add LTC generator

git-svn-id: svn://localhost/ardour2/branches/3.0@13315 d708f5d6-7413-0410-9779-e7cbd77b26cf

10 files changed, 473 insertions, 1 deletions

diff --git a/libs/ardour/ardour/audioengine.h b/libs/ardour/ardour/audioengine.h
index 49e3c15457..a908cf0bc1 100644
--- a/libs/ardour/ardour/audioengine.h
+++ b/libs/ardour/ardour/audioengine.h
@@ -261,6 +261,7 @@ _	   the regular process() call to session->process() is not made.
 	int create_process_thread (boost::function<void()>, pthread_t*, size_t stacksize);
 
         boost::shared_ptr<Port> ltc_input_port() const { return _ltc_input; }
+        boost::shared_ptr<Port> ltc_output_port() const { return _ltc_output; }
 
 private:
 	static AudioEngine*       _instance;
@@ -292,6 +293,7 @@ private:
 	ProcessThread*            _main_thread;
 
         boost::shared_ptr<Port>   _ltc_input;
+        boost::shared_ptr<Port>   _ltc_output;
         void reconnect_ltc ();
 
 	SerializedRCUManager<Ports> ports;
diff --git a/libs/ardour/ardour/rc_configuration_vars.h b/libs/ardour/ardour/rc_configuration_vars.h
index 9432b7230f..b05b90fa14 100644
--- a/libs/ardour/ardour/rc_configuration_vars.h
+++ b/libs/ardour/ardour/rc_configuration_vars.h
@@ -52,6 +52,8 @@ CONFIG_VARIABLE (bool, timecode_sync_frame_rate, "timecode-sync-frame-rate", tru
 CONFIG_VARIABLE (bool, timecode_source_is_synced, "timecode-source-is-synced", true)
 CONFIG_VARIABLE (SyncSource, sync_source, "sync-source", JACK)
 CONFIG_VARIABLE (std::string, ltc_source_port, "ltc-source-port", "system:capture_1")
+CONFIG_VARIABLE (bool, send_ltc, "send-ltc", false)
+CONFIG_VARIABLE (std::string, ltc_output_port, "ltc-sink-port", "")
 
 /* control surfaces */
 
diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index df04971e02..c9389f60b1 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -64,6 +64,10 @@
 #include <jack/session.h>
 #endif
 
+#ifdef HAVE_LTC
+#include <ltc.h>
+#endif
+
 class XMLTree;
 class XMLNode;
 struct _AEffect;
@@ -1178,6 +1182,23 @@ class Session : public PBD::StatefulDestructible, public PBD::ScopedConnectionLi
 
 	int send_midi_time_code_for_cycle (framepos_t, framepos_t, pframes_t nframes);
 
+#ifdef HAVE_LTC
+	LTCEncoder*       ltc_encoder;
+	ltcsnd_sample_t*  ltc_enc_buf;
+
+	Timecode::TimecodeFormat ltc_enc_tcformat;
+	framepos_t        ltc_enc_pos;
+	int32_t           ltc_buf_off;
+	int32_t           ltc_buf_len;
+	int32_t           ltc_enc_byte;
+	double            ltc_speed;
+
+	void ltc_tx_initialize();
+	void ltc_tx_cleanup();
+	void ltc_tx_reset();
+	int  ltc_tx_send_time_code_for_cycle (framepos_t, framepos_t, double, double, pframes_t nframes);
+#endif
+
 	void reset_record_status ();
 
 	int no_roll (pframes_t nframes);
diff --git a/libs/ardour/audioengine.cc b/libs/ardour/audioengine.cc
index cc04c343e1..ef3899bf2f 100644
--- a/libs/ardour/audioengine.cc
+++ b/libs/ardour/audioengine.cc
@@ -79,6 +79,7 @@ AudioEngine::AudioEngine (string client_name, string session_uuid)
 	, m_meter_thread (0)
 	, _main_thread (0)
 	, _ltc_input ()
+	, _ltc_output ()
 	, ports (new Ports)
 {
 	_instance = this; /* singleton */
@@ -94,6 +95,12 @@ AudioEngine::AudioEngine (string client_name, string session_uuid)
 #ifdef HAVE_LTC
 	_ltc_input = register_port (DataType::AUDIO, _("LTC in"), true);
 
