when calling Session::engine_halted() after a user-driven engine stop, make sure...
[ardour.git] / libs / ardour / session_ltc.cc
index 2ce25b5a4808853754f969707b918f1db40f21fc..c2cd0ef681a8e4c5256f9a0877ca7efbee5ecdbc 100644 (file)
 
 */
 
-#include "timecode/time.h"
+#include "temporal/time.h"
 
 #include "ardour/audioengine.h"
 #include "ardour/audio_port.h"
 #include "ardour/debug.h"
 #include "ardour/io.h"
 #include "ardour/session.h"
-#include "ardour/slave.h"
+#include "ardour/transport_master.h"
+#include "ardour/transport_master_manager.h"
 
-#include "i18n.h"
+#include "pbd/i18n.h"
 
 using namespace std;
 using namespace ARDOUR;
@@ -64,35 +65,37 @@ using namespace Timecode;
 void
 Session::ltc_tx_initialize()
 {
+       assert (!ltc_encoder && !ltc_enc_buf);
        ltc_enc_tcformat = config.get_timecode_format();
 
        ltc_tx_parse_offset();
-       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(),
+       DEBUG_TRACE (DEBUG::TXLTC, string_compose("LTC TX init sr: %1 fps: %2\n", nominal_sample_rate(), timecode_to_frames_per_second(ltc_enc_tcformat)));
+       ltc_encoder = ltc_encoder_create(nominal_sample_rate(),
                        timecode_to_frames_per_second(ltc_enc_tcformat),
                        TV_STANDARD(ltc_enc_tcformat), 0);
 
-       ltc_encoder_set_bufsize(ltc_encoder, nominal_frame_rate(), 23.0);
+       ltc_encoder_set_bufsize(ltc_encoder, nominal_sample_rate(), 23.0);
        ltc_encoder_set_filter(ltc_encoder, LTC_RISE_TIME(1.0));
 
-       /* buffersize for 1 LTC frame: (1 + sample-rate / fps) bytes
+       /* buffersize for 1 LTC sample: (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_enc_buf = (ltcsnd_sample_t*) calloc((nominal_sample_rate() / 23), sizeof(ltcsnd_sample_t));
        ltc_speed = 0;
        ltc_prev_cycle = -1;
        ltc_tx_reset();
        ltc_tx_resync_latency();
-       Xrun.connect_same_thread (*this, boost::bind (&Session::ltc_tx_reset, this));
-       engine().GraphReordered.connect_same_thread (*this, boost::bind (&Session::ltc_tx_resync_latency, this));
+       Xrun.connect_same_thread (ltc_tx_connections, boost::bind (&Session::ltc_tx_reset, this));
+       engine().GraphReordered.connect_same_thread (ltc_tx_connections, boost::bind (&Session::ltc_tx_resync_latency, this));
        restarting = false;
 }
 
 void
 Session::ltc_tx_cleanup()
 {
-       DEBUG_TRACE (DEBUG::LTC, "LTC TX cleanup\n");
+       DEBUG_TRACE (DEBUG::TXLTC, "cleanup\n");
+       ltc_tx_connections.drop_connections ();
        free(ltc_enc_buf);
        ltc_enc_buf = NULL;
        ltc_encoder_free(ltc_encoder);
@@ -102,7 +105,7 @@ Session::ltc_tx_cleanup()
 void
 Session::ltc_tx_resync_latency()
 {
-       DEBUG_TRACE (DEBUG::LTC, "LTC TX resync latency\n");
+       DEBUG_TRACE (DEBUG::TXLTC, "resync latency\n");
        if (!deletion_in_progress()) {
                boost::shared_ptr<Port> ltcport = ltc_output_port();
                if (ltcport) {
@@ -114,7 +117,8 @@ Session::ltc_tx_resync_latency()
 void
 Session::ltc_tx_reset()
 {
-       DEBUG_TRACE (DEBUG::LTC, "LTC TX reset\n");
+       DEBUG_TRACE (DEBUG::TXLTC, "reset\n");
+       assert (ltc_encoder);
        ltc_enc_pos = -9999; // force re-start
        ltc_buf_len = 0;
        ltc_buf_off = 0;
@@ -150,7 +154,7 @@ Session::ltc_tx_recalculate_position()
        a3tc.drop = timecode_has_drop_frames(ltc_enc_tcformat);
 
        Timecode::timecode_to_sample (a3tc, ltc_enc_pos, true, false,
-               (double)frame_rate(),
+               (double)sample_rate(),
                config.get_subframes_per_frame(),
                ltc_timecode_negative_offset, ltc_timecode_offset
                );
@@ -158,7 +162,7 @@ Session::ltc_tx_recalculate_position()
 }
 
 void
-Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end_frame,
+Session::ltc_tx_send_time_code_for_cycle (samplepos_t start_sample, samplepos_t end_sample,
                                          double target_speed, double current_speed,
                                          pframes_t nframes)
 {
@@ -168,13 +172,19 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
        pframes_t txf = 0;
        boost::shared_ptr<Port> ltcport = ltc_output_port();
 
