X-Git-Url: https://git.carlh.net/gitweb/?a=blobdiff_plain;f=libs%2Fardour%2Fltc_slave.cc;h=bdb4fbead9ca115fd44c4223dfd327324a3951da;hb=06cc5e5240cc2bfeb4e22c742a5705566bd11dbe;hp=0e4f50b55a35b90bda69c291c744b3153e8a6f1d;hpb=f4ae7cc709d5c828bbba9bc0ca35ea72d87bb29f;p=ardour.git

diff --git a/libs/ardour/ltc_slave.cc b/libs/ardour/ltc_slave.cc
index 0e4f50b55a..bdb4fbead9 100644
--- a/libs/ardour/ltc_slave.cc
+++ b/libs/ardour/ltc_slave.cc
@@ -39,34 +39,41 @@ using namespace MIDI;
 using namespace PBD;
 using namespace Timecode;
 
-#define FLYWHEEL_TIMEOUT ( 3 * session.frame_rate() )
+#define FLYWHEEL_TIMEOUT ( 1 * session.frame_rate() )
 
 LTC_Slave::LTC_Slave (Session& s)
 	: session (s)
 {
-	frames_per_ltc_frame = session.frames_per_timecode_frame(); // XXX at most 30fps ?
+	frames_per_ltc_frame = session.frames_per_timecode_frame();
 	timecode.rate = session.timecode_frames_per_second();
 	timecode.drop  = session.timecode_drop_frames();
 
-	ltc_transport_pos = 0;
 	did_reset_tc_format = false;
 	delayedlocked = 10;
-	engine_dll_initstate = 0;
 	monotonic_cnt = 0;
+	fps_detected=false;
 
-	memset(&prev_ltc_frame, 0, sizeof(LTCFrame));
-
-	ltc_timecode = timecode_60; // track changes of LTC timecode
-	a3e_timecode = timecode_60; // track canges of Ardour's timecode
+	ltc_timecode = session.config.get_timecode_format();
+	a3e_timecode = session.config.get_timecode_format();
 	printed_timecode_warning = false;
+	ltc_detect_fps_cnt = ltc_detect_fps_max = 0;
+	memset(&prev_frame, 0, sizeof(LTCFrameExt));
 
 	decoder = ltc_decoder_create((int) frames_per_ltc_frame, 128 /*queue size*/);
+
+	session.config.ParameterChanged.connect_same_thread (config_connection, boost::bind (&LTC_Slave::parameter_changed, this, _1));
+	parse_timecode_offset();
 	reset();
-	//session.engine().Xrun.connect_same_thread (*this, boost::bind (&LTC_Slave::reset, this));
+	resync_latency();
+	session.Xrun.connect_same_thread (port_connections, boost::bind (&LTC_Slave::resync_xrun, this));
+	session.engine().GraphReordered.connect_same_thread (port_connections, boost::bind (&LTC_Slave::resync_latency, this));
 }
 
 LTC_Slave::~LTC_Slave()
 {
+	port_connections.drop_connections();
+	config_connection.disconnect();
+
 	if (did_reset_tc_format) {
 		session.config.set_timecode_format (saved_tc_format);
 	}
@@ -74,23 +81,30 @@ LTC_Slave::~LTC_Slave()
 	ltc_decoder_free(decoder);
 }
 
-bool
-LTC_Slave::give_slave_full_control_over_transport_speed() const
-{
-	return true; // DLL align to engine transport
-	// return false; // for Session-level computed varispeed
+void
+LTC_Slave::parse_timecode_offset() {
+	Timecode::Time offset_tc;
+	Timecode::parse_timecode_format(session.config.get_slave_timecode_offset(), offset_tc);
+	offset_tc.rate = session.timecode_frames_per_second();
+	offset_tc.drop = session.timecode_drop_frames();
+	session.timecode_to_sample(offset_tc, timecode_offset, false, false);
+	timecode_negative_offset = offset_tc.negative;
 }
 
-ARDOUR::framecnt_t
-LTC_Slave::resolution () const
+void
+LTC_Slave::parameter_changed (std::string const & p)
 {
-	return (framecnt_t) (frames_per_ltc_frame);
+	if (p == "slave-timecode-offset"
+			|| p == "timecode-format"
+			) {
+		parse_timecode_offset();
+	}
 }
 