+	/* register_port() would allocate buffers and pass a shadow copy
+	 * which is subject to ardour's route buffering behavioud and
+	 * not suitable for generating LTC independent of transport state.
+	 */
+	_ltc_output.reset(new AudioPort ("LTC out", Port::IsOutput));
+
 	/* As of October 2012, the LTC source port is the only thing that needs
 	 * to care about Config parameters, so don't bother to listen if we're
 	 * not doing LTC stuff. This might change if other parameters show up
@@ -107,6 +114,11 @@ AudioEngine::AudioEngine (string client_name, string session_uuid)
 AudioEngine::~AudioEngine ()
 {
 	config_connection.disconnect ();
+#ifdef HAVE_LTC
+	if (_ltc_output && _ltc_output->jack_port()) {
+		jack_port_disconnect (_jack, _ltc_output->jack_port());
+	}
+#endif
 
 	{
 		Glib::Threads::Mutex::Lock tm (_process_lock);
@@ -537,6 +549,15 @@ AudioEngine::process_callback (pframes_t nframes)
 	}
 
 	if (_session == 0) {
+#ifdef HAVE_LTC
+		// silence LTC
+		jack_default_audio_sample_t *out;
+		boost::shared_ptr<Port> ltcport = ltc_output_port();
+		if (ltcport && ltcport->jack_port()) {
+			out = (jack_default_audio_sample_t*) jack_port_get_buffer (ltcport->jack_port(), nframes);
+			if (out) memset(out, 0, nframes * sizeof(jack_default_audio_sample_t));
+		}
+#endif
 
 		if (!_freewheeling) {
 			MIDI::Manager::instance()->cycle_start(nframes);
@@ -1644,6 +1665,9 @@ AudioEngine::parameter_changed (const std::string& s)
 	if (s == "ltc-source-port") {
 		reconnect_ltc ();
 	}
+	else if (s == "ltc-sink-port") {
+		// TODO
+	}
 
 }
 
diff --git a/libs/ardour/session.cc b/libs/ardour/session.cc
index 3a18b1f7f7..e742dd372f 100644
--- a/libs/ardour/session.cc
+++ b/libs/ardour/session.cc
@@ -153,6 +153,9 @@ Session::Session (AudioEngine &eng,
 	, _suspend_timecode_transmission (0)
 {
 	_locations = new Locations (*this);
+#ifdef HAVE_LTC
+	ltc_encoder = NULL;
+#endif
 
 	if (how_many_dsp_threads () > 1) {
 		/* For now, only create the graph if we are using >1 DSP threads, as
@@ -238,6 +241,10 @@ Session::destroy ()
 
 	Port::PortDrop (); /* EMIT SIGNAL */
 
+#ifdef HAVE_LTC
+	ltc_tx_cleanup();
+#endif
+
 	/* clear history so that no references to objects are held any more */
 