+       if (!ltcport) {
+               assert (deletion_in_progress ());
+               return;
+       }
+
+       /* marks buffer as not written */
        Buffer& buf (ltcport->get_buffer (nframes));
 
        if (!ltc_encoder || !ltc_enc_buf) {
                return;
        }
 
-       SyncSource sync_src = Config->get_sync_source();
+       SyncSource sync_src = TransportMasterManager::instance().current()->type();
        if (engine().freewheeling() || !Config->get_send_ltc()
            /* TODO
             * decide which time-sources we can generated LTC from.
@@ -194,18 +204,18 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
        /* range from libltc (38..218) || - 128.0  -> (-90..90) */
        const float ltcvol = Config->get_ltc_output_volume()/(90.0); // pow(10, db/20.0)/(90.0);
 
-       DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX %1 to %2 / %3 | lat: %4\n", start_frame, end_frame, nframes, ltc_out_latency.max));
+       DEBUG_TRACE (DEBUG::TXLTC, string_compose("LTC TX %1 to %2 / %3 | lat: %4\n", start_sample, end_sample, nframes, ltc_out_latency.max));
 
        /* all systems go. Now here's the plan:
         *
         *  1) check if fps has changed
         *  2) check direction of encoding, calc speed, re-sample existing buffer
-        *  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
+        *  3) calculate sample and byte to send aligned to jack-period size
+        *  4) check if it's the sample/byte that is already in the queue
+        *  5) if (4) mismatch, re-calculate offset of LTC sample 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
+        *  6a) send remaining part of already queued sample; break on nframes
+        *  6b) encode new LTC-sample byte
         *  6c) goto 6a
         *  7) done
         */
@@ -213,8 +223,8 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
        // (1) check fps
        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(),
+               DEBUG_TRACE (DEBUG::TXLTC, string_compose("1: TC format mismatch - reinit sr: %1 fps: %2\n", nominal_sample_rate(), timecode_to_frames_per_second(cur_timecode)));
+               if (ltc_encoder_reinit(ltc_encoder, nominal_sample_rate(),
                                        timecode_to_frames_per_second(cur_timecode),
                                        TV_STANDARD(cur_timecode), 0
                                        )) {
@@ -236,7 +246,7 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
        // (2) speed & direction
 
        /* speed 0 aka transport stopped is interpreted as rolling forward.
-        * keep repeating current frame
+        * keep repeating current sample
         */
 #define SIGNUM(a) ( (a) < 0 ? -1 : 1)
        bool speed_changed = false;
@@ -244,43 +254,55 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
        /* port latency compensation:
         * The _generated timecode_ is offset by the port-latency,
         * therefore the offset depends on the direction of transport.
+        *
+        * latency is compensated by adding it to the timecode to
+        * be generated. e.g. if the signal will reach the output in
+        * N samples time from now, generate the timecode for (now + N).
+        *
+        * sample-sync is achieved by further calculating the difference
+        * between the timecode and the session-transport and offsetting the
+        * buffer.
+        *
+        * The timecode is generated directly in the Session process callback
+        * using _transport_sample (which is the audible frame at the
+        * output).
         */
-       framepos_t cycle_start_frame;
+       samplepos_t cycle_start_sample;
 
        if (current_speed < 0) {
-               cycle_start_frame = (start_frame - ltc_out_latency.max);
+               cycle_start_sample = (start_sample + ltc_out_latency.max);
        } else if (current_speed > 0) {
-               cycle_start_frame = (start_frame + ltc_out_latency.max);
+               cycle_start_sample = (start_sample - ltc_out_latency.max);
        } else {
                /* There is no need to compensate for latency when not rolling
                 * rather send the accurate NOW timecode
                 * (LTC encoder compenates latency by sending earlier timecode)
                 */
-               cycle_start_frame = start_frame;
+               cycle_start_sample = start_sample;
        }
 
        /* LTC TV standard offset */
        if (current_speed != 0) {
                /* ditto - send "NOW" if not rolling */
-               cycle_start_frame -= ltc_frame_alignment(frames_per_timecode_frame(), TV_STANDARD(cur_timecode));
+               cycle_start_sample -= ltc_frame_alignment(samples_per_timecode_frame(), TV_STANDARD(cur_timecode));
        }
 
        /* cycle-start may become negative due to latency compensation */
-       if (cycle_start_frame < 0) { cycle_start_frame = 0; }
+       if (cycle_start_sample < 0) { cycle_start_sample = 0; }
 