 ARDOUR::framecnt_t
-LTC_Slave::seekahead_distance () const
+LTC_Slave::resolution () const
 {
-	return 0;
+	return (framecnt_t) (session.frame_rate() / 1000);
 }
 
 bool
@@ -105,59 +119,126 @@ LTC_Slave::ok() const
 	return true;
 }
 
+void
+LTC_Slave::resync_xrun()
+{
+	DEBUG_TRACE (DEBUG::LTC, "LTC resync_xrun()\n");
+	engine_dll_initstate = 0;
+}
+
+void
+LTC_Slave::resync_latency()
+{
+	DEBUG_TRACE (DEBUG::LTC, "LTC resync_latency()\n");
+	engine_dll_initstate = 0;
+
+	if (!session.deletion_in_progress() && session.ltc_output_io()) { /* check if Port exits */
+		boost::shared_ptr<Port> ltcport = session.ltc_input_port();
+		ltcport->get_connected_latency_range (ltc_slave_latency, false);
+	}
+}
+
 void
 LTC_Slave::reset()
 {
 	DEBUG_TRACE (DEBUG::LTC, "LTC reset()\n");
-	frames_in_sequence = 0;
-	ltc_detect_fps_cnt = ltc_detect_fps_max = 0;
 	last_timestamp = 0;
 	current_delta = 0;
 	transport_direction = 0;
 	ltc_speed = 0;
-	ltc_decoder_queue_flush(decoder);
+	engine_dll_initstate = 0;
 }
 
-int
-LTC_Slave::parse_ltc(const jack_nframes_t nframes, const jack_default_audio_sample_t * const in, const framecnt_t posinfo)
+void
+LTC_Slave::parse_ltc(const pframes_t nframes, const Sample* const in, const framecnt_t posinfo)
 {
-	jack_nframes_t i;
+	pframes_t i;
 	unsigned char sound[8192];
-	if (nframes > 8192) return 1;
+	if (nframes > 8192) {
+		/* TODO warn once or wrap, loop conversion below
+		 * does jack/A3 support > 8192 spp anyway?
+		 */
+		return;
+	}
 
 	for (i = 0; i < nframes; i++) {
 		const int snd=(int)rint((127.0*in[i])+128.0);
 		sound[i] = (unsigned char) (snd&0xff);
 	}
 	ltc_decoder_write(decoder, sound, nframes, posinfo);
-	return 0;
+	return;
+}
+
+bool
+LTC_Slave::equal_ltc_frame_time(LTCFrame *a, LTCFrame *b) {
+	if (       a->frame_units != b->frame_units
+		|| a->frame_tens  != b->frame_tens
+		|| a->dfbit       != b->dfbit
+		|| a->secs_units  != b->secs_units
+		|| a->secs_tens   != b->secs_tens
+		|| a->mins_units  != b->mins_units
+		|| a->mins_tens   != b->mins_tens
+		|| a->hours_units != b->hours_units
+		|| a->hours_tens  != b->hours_tens
+	     ) {
+		return false;
+	}
+	return true;
+}
+
+bool
+LTC_Slave::detect_discontinuity(LTCFrameExt *frame, int fps, bool fuzzy) {
+	bool discontinuity_detected = false;
+
+	if (fuzzy && (
+		  ( frame->reverse && prev_frame.ltc.frame_units == 0)
+		||(!frame->reverse && frame->ltc.frame_units == 0)
+		)) {
+		memcpy(&prev_frame, frame, sizeof(LTCFrameExt));
+		return false;
+	}
+
+	if (frame->reverse) {
+		ltc_frame_decrement(&prev_frame.ltc, fps, LTC_TV_525_60, 0);
+	} else {
+		ltc_frame_increment(&prev_frame.ltc, fps, LTC_TV_525_60, 0);
+	}
+	if (!equal_ltc_frame_time(&prev_frame.ltc, &frame->ltc)) {
+		discontinuity_detected = true;
+	}
+
+    memcpy(&prev_frame, frame, sizeof(LTCFrameExt));
+    return discontinuity_detected;
 }
 