 	_history.clear ();
diff --git a/libs/ardour/session_ltc.cc b/libs/ardour/session_ltc.cc
new file mode 100644
index 0000000000..2982255024
--- /dev/null
+++ b/libs/ardour/session_ltc.cc
@@ -0,0 +1,393 @@
+/*
+  Copyright (C) 2012 Paul Davis
+  Written by Robin Gareus <robin@gareus.org>
+
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+
+*/
+#include "ardour/debug.h"
+#include "timecode/time.h"
+#include "ardour/session.h"
+#include "ardour/audioengine.h"
+#include "ardour/audio_port.h"
+
+#include "i18n.h"
+
+using namespace std;
+using namespace ARDOUR;
+using namespace MIDI;
+using namespace PBD;
+using namespace Timecode;
+
+//#define LTC_GEN_FRAMEDBUG
+
+void
+Session::ltc_tx_initialize()
+{
+	ltc_enc_tcformat = config.get_timecode_format();
+
+	DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX init sr: %1 fps: %2\n", nominal_frame_rate(), timecode_to_frames_per_second(ltc_enc_tcformat)));
+	ltc_encoder = ltc_encoder_create(nominal_frame_rate(),
+			timecode_to_frames_per_second(ltc_enc_tcformat),
+			0);
+
+	ltc_encoder_set_bufsize(ltc_encoder, nominal_frame_rate(), 23.0);
+
+	/* buffersize for 1 LTC frame: (1 + sample-rate / fps) bytes
+	 * usually returned by ltc_encoder_get_buffersize(encoder)
+	 *
+	 * since the fps can change and A3's  min fps: 24000/1001 */
+	ltc_enc_buf = (ltcsnd_sample_t*) calloc((nominal_frame_rate() / 23), sizeof(ltcsnd_sample_t));
+	ltc_speed = 0;
+	ltc_tx_reset();
+}
+
+void
+Session::ltc_tx_cleanup()
+{
+	DEBUG_TRACE (DEBUG::LTC, "LTC TX cleanup\n");
+	if (ltc_enc_buf) free(ltc_enc_buf);
+	ltc_encoder_free(ltc_encoder);
+	ltc_encoder = NULL;
+}
+
+void
+Session::ltc_tx_reset()
+{
+	DEBUG_TRACE (DEBUG::LTC, "LTC TX reset\n");
+	ltc_enc_pos = -1; // force re-start
+	ltc_buf_len = 0;
+	ltc_buf_off = 0;
+	ltc_enc_byte = 0;
+}
+
+int
+Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end_frame, 
+		double target_speed, double current_speed,
+		pframes_t nframes)
+{
+	assert(nframes > 0);
+
+	const float smult = 2.0/(3.0*255.0);
+	SMPTETimecode tc;
+	jack_default_audio_sample_t *out;
+	pframes_t txf = 0;
+	boost::shared_ptr<Port> ltcport = engine().ltc_output_port();
+
+	if (!ltc_encoder || !ltc_enc_buf || !ltcport || ! ltcport->jack_port()) return 0;
+
+	out = (jack_default_audio_sample_t*) jack_port_get_buffer (ltcport->jack_port(), nframes);
+	if (!out) return 0;
+
+	if (engine().freewheeling() || !Config->get_send_ltc()) {
+		memset(out, 0, nframes * sizeof(jack_default_audio_sample_t));
+		return nframes;
+	}
+
+	DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX %1 to %2 / %3\n", start_frame, end_frame, nframes));
+
+	/* all systems go. Now here's the plan:
+	 *
+	 *  1) check if fps has changed
+	 *  2) check direction of encoding, calc speed
+	 *  3) calculate frame and byte to send aligned to jack-period size
+	 *  4) check if it's the frame/byte that is already in the queue
+	 *  5) if (4) mismatch, re-calculate offset of LTC frame relative to period size
+	 *  6) actual LTC audio output
+	 *  6a) send remaining part of already queued frame; break on nframes
+	 *  6b) encode new LTC-frame byte
+	 *  6c) goto 6a
+	 *  7) done
+	 */
+
+	// (1)
+	TimecodeFormat cur_timecode = config.get_timecode_format();
+	if (cur_timecode != ltc_enc_tcformat) {
+		DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX1: TC format mismatch - reinit sr: %1 fps: %2\n", nominal_frame_rate(), timecode_to_frames_per_second(cur_timecode)));
+		if (ltc_encoder_reinit(ltc_encoder, nominal_frame_rate(), timecode_to_frames_per_second(cur_timecode), 0)) {