-       double new_ltc_speed = (double)(labs(end_frame - start_frame) * SIGNUM(current_speed)) / (double)nframes;
-       if (nominal_frame_rate() != frame_rate()) {
-               new_ltc_speed *= (double)nominal_frame_rate() / (double)frame_rate();
+       double new_ltc_speed = (double)(labs(end_sample - start_sample) * SIGNUM(current_speed)) / (double)nframes;
+       if (nominal_sample_rate() != sample_rate()) {
+               new_ltc_speed *= (double)nominal_sample_rate() / (double)sample_rate();
        }
 
        if (SIGNUM(new_ltc_speed) != SIGNUM (ltc_speed)) {
-               DEBUG_TRACE (DEBUG::LTC, "LTC TX2: transport changed direction\n");
+               DEBUG_TRACE (DEBUG::TXLTC, "transport changed direction\n");
                ltc_tx_reset();
        }
 
        if (ltc_speed != new_ltc_speed
                        /* but only once if, current_speed changes to 0. In that case
-                        * new_ltc_speed is > 0 because (end_frame - start_frame) == jack-period for no-roll
+                        * new_ltc_speed is > 0 because (end_sample - start_sample) == jack-period for no-roll
                         * but ltc_speed will still be 0
                         */
                        && (current_speed != 0 || ltc_speed != current_speed)
@@ -290,18 +312,18 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
                 *
                 * However, currency in A3 target_speed == current_speed for each process cycle
                 * (except for the sign and if target_speed > 8.0).
-                * Besides, above speed calculation uses the difference (end_frame - start_frame).
-                * end_frame is calculated from 'frames_moved' which includes the interpolation.
+                * Besides, above speed calculation uses the difference (end_sample - start_sample).
+                * end_sample is calculated from 'samples_moved' which includes the interpolation.
                 * so we're good.
                 */
-               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, new_ltc_speed));
+               DEBUG_TRACE (DEBUG::TXLTC, string_compose("2: speed change old: %1 cur: %2 tgt: %3 ctd: %4\n", ltc_speed, current_speed, target_speed, fabs(current_speed) - target_speed, new_ltc_speed));
                speed_changed = true;
                ltc_encoder_set_filter(ltc_encoder, LTC_RISE_TIME(new_ltc_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
+       if (end_sample == start_sample || fabs(current_speed) < 0.1 ) {
+               DEBUG_TRACE (DEBUG::TXLTC, "transport is not rolling or absolute-speed < 0.1\n");
+               /* keep repeating current sample
                 *
                 * 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:
@@ -314,20 +336,20 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
                        ltc_speed = new_ltc_speed;
                        return;
                }
-               if (start_frame != ltc_prev_cycle) {
-                       DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: no-roll seek from %1 to %2 (%3)\n", ltc_prev_cycle, start_frame, cycle_start_frame));
+               if (start_sample != ltc_prev_cycle) {
+                       DEBUG_TRACE (DEBUG::TXLTC, string_compose("2: no-roll seek from %1 to %2 (%3)\n", ltc_prev_cycle, start_sample, cycle_start_sample));
                        ltc_tx_reset();
                }
        }
 
        if (fabs(new_ltc_speed) > 10.0) {
-               DEBUG_TRACE (DEBUG::LTC, "LTC TX2: speed is out of bounds.\n");
+               DEBUG_TRACE (DEBUG::TXLTC, "speed is out of bounds.\n");
                ltc_tx_reset();
                return;
        }
 
        if (ltc_speed == 0 && new_ltc_speed != 0) {
-               DEBUG_TRACE (DEBUG::LTC, "LTC TX2: transport started rolling - reset\n");
+               DEBUG_TRACE (DEBUG::TXLTC, "transport started rolling - reset\n");
                ltc_tx_reset();
        }
 
@@ -353,21 +375,21 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
                double oldbuflen = (double)(ltc_buf_len - ltc_buf_off);
                double newbuflen = (double)(ltc_buf_len - ltc_buf_off) * fabs(ltc_speed / new_ltc_speed);
 
-               DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: bufOld %1 bufNew %2 | diff %3\n",
+               DEBUG_TRACE (DEBUG::TXLTC, string_compose("2: bufOld %1 bufNew %2 | diff %3\n",
                                        (ltc_buf_len - ltc_buf_off), newbuflen, newbuflen - oldbuflen
                                        ));
 
                double bufrspdiff = rint(newbuflen - oldbuflen);
 
                if (abs(bufrspdiff) > newbuflen || abs(bufrspdiff) > oldbuflen) {
-                       DEBUG_TRACE (DEBUG::LTC, "LTC TX2: resampling buffer would destroy information.\n");
+                       DEBUG_TRACE (DEBUG::TXLTC, "resampling buffer would destroy information.\n");
                        ltc_tx