 bool
 LTC_Slave::detect_ltc_fps(int frameno, bool df)
 {
+	bool fps_changed = false;
 	double detected_fps = 0;
 	if (frameno > ltc_detect_fps_max)
 	{
 		ltc_detect_fps_max = frameno;
 	}
 	ltc_detect_fps_cnt++;
-	if (ltc_detect_fps_cnt > 60)
-	{
-		if (ltc_detect_fps_cnt > ltc_detect_fps_max
-		    && (   ceil(timecode.rate) != (ltc_detect_fps_max + 1)
-			|| timecode.drop != df
-			)
-		    )
-		{
-			DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC detected FPS %1%2",
-					ltc_detect_fps_max + 1, timecode.drop ? "df" : ""));
+
+	if (ltc_detect_fps_cnt > 40) {
+		if (ltc_detect_fps_cnt > ltc_detect_fps_max) {
 			detected_fps = ltc_detect_fps_max + 1;
 			if (df) {
 				/* LTC df -> indicates fractional framerate */
-				detected_fps = detected_fps * 1000.0 / 1001.0;
+				if (Config->get_timecode_source_2997()) {
+					detected_fps = detected_fps * 999.0 / 1000.0;
+				} else {
+					detected_fps = detected_fps * 1000.0 / 1001.0;
+				}
+			}
+
+			if (timecode.rate != detected_fps || timecode.drop != df) {
+				DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC detected FPS: %1%2\n", detected_fps, df?"df":"ndf"));
+			} else {
+				detected_fps = 0; /* no cange */
 			}
-			DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC detected FPS: %1%2\n", detected_fps, df?"df":"ndf"));
 		}
 		ltc_detect_fps_cnt = ltc_detect_fps_max = 0;
 	}
@@ -169,92 +250,72 @@ LTC_Slave::detect_ltc_fps(int frameno, bool df)
 		frames_per_ltc_frame = double(session.frame_rate()) / timecode.rate;
 		DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC reset to FPS: %1%2 ; audio-frames per LTC: %3\n",
 				detected_fps, df?"df":"ndf", frames_per_ltc_frame));
-		return true; // reset()
+		fps_changed=true;
 	}
 
 	/* poll and check session TC */
-	if (1) {
-		TimecodeFormat tc_format = apparent_timecode_format();
-		TimecodeFormat cur_timecode = session.config.get_timecode_format();
-		if (Config->get_timecode_sync_frame_rate()) {
-			/* enforce time-code */
-			if (!did_reset_tc_format) {
-				saved_tc_format = cur_timecode;
-				did_reset_tc_format = true;
-			}
-			if (cur_timecode != tc_format) {
-				warning << string_compose(_("Session framerate adjusted from %1 TO: LTC's %2."),
+	TimecodeFormat tc_format = apparent_timecode_format();
+	TimecodeFormat cur_timecode = session.config.get_timecode_format();
+
+	if (Config->get_timecode_sync_frame_rate()) {
+		/* enforce time-code */
+		if (!did_reset_tc_format) {
+			saved_tc_format = cur_timecode;
+			did_reset_tc_format = true;
+		}
+		if (cur_timecode != tc_format) {
+			if (ceil(Timecode::timecode_to_frames_per_second(cur_timecode)) != ceil(Timecode::timecode_to_frames_per_second(tc_format))) {
+				warning << string_compose(_("Session framerate adjusted from %1 to LTC's %2."),
 						Timecode::timecode_format_name(cur_timecode),
 						Timecode::timecode_format_name(tc_format))
 					<< endmsg;
 			}
 			session.config.set_timecode_format (tc_format);
-		} else {
-			/* only warn about TC mismatch */
-			if (ltc_timecode != tc_format) printed_timecode_warning = false;
-			if (a3e_timecode != cur_timecode) printed_timecode_warning = false;
+		}
+	} else {
+		/* only warn about TC mismatch */
+		if (ltc_timecode != tc_format) printed_timecode_warning = false;
+		if (a3e_timecode != cur_timecode) printed_timecode_warning = false;
 
-			if (cur_timecode != tc_format && ! printed_timecode_warning) {
+		if (cur_timecode != tc_format && ! printed_timecode_warning) {
+			if (ceil(Timecode::timecode_to_frames_per_second(cur_timecode)) != ceil(Timecode::timecode_to_frames_per_second(tc_format))) {
 				warning << string_compose(_("Session and LTC framerate mismatch: LTC:%1 Session:%2."),
 						Timecode::timecode_format_name(tc_format),
 						Timecode::timecode_format_name(cur_timecode))
 					<< endmsg;
-				printed_timecode_warning = true;
 			}
+			printed_timecode_warning = true;
 		}
-		ltc_timecode = tc_format;
-		a3e_timecode = cur_timecode;
 	}
-	return false;
-}
+	ltc_timecode = tc_format;
+	a3e_timecode = cur_timecode;
 
