Remove some namespace ambiguity
[ardour.git] / libs / ardour / session_process.cc
index d16f7d3b0cad3f6ee12ed624e28e28467f865454..720104c4191733c2ca9ab9ef87f0cbde92b4219c 100644 (file)
@@ -38,7 +38,8 @@
 #include "ardour/process_thread.h"
 #include "ardour/scene_changer.h"
 #include "ardour/session.h"
-#include "ardour/slave.h"
+#include "ardour/transport_master.h"
+#include "ardour/transport_master_manager.h"
 #include "ardour/ticker.h"
 #include "ardour/types.h"
 #include "ardour/vca.h"
@@ -65,6 +66,7 @@ Session::process (pframes_t nframes)
 
        if (processing_blocked()) {
                _silent = true;
+               cerr << "%%%%%%%%%%%%%% session process blocked\n";
                return;
        }
 
@@ -136,7 +138,6 @@ Session::no_roll (pframes_t nframes)
 
        samplepos_t end_sample = _transport_sample + nframes; // FIXME: varispeed + no_roll ??
        int ret = 0;
-       int declick = (config.get_use_transport_fades() ? get_transport_declick_required() : false);
        boost::shared_ptr<RouteList> r = routes.reader ();
 
        if (_click_io) {
@@ -152,7 +153,7 @@ Session::no_roll (pframes_t nframes)
 
        if (_process_graph) {
                DEBUG_TRACE(DEBUG::ProcessThreads,"calling graph/no-roll\n");
-               _process_graph->routes_no_roll( nframes, _transport_sample, end_sample, non_realtime_work_pending(), declick);
+               _process_graph->routes_no_roll( nframes, _transport_sample, end_sample, non_realtime_work_pending());
        } else {
                PT_TIMING_CHECK (10);
                for (RouteList::iterator i = r->begin(); i != r->end(); ++i) {
@@ -161,8 +162,6 @@ Session::no_roll (pframes_t nframes)
                                continue;
                        }
 
-                       (*i)->set_pending_declick (declick);
-
                        if ((*i)->no_roll (nframes, _transport_sample, end_sample, non_realtime_work_pending())) {
                                error << string_compose(_("Session: error in no roll for %1"), (*i)->name()) << endmsg;
                                ret = -1;
@@ -182,7 +181,6 @@ Session::no_roll (pframes_t nframes)
 int
 Session::process_routes (pframes_t nframes, bool& need_butler)
 {
-       int declick = (config.get_use_transport_fades() ? get_transport_declick_required() : false);
        boost::shared_ptr<RouteList> r = routes.reader ();
 
        const samplepos_t start_sample = _transport_sample;
@@ -197,7 +195,7 @@ Session::process_routes (pframes_t nframes, bool& need_butler)
 
        if (_process_graph) {
                DEBUG_TRACE(DEBUG::ProcessThreads,"calling graph/process-routes\n");
-               if (_process_graph->process_routes (nframes, start_sample, end_sample, declick, need_butler) < 0) {
+               if (_process_graph->process_routes (nframes, start_sample, end_sample, need_butler) < 0) {
                        stop_transport ();
                        return -1;
                }
@@ -211,11 +209,9 @@ Session::process_routes (pframes_t nframes, bool& need_butler)
                                continue;
                        }
 
-                       (*i)->set_pending_declick (declick);
-
                        bool b = false;
 
-                       if ((ret = (*i)->roll (nframes, start_sample, end_sample, declick, b)) < 0) {
+                       if ((ret = (*i)->roll (nframes, start_sample, end_sample, b)) < 0) {
                                stop_transport ();
                                return -1;
                        }
@@ -257,6 +253,23 @@ Session::get_track_statistics ()
        }
 }
 