+			PBD::error << _("LTC encoder: invalid framerate - LTC encoding is disabled for the remainder of this session.") << endmsg;
+			ltc_tx_cleanup();
+			return 0;
+		}
+		ltc_enc_tcformat = cur_timecode;
+		ltc_tx_reset();
+	}
+
+	/* LTC is max. 30 fps */
+	if (timecode_to_frames_per_second(cur_timecode) > 30) {
+		memset(out, 0, nframes * sizeof(jack_default_audio_sample_t));
+		return nframes;
+	}
+
+	// (2)
+#define SIGNUM(a) ( (a) < 0 ? -1 : 1)
+
+	framepos_t cycle_start_frame = (current_speed < 0) ? end_frame :start_frame;
+	double new_ltc_speed = double(labs(end_frame - start_frame) * SIGNUM(current_speed)) / double(nframes);
+
+	if (SIGNUM(new_ltc_speed) != SIGNUM (ltc_speed)) {
+		// transport changed direction
+		DEBUG_TRACE (DEBUG::LTC, "LTC TX2: transport direction changed\n");
+		ltc_tx_reset();
+	}
+
+	if (ltc_speed != current_speed || target_speed != fabs(current_speed)) {
+		/* TODO check ./libs/ardour/interpolation.cc  CubicInterpolation::interpolate
+		 * if target_speed != current_speed we should interpolate, too.
+		 *
+		 * However, currenly in A3 target_speed == current_speed for each process cycle
+		 * (except for the sign). Besides, above speed calulation uses the
+		 * difference (end_frame - start_frame).
+		 * end_frame is calculated from 'frames_moved' which includes the interpolation.
+		 * so we're good, except for the fact that each LTC byte is sent at fixed speed.
+		 */
+		DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: speed change old: %1 cur: %2 tgt: %3 ctd: %4\n", ltc_speed, current_speed, target_speed, fabs(current_speed) - target_speed));
+	}
+
+	if (end_frame == start_frame || fabs(current_speed) < 0.1 ) {
+		DEBUG_TRACE (DEBUG::LTC, "LTC TX2: transport is not rolling or absolute-speed < 0.1\n");
+		/* keep repeating current frame
+		 *
+		 * an LTC generator must be able to continue generating LTC when Ardours transport is in stop
+		 * some machines do odd things if LTC goes away:
+		 * e.g. a tape based machine (video or audio), some think they have gone into park if LTC goes away,
+		 * so unspool the tape from the playhead. That might be inconvenient.
+		 * If LTC keeps arriving they remain in a stop position with the tape on the playhead.
+		 */
+		new_ltc_speed = 0;
+	}
+
+	ltc_speed = new_ltc_speed;
+	DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: transport speed %1.\n", ltc_speed));
+
+	if (fabs(ltc_speed) > 10.0) {
+		DEBUG_TRACE (DEBUG::LTC, "LTC TX2: speed is out of bounds.\n");
+		ltc_tx_reset();
+		memset(out, 0, nframes * sizeof(jack_default_audio_sample_t));
+		return nframes;
+	}
+
+	// (3)
+	Timecode::Time tc_start;
+	framepos_t tc_sample_start;
+
+	/* calc timecode frame from current position - round down to nearest timecode */
+	int boff;
+	if (ltc_speed == 0) {
+		boff = 0;
+	}	else if (ltc_speed < 0) {
+		boff = (ltc_enc_byte - 9) * frames_per_timecode_frame() / 10;
+	} else {
+		boff = ltc_enc_byte * frames_per_timecode_frame() / 10;
+	}
+
+	sample_to_timecode(cycle_start_frame
+			- boff
+			- ltc_speed * (ltc_buf_len - ltc_buf_off),
+			tc_start, true, false);
+
+	/* convert timecode back to sample-position */
+	Timecode::timecode_to_sample (tc_start, tc_sample_start, true, false,
+		double(frame_rate()),
+		config.get_subframes_per_frame(),
+		config.get_timecode_offset_negative(), config.get_timecode_offset()
+		);
+
+	/* difference between current frame and TC frame in samples */
+	frameoffset_t soff = cycle_start_frame - tc_sample_start;
+	DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX3: now: %1 tra: %2 eoff %3\n", cycle_start_frame, tc_sample_start, soff));