-bool
-LTC_Slave::detect_ltc_discontinuity(LTCFrameExt *frame) {
-	bool discontinuity_detected = false;
-	/* detect discontinuities */
-	if (frame->reverse) {
-		ltc_frame_decrement(&prev_ltc_frame, ceil(timecode.rate), 0);
-	} else {
-		ltc_frame_increment(&prev_ltc_frame, ceil(timecode.rate), 0);
-	}
-
-	if (memcmp(&prev_ltc_frame, &frame->ltc, sizeof(LTCFrame))) {
-		discontinuity_detected = true;
-	}
-	memcpy(&prev_ltc_frame, &frame->ltc, sizeof(LTCFrame));
-
-	/* notfify about discontinuities */
-	if (frames_in_sequence > 0 && discontinuity_detected) {
-		DEBUG_TRACE (DEBUG::LTC, "# LTC DISCONTINUITY\n");
-		frames_in_sequence=0;
-		return true;
-	}
-	frames_in_sequence++;
-
-	return false;
+	return fps_changed;
 }
 
-bool
-LTC_Slave::process_ltc(framepos_t const now, framepos_t const sess_pos, framecnt_t const nframes)
+void
+LTC_Slave::process_ltc(framepos_t const /*now*/)
 {
-	bool have_frame = false;
-	DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC Process eng-tme: %1 eng-pos: %2\n", now, sess_pos));
-
 	LTCFrameExt frame;
-	while (ltc_decoder_read(decoder,&frame)) {
-		bool reinitialize_ltc_dll = false;
+	enum LTC_TV_STANDARD tv_standard = LTC_TV_625_50;
+	while (ltc_decoder_read(decoder, &frame)) {
 		SMPTETimecode stime;
 
 		ltc_frame_to_time(&stime, &frame.ltc, 0);
 		timecode.negative  = false;
 		timecode.subframes  = 0;
+
 		/* set timecode.rate and timecode.drop: */
-		if (detect_ltc_fps(stime.frame, (frame.ltc.dfbit)? true : false)) {
-			reset();
-			break;
+		bool ltc_is_static = equal_ltc_frame_time(&prev_frame.ltc, &frame.ltc);
+
+		if (detect_discontinuity(&frame, ceil(timecode.rate), !fps_detected)) {
+			if (fps_detected) { ltc_detect_fps_cnt = ltc_detect_fps_max = 0; }
+			fps_detected=false;
 		}
-		if (detect_ltc_discontinuity(&frame)) {
-			ltc_discontinuity = true;
+
+		if (!ltc_is_static && detect_ltc_fps(stime.frame, (frame.ltc.dfbit)? true : false)) {
+			reset();
+			fps_detected=true;
 		}
 
 #if 0 // Devel/Debug
@@ -268,34 +329,43 @@ LTC_Slave::process_ltc(framepos_t const now, framepos_t const sess_pos, framecnt
 			frame.off_end,
 			frame.reverse ? " R" : "  "
 			);
-
-		if (frames_in_sequence < 1) {
-			fprintf(stdout, " ####### FIRST LTC FRAME in SEQ #######\n");
-		}
-
-		if (ltc_discontinuity) {
-			fprintf(stdout, " ####### LTC DISCONTINUITY #######\n");
-		}
 #endif
 
-		if (frames_in_sequence < 1) {
-			continue;
-		}
-
 		/* when a full LTC frame is decoded, the timecode the LTC frame
 		 * is referring has just passed.
 		 * So we send the _next_ timecode which
 		 * is expected to start at the end of the current frame
 		 */
 		int fps_i = ceil(timecode.rate);
+
+		switch(fps_i) {
+			case 30:
+				if (timecode.drop) {
+					tv_standard = LTC_TV_525_60;
+				} else {
+					tv_standard = LTC_TV_1125_60;
+				}
+				break;
+			case 25:
+				tv_standard = LTC_TV_625_50;
+				break;
+			default:
+				tv_standard = LTC_TV_FILM_24; /* == LTC_TV_1125_60 == no offset, 24,30fps BGF */
+				break;
+		}
+
 		if (!frame.reverse) {
-			ltc_frame_increment(&frame.ltc, fps_i , 0);
+			ltc_frame_increment(&frame.ltc, fps_i, tv_standard, 0);
 			ltc_frame_to_time(&stime, &frame.ltc, 0);
+			transport_direction = 1;
+			frame.off_start -= ltc_frame_alignment(session.frames_per_timecode_frame(), tv_standard);
+			frame.off_end -= ltc_frame_alignment(session.frames_per_timecode_frame(), tv_standard);
 		} else {
-			ltc_frame_decrement(&frame.ltc, fps_i , 0);
+			ltc_frame_decrement(&frame.ltc, fps_i, tv_standard, 0);
 			int off = frame.off_end - frame.off_start;
-			frame.off_start += off;
-			frame.off_end += off;
+			frame.off_start += off - ltc_frame_alignment(session.frames_per_timecode_frame(), tv_standard);
+			frame.off_end += off - ltc_frame_alignment(session.frames_per_timecode_frame(), tv_standard);
+			transport_direction = -1;
 		}
 