+bool
+Session::compute_audible_delta (samplepos_t& pos_and_delta) const
+{
+       if (_transport_speed == 0.0 || _count_in_samples > 0 || _remaining_latency_preroll > 0) {
+               /* cannot compute audible delta, because the session is
+                  generating silence that does not correspond to the timeline,
+                  but is instead filling playback buffers to manage latency
+                  alignment.
+               */
+               DEBUG_TRACE (DEBUG::Slave, string_compose ("still adjusting for latency (%1) and/or count-in (%2) or stopped %1\n", _remaining_latency_preroll, _count_in_samples, _transport_speed));
+               return false;
+       }
+
+       pos_and_delta -= _transport_sample;
+       return true;
+}
+
 /** Process callback used when the auditioner is not active */
 void
 Session::process_with_events (pframes_t nframes)
@@ -291,7 +304,6 @@ Session::process_with_events (pframes_t nframes)
                immediate_events.pop_front ();
                process_event (ev);
        }
-
        /* only count-in when going to roll at speed 1.0 */
        if (_transport_speed != 1.0 && _count_in_samples > 0) {
                _count_in_samples = 0;
@@ -302,7 +314,9 @@ Session::process_with_events (pframes_t nframes)
 
        assert (_count_in_samples == 0 || _remaining_latency_preroll == 0 || _count_in_samples == _remaining_latency_preroll);
 
-       if (_count_in_samples > 0 || _remaining_latency_preroll > 0) {
+       DEBUG_TRACE (DEBUG::Transport, string_compose ("Running count in/latency preroll of %1 & %2\n", _count_in_samples, _remaining_latency_preroll));
+
+       while (_count_in_samples > 0 || _remaining_latency_preroll > 0) {
                samplecnt_t ns;
 
                if (_remaining_latency_preroll > 0) {
@@ -369,8 +383,6 @@ Session::process_with_events (pframes_t nframes)
                        set_next_event ();
                }
 
-               check_declick_out ();
-
                if (nframes == 0) {
                        return;
                } else {
@@ -433,16 +445,9 @@ Session::process_with_events (pframes_t nframes)
                }
        }
 
-       if (_transport_speed == 1.0) {
-               samples_moved = (samplecnt_t) nframes;
-       } else {
-               /* use a cubic midi interpolation to compute the number of
-                * samples we will move at the current speed.
-                */
-               CubicInterpolation interp;
-               interp.set_speed (_transport_speed);
-               samples_moved = interp.distance (nframes);
-       }
+       assert (_transport_speed == 0 || _transport_speed == 1.0 || _transport_speed == -1.0);
+
+       samples_moved = (samplecnt_t) nframes * _transport_speed;
 
        end_sample = _transport_sample + samples_moved;
 
@@ -455,8 +460,9 @@ Session::process_with_events (pframes_t nframes)
                        return;
                }
 
-               if (!_exporting && _slave) {
-                       if (!follow_slave (nframes)) {
+               if (!_exporting && config.get_external_sync()) {
+                       if (!follow_transport_master (nframes)) {
+                               ltc_tx_send_time_code_for_cycle (_transport_sample, end_sample, _target_transport_speed, _transport_speed, nframes);
                                return;
                        }
                }
@@ -521,7 +527,6 @@ Session::process_with_events (pframes_t nframes)
                                }
 
                                maybe_stop (stop_limit);
-                               check_declick_out ();
                        }
 
                        if (nframes > 0) {
@@ -562,308 +567,16 @@ Session::process_with_events (pframes_t nframes)
        }
 }
 