+
+	// (4)
+	DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: enc: %1 boff: %2 || enc-byte:%3\n", ltc_enc_pos, boff, ltc_enc_byte));
+	if (ltc_enc_pos != tc_sample_start) {
+
+		/* re-calc timecode w/o buffer offset */
+		sample_to_timecode(cycle_start_frame, tc_start, true, false);
+		Timecode::timecode_to_sample (tc_start, tc_sample_start, true, false,
+			double(frame_rate()),
+			config.get_subframes_per_frame(),
+			config.get_timecode_offset_negative(), config.get_timecode_offset()
+			);
+		soff = cycle_start_frame - tc_sample_start;
+		DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: now: %1 trs: %2 toff %3\n", cycle_start_frame, tc_sample_start, soff));
+
+		tc.hours = tc_start.hours;
+		tc.mins = tc_start.minutes;
+		tc.secs = tc_start.seconds;
+		tc.frame = tc_start.frames;
+		ltc_encoder_set_timecode(ltc_encoder, &tc);
+
+#if 1
+		/* workaround for libltc recognizing 29.97 and 30000/1001 as drop-frame TC.
+		 * in A3 only 30000/1001 is drop-frame and there are also other questionable
+		 * DF timecodes  such as 24k/1001 and 25k/1001.
+		 */
+		LTCFrame ltcframe;
+		ltc_encoder_get_frame(ltc_encoder, &ltcframe);
+		ltcframe.dfbit = timecode_has_drop_frames(cur_timecode)?1:0;
+		ltc_encoder_set_frame(ltc_encoder, &ltcframe);
+#endif
+
+		// (5)
+		int fdiff = 0;
+		if (soff < 0) {
+			fdiff = ceil(-soff / frames_per_timecode_frame());
+			soff += fdiff * frames_per_timecode_frame();
+			for (int i=0; i < fdiff; ++i) {
+				ltc_encoder_inc_timecode(ltc_encoder);
+			}
+		}
+		else if (soff >= frames_per_timecode_frame()) {
+			fdiff = floor(soff / frames_per_timecode_frame());
+			soff -= fdiff * frames_per_timecode_frame();
+			for (int i=0; i < fdiff; ++i) {
+				ltc_encoder_dec_timecode(ltc_encoder);
+			}
+		}
+
+		assert(soff >= 0 && soff < frames_per_timecode_frame());
+
+		DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX5 restart encoder fdiff %1 sdiff %2\n", fdiff, soff));
+		ltc_tx_reset();
+
+		if (ltc_speed == 0) {
+			// offset is irrelevant when not rolling
+			soff = 0;
+		}
+		if (soff > 0 && soff <= nframes) {
+			txf=soff;
+			memset(out, 0, soff * sizeof(jack_default_audio_sample_t));
+		} else if (soff > 0) {
+			/* resync next cycle */
+			memset(out, 0, soff * sizeof(jack_default_audio_sample_t));
+			return nframes;
+		}
+
+		ltc_enc_byte = soff * 10 / frames_per_timecode_frame();
+
+		if (ltc_speed < 0 ) {
+			ltc_enc_byte = 9 - ltc_enc_byte;
+		}
+
+		ltc_enc_pos = tc_sample_start;
+		DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX5 restart @ %1 byte %2\n", ltc_enc_pos, ltc_enc_byte));
+	}
+
+	// (6)
+	while (1) {
+#ifdef LTC_GEN_FRAMEDBUG
+		DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.1 @%1  [ %2 / %3 ]\n", txf, ltc_buf_off, ltc_buf_len));
+#endif
+		// (6a)
+		while ((ltc_buf_off < ltc_buf_len) && (txf < nframes)) {
+			const float v1 = ltc_enc_buf[ltc_buf_off++] - 128.0;
+			const jack_default_audio_sample_t val = (jack_default_audio_sample_t) (v1*smult);
+			out[txf++] = val;
+		}
+#ifdef LTC_GEN_FRAMEDBUG
+		DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.2 @%1  [ %2 / %3 ]\n", txf, ltc_buf_off, ltc_buf_len));
+#endif
+
+		if (txf >= nframes) {
+			DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX7 txf = %1 nframes = %2\n", txf, nframes));
+			return nframes;
+		}
+
+		ltc_buf_len = 0;
+		ltc_buf_off = 0;
+
+		// (6b)
+
+		if (SIGNUM(ltc_speed) == -1) {
+			ltc_enc_byte = (ltc_enc_byte + 9)%10;
+			if (ltc_enc_byte == 9) {
+				ltc_encoder_dec_timecode(ltc_encoder);
+#if 0 // this does not work for fractional or drop-frame TC
