frame;
-
-        PositionChanged (tf); /* EMIT SIGNAL */
+       PositionChanged (_transport_frame); /* EMIT SIGNAL */
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("send TSC with speed = %1\n", _transport_speed));
        TransportStateChange (); /* EMIT SIGNAL */
 
        /* and start it up again if relevant */
 
-       if ((post_transport_work & PostTransportLocate) && Config->get_slave_source() == None && pending_locate_roll) {
+       if ((ptw & PostTransportLocate) && !config.get_external_sync() && pending_locate_roll) {
                request_transport_speed (1.0);
-               pending_locate_roll = false;
        }
+
+       /* Even if we didn't do a pending locate roll this time, we don't want it hanging
+          around for next time.
+       */
+       pending_locate_roll = false;
 }
 
 void
@@ -514,7 +891,7 @@ Session::check_declick_out ()
 
        /* this is called after a process() iteration. if PendingDeclickOut was set,
           it means that we were waiting to declick the output (which has just been
-          done) before doing something else. this is where we do that "something else".
+          done) before maybe doing something else. this is where we do that "something else".
 
           note: called from the audio thread.
        */
@@ -525,90 +902,137 @@ Session::check_declick_out ()
                        start_locate (pending_locate_frame, pending_locate_roll, pending_locate_flush);
                        transport_sub_state &= ~(PendingDeclickOut|PendingLocate);
                } else {
-                       stop_transport (pending_abort);
-                       transport_sub_state &= ~(PendingDeclickOut|PendingLocate);
+                       if (!(transport_sub_state & StopPendingCapture)) {
+                               stop_transport (pending_abort);
+                               transport_sub_state &= ~(PendingDeclickOut|PendingLocate);
+                       }
+               }
+
+       } else if (transport_sub_state & PendingLoopDeclickOut) {
+               /* Nothing else to do here; we've declicked, and the loop event will be along shortly */
+               transport_sub_state &= ~PendingLoopDeclickOut;
+       }
+}
+
+void
+Session::unset_play_loop ()
+{
+       if (play_loop) {
+               play_loop = false;
+               clear_events (SessionEvent::AutoLoop);
+               clear_events (SessionEvent::AutoLoopDeclick);
+               set_track_loop (false);
+
+
+               if (Config->get_seamless_loop()) {
+                       /* likely need to flush track buffers: this will locate us to wherever we are */
+                       add_post_transport_work (PostTransportLocate);
+                       _butler->schedule_transport_work ();
                }
        }
 }
 
 void
-Session::set_play_loop (bool yn)
+Session::set_track_loop (bool yn)
+{
+       Location* loc = _locations->auto_loop_location ();
+
+       if (!loc) {
+               yn = false;
+       }
+
+       boost::shared_ptr<RouteList> rl = routes.reader ();
+
+       for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
+               boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+               if (tr && !tr->hidden()) {
+                       tr->set_loop (yn ? loc : 0);
+               }
+       }
+}
+
+void
+Session::set_play_loop (bool yn, double speed)
 {
        /* Called from event-handling context */
 
-       if ((actively_recording() && yn) || _locations.auto_loop_location() == 0) {
+       Location *loc;
+
+       if (yn == play_loop || (actively_recording() && yn) || (loc = _locations->auto_loop_location()) == 0) {
+               /* nothing to do, or can't change loop status while recording */
                return;
        }
 
-       set_dirty();
-
-       if (yn && Config->get_seamless_loop() && synced_to_jack()) {
-               warning << _("Seamless looping cannot be supported while Ardour is using JACK transport.\n"
-                            "Recommend changing the configured options")
+       if (yn && Config->get_seamless_loop() && synced_to_engine()) {
+               warning << string_compose (
+                       _("Seamless looping cannot be supported while %1 is using JACK transport.\n"
+                         "Recommend changing the configured options"), PROGRAM_NAME)
                        << endmsg;
                return;
        }
 
+       if (yn) {
 
-       if ((play_loop = yn)) {
-
-               Location *loc;
+               play_loop = true;
+               have_looped = false;
 
+               if (loc) {
 
-               if ((loc = _locations.auto_loop_location()) != 0) {
+                       unset_play_range ();
 
                        if (Config->get_seamless_loop()) {
-                               // set all diskstreams to use internal looping
-                               boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
-                               for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-                                       if (!(*i)->hidden()) {
-                                               (*i)->set_loop (loc);
-                                       }
-                               }
-                       }
-                       else {
-                               // set all diskstreams to NOT use internal looping
-                               boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
-                               for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-                                       if (!(*i)->hidden()) {
-                                               (*i)->set_loop (0);
-                                       }
+                               if (!Config->get_loop_is_mode()) {
+                                       /* set all tracks to use internal looping */
+                                       set_track_loop (true);
+                               } else {
+                                       /* we will do this in the locate to the start OR when we hit the end
+                                        * of the loop for the first time
+                                        */
                                }
+                       } else {
+                               /* set all tracks to NOT use internal looping */
+                               set_track_loop (false);
                        }
 
-                       /* stick in the loop event */
-
-                       Event* event = new Event (Event::AutoLoop, Event::Replace, loc->end(), loc->start(), 0.0f);
-                       merge_event (event);
-
-                       /* locate to start of loop and roll if current pos is outside of the loop range */
-                       if (_transport_frame < loc->start() || _transport_frame > loc->end()) {
-                               event = new Event (Event::LocateRoll, Event::Add, Event::Immediate, loc->start(), 0, !synced_to_jack());
-                               merge_event (event);
-                       }
-                       else {
-                               // locate to current position (+ 1 to force reload)
-                               event = new Event (Event::LocateRoll, Event::Add, Event::Immediate, _transport_frame + 1, 0, !synced_to_jack());
-                               merge_event (event);
-                       }
-               }
+                       /* Put the delick and loop events in into the event list.  The declick event will
+                          cause a de-clicking fade-out just before the end of the loop, and it will also result
+                          in a fade-in when the loop restarts.  The AutoLoop event will peform the actual loop.
+                       */
 
+                       framepos_t dcp;
+                       framecnt_t dcl;
+                       auto_loop_declick_range (loc, dcp, dcl);
+                       merge_event (new SessionEvent (SessionEvent::AutoLoopDeclick, SessionEvent::Replace, dcp, dcl, 0.0f));
+                       merge_event (new SessionEvent (SessionEvent::AutoLoop, SessionEvent::Replace, loc->end(), loc->start(), 0.0f));
 
+                       /* if requested to roll, locate to start of loop and
+                        * roll but ONLY if we're not already rolling.
 
