add new ::update_interval() method for transport masters, and use in shared ::speed_and_position() implementation

libs/ardour/ardour/transport_master.h

@@ -244,6 +244,14 @@ class LIBARDOUR_API TransportMaster : public PBD::Stateful {
 	 */
 	virtual samplecnt_t resolution() const = 0;
 
+	/**
+	 * @return - the expected update interval for the data source used by
+	 * this transport master. Even if the data is effectively continuous,
+	 * this number indicates how long it is between changes to the known
+	 * position of the master.
+	 */
+	virtual samplecnt_t update_interval() const = 0;
+
 	/**
 	 * @return - when returning true, ARDOUR will wait for seekahead_distance() before transport
 	 * starts rolling
@@ -409,6 +417,7 @@ class LIBARDOUR_API MTC_TransportMaster : public TimecodeTransportMaster, public
 	bool ok() const;
 	void handle_locate (const MIDI::byte*);
 
+	samplecnt_t update_interval () const;
 	samplecnt_t resolution () const;
 	bool requires_seekahead () const { return false; }
 	samplecnt_t seekahead_distance() const;
@@ -474,6 +483,7 @@ public:
 	bool locked() const;
 	bool ok() const;
 
+	samplecnt_t update_interval () const;
 	samplecnt_t resolution () const;
 	bool requires_seekahead () const { return false; }
 	samplecnt_t seekahead_distance () const { return 0; }
@@ -538,6 +548,7 @@ class LIBARDOUR_API MIDIClock_TransportMaster : public TransportMaster, public T
 	bool ok() const;
 	bool starting() const;
 
+	samplecnt_t update_interval () const;
 	samplecnt_t resolution () const;
 	bool requires_seekahead () const { return false; }
 	void init ();
@@ -597,6 +608,7 @@ class LIBARDOUR_API Engine_TransportMaster : public TransportMaster
 	bool starting() const { return _starting; }
 	bool locked() const;
 	bool ok() const;
+	samplecnt_t update_interval () const;
 	samplecnt_t resolution () const { return 1; }
 	bool requires_seekahead () const { return false; }
 	bool sample_clock_synced() const { return true; }

libs/ardour/disk_reader.cc

@@ -345,7 +345,9 @@ DiskReader::run (BufferSet& bufs, samplepos_t start_sample, samplepos_t end_samp
 			}
 
 			if ((speed > 0) && (start_sample != playback_sample)) {
-				cerr << owner()->name() << " playback not aligned, jump ahead " << (start_sample - playback_sample) << endl;
+				stringstream str;
+				str << owner()->name() << " playback @ " << start_sample << " not aligned with " << playback_sample << " jump ahead " << (start_sample - playback_sample) << endl;
+				cerr << str.str();
 
 				if (can_internal_playback_seek (start_sample - playback_sample)) {
 					internal_playback_seek (start_sample - playback_sample);

libs/ardour/engine_slave.cc

@@ -125,3 +125,10 @@ Engine_TransportMaster::allow_request (TransportRequestSource src, TransportRequ
 
 	return true;
 }
+
+samplecnt_t
+Engine_TransportMaster::update_interval () const
+{
+	return AudioEngine::instance()->samples_per_cycle();
+}
+

libs/ardour/ltc_slave.cc

@@ -142,6 +142,16 @@ LTC_TransportMaster::parameter_changed (std::string const & p)
 	}
 }
 
+ARDOUR::samplecnt_t
+LTC_TransportMaster::update_interval() const
+{
+	if (timecode.rate) {
+		return AudioEngine::instance()->sample_rate() / timecode.rate;
+	}
+
+	return AudioEngine::instance()->sample_rate(); /* useless but what other answer is there? */
+}
+
 ARDOUR::samplecnt_t
 LTC_TransportMaster::resolution () const
 {
@@ -459,7 +469,7 @@ LTC_TransportMaster::process_ltc(samplepos_t const now)
 		samplepos_t cur_timestamp = sample.off_end + 1;
 		double ltc_speed = current.speed;
 
-		DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC S: %1 LS: %2  N: %3 L: %4\n", ltc_sample, current.position, cur_timestamp, current.timestamp));
+		DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC S: %1 LS: %2  N: %3 L: %4 span %5..%6\n", ltc_sample, current.position, cur_timestamp, current.timestamp, sample.off_start, sample.off_end));
 
 		if (cur_timestamp <= current.timestamp || current.timestamp == 0) {
 			DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC speed: UNCHANGED: %1\n", current.speed));
@@ -477,7 +487,7 @@ LTC_TransportMaster::process_ltc(samplepos_t const now)
 
 			DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC speed: %1\n", ltc_speed));
 		}
-
+		DEBUG_TRACE (DEBUG::LTC, string_compose ("update current to %1 %2 %3\n", ltc_sample, cur_timestamp, ltc_speed));
 		current.update (ltc_sample, cur_timestamp, ltc_speed);
 
 	} /* end foreach decoded LTC sample */

libs/ardour/midi_clock_slave.cc

@@ -375,6 +375,16 @@ MIDIClock_TransportMaster::starting() const
 	return false;
 }
 
+ARDOUR::samplecnt_t
+MIDIClock_TransportMaster::update_interval() const
+{
+	if (one_ppqn_in_samples) {
+		return resolution ();
+	}
+
+	return AudioEngine::instance()->sample_rate() / 120 / 4; /* pure guesswork */
+}
+
 ARDOUR::samplecnt_t
 MIDIClock_TransportMaster::resolution() const
 {

libs/ardour/mtc_slave.cc

@@ -164,6 +164,16 @@ MTC_TransportMaster::parameter_changed (std::string const & p)
 	}
 }
 
+ARDOUR::samplecnt_t
+MTC_TransportMaster::update_interval() const
+{
+	if (timecode.rate) {
+		return AudioEngine::instance()->sample_rate() / timecode.rate;
+	}
+
+	return AudioEngine::instance()->sample_rate(); /* useless but what other answer is there? */
+}
+
 ARDOUR::samplecnt_t
 MTC_TransportMaster::resolution () const
 {

libs/ardour/transport_master.cc

@@ -99,7 +99,7 @@ TransportMaster::speed_and_position (double& speed, samplepos_t& pos, samplepos_
 		return false;
 	}
 
-	if (last.timestamp && now > last.timestamp && now - last.timestamp > labs (seekahead_distance())) {
+	if (last.timestamp && now > last.timestamp && now - last.timestamp > (2.0 * update_interval())) {
 		/* no timecode for two cycles - conclude that it's stopped */
 
 		if (!Config->get_transport_masters_just_roll_when_sync_lost()) {
@@ -109,7 +109,7 @@ TransportMaster::speed_and_position (double& speed, samplepos_t& pos, samplepos_
 			when = last.timestamp;
 			_current_delta = 0;
 			// queue_reset (false);
-			DEBUG_TRACE (DEBUG::Slave, string_compose ("%1 not seen for 2 samples - reset pending, pos = %2\n", name(), pos));
+			DEBUG_TRACE (DEBUG::Slave, string_compose ("%1 not seen since %2 vs %3 (%4) with seekahead = %5 reset pending, pos = %6\n", name(), last.timestamp, now, (now - last.timestamp), update_interval(), pos));
 			return false;
 		}
 	}