+				ltc_enc_pos -= frames_per_timecode_frame();
+#else // TODO make this a function
+				SMPTETimecode enctc;
+				Timecode::Time a3tc;
+				ltc_encoder_get_timecode(ltc_encoder, &enctc);
+
+				a3tc.hours   = enctc.hours ;
+				a3tc.minutes = enctc.mins  ;
+				a3tc.seconds = enctc.secs  ;
+				a3tc.frames  = enctc.frame ;
+				a3tc.rate = timecode_to_frames_per_second(cur_timecode);
+				a3tc.drop = timecode_has_drop_frames(cur_timecode);
+
+				Timecode::timecode_to_sample (a3tc, ltc_enc_pos, true, false,
+					double(frame_rate()),
+					config.get_subframes_per_frame(),
+					config.get_timecode_offset_negative(), config.get_timecode_offset()
+					);
+#endif
+			}
+		}
+
+		if (ltc_encoder_encode_byte(ltc_encoder, ltc_enc_byte, (ltc_speed==0)?1.0:(1.0/ltc_speed))) {
+			DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.3 encoder error byte %1\n", ltc_enc_byte));
+			ltc_encoder_buffer_flush(ltc_encoder);
+			ltc_tx_reset();
+			memset(out, 0, nframes * sizeof(jack_default_audio_sample_t));
+			return -1;
+		}
+		int enc_frames = ltc_encoder_get_buffer(ltc_encoder, &(ltc_enc_buf[ltc_buf_len]));
+#ifdef LTC_GEN_FRAMEDBUG
+		DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.3 encoded %1 bytes LTC-byte %2 at spd %3\n", enc_frames, ltc_enc_byte, ltc_speed));
+#endif
+		if (enc_frames <=0) {
+			DEBUG_TRACE (DEBUG::LTC, "LTC TX6.3 encoder empty buffer.\n");
+			ltc_encoder_buffer_flush(ltc_encoder);
+			ltc_tx_reset();
+			memset(out, 0, nframes * sizeof(jack_default_audio_sample_t));
+			return -1;
+		}
+
+		ltc_buf_len += enc_frames;
+
+		if (SIGNUM(ltc_speed) == 1) {
+			ltc_enc_byte = (ltc_enc_byte + 1)%10;
+			if (ltc_enc_byte == 0 && ltc_speed != 0) {
+				ltc_encoder_inc_timecode(ltc_encoder);
+#if 0 // this does not work for fractional or drop-frame TC
+				ltc_enc_pos += frames_per_timecode_frame();
+#else // TODO make this a function
+				SMPTETimecode enctc;
+				Timecode::Time a3tc;
+				ltc_encoder_get_timecode(ltc_encoder, &enctc);
+
+				a3tc.hours   = enctc.hours ;
+				a3tc.minutes = enctc.mins  ;
+				a3tc.seconds = enctc.secs  ;
+				a3tc.frames  = enctc.frame ;
+				a3tc.rate = timecode_to_frames_per_second(cur_timecode);
+				a3tc.drop = timecode_has_drop_frames(cur_timecode);
+
+				Timecode::timecode_to_sample (a3tc, ltc_enc_pos, true, false,
+					double(frame_rate()),
+					config.get_subframes_per_frame(),
+					config.get_timecode_offset_negative(), config.get_timecode_offset()
+					);
+#endif
+			}
+		}
+#ifdef LTC_GEN_FRAMEDBUG
+		DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.4 fno: %1  [ %2 / %3 ] spd %4\n", ltc_enc_pos, ltc_buf_off, ltc_buf_len, ltc_speed));
+#endif
+	}
+
+	return nframes;
+}
diff --git a/libs/ardour/session_midi.cc b/libs/ardour/session_midi.cc
index caceebf853..85410277a0 100644
--- a/libs/ardour/session_midi.cc
+++ b/libs/ardour/session_midi.cc
@@ -412,6 +412,7 @@ Session::send_full_time_code (framepos_t const t)
 int
 Session::send_midi_time_code_for_cycle (framepos_t start_frame, framepos_t end_frame, pframes_t nframes)
 {
+	// XXX only if _slave == MTC_slave; we could generate MTC from jack or LTC
 	if (_engine.freewheeling() || _slave || !_send_qf_mtc || transmitting_timecode_time.negative || (next_quarter_frame_to_send < 0)) {
 		// cerr << "(MTC) Not sending MTC\n";
 		return 0;
diff --git a/libs/ardour/session_process.cc b/libs/ardour/session_process.cc
index 1d11de79d3..bd386a943d 100644
--- a/libs/ardour/session_process.cc
+++ b/libs/ardour/session_process.cc
@@ -348,6 +348,10 @@ Session::process_with_events (pframes_t nframes)
 