-       } else {
-               clear_events (Event::AutoLoop);
+                          args: positition, roll=true, flush=true, with_loop=false, force buffer refill if seamless looping
+                       */
 
-               // set all diskstreams to NOT use internal looping
-               boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
-               for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-                       if (!(*i)->hidden()) {
-                               (*i)->set_loop (0);
+                       if (Config->get_loop_is_mode()) {
+                               /* loop IS a transport mode: if already
+                                  rolling, do not locate to loop start.
+                               */
+                               if (!transport_rolling() && (speed != 0.0)) {
+                                       start_locate (loc->start(), true, true, false, true);
+                               }
+                       } else {
+                               if (speed != 0.0) {
+                                       start_locate (loc->start(), true, true, false, true);
+                               }
                        }
                }
 
+       } else {
+
+               unset_play_loop ();
        }
-}
 
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("send TSC2 with speed = %1\n", _transport_speed));
+       TransportStateChange ();
+}
 void
 Session::flush_all_inserts ()
 {
@@ -620,17 +1044,30 @@ Session::flush_all_inserts ()
 }
 
 void
-Session::start_locate (nframes_t target_frame, bool with_roll, bool with_flush, bool with_loop)
+Session::start_locate (framepos_t target_frame, bool with_roll, bool with_flush, bool for_loop_enabled, bool force)
 {
-       if (synced_to_jack()) {
+       if (target_frame < 0) {
+               error << _("Locate called for negative sample position - ignored") << endmsg;
+               return;
+       }
+
+       if (synced_to_engine()) {
 
                double sp;
-               nframes_t pos;
+               framepos_t pos;
 
                _slave->speed_and_position (sp, pos);
 
                if (target_frame != pos) {
 
+                       if (config.get_jack_time_master()) {
+                               /* actually locate now, since otherwise jack_timebase_callback
+                                  will use the incorrect _transport_frame and report an old
+                                  and incorrect time to Jack transport
+                               */
+                               locate (target_frame, with_roll, with_flush, for_loop_enabled, force);
+                       }
+
                        /* tell JACK to change transport position, and we will
                           follow along later in ::follow_slave()
                        */
@@ -644,57 +1081,70 @@ Session::start_locate (nframes_t target_frame, bool with_roll, bool with_flush,
                }
 
        } else {
-               locate (target_frame, with_roll, with_flush, with_loop);
+               locate (target_frame, with_roll, with_flush, for_loop_enabled, force);
        }
-
-       /* XXX: not sure if this should be emitted here in the synced_to_jack () case;
-        * perhaps it should happen when the slave is actually followed */
-       Located (); /* EMIT SIGNAL */
 }
 
 int
-Session::micro_locate (nframes_t distance)
+Session::micro_locate (framecnt_t distance)
 {
-       boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
-       
-       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-               if (!(*i)->can_internal_playback_seek (distance)) {
+       boost::shared_ptr<RouteList> rl = routes.reader();
+       for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
+               boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+               if (tr && !tr->can_internal_playback_seek (distance)) {
                        return -1;
                }
        }
 
-       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-               (*i)->internal_playback_seek (distance);
+       for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
+               boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+               if (tr) {
+                       tr->internal_playback_seek (distance);
+               }
        }
-       
+
        _transport_frame += distance;
        return 0;
 }
 
+/** @param with_mmc true to send a MMC locate command when the locate is done */
 void
-Session::locate (nframes_t target_frame, bool with_roll, bool with_flush, bool with_loop)
+Session::locate (framepos_t target_frame, bool with_roll, bool with_flush, bool for_loop_enabled, bool force, bool with_mmc)
 {
-       if (actively_recording() && !with_loop) {
-               return;
-       }
+       bool need_butler = false;
+
+       /* Locates for seamless looping are fairly different from other
+        * locates. They assume that the diskstream buffers for each track
+        * already have the correct data in them, and thus there is no need to
+        * actually tell the tracks to locate. What does need to be done,
+        * though, is all the housekeeping that is associated with non-linear
+        * changes in the value of _transport_frame.
+        */
+
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("rt-locate to %1, roll %2 flush %3 loop-enabled %4 force %5 mmc %6\n",
+                                                      target_frame, with_roll, with_flush, for_loop_enabled, force, with_mmc));
+
+       if (!force && _transport_frame == target_frame && !loop_changing && !for_loop_enabled) {
+
+               /* already at the desired position. Not forced to locate,
+                  the loop isn't changing, so unless we're told to
+                  start rolling also, there's nothing to do but
+                  tell the world where we are (again).
+               */
 
-       if (_transport_frame == target_frame && !loop_changing && !with_loop) {
                if (with_roll) {
-                       set_transport_speed (1.0, false);
+                       set_transport_speed (1.0, 0, false);
                }
                loop_changing = false;
+               Located (); /* EMIT SIGNAL */
                return;
        }
 
-       // Update SMPTE time
-       // [DR] FIXME: find out exactly where this should go below
-       _transport_frame = target_frame;
-       smpte_time(_transport_frame, transmitting_smpte_time);
-       outbound_mtc_smpte_frame = _transport_frame;
-       next_quarter_frame_to_send = 0;
-
-       if (_transport_speed && (!with_loop || loop_changing)) {
-               /* schedule a declick. we'll be called again when its done */
+       if (_transport_speed && !(for_loop_enabled && Config->get_seamless_loop())) {
+               /* Schedule a declick.  We'll be called again when its done.
+                  We only do it this way for ordinary locates, not those
+                  due to **seamless** loops.
+               */
 
                if (!(transport_sub_state & PendingDeclickOut)) {
                        transport_sub_state |= (PendingDeclickOut|PendingLocate);
@@ -705,25 +1155,47 @@ Session::locate (nframes_t target_frame, bool with_roll, bool with_flush, bool w
                }
        }
 