-void
-Session::reset_slave_state ()
-{
-       average_slave_delta = 1800;
-       delta_accumulator_cnt = 0;
-       have_first_delta_accumulator = false;
-       _slave_state = Stopped;
-       DiskReader::set_no_disk_output (false);
-}
-
 bool
 Session::transport_locked () const
 {
-       Slave* sl = _slave;
-
-       if (!locate_pending() && (!config.get_external_sync() || (sl && sl->ok() && sl->locked()))) {
+       if (!locate_pending() && (!config.get_external_sync() || (transport_master()->ok() && transport_master()->locked()))) {
                return true;
        }
 
        return false;
 }
 
-bool
-Session::follow_slave (pframes_t nframes)
-{
-       double slave_speed;
-       samplepos_t slave_transport_sample;
-       samplecnt_t this_delta;
-       int dir;
-
-       if (!_slave->ok()) {
-               stop_transport ();
-               config.set_external_sync (false);
-               goto noroll;
-       }
-
-       _slave->speed_and_position (slave_speed, slave_transport_sample);
-
-       DEBUG_TRACE (DEBUG::Slave, string_compose ("Slave position %1 speed %2\n", slave_transport_sample, slave_speed));
-
-       if (!_slave->locked()) {
-               DEBUG_TRACE (DEBUG::Slave, "slave not locked\n");
-               goto noroll;
-       }
-
-       if (slave_transport_sample > _transport_sample) {
-               this_delta = slave_transport_sample - _transport_sample;
-               dir = 1;
-       } else {
-               this_delta = _transport_sample - slave_transport_sample;
-               dir = -1;
-       }
-
-       if (_slave->starting()) {
-               slave_speed = 0.0f;
-       }
-
-       if (_slave->is_always_synced() ||
-                       (Config->get_timecode_source_is_synced() && (dynamic_cast<TimecodeSlave*>(_slave)) != 0)
-                       ) {
-
-               /* if the TC source is synced, then we assume that its
-                  speed is binary: 0.0 or 1.0
-               */
-
-               if (slave_speed != 0.0f) {
-                       slave_speed = 1.0f;
-               }
-
-       } else {
-
-               /* if we are chasing and the average delta between us and the
-                  master gets too big, we want to switch to silent
-                  motion. so keep track of that here.
-               */
-
-               if (_slave_state == Running) {
-                       calculate_moving_average_of_slave_delta(dir, abs(this_delta));
-               }
-       }
-
-       track_slave_state (slave_speed, slave_transport_sample, this_delta);
-
-       DEBUG_TRACE (DEBUG::Slave, string_compose ("slave state %1 @ %2 speed %3 cur delta %4 avg delta %5\n",
-                                                  _slave_state, slave_transport_sample, slave_speed, this_delta, average_slave_delta));
-
-
-       if (_slave_state == Running && !_slave->is_always_synced() && !(Config->get_timecode_source_is_synced() && (dynamic_cast<TimecodeSlave*>(_slave)) != 0)) {
-
-               /* may need to varispeed to sync with slave */
-
-               if (_transport_speed != 0.0f) {
-
-                       /*
-                          note that average_dir is +1 or -1
-                       */
-
-                       float delta;
-
-                       if (average_slave_delta == 0) {
-                               delta = this_delta;
-                               delta *= dir;
-                       } else {
-                               delta = average_slave_delta;
-                               delta *= average_dir;
-                       }
-
-#ifndef NDEBUG
-                       if (slave_speed != 0.0) {
-                               DEBUG_TRACE (DEBUG::Slave, string_compose ("delta = %1 speed = %2 ts = %3 M@%4 S@%5 avgdelta %6\n",
-                                                                          (int) (dir * this_delta),
-                                                                          slave_speed,
-                                                                          _transport_speed,
-                                                                          _transport_sample,
-                                                                          slave_transport_sample,
-                                                                          average_slave_delta));
-                       }
-#endif
-
-                       if (_slave->give_slave_full_control_over_transport_speed()) {
-                               set_transport_speed (slave_speed, 0, false, false);
-                               //std::cout << "set speed = " << slave_speed << "\n";
-                       } else {
-                               float adjusted_speed = slave_speed + (1.5 * (delta /  float(_current_sample_rate)));
-                               request_transport_speed (adjusted_speed);
-                               DEBUG_TRACE (DEBUG::Slave, string_compose ("adjust using %1 towards %2 ratio %3 current %4 slave @ %5\n",
-                                                                          delta, adjusted_speed, adjusted_speed/slave_speed, _transport_speed,
-                                                                          slave_speed));
-                       }
-
-                       if (!actively_recording() && (samplecnt_t) average_slave_delta > _slave->resolution()) {
-                               DEBUG_TRACE (DEBUG::Slave, string_compose ("average slave delta %1 greater than slave resolution %2 => no disk output\n", average_slave_delta, _slave->resolution()));
-                               /* run routes as normal, but no disk output */
-                               DiskReader::set_no_disk_output (true);
-                               return true;
-                       }
-
-                       if (!have_first_delta_accumulator) {
-                               DEBUG_TRACE (DEBUG::Slave, "waiting for first slave delta accumulator to be ready, no disk output\n");
-                               /* run routes as normal, but no disk output */
-                               DiskReader::set_no_disk_output (true);
-                               return true;
-                       }
-               }
-       }
-
-
-       if (!have_first_delta_accumulator) {
-               DEBUG_TRACE (DEBUG::Slave, "still waiting to compute slave delta, no disk output\n");