 	end_frame = _transport_frame + frames_moved;
 
+#ifdef HAVE_LTC
+	ltc_tx_send_time_code_for_cycle (_transport_frame, end_frame, _target_transport_speed, _transport_speed, nframes);
+#endif
+
 	{
 		SessionEvent* this_event;
 		Events::iterator the_next_one;
@@ -789,12 +793,20 @@ Session::process_without_events (pframes_t nframes)
 
 	if (!_exporting && _slave) {
 		if (!follow_slave (nframes)) {
+#ifdef HAVE_LTC
+			ltc_tx_send_time_code_for_cycle (_transport_frame, _transport_frame, 0, 0 , nframes);
+#endif
 			return;
 		}
 	}
 
 	if (_transport_speed == 0) {
 		fail_roll (nframes);
+#ifdef HAVE_LTC
+		if (!_exporting) {
+			ltc_tx_send_time_code_for_cycle (_transport_frame, _transport_frame, 0, 0 , nframes);
+		}
+#endif
 		return;
 	}
 
@@ -810,6 +822,12 @@ Session::process_without_events (pframes_t nframes)
 		send_midi_time_code_for_cycle (_transport_frame, _transport_frame + frames_moved, nframes);
 	}
 
+#ifdef HAVE_LTC
+	if (!_exporting) {
+		ltc_tx_send_time_code_for_cycle (_transport_frame, _transport_frame + frames_moved, _target_transport_speed, _transport_speed, nframes);
+	}
+#endif
+
 	framepos_t const stop_limit = compute_stop_limit ();
 
 	if (maybe_stop (stop_limit)) {
diff --git a/libs/ardour/session_state.cc b/libs/ardour/session_state.cc
index 51f6f1352c..8cf58a7793 100644
--- a/libs/ardour/session_state.cc
+++ b/libs/ardour/session_state.cc
@@ -366,6 +366,9 @@ Session::second_stage_init ()
 
 	MIDI::Name::MidiPatchManager::instance().set_session (this);
 
+#ifdef HAVE_LTC
+	ltc_tx_initialize();
+#endif
 	/* initial program change will be delivered later; see ::config_changed() */
 
 	_state_of_the_state = Clean;
diff --git a/libs/ardour/wscript b/libs/ardour/wscript
index ddcb5e00e5..f17fe8f7a4 100644
--- a/libs/ardour/wscript
+++ b/libs/ardour/wscript
@@ -282,7 +282,7 @@ def configure(conf):
     autowaf.check_pkg(conf, 'libcurl', uselib_store='CURL',
                       atleast_version='7.0.0')
     autowaf.check_pkg(conf, 'ltc', uselib_store='LTC',
-                      atleast_version='0.3.2', mandatory=False)
+                      atleast_version='0.7.0', mandatory=False)
 
     # we don't try to detect this, since its part of our source tree
 
@@ -385,6 +385,7 @@ def build(bld):
 
     if bld.is_defined('HAVE_LTC') :
         obj.source += ['ltc_slave.cc']
+        obj.source += ['session_ltc.cc']
         obj.uselib += ['LTC']
 
     if bld.is_defined('HAVE_LILV') :