-       if (transport_rolling() && (!auto_play_legal || !Config->get_auto_play()) && !with_roll && !(synced_to_jack() && play_loop)) {
-               realtime_stop (false);
+       // Update Timecode time
+       _transport_frame = target_frame;
+       _last_roll_or_reversal_location = target_frame;
+       timecode_time(_transport_frame, transmitting_timecode_time);
+
+       /* do "stopped" stuff if:
+        *
+        * we are rolling AND
+        *    no autoplay in effect AND
+         *       we're not going to keep rolling after the locate AND
+         *           !(playing a loop with JACK sync)
+         *
+        */
+
+       bool transport_was_stopped = !transport_rolling();
+
+       if (!transport_was_stopped && (!auto_play_legal || !config.get_auto_play()) && !with_roll && !(synced_to_engine() && play_loop) &&
+           (!Profile->get_trx() || !(config.get_external_sync() && !synced_to_engine()))) {
+               realtime_stop (false, true); // XXX paul - check if the 2nd arg is really correct
+               transport_was_stopped = true;
+       } else {
+               /* otherwise tell the world that we located */
+               realtime_locate ();
        }
 
-       if ( !with_loop || loop_changing) {
+       if (force || !for_loop_enabled || loop_changing) {
 
-               post_transport_work = PostTransportWork (post_transport_work | PostTransportLocate);
+               PostTransportWork todo = PostTransportLocate;
 
-               if (with_roll) {
-                       post_transport_work = PostTransportWork (post_transport_work | PostTransportRoll);
+               if (with_roll && transport_was_stopped) {
+                       todo = PostTransportWork (todo | PostTransportRoll);
                }
 
-               schedule_butler_transport_work ();
+               add_post_transport_work (todo);
+               need_butler = true;
 
        } else {
 
                /* this is functionally what clear_clicks() does but with a tentative lock */
 
-               Glib::RWLock::WriterLock clickm (click_lock, Glib::TRY_LOCK);
+               Glib::Threads::RWLock::WriterLock clickm (click_lock, Glib::Threads::TRY_LOCK);
 
                if (clickm.locked()) {
 
@@ -738,74 +1210,119 @@ Session::locate (nframes_t target_frame, bool with_roll, bool with_flush, bool w
        if (with_roll) {
                /* switch from input if we're going to roll */
                if (Config->get_monitoring_model() == HardwareMonitoring) {
-
-                       boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
-
-                       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-                               if ((*i)->record_enabled ()) {
-                                       //cerr << "switching from input" << __FILE__ << __LINE__ << endl << endl;
-                                       (*i)->monitor_input (!Config->get_auto_input());
-                               }
-                       }
+                       set_track_monitor_input_status (!config.get_auto_input());
                }
        } else {
                /* otherwise we're going to stop, so do the opposite */
                if (Config->get_monitoring_model() == HardwareMonitoring) {
-                       boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
-
-                       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-                               if ((*i)->record_enabled ()) {
-                                       //cerr << "switching to input" << __FILE__ << __LINE__ << endl << endl;
-                                       (*i)->monitor_input (true);
-                               }
-                       }
+                       set_track_monitor_input_status (true);
                }
        }
 
        /* cancel looped playback if transport pos outside of loop range */
        if (play_loop) {
-               Location* al = _locations.auto_loop_location();
 
-               if (al && (_transport_frame < al->start() || _transport_frame > al->end())) {
-                       // cancel looping directly, this is called from event handling context
-                       set_play_loop (false);
-               }
-               else if (al && _transport_frame == al->start()) {
-                       if (with_loop) {
-                               // this is only necessary for seamless looping
+               Location* al = _locations->auto_loop_location();
+
+               if (al) {
+                       if (_transport_frame < al->start() || _transport_frame >= al->end()) {
+
+                               // located outside the loop: cancel looping directly, this is called from event handling context
+
+                               have_looped = false;
+
+                               if (!Config->get_loop_is_mode()) {
+                                       set_play_loop (false, _transport_speed);
+                               } else {
+                                       if (Config->get_seamless_loop()) {
+                                               /* this will make the non_realtime_locate() in the butler
+                                                  which then causes seek() in tracks actually do the right
+                                                  thing.
+                                               */
+                                               set_track_loop (false);
+                                       }
+                               }
+
+                       } else if (_transport_frame == al->start()) {
+
+                               // located to start of loop - this is looping, basically
 
-                               boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+                               if (!have_looped) {
+                                       /* first time */
+                                       if (_last_roll_location != al->start()) {
+                                               /* didn't start at loop start - playback must have
+                                                * started before loop since we've now hit the loop
+                                                * end.
+                                                */
+                                               add_post_transport_work (PostTransportLocate);
+                                               need_butler = true;
+                                       }
+
+                               }
+
+                               boost::shared_ptr<RouteList> rl = routes.reader();
 
-                               for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-                                       if ((*i)->record_enabled ()) {
+                               for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
+                                       boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+
+                                       if (tr && tr->rec_enable_control()->get_value()) {
                                                // tell it we've looped, so it can deal with the record state
-                                               (*i)->transport_looped(_transport_frame);
+                                               tr->transport_looped (_transport_frame);
                                        }
                                }
+
+                               have_looped = true;
+                               TransportLooped(); // EMIT SIGNAL
                        }
-                       have_looped = true;
-                       TransportLooped(); // EMIT SIGNAL
                }
        }
 
+       if (need_butler) {
+               _butler->schedule_transport_work ();
+       }
+
        loop_changing = false;
 
-       _send_smpte_update = true;
+       _send_timecode_update = true;
+
+       if (with_mmc) {
+               send_mmc_locate (_transport_frame);
+       }
+
+       _last_roll_location = _last_roll_or_reversal_location =  _transport_frame;
+       Located (); /* EMIT SIGNAL */
 }
 
 /** Set the transport speed.
- * @param speed New speed
- * @param abort
+ *  Called from the process thread.
+ *  @param speed New speed
  */
 void
-Session::set_transport_speed (double speed, bool abort)
+Session::set_transport_speed (double speed, framepos_t destination_frame, bool abort, bool clear_state, bool as_default)
 {
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("@ %5 Set transport speed to %1, abort = %2 clear_state = %3, current = %4 as_default %6\n",
+                                                      speed, abort, clear_state, _transport_speed, _transport_frame, as_default));
+
        if (_transport_speed == speed) {
+               if (as_default && speed == 0.0) { // => reset default transport speed. hacky or what?
+                       _default_transport_speed = 1.0;
+               }
+               return;
+       }
+
+       if (actively_recording() && speed != 1.0 && speed != 0.0) {
+               /* no varispeed during recording */
+               DEBUG_TRACE (DEBUG::Transport, string_compose ("No varispeed during recording cur_speed %1, frame %2\n",
+                                                      _transport_speed, _transport_frame));
                return;
        }
 