 		timecode.hours   = stime.hours;
@@ -308,210 +378,177 @@ LTC_Slave::process_ltc(framepos_t const now, framepos_t const sess_pos, framecnt
 		Timecode::timecode_to_sample (timecode, ltc_frame, true, false,
 			double(session.frame_rate()),
 			session.config.get_subframes_per_frame(),
-			session.config.get_timecode_offset_negative(), session.config.get_timecode_offset()
+			timecode_negative_offset, timecode_offset
 			);
 
-		/* (frame.off_end + 1) = start of next LTC frame */
-		double poff = (frame.off_end + 1 - now);
-		ltc_transport_pos = ltc_frame - poff;
-
-#if 0 // vari-speed LTC, no DLL
-			frames_per_ltc_frame = 1 + frame.off_end - frame.off_start;
-#else
-			frames_per_ltc_frame = (double(session.frame_rate()) / timecode.rate);
-#endif
-
-		DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC frame: %1 poff: %2 pos: %3\n", ltc_frame, poff, ltc_transport_pos));
-
-		if (ltc_discontinuity) {
-			ltc_discontinuity=false;
-			if (ltc_speed==0
-					|| !locked()
-					|| (ltc_transport_pos - sess_pos) > FLYWHEEL_TIMEOUT)
-			{
-				engine_dll_initstate = 0;
-				reset();
-			}
-			reinitialize_ltc_dll = true;
-		}
-
-		if (last_timestamp == 0
-			|| ((now - last_timestamp) > FLYWHEEL_TIMEOUT)
-			|| (abs(current_delta) >  FLYWHEEL_TIMEOUT) // TODO LTC-delta not engine delta
-			|| (frame.reverse && transport_direction != -1)
-			|| (!frame.reverse && transport_direction != 1)
-			) {
-			reinitialize_ltc_dll = true;
-			engine_dll_initstate = 0;
-			reset();
-		}
-
-		if (reinitialize_ltc_dll) {
-			init_ltc_dll(ltc_transport_pos, frames_per_ltc_frame);
-
-			if (ltc_speed==0 || !locked()) {
-				if (frame.reverse) {
-					transport_direction = -1;
-					ltc_transport_pos -= nframes * rint((2 * frames_per_ltc_frame + poff)/nframes);
-				} else {
-					transport_direction = 1;
-					ltc_transport_pos += nframes * rint((2 * frames_per_ltc_frame + poff)/nframes);
-				}
-			}
-
+		framepos_t cur_timestamp = frame.off_end + 1;
+		DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC F: %1 LF: %2  N: %3 L: %4\n", ltc_frame, last_ltc_frame, cur_timestamp, last_timestamp));
+		if (frame.off_end + 1 <= last_timestamp || last_timestamp == 0) {
+			DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC speed: UNCHANGED: %1\n", ltc_speed));
 		} else {
-			// update DLL
-			double e = (double(ltc_frame) - poff - double(sess_pos));
-			t0 = t1;
-			t1 += b * e + e2;
-			e2 += c * e;
-
-			ltc_speed = (t1 - t0) / frames_per_ltc_frame;
-			current_delta = (ltc_transport_pos - sess_pos);
-			DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC DLL t0:%1 t1:%2 err:%3 spd:%4 ddt:%5\n", t0, t1, e, ltc_speed, e2 - frames_per_ltc_frame));
+			ltc_speed = double(ltc_frame - last_ltc_frame) / double(cur_timestamp - last_timestamp);
+			DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC speed: %1\n", ltc_speed));
+		}
 