-               DiskReader::set_no_disk_output (true);
-       } else {
-               DiskReader::set_no_disk_output (false);
-       }
-
-       if ((_slave_state == Running) && (0 == (post_transport_work () & ~PostTransportSpeed))) {
-               /* speed is set, we're locked, and good to go */
-               return true;
-       }
-
-  noroll:
-       /* don't move at all */
-       DEBUG_TRACE (DEBUG::Slave, "no roll\n")
-       no_roll (nframes);
-       return false;
-}
-
-void
-Session::calculate_moving_average_of_slave_delta (int dir, samplecnt_t this_delta)
-{
-       if (delta_accumulator_cnt >= delta_accumulator_size) {
-               have_first_delta_accumulator = true;
-               delta_accumulator_cnt = 0;
-       }
-
-       if (delta_accumulator_cnt != 0 || this_delta < _current_sample_rate) {
-               delta_accumulator[delta_accumulator_cnt++] = (samplecnt_t) dir *  (samplecnt_t) this_delta;
-       }
-
-       if (have_first_delta_accumulator) {
-               average_slave_delta = 0L;
-               for (int i = 0; i < delta_accumulator_size; ++i) {
-                       average_slave_delta += delta_accumulator[i];
-               }
-               average_slave_delta /= (int32_t) delta_accumulator_size;
-               if (average_slave_delta < 0L) {
-                       average_dir = -1;
-                       average_slave_delta = average_slave_delta;
-               } else {
-                       average_dir = 1;
-               }
-       }
-}
-
-void
-Session::track_slave_state (float slave_speed, samplepos_t slave_transport_sample, samplecnt_t /*this_delta*/)
-{
-       if (slave_speed != 0.0f) {
-
-               /* slave is running */
-
-               switch (_slave_state) {
-               case Stopped:
-                       if (_slave->requires_seekahead()) {
-                               slave_wait_end = slave_transport_sample + _slave->seekahead_distance ();
-                               DEBUG_TRACE (DEBUG::Slave, string_compose ("slave stopped, but running, requires seekahead to %1\n", slave_wait_end));
-                               /* we can call locate() here because we are in process context */
-                               locate (slave_wait_end, false, false);
-                               _slave_state = Waiting;
-
-                       } else {
-
-                               DEBUG_TRACE (DEBUG::Slave, string_compose ("slave stopped -> running at %1\n", slave_transport_sample));
-
-                               memset (delta_accumulator, 0, sizeof (int32_t) * delta_accumulator_size);
-                               average_slave_delta = 0L;
-
-                               Location* al = _locations->auto_loop_location();
-
-                               if (al && play_loop && (slave_transport_sample < al->start() || slave_transport_sample > al->end())) {
-                                       // cancel looping
-                                       request_play_loop(false);
-                               }
-
-                               if (slave_transport_sample != _transport_sample) {
-                                       DEBUG_TRACE (DEBUG::Slave, string_compose ("require locate to run. eng: %1 -> sl: %2\n", _transport_sample, slave_transport_sample));
-                                       locate (slave_transport_sample, false, false);
-                               }
-                               _slave_state = Running;
-                       }
-                       break;
-
-               case Waiting:
-               default:
-                       break;
-               }
-
-               if (_slave_state == Waiting) {
-
-                       DEBUG_TRACE (DEBUG::Slave, string_compose ("slave waiting at %1\n", slave_transport_sample));
-
-                       if (slave_transport_sample >= slave_wait_end) {
-
-                               DEBUG_TRACE (DEBUG::Slave, string_compose ("slave start at %1 vs %2\n", slave_transport_sample, _transport_sample));
-
-                               _slave_state = Running;
-
-                               /* now perform a "micro-seek" within the disk buffers to realign ourselves
-                                  precisely with the master.
-                               */
-
-
-                               bool ok = true;
-                               samplecnt_t sample_delta = slave_transport_sample - _transport_sample;
-
-                               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 (sample_delta)) {
-                                               ok = false;
-                                               break;
-                                       }
-                               }
-
-                               if (ok) {
-                                       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 (sample_delta);
-                                               }
-                                       }
-                                       _transport_sample += sample_delta;
-
-                               } else {
-                                       cerr << "cannot micro-seek\n";
-                                       /* XXX what? */
-                               }
-                       }
-               }
-
-               if (_slave_state == Running && _transport_speed == 0.0f) {
-                       DEBUG_TRACE (DEBUG::Slave, "slave starts transport\n");
-                       start_transport ();
-               }
-
-       } else { // slave_speed is 0
-
-               /* slave has stopped */
-
-               if (_transport_speed != 0.0f) {
-                       DEBUG_TRACE (DEBUG::Slave, string_compose ("slave stops transport: %1 sample %2 tf %3\n", slave_speed, slave_transport_sample, _transport_sample));
-                       stop_transport ();
-               }
-
-               if (slave_transport_sample != _transport_sample) {
-                       DEBUG_TRACE (DEBUG::Slave, string_compose ("slave stopped, move to %1\n", slave_transport_sample));
-                       force_locate (slave_transport_sample, false);
-               }
-
-               reset_slave_state();
-       }
-}
-
 void
 Session::process_without_events (pframes_t nframes)
 {
@@ -875,23 +588,20 @@ Session::process_without_events (pframes_t nframes)
                return;
        }
 