-       target_phi = (uint64_t) (0x1000000 * fabs(speed));
-       
+       _target_transport_speed = fabs(speed);
+
+       /* 8.0 max speed is somewhat arbitrary but based on guestimates regarding disk i/o capability
+          and user needs. We really need CD-style "skip" playback for ffwd and rewind.
+       */
+
        if (speed > 0) {
                speed = min (8.0, speed);
        } else if (speed < 0) {
@@ -816,45 +1333,60 @@ Session::set_transport_speed (double speed, bool abort)
 
                /* we are rolling and we want to stop */
 
-               if (Config->get_monitoring_model() == HardwareMonitoring)
-               {
-                       boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
-
-                       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-                               if ((*i)->record_enabled ()) {
-                                       //cerr << "switching to input" << __FILE__ << __LINE__ << endl << endl;
-                                       (*i)->monitor_input (true);
-                               }
-                       }
+               if (Config->get_monitoring_model() == HardwareMonitoring) {
+                       set_track_monitor_input_status (true);
                }
 
-               if (synced_to_jack ()) {
+               if (synced_to_engine ()) {
+                       if (clear_state) {
+                               /* do this here because our response to the slave won't
+                                  take care of it.
+                               */
+                               _play_range = false;
+                               unset_play_loop ();
+                       }
                        _engine.transport_stop ();
                } else {
+                       bool const auto_return_enabled = (!config.get_external_sync() && (Config->get_auto_return_target_list() || abort));
+
+                       if (!auto_return_enabled) {
+                               _requested_return_frame = destination_frame;
+                       }
+
                        stop_transport (abort);
                }
 
        } else if (transport_stopped() && speed == 1.0) {
-
+               if (as_default) {
+                       _default_transport_speed = speed;
+               }
                /* we are stopped and we want to start rolling at speed 1 */
 
-               if (!get_record_enabled() && Config->get_stop_at_session_end() && _transport_frame >= current_end_frame()) {
-                       return;
-               }
+               if (Config->get_loop_is_mode() && play_loop) {
 
-               if (Config->get_monitoring_model() == HardwareMonitoring) {
+                       Location *location = _locations->auto_loop_location();
+
+                       if (location != 0) {
+                               if (_transport_frame != location->start()) {
+
+                                       if (Config->get_seamless_loop()) {
+                                               /* force tracks to do their thing */
+                                               set_track_loop (true);
+                                       }
 
-                       boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
+                                       /* jump to start and then roll from there */
 
-                       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-                               if (Config->get_auto_input() && (*i)->record_enabled ()) {
-                                       //cerr << "switching from input" << __FILE__ << __LINE__ << endl << endl;
-                                       (*i)->monitor_input (false);
+                                       request_locate (location->start(), true);
+                                       return;
                                }
                        }
                }
 
-               if (synced_to_jack()) {
+               if (Config->get_monitoring_model() == HardwareMonitoring && config.get_auto_input()) {
+                       set_track_monitor_input_status (false);
+               }
+
+               if (synced_to_engine()) {
                        _engine.transport_start ();
                } else {
                        start_transport ();
@@ -862,12 +1394,12 @@ Session::set_transport_speed (double speed, bool abort)
 
        } else {
 
-               if (!get_record_enabled() && Config->get_stop_at_session_end() && _transport_frame >= current_end_frame()) {
-                       return;
-               }
+               /* not zero, not 1.0 ... varispeed */
 
-               if ((synced_to_jack()) && speed != 0.0 && speed != 1.0) {
-                       warning << _("Global varispeed cannot be supported while Ardour is connected to JACK transport control")
+               if ((synced_to_engine()) && speed != 0.0 && speed != 1.0) {
+                       warning << string_compose (
+                               _("Global varispeed cannot be supported while %1 is connected to JACK transport control"),
+                               PROGRAM_NAME)
                                << endmsg;
                        return;
                }
@@ -890,22 +1422,55 @@ Session::set_transport_speed (double speed, bool abort)
                   before the last stop, then we have to do extra work.
                */
 
-               if ((_transport_speed && speed * _transport_speed < 0.0) || (_last_transport_speed * speed < 0.0) || (_last_transport_speed == 0.0f && speed < 0.0f)) {
-                       post_transport_work = PostTransportWork (post_transport_work | PostTransportReverse);
+               PostTransportWork todo = PostTransportWork (0);
+
+               if ((_transport_speed && speed * _transport_speed < 0.0) || (_last_transport_speed * speed < 0.0) || (_last_transport_speed == 0.0 && speed < 0.0)) {
+                       todo = PostTransportWork (todo | PostTransportReverse);
+                       _last_roll_or_reversal_location = _transport_frame;
                }
 
                _last_transport_speed = _transport_speed;
                _transport_speed = speed;
 
-               boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
-               for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-                       if ((*i)->realtime_set_speed ((*i)->speed(), true)) {
-                               post_transport_work = PostTransportWork (post_transport_work | PostTransportSpeed);
+               if (as_default) {
+                       _default_transport_speed = speed;
+               }
+
+               boost::shared_ptr<RouteList> rl = routes.reader();
+               for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
+                       boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+                       if (tr && tr->realtime_set_speed (tr->speed(), true)) {
+                               todo = PostTransportWork (todo | PostTransportSpeed);
                        }
                }
 
-               if (post_transport_work & (PostTransportSpeed|PostTransportReverse)) {
-                       schedule_butler_transport_work ();
+               if (todo) {
+                       add_post_transport_work (todo);
+                       _butler->schedule_transport_work ();
+               }
+
+               DEBUG_TRACE (DEBUG::Transport, string_compose ("send TSC3 with speed = %1\n", _transport_speed));
+
+               /* throttle signal emissions.
+                * when slaved [_last]_transport_speed
+                * usually changes every cycle (tiny amounts due to DLL).
+                * Emitting a signal every cycle is overkill and unwarranted.
+                *
+                * Using _last_transport_speed is not acceptable,
+                * since it allows for large changes over a long period
+                * of time. Hence we introduce a dedicated variable to keep track
+                *
+                * The 0.2% dead-zone is somewhat arbitrary. Main use-case
+                * for TransportStateChange() here is the ShuttleControl display.
+                */
+               if (fabs (_signalled_varispeed - speed) > .002
+                   // still, signal hard changes to 1.0 and 0.0:
+                   || ( speed == 1.0 && _signalled_varispeed != 1.0)
+                   || ( speed == 0.0 && _signalled_varispeed != 0.0)
+                  )
+               {
+                       TransportStateChange (); /* EMIT SIGNAL */
+                       _signalled_varispeed = speed;
                }
        }
 }
@@ -913,50 +1478,98 @@ Session::set_transport_speed (double speed, bool abort)
 