+		if (fabs(ltc_speed) > 10.0) {
+			ltc_speed = 0;
 		}
 
-		/* the are equivalent
-		 * TODO: choose the value with larger diff ->
-		 * minimize roundig errors when extrapolating
-		 */
-#if 1
-		last_timestamp = now;
-		last_ltc_frame = ltc_transport_pos;
-#else
 		last_timestamp = frame.off_end + 1;
 		last_ltc_frame = ltc_frame;
-#endif
-
-		have_frame = true;
 	} /* end foreach decoded LTC frame */
-
-	return have_frame;
 }
 
 void
-LTC_Slave::init_ltc_dll(framepos_t const tme, double const dt)
+LTC_Slave::init_engine_dll (framepos_t pos, int32_t inc)
 {
-	omega = 2.0 * M_PI * dt / double(session.frame_rate());
+	double omega = 2.0 * M_PI * double(inc) / double(session.frame_rate());
 	b = 1.4142135623730950488 * omega;
 	c = omega * omega;
 
-	e2 = dt;
-	t0 = double(tme);
+	e2 = double(ltc_speed * inc);
+	t0 = double(pos);
 	t1 = t0 + e2;
-	DEBUG_TRACE (DEBUG::LTC, string_compose ("[re-]init LTC DLL %1 %2 %3\n", t0, t1, e2));
-}
-
-void
-LTC_Slave::init_engine_dll (framepos_t pos, framepos_t inc)
-{
-	/* the bandwidth of the DLL is a trade-off,
-	 * because the max-speed of the transport in ardour is
-	 * limited to +-8.0, a larger bandwidth would cause oscillations
-	 *
-	 * But this is only really a problem if the user performs manual
-	 * seeks while transport is running and slaved to LTC.
-	 */
-	oe = 2.0 * M_PI * double(inc/2.0) / double(session.frame_rate());
-	be = 1.4142135623730950488 * oe;
-	ce = oe * oe;
-
-	ee2 = double(transport_direction * inc);
-	te0 = double(pos);
-	te1 = te0 + ee2;
-	DEBUG_TRACE (DEBUG::LTC, string_compose ("[re-]init Engine DLL %1 %2 %3\n", te0, te1, ee2));
+	DEBUG_TRACE (DEBUG::LTC, string_compose ("[re-]init Engine DLL %1 %2 %3\n", t0, t1, e2));
 }
 
 /* main entry point from session_process.cc
- * called from jack_process callback context
- * so it is OK to use jack_port_get_buffer() etc
+ * called from process callback context
+ * so it is OK to use get_buffer()
  */
 bool
 LTC_Slave::speed_and_position (double& speed, framepos_t& pos)
 {
-	//framepos_t now = session.engine().frame_time_at_cycle_start();
-	//framepos_t now = session.engine().processed_frames();
-	framepos_t now = monotonic_cnt;
+	bool engine_init_called = false;
+	framepos_t now = session.engine().sample_time_at_cycle_start();
 	framepos_t sess_pos = session.transport_frame(); // corresponds to now
-	framecnt_t nframes = session.engine().frames_per_cycle();
-	jack_default_audio_sample_t *in;
-	jack_latency_range_t ltc_latency;
+	framecnt_t nframes = session.engine().samples_per_cycle();
+
+	Sample* in;
 
-	monotonic_cnt += nframes;
+	boost::shared_ptr<Port> ltcport = session.ltc_input_port();
 
-	boost::shared_ptr<Port> ltcport = session.engine().ltc_input_port();
-	ltcport->get_connected_latency_range(ltc_latency, false);
-	in = (jack_default_audio_sample_t*) jack_port_get_buffer (ltcport->jack_port(), nframes);
+	in = (Sample*) AudioEngine::instance()->port_engine().get_buffer (ltcport->port_handle(), nframes);
 
-	DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC_Slave::speed_and_position - TID:%1 | latency: %2\n", ::pthread_self(), ltc_latency.max));
+	frameoffset_t skip = now - (monotonic_cnt + nframes);
+	monotonic_cnt = now;
+	DEBUG_TRACE (DEBUG::LTC, string_compose ("speed_and_position - TID:%1 | latency: %2 | skip %3\n", ::pthread_self(), ltc_slave_latency.max, skip));
 
 	if (last_timestamp == 0) {
 		engine_dll_initstate = 0;
 		delayedlocked++;
 	}
-	else if (engine_dll_initstate != transport_direction) {
+	else if (engine_dll_initstate != transport_direction && ltc_speed != 0) {
 		engine_dll_initstate = transport_direction;
-		init_engine_dll(last_ltc_frame, session.engine().frames_per_cycle());
+		init_engine_dll(last_ltc_frame + rint(ltc_speed * double(2 * nframes + now - last_timestamp)),
+				session.engine().samples_per_cycle());
+		engine_init_called = true;
 	}
 