-       if (!_exporting && _slave) {
-               if (!follow_slave (nframes)) {
+       if (!_exporting && config.get_external_sync()) {
+               if (!follow_transport_master (nframes)) {
                        ltc_tx_send_time_code_for_cycle (_transport_sample, _transport_sample, 0, 0 , nframes);
                        return;
                }
        }
 
+       assert (_transport_speed == 0 || _transport_speed == 1.0 || _transport_speed == -1.0);
+
        if (_transport_speed == 0) {
                no_roll (nframes);
                return;
-       }
-
-       if (_transport_speed == 1.0) {
-               samples_moved = (samplecnt_t) nframes;
        } else {
-               interpolation.set_speed (_transport_speed);
-               samples_moved = interpolation.distance (nframes);
+               samples_moved = (samplecnt_t) nframes;
        }
 
        if (!_exporting && !timecode_transmission_suspended()) {
@@ -927,7 +637,6 @@ Session::process_without_events (pframes_t nframes)
        }
 
        maybe_stop (stop_limit);
-       check_declick_out ();
 
        if (session_needs_butler) {
                DEBUG_TRACE (DEBUG::Butler, "p-without-events: session needs butler, call it\n");
@@ -960,7 +669,7 @@ Session::process_audition (pframes_t nframes)
        /* if using a monitor section, run it because otherwise we don't hear anything */
 
        if (_monitor_out && auditioner->needs_monitor()) {
-               _monitor_out->monitor_run (_transport_sample, _transport_sample + nframes, nframes, false);
+               _monitor_out->monitor_run (_transport_sample, _transport_sample + nframes, nframes);
        }
 