 /** Stop the transport.  */
 void
-Session::stop_transport (bool abort)
+Session::stop_transport (bool abort, bool clear_state)
 {
        if (_transport_speed == 0.0f) {
                return;
        }
 
-       if (actively_recording() && !(transport_sub_state & StopPendingCapture) &&
-           _worst_output_latency > current_block_size)
-       {
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("stop_transport, declick required? %1\n", get_transport_declick_required()));
 
-               /* we need to capture the audio that has still not yet been received by the system
-                  at the time the stop is requested, so we have to roll past that time.
+       if (!get_transport_declick_required()) {
 
-                  we want to declick before stopping, so schedule the autostop for one
-                  block before the actual end. we'll declick in the subsequent block,
-                  and then we'll really be stopped.
-               */
+               /* stop has not yet been scheduled */
 
-               Event *ev = new Event (Event::StopOnce, Event::Replace,
-                                      _transport_frame + _worst_output_latency - current_block_size,
-                                      0, 0, abort);
+               boost::shared_ptr<RouteList> rl = routes.reader();
+               framepos_t stop_target = audible_frame();
 
-               merge_event (ev);
-               transport_sub_state |= StopPendingCapture;
-               pending_abort = abort;
-               return;
-       }
+               for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
+                       boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+                       if (tr) {
+                               tr->prepare_to_stop (_transport_frame, stop_target);
+                       }
+               }
+
+               SubState new_bits;
+
+               if (actively_recording() &&                           /* we are recording */
+                   worst_input_latency() > current_block_size) {     /* input latency exceeds block size, so simple 1 cycle delay before stop is not enough */
+
+                       /* we need to capture the audio that is still somewhere in the pipeline between
+                          wherever it was generated and the process callback. This means that even though
+                          the user (or something else)  has asked us to stop, we have to roll
+                          past this point and then reset the playhead/transport location to
+                          the position at which the stop was requested.
+
+                          we still need playback to "stop" now, however, which is why we schedule
+                          a declick below.
+                       */
+
+                       DEBUG_TRACE (DEBUG::Transport, string_compose ("stop transport requested @ %1, scheduled for + %2 = %3, abort = %4\n",
+                                                                      _transport_frame, _worst_input_latency,
+                                                                      _transport_frame + _worst_input_latency,
+                                                                      abort));
+
+                       SessionEvent *ev = new SessionEvent (SessionEvent::StopOnce, SessionEvent::Replace,
+                                                            _transport_frame + _worst_input_latency,
+                                                            0, 0, abort);
+
+                       merge_event (ev);
 
+                       /* request a declick at the start of the next process cycle() so that playback ceases.
+                          It will remain silent until we actually stop (at the StopOnce event somewhere in
+                          the future). The extra flag (StopPendingCapture) is set to ensure that check_declick_out()
+                          does not stop the transport too early.
+                        */
+                       new_bits = SubState (PendingDeclickOut|StopPendingCapture);
+
+               } else {
+
+                       /* Not recording, schedule a declick in the next process() cycle and then stop at its end */
+
+                       new_bits = PendingDeclickOut;
+                       DEBUG_TRACE (DEBUG::Transport, string_compose ("stop scheduled for next process cycle @ %1\n", _transport_frame));
+               }
 
-       if ((transport_sub_state & PendingDeclickOut) == 0) {
-               transport_sub_state |= PendingDeclickOut;
                /* we'll be called again after the declick */
+               transport_sub_state = SubState (transport_sub_state|new_bits);
                pending_abort = abort;
+
                return;
-       }
 
-       realtime_stop (abort);
-       schedule_butler_transport_work ();
+       } else {
+
+               DEBUG_TRACE (DEBUG::Transport, "time to actually stop\n");
+
+               /* declick was scheduled, but we've been called again, which means it is really time to stop
+
+                  XXX: we should probably split this off into its own method and call it explicitly.
+               */
+
+               realtime_stop (abort, clear_state);
+               _butler->schedule_transport_work ();
+       }
 }
 
+/** Called from the process thread */
 void
 Session::start_transport ()
 {
+       DEBUG_TRACE (DEBUG::Transport, "start_transport\n");
+
        _last_roll_location = _transport_frame;
+       _last_roll_or_reversal_location = _transport_frame;
+
        have_looped = false;
 
        /* if record status is Enabled, move it to Recording. if its
@@ -965,7 +1578,7 @@ Session::start_transport ()
 
        switch (record_status()) {
        case Enabled:
-               if (!Config->get_punch_in()) {
+               if (!config.get_punch_in()) {
                        enable_record ();
                }
                break;
@@ -981,19 +1594,27 @@ Session::start_transport ()
        }
 
        transport_sub_state |= PendingDeclickIn;
-       
-       _transport_speed = 1.0;
-       target_phi       = 0x1000000; // speed = 1
-       phi              = target_phi;
-       phase            = 0;
 
-       boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
-       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-               (*i)->realtime_set_speed ((*i)->speed(), true);
+       _transport_speed = _default_transport_speed;
+       _target_transport_speed = _transport_speed;
+
+       boost::shared_ptr<RouteList> rl = routes.reader();
+       for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
+               boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+               if (tr) {
+                       tr->realtime_set_speed (tr->speed(), true);
+               }
        }
 
-       deliver_mmc(MIDI::MachineControl::cmdDeferredPlay, _transport_frame);
+       if (!_engine.freewheeling()) {
+               Timecode::Time time;
+               timecode_time_subframes (_transport_frame, time);
+               if (!dynamic_cast<MTC_Slave*>(_slave)) {
+                       send_immediate_mmc (MIDI::MachineControlCommand (MIDI::MachineControl::cmdDeferredPlay));
+               }
+       }
 
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("send TSC4 with speed = %1\n", _transport_speed));
        TransportStateChange (); /* EMIT SIGNAL */
 }
 
@@ -1003,36 +1624,39 @@ Session::start_transport ()
 void
 Session::post_transport ()
 {
-       if (post_transport_work & PostTransportAudition) {
-               if (auditioner && auditioner->active()) {
+       PostTransportWork ptw = post_transport_work ();
+
+       if (ptw & PostTransportAudition) {
+               if (auditioner && auditioner->auditioning()) {
                        process_function = &Session::process_audition;
                } else {
                        process_function = &Session::process_with_events;
                }
        }
 