 	if (in) {
-		parse_ltc(nframes, in, now  + ltc_latency.max );
-		if (!process_ltc(now, sess_pos, nframes) && ltc_speed != 0) {
+		DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC Process eng-tme: %1 eng-pos: %2\n", now, sess_pos));
+		/* when the jack-graph changes and if ardour performs
+		 * locates, the audioengine is stopped (skipping frames) while
+		 * jack [time] moves along.
+		 */
+		if (skip > 0) {
+			DEBUG_TRACE (DEBUG::LTC, string_compose("engine skipped %1 frames. Feeding silence to LTC parser.\n", skip));
+			if (skip >= 8192) skip = 8192;
+			unsigned char sound[8192];
+			memset(sound, 0, sizeof(char) * skip);
+			ltc_decoder_write(decoder, sound, nframes, now);
+		} else if (skip != 0) {
+			/* this should never happen. it may if monotonic_cnt, now overflow on 64bit */
+			DEBUG_TRACE (DEBUG::LTC, string_compose("engine skipped %1 frames\n", skip));
+			reset();
 		}
-	}
 
-	/* interpolate position according to speed and time since last LTC-frame*/
-	double speed_flt = ltc_speed;
-	framecnt_t elapsed;
-	if (speed_flt == 0.0f) {
-		elapsed = 0;
-	} else {
-		/* scale elapsed time by the current LTC speed */
-		if (last_timestamp && (now > last_timestamp)) {
-			elapsed = (now - last_timestamp) * speed_flt;
-		} else {
-			elapsed = 0;
-		}
-		/* update engine DLL and calculate speed */
-		const double e = double (last_ltc_frame + elapsed - sess_pos);
-		te0 = te1;
-		te1 += be * e + ee2;
-		ee2 += ce * e;
-		speed_flt = (te1 - te0) / double(session.engine().frames_per_cycle());
-		DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC engine DLL t0:%1 t1:%2 err:%3 spd:%4 ddt:%5\n", te0, te1, e, speed_flt, ee2 - session.engine().frames_per_cycle() ));
+		parse_ltc(nframes, in, now - ltc_slave_latency.max );
+		process_ltc(now);
 	}
 
-	pos = last_ltc_frame + elapsed;
-	speed = speed_flt;
-	current_delta = (pos - sess_pos);
-
-	DEBUG_TRACE (DEBUG::LTC, string_compose ("LTCsync spd: %1 pos: %2 | last-pos: %3 elapsed: %4 delta: %5\n",
-						 speed, pos, last_ltc_frame, elapsed, current_delta));
-
-	if (last_timestamp != 0 /* && frames_in_sequence > 8*/) {
+	if (last_timestamp == 0) {
+		DEBUG_TRACE (DEBUG::LTC, "last timestamp == 0\n");
+		speed = 0;
+		pos = session.transport_frame();
+		return true;
+	} else if (ltc_speed != 0) {
 		delayedlocked = 0;
 	}
 
-	if (last_timestamp == 0 || ((now - last_timestamp) > FLYWHEEL_TIMEOUT)) {
-		DEBUG_TRACE (DEBUG::LTC, "LTC no-signal - reset\n");
+	if (abs(now - last_timestamp) > FLYWHEEL_TIMEOUT) {
+		DEBUG_TRACE (DEBUG::LTC, "flywheel timeout\n");
 		reset();
-		engine_dll_initstate = 0;
 		speed = 0;
 		pos = session.transport_frame();
 		return true;
 	}
 