        /* handle pending events */
@@ -1109,17 +818,6 @@ Session::process_event (SessionEvent* ev)
                del = false;
                break;
 
-       case SessionEvent::AutoLoopDeclick:
-               if (play_loop) {
-                       /* Request a declick fade-out and a fade-in; the fade-out will happen
-                          at the end of the loop, and the fade-in at the start.
-                       */
-                       transport_sub_state |= (PendingLoopDeclickOut | PendingLoopDeclickIn);
-               }
-               remove = false;
-               del = false;
-               break;
-
        case SessionEvent::Locate:
                if (ev->yes_or_no) { /* force locate */
                        /* args: do not roll after locate, do flush, not with loop */
@@ -1162,6 +860,10 @@ Session::process_event (SessionEvent* ev)
                set_transport_speed (ev->speed, ev->target_sample, ev->yes_or_no, ev->second_yes_or_no, ev->third_yes_or_no);
                break;
 
+       case SessionEvent::SetTransportMaster:
+               TransportMasterManager::instance().set_current (ev->transport_master);
+               break;
+
        case SessionEvent::PunchIn:
                // cerr << "PunchIN at " << transport_sample() << endl;
                if (config.get_punch_in() && record_status() == Enabled) {
@@ -1208,11 +910,6 @@ Session::process_event (SessionEvent* ev)
                overwrite_some_buffers (static_cast<Track*>(ev->ptr));
                break;
 
-       case SessionEvent::SetSyncSource:
-               DEBUG_TRACE (DEBUG::Slave, "seen request for new slave\n");
-               use_sync_source (ev->slave);
-               break;
-
        case SessionEvent::Audition:
                set_audition (ev->region);
                // drop reference to region
@@ -1266,7 +963,7 @@ Session::compute_stop_limit () const
                return max_samplepos;
        }
 
-       if (_slave) {
+       if (config.get_external_sync()) {
                return max_samplepos;
        }
 