-       if (post_transport_work & PostTransportStop) {
+       if (ptw & PostTransportStop) {
 
                transport_sub_state = 0;
        }
 
-       if (post_transport_work & PostTransportLocate) {
+       if (ptw & PostTransportLocate) {
 
-               if (((Config->get_slave_source() == None && (auto_play_legal && Config->get_auto_play())) && !_exporting) || (post_transport_work & PostTransportRoll)) {
+               if (((!config.get_external_sync() && (auto_play_legal && config.get_auto_play())) && !_exporting) || (ptw & PostTransportRoll)) {
                        start_transport ();
-
                } else {
                        transport_sub_state = 0;
                }
        }
 
        set_next_event ();
-
-       post_transport_work = PostTransportWork (0);
+       /* XXX is this really safe? shouldn't we just be unsetting the bits that we actually
+          know were handled ?
+       */
+       set_post_transport_work (PostTransportWork (0));
 }
 
 void
-Session::reset_rf_scale (nframes_t motion)
+Session::reset_rf_scale (framecnt_t motion)
 {
        cumulative_rf_motion += motion;
 
@@ -1052,165 +1676,207 @@ Session::reset_rf_scale (nframes_t motion)
 }
 
 void
-Session::set_slave_source (SlaveSource src)
+Session::mtc_status_changed (bool yn)
+{
+       g_atomic_int_set (&_mtc_active, yn);
+       MTCSyncStateChanged( yn );
+}
+
+void
+Session::ltc_status_changed (bool yn)
+{
+       g_atomic_int_set (&_ltc_active, yn);
+       LTCSyncStateChanged( yn );
+}
+
+void
+Session::use_sync_source (Slave* new_slave)
 {
-       bool reverse = false;
+       /* Runs in process() context */
+
        bool non_rt_required = false;
 
-       if (_transport_speed) {
-               error << _("please stop the transport before adjusting slave settings") << endmsg;
-               return;
+       /* XXX this deletion is problematic because we're in RT context */
+
+       delete _slave;
+       _slave = new_slave;
+
+       MTC_Slave* mtc_slave = dynamic_cast<MTC_Slave*>(_slave);
+       if (mtc_slave) {
+               mtc_slave->ActiveChanged.connect_same_thread (mtc_status_connection, boost::bind (&Session::mtc_status_changed, this, _1));
+               MTCSyncStateChanged(mtc_slave->locked() );
+       } else {
+               if (g_atomic_int_get (&_mtc_active) ){
+                       g_atomic_int_set (&_mtc_active, 0);
+                       MTCSyncStateChanged( false );
+               }
+               mtc_status_connection.disconnect ();
        }
 
-//     if (src == JACK && Config->get_jack_time_master()) {
-//             return;
-//     }
+       LTC_Slave* ltc_slave = dynamic_cast<LTC_Slave*> (_slave);
+       if (ltc_slave) {
+               ltc_slave->ActiveChanged.connect_same_thread (ltc_status_connection, boost::bind (&Session::ltc_status_changed, this, _1));
+               LTCSyncStateChanged (ltc_slave->locked() );
+       } else {
+               if (g_atomic_int_get (&_ltc_active) ){
+                       g_atomic_int_set (&_ltc_active, 0);
+                       LTCSyncStateChanged( false );
+               }
+               ltc_status_connection.disconnect ();
+       }
 
-       delete _slave;
-       _slave = 0;
+       DEBUG_TRACE (DEBUG::Slave, string_compose ("set new slave to %1\n", _slave));
+
+       // need to queue this for next process() cycle
+       _send_timecode_update = true;
+
+       boost::shared_ptr<RouteList> rl = routes.reader();
+       for (RouteList::iterator i = rl->begin(); i != rl->end(); ++i) {
+               boost::shared_ptr<Track> tr = boost::dynamic_pointer_cast<Track> (*i);
+               if (tr && !tr->hidden()) {
+                       if (tr->realtime_set_speed (tr->speed(), true)) {
+                               non_rt_required = true;
+                       }
+                       tr->set_slaved (_slave != 0);
+               }
+       }
 
-       if (_transport_speed < 0.0) {
-               reverse = true;
+       if (non_rt_required) {
+               add_post_transport_work (PostTransportSpeed);
+               _butler->schedule_transport_work ();
        }
 
-       switch (src) {
-       case None:
-               stop_transport ();
-               break;
+       set_dirty();
+}
+
+void
+Session::drop_sync_source ()
+{
+       request_sync_source (0);
+}
+
+void
+Session::switch_to_sync_source (SyncSource src)
+{
+       Slave* new_slave;
 
+       DEBUG_TRACE (DEBUG::Slave, string_compose ("Setting up sync source %1\n", enum_2_string (src)));
+
+       switch (src) {
        case MTC:
-               if (_mtc_port) {
-                       try {
-                               _slave = new MTC_Slave (*this, *_mtc_port);
-                       }
+               if (_slave && dynamic_cast<MTC_Slave*>(_slave)) {
+                       return;
+               }
 
-                       catch (failed_constructor& err) {
-                               return;
-                       }
+               try {
+                       new_slave = new MTC_Slave (*this, *_midi_ports->mtc_input_port());
+               }
 
-               } else {
-                       error << _("No MTC port defined: MTC slaving is impossible.") << endmsg;
+               catch (failed_constructor& err) {
                        return;
                }
                break;
 
-       case MIDIClock:
-               if (_midi_clock_port) {
-                       try {
-                               _slave = new MIDIClock_Slave (*this, *_midi_clock_port, 24);
-                       }
+       case LTC:
+               if (_slave && dynamic_cast<LTC_Slave*>(_slave)) {
+                       return;
+               }
 
-                       catch (failed_constructor& err) {
-                               return;
-                       }
+               try {
+                       new_slave = new LTC_Slave (*this);
+               }
 
-               } else {
-                       error << _("No MIDI Clock port defined: MIDI Clock slaving is impossible.") << endmsg;
+               catch (failed_constructor& err) {
                        return;
                }
-               break;
 
-       case JACK:
-               _slave = new JACK_Slave (_engine.jack());
                break;
 
-       };
+       case MIDIClock:
+               if (_slave && dynamic_cast<MIDIClock_Slave*>(_slave)) {
+                       return;
+               }
 