-	if (last_timestamp != 0  && ltc_speed != 0 && ((ltc_transport_pos < 0) || (labs(current_delta) > 10 * session.frame_rate()))) {
-		DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC large drift. %1\n", current_delta));
-		// XXX only re-init engine DLL ?
+	/* it take 2 cycles from naught to rolling.
+	 * during these to initial cycles the speed == 0
+	 *
+	 * the first cycle:
+	 * DEBUG::Slave: slave stopped, move to NNN
+	 * DEBUG::Transport: Request forced locate to NNN
+	 * DEBUG::Slave: slave state 0 @ NNN speed 0 cur delta VERY-LARGE-DELTA avg delta 1800
+	 * DEBUG::Slave: silent motion
+	 * DEBUG::Transport: realtime stop @ NNN
+	 * DEBUG::Transport: Butler transport work, todo = PostTransportStop,PostTransportLocate,PostTransportClearSubstate
+	 *
+	 * [engine skips frames to locate, jack time keeps rolling on]
+	 *
+	 * the second cycle:
+	 *
+	 * DEBUG::LTC: [re-]init Engine DLL
+	 * DEBUG::Slave: slave stopped, move to NNN+
+	 * ...
+	 *
+	 * we need to seek two cycles ahead: 2 * nframes
+	 */
+	if (engine_dll_initstate == 0) {
+		DEBUG_TRACE (DEBUG::LTC, "engine DLL not initialized. ltc_speed\n");
+		speed = 0;
+		pos = last_ltc_frame + rint(ltc_speed * double(2 * nframes + now - last_timestamp));
+		return true;
+	}
+
+	/* interpolate position according to speed and time since last LTC-frame*/
+	double speed_flt = ltc_speed;
+	double elapsed = (now - last_timestamp) * speed_flt;
+
+	if (!engine_init_called) {
+		const double e = elapsed + double (last_ltc_frame - sess_pos);
+		t0 = t1;
+		t1 += b * e + e2;
+		e2 += c * e;
+		speed_flt = (t1 - t0) / double(session.engine().samples_per_cycle());
+		DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC engine DLL t0:%1 t1:%2 err:%3 spd:%4 ddt:%5\n", t0, t1, e, speed_flt, e2 - session.engine().samples_per_cycle() ));
+	} else {
+		DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC adjusting elapsed (no DLL) from %1 by %2\n", elapsed, (2 * nframes * ltc_speed)));
+		speed_flt = 0;
+		elapsed += 2.0 * nframes * ltc_speed; /* see note above */
+	}
+
+	pos = last_ltc_frame + rint(elapsed);
+	speed = speed_flt;
+	current_delta = (pos - sess_pos);
+
+	if (((pos < 0) || (labs(current_delta) > 2 * session.frame_rate()))) {
+		DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC large drift: %1\n", current_delta));
 		reset();
-		engine_dll_initstate = 0;
 		speed = 0;
 		pos = session.transport_frame();
 		return true;
 	}
 
+	DEBUG_TRACE (DEBUG::LTC, string_compose ("LTCsync spd: %1 pos: %2 | last-pos: %3 elapsed: %4 delta: %5\n",
+						 speed, pos, last_ltc_frame, elapsed, current_delta));
+
+	/* provide a .1% deadzone to lock the speed */
+	if (fabs(speed - 1.0) <= 0.001) {
+	        speed = 1.0;
+	}
+
 	return true;
 }
 
@@ -523,9 +560,9 @@ LTC_Slave::apparent_timecode_format () const
 	else if (timecode.rate == 25 && !timecode.drop)
 		return timecode_25;
 	else if (rint(timecode.rate * 100) == 2997 && !timecode.drop)
-		return timecode_2997;
+		return (Config->get_timecode_source_2997() ? timecode_2997000 : timecode_2997);
 	else if (rint(timecode.rate * 100) == 2997 &&  timecode.drop)
-		return timecode_2997drop;
+		return (Config->get_timecode_source_2997() ? timecode_2997000drop : timecode_2997drop);
 	else if (timecode.rate == 30 &&  timecode.drop)
 		return timecode_2997drop; // timecode_30drop; // LTC counting to 30 frames w/DF *means* 29.97 df
 	else if (timecode.rate == 30 && !timecode.drop)
@@ -547,15 +584,14 @@ LTC_Slave::approximate_current_position() const
 std::string
 LTC_Slave::approximate_current_delta() const
 {
-	char delta[24];
-	if (last_timestamp == 0 || frames_in_sequence < 2) {
-		snprintf(delta, sizeof(delta), "---");
+	char delta[80];
+	if (last_timestamp == 0 || engine_dll_initstate == 0) {
+		snprintf(delta, sizeof(delta), "\u2012\u2012\u2012\u2012");
 	} else if ((monotonic_cnt - last_timestamp) > 2 * frames_per_ltc_frame) {
-		snprintf(delta, sizeof(delta), "flywheel");
+		snprintf(delta, sizeof(delta), _("flywheel"));
 	} else {
-		// TODO if current_delta > 1 frame -> display timecode.
-		// delta >0 if A3's transport is _behind_ LTC
-		snprintf(delta, sizeof(delta), "%+4" PRIi64 " sm", current_delta);
+		snprintf(delta, sizeof(delta), "\u0394<span foreground=\"green\" face=\"monospace\" >%s%s%" PRIi64 "</span>sm",
+				LEADINGZERO(abs(current_delta)), PLUSMINUS(-current_delta), abs(current_delta));
 	}
 	return std::string(delta);
 }