@@ -1362,3 +1059,146 @@ Session::emit_thread_run ()
        }
        pthread_mutex_unlock (&_rt_emit_mutex);
 }
+
+bool
+Session::follow_transport_master (pframes_t nframes)
+{
+       TransportMasterManager& tmm (TransportMasterManager::instance());
+
+       double slave_speed;
+       samplepos_t slave_transport_sample;
+       sampleoffset_t delta;
+
+       if (tmm.master_invalid_this_cycle()) {
+               DEBUG_TRACE (DEBUG::Slave, "session told not to use the transport master this cycle\n");
+               goto noroll;
+       }
+
+       slave_speed = tmm.get_current_speed_in_process_context();
+       slave_transport_sample = tmm.get_current_position_in_process_context ();
+       delta = _transport_sample - slave_transport_sample;
+
+       DEBUG_TRACE (DEBUG::Slave, string_compose ("session at %1, master at %2, delta: %3 res: %4\n", _transport_sample, slave_transport_sample, delta, tmm.current()->resolution()));
+
+       track_transport_master (slave_speed, slave_transport_sample);
+
+       if (transport_master_tracking_state == Running) {
+
+               if (!actively_recording() && delta > tmm.current()->resolution()) {
+                       DEBUG_TRACE (DEBUG::Slave, string_compose ("average slave delta %1 greater than slave resolution %2\n", delta, tmm.current()->resolution()));
+                       if (micro_locate (-delta) != 0) {
+                               DEBUG_TRACE (DEBUG::Slave, "micro-locate didn't work, set no disk output true\n");
+
+                               /* run routes as normal, but no disk output */
+                               DiskReader::set_no_disk_output (true);
+                       }
+                       return true;
+               }
+
+               if (transport_master_tracking_state == Running) {
+                       /* speed is set, we're locked, and good to go */
+                       DiskReader::set_no_disk_output (false);
+                       return true;
+               }
+       }
+
+  noroll:
+       /* don't move at all */
+       DEBUG_TRACE (DEBUG::Slave, "no roll\n")
+       no_roll (nframes);
+       return false;
+}
+
+void
+Session::track_transport_master (float slave_speed, samplepos_t slave_transport_sample)
+{
+       boost::shared_ptr<TransportMaster> master (TransportMasterManager::instance().current());
+
+       assert (master);
+
+       DEBUG_TRACE (DEBUG::Slave, string_compose ("session has master tracking state as %1\n", transport_master_tracking_state));
+
+       if (slave_speed != 0.0f) {
+
+               /* slave is running */
+
+               switch (transport_master_tracking_state) {
+               case Stopped:
+                       if (master->requires_seekahead()) {
+                               master_wait_end = slave_transport_sample + master->seekahead_distance ();
+                               DEBUG_TRACE (DEBUG::Slave, string_compose ("slave stopped, but running, requires seekahead to %1\n", master_wait_end));
+                               /* we can call locate() here because we are in process context */
+                               if (micro_locate (master_wait_end - _transport_sample) != 0) {
+                                       locate (master_wait_end, false, false);
+                               }
+                               transport_master_tracking_state = Waiting;
+
+                       } else {
+
+                               DEBUG_TRACE (DEBUG::Slave, string_compose ("slave stopped -> running at %1\n", slave_transport_sample));
+
+                               if (slave_transport_sample != _transport_sample) {
+                                       DEBUG_TRACE (DEBUG::Slave, string_compose ("require locate to run. eng: %1 -> sl: %2\n", _transport_sample, slave_transport_sample));
+                                       if (micro_locate (slave_transport_sample - _transport_sample) != 0) {
+                                               locate (slave_transport_sample, false, false);
+                                       }
+                               }
+                               transport_master_tracking_state = Running;
+                       }
+                       break;
+
+               case Waiting:
+               default:
+                       break;
+               }
+
+               if (transport_master_tracking_state == Waiting) {
+
+                       DEBUG_TRACE (DEBUG::Slave, string_compose ("slave waiting at %1\n", slave_transport_sample));
+
+                       if (slave_transport_sample >= master_wait_end) {
+
+                               DEBUG_TRACE (DEBUG::Slave, string_compose ("slave start at %1 vs %2\n", slave_transport_sample, _transport_sample));
+
+                               transport_master_tracking_state = Running;
+
+                               /* now perform a "micro-seek" within the disk buffers to realign ourselves
+                                  precisely with the master.
+                               */
+
+                               if (micro_locate (slave_transport_sample - _transport_sample) != 0) {
+                                       cerr << "cannot micro-seek\n";
+                                       /* XXX what? */
+                               }
+                       }
+               }
+
+               if (transport_master_tracking_state == Running && _transport_speed == 0.0f) {
+                       DEBUG_TRACE (DEBUG::Slave, "slave starts transport\n");
+                       start_transport ();
+               }
+
+       } else { // slave_speed is 0
+
+               /* slave has stopped */
+
+               if (_transport_speed != 0.0f) {
+                       DEBUG_TRACE (DEBUG::Slave, string_compose ("slave stops transport: %1 sample %2 tf %3\n", slave_speed, slave_transport_sample, _transport_sample));
+                       stop_transport ();
+               }
+
+               if (slave_transport_sample != _transport_sample) {
+                       DEBUG_TRACE (DEBUG::Slave, string_compose ("slave stopped, move to %1\n", slave_transport_sample));
+                       force_locate (slave_transport_sample, false);
+               }
+
+               reset_slave_state();
+       }
+}
+
+void
+Session::reset_slave_state ()
+{
+       transport_master_tracking_state = Stopped;
+       DiskReader::set_no_disk_output (false);
+}