-       Config->set_slave_source (src);
+               try {
+                       new_slave = new MIDIClock_Slave (*this, *_midi_ports->midi_clock_input_port(), 24);
+               }
 
-       boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
-       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-               if (!(*i)->hidden()) {
-                       if ((*i)->realtime_set_speed ((*i)->speed(), true)) {
-                               non_rt_required = true;
-                       }
-                       (*i)->set_slaved (_slave);
+               catch (failed_constructor& err) {
+                       return;
                }
-       }
+               break;
 
-       if (reverse) {
-               reverse_diskstream_buffers ();
-       }
+       case Engine:
+               if (_slave && dynamic_cast<Engine_Slave*>(_slave)) {
+                       return;
+               }
 
-       if (non_rt_required) {
-               post_transport_work = PostTransportWork (post_transport_work | PostTransportSpeed);
-               schedule_butler_transport_work ();
-       }
+               if (config.get_video_pullup() != 0.0f) {
+                       return;
+               }
 
-       set_dirty();
-}
+               new_slave = new Engine_Slave (*AudioEngine::instance());
+               break;
 
-void
-Session::reverse_diskstream_buffers ()
-{
-       post_transport_work = PostTransportWork (post_transport_work | PostTransportReverse);
-       schedule_butler_transport_work ();
+       default:
+               new_slave = 0;
+               break;
+       };
+
+       request_sync_source (new_slave);
 }
 
 void
-Session::set_diskstream_speed (Diskstream* stream, double speed)
+Session::set_track_speed (Track* track, double speed)
 {
-       if (stream->realtime_set_speed (speed, false)) {
-               post_transport_work = PostTransportWork (post_transport_work | PostTransportSpeed);
-               schedule_butler_transport_work ();
+       if (track->realtime_set_speed (speed, false)) {
+               add_post_transport_work (PostTransportSpeed);
+               _butler->schedule_transport_work ();
                set_dirty ();
        }
 }
 
 void
-Session::set_audio_range (list<AudioRange>& range)
+Session::unset_play_range ()
 {
-       Event *ev = new Event (Event::SetAudioRange, Event::Add, Event::Immediate, 0, 0.0f);
-       ev->audio_range = range;
-       queue_event (ev);
+       _play_range = false;
+       _clear_event_type (SessionEvent::RangeStop);
+       _clear_event_type (SessionEvent::RangeLocate);
 }
 
 void
-Session::request_play_range (bool yn)
+Session::set_play_range (list<AudioRange>& range, bool leave_rolling)
 {
-       Event* ev = new Event (Event::SetPlayRange, Event::Add, Event::Immediate, 0, 0.0f, yn);
-       queue_event (ev);
-}
+       SessionEvent* ev;
 
-void
-Session::set_play_range (bool yn)
-{
        /* Called from event-processing context */
 
-       if (_play_range != yn) {
-               _play_range = yn;
-               setup_auto_play ();
+       unset_play_range ();
 
-               if (!_play_range) {
+       if (range.empty()) {
+               /* _play_range set to false in unset_play_range()
+                */
+               if (!leave_rolling) {
                        /* stop transport */
-                       Event* ev = new Event (Event::SetTransportSpeed, Event::Add, Event::Immediate, 0, 0.0f, false);
+                       SessionEvent* ev = new SessionEvent (SessionEvent::SetTransportSpeed, SessionEvent::Add, SessionEvent::Immediate, 0, 0.0f, false);
                        merge_event (ev);
                }
+               return;
        }
-}
-
-void
-Session::setup_auto_play ()
-{
-       /* Called from event-processing context */
-
-       Event* ev;
 
-       _clear_event_type (Event::RangeStop);
-       _clear_event_type (Event::RangeLocate);
+       _play_range = true;
 
-       if (!_play_range) {
-               return;
-       }
+       /* cancel loop play */
+       unset_play_loop ();
 
-       list<AudioRange>::size_type sz = current_audio_range.size();
+       list<AudioRange>::size_type sz = range.size();
 
        if (sz > 1) {
 
-               list<AudioRange>::iterator i = current_audio_range.begin();
+               list<AudioRange>::iterator i = range.begin();
                list<AudioRange>::iterator next;
 
-               while (i != current_audio_range.end()) {
+               while (i != range.end()) {
 
                        next = i;
                        ++next;
@@ -1218,7 +1884,7 @@ Session::setup_auto_play ()
                        /* locating/stopping is subject to delays for declicking.
                         */
 
-                       nframes_t requested_frame = (*i).end;
+                       framepos_t requested_frame = i->end;
 
                        if (requested_frame > current_block_size) {
                                requested_frame -= current_block_size;
@@ -1226,10 +1892,10 @@ Session::setup_auto_play ()
                                requested_frame = 0;
                        }
 
-                       if (next == current_audio_range.end()) {
-                               ev = new Event (Event::RangeStop, Event::Add, requested_frame, 0, 0.0f);
+                       if (next == range.end()) {
+                               ev = new SessionEvent (SessionEvent::RangeStop, SessionEvent::Add, requested_frame, 0, 0.0f);
                        } else {
-                               ev = new Event (Event::RangeLocate, Event::Add, requested_frame, (*next).start, 0.0f);
+                               ev = new SessionEvent (SessionEvent::RangeLocate, SessionEvent::Add, requested_frame, (*next).start, 0.0f);
                        }
 
                        merge_event (ev);
@@ -1239,32 +1905,46 @@ Session::setup_auto_play ()
 
        } else if (sz == 1) {
 
-               ev = new Event (Event::RangeStop, Event::Add, current_audio_range.front().end, 0, 0.0f);
+               ev = new SessionEvent (SessionEvent::RangeStop, SessionEvent::Add, range.front().end, 0, 0.0f);
                merge_event (ev);
 
        }
 
+       /* save range so we can do auto-return etc. */
+
+       current_audio_range = range;
+
        /* now start rolling at the right place */
 
-       ev = new Event (Event::LocateRoll, Event::Add, Event::Immediate, current_audio_range.front().start, 0.0f, false);
+       ev = new SessionEvent (SessionEvent::LocateRoll, SessionEvent::Add, SessionEvent::Immediate, range.front().start, 0.0f, false);
        merge_event (ev);
+
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("send TSC5 with speed = %1\n", _transport_speed));
+       TransportStateChange ();
 }
 
 void
-Session::request_roll_at_and_return (nframes_t start, nframes_t return_to)
+Session::request_bounded_roll (framepos_t start, framepos_t end)
 {
-       Event *ev = new Event (Event::LocateRollLocate, Event::Add, Event::Immediate, return_to, 1.0);
-       ev->target2_frame = start;
-       queue_event (ev);
+       AudioRange ar (start, end, 0);
+       list<AudioRange> lar;
+
+       lar.push_back (ar);
+       request_play_range (&lar, true);
+}
+
+void
+Session::set_requested_return_frame (framepos_t return_to)
+{
+       _requested_return_frame = return_to;
 }
 
 void
-Session::request_bounded_roll (nframes_t start, nframes_t end)
+Session::request_roll_at_and_return (framepos_t start, framepos_t return_to)
 {
-       request_stop ();
-       Event *ev = new Event (Event::StopOnce, Event::Replace, end, Event::Immediate, 0.0);
+       SessionEvent *ev = new SessionEvent (SessionEvent::LocateRollLocate, SessionEvent::Add, SessionEvent::Immediate, return_to, 1.0);
+       ev->target2_frame = start;
        queue_event (ev);
-       request_locate (start, true);
 }
 
 void
@@ -1279,14 +1959,15 @@ Session::engine_halted ()
           the picture.
        */
 
-       g_atomic_int_set (&butler_should_do_transport_work, 0);
-       post_transport_work = PostTransportWork (0);
-       stop_butler ();
+       if (_butler) {
+               _butler->stop ();
+       }
 
-       realtime_stop (false);
+       realtime_stop (false, true);
        non_realtime_stop (false, 0, ignored);
        transport_sub_state = 0;
 
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("send TSC6 with speed = %1\n", _transport_speed));
        TransportStateChange (); /* EMIT SIGNAL */
 }
 
@@ -1294,7 +1975,9 @@ Session::engine_halted ()
 void
 Session::xrun_recovery ()
 {
-       Xrun (transport_frame()); //EMIT SIGNAL
+       ++_xrun_count;
+
+       Xrun (_transport_frame); /* EMIT SIGNAL */
 
        if (Config->get_stop_recording_on_xrun() && actively_recording()) {
 
@@ -1307,79 +1990,82 @@ Session::xrun_recovery ()
 }
 
 void
-Session::update_latency_compensation (bool with_stop, bool abort)
+Session::route_processors_changed (RouteProcessorChange c)
 {
-       bool update_jack = false;
-
-       if (_state_of_the_state & Deletion) {
+       if (ignore_route_processor_changes) {
                return;
        }
 
-       _worst_track_latency = 0;
-
-#undef DEBUG_LATENCY
-#ifdef DEBUG_LATENCY
-       cerr << "\n---------------------------------\nUPDATE LATENCY\n";
-#endif
-
-       boost::shared_ptr<RouteList> r = routes.reader ();
+       if (c.type == RouteProcessorChange::MeterPointChange) {
+               set_dirty ();
+               return;
+       }
 
-       for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
+       if (c.type == RouteProcessorChange::RealTimeChange) {
+               set_dirty ();
+               return;
+       }
 
-               if (with_stop) {
-                       (*i)->handle_transport_stopped (abort, (post_transport_work & PostTransportLocate),
-                                                       (!(post_transport_work & PostTransportLocate) || pending_locate_flush));
-               }
+       update_latency_compensation ();
+       resort_routes ();
 
-               nframes_t old_latency = (*i)->signal_latency ();
-               nframes_t track_latency = (*i)->update_total_latency ();
+       set_dirty ();
+}
 
-               if (old_latency != track_latency) {
-                       (*i)->update_port_total_latencies ();
-                       update_jack = true;
-               }
+void
+Session::allow_auto_play (bool yn)
+{
+       auto_play_legal = yn;
+}
 
-               if (!(*i)->is_hidden() && ((*i)->active())) {
-                       _worst_track_latency = max (_worst_track_latency, track_latency);
+bool
+Session::maybe_stop (framepos_t limit)
+{
+       if ((_transport_speed > 0.0f && _transport_frame >= limit) || (_transport_speed < 0.0f && _transport_frame == 0)) {
+               if (synced_to_engine () && config.get_jack_time_master ()) {
+                       _engine.transport_stop ();
+               } else if (!synced_to_engine ()) {
+                       stop_transport ();
                }
+               return true;
        }
+       return false;
+}
 
-       if (update_jack) {
-               _engine.update_total_latencies ();
-       }
-
-#ifdef DEBUG_LATENCY
-       cerr << "\tworst was " << _worst_track_latency << endl;
-#endif
-
-       for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
-               (*i)->set_latency_delay (_worst_track_latency);
+void
+Session::send_mmc_locate (framepos_t t)
+{
+       if (t < 0) {
+               return;
        }
 
-       set_worst_io_latencies ();
-
-       /* reflect any changes in latencies into capture offsets
-       */
-
-       boost::shared_ptr<DiskstreamList> dsl = diskstreams.reader();
-
-       for (DiskstreamList::iterator i = dsl->begin(); i != dsl->end(); ++i) {
-               (*i)->set_capture_offset ();
+       if (!_engine.freewheeling()) {
+               Timecode::Time time;
+               timecode_time_subframes (t, time);
+               send_immediate_mmc (MIDI::MachineControlCommand (time));
        }
 }
 
+/** Ask the transport to not send timecode until further notice.  The suspension
+ *  will come into effect some finite time after this call, and timecode_transmission_suspended()
+ *  should be checked by the caller to find out when.
+ */
 void
-Session::allow_auto_play (bool yn)
+Session::request_suspend_timecode_transmission ()
 {
-       auto_play_legal = yn;
+       SessionEvent* ev = new SessionEvent (SessionEvent::SetTimecodeTransmission, SessionEvent::Add, SessionEvent::Immediate, 0, 0, false);
+       queue_event (ev);
 }
 
 void
-Session::reset_jack_connection (jack_client_t* jack)
+Session::request_resume_timecode_transmission ()
 {
-       JACK_Slave* js;
+       SessionEvent* ev = new SessionEvent (SessionEvent::SetTimecodeTransmission, SessionEvent::Add, SessionEvent::Immediate, 0, 0, true);
+       queue_event (ev);
+}
 
-       if (_slave && ((js = dynamic_cast<JACK_Slave*> (_slave)) != 0)) {
-               js->reset_client (jack);
-       }
+bool
+Session::timecode_transmission_suspended () const
+{
+       return g_atomic_int_get (&_suspend_timecode_transmission) == 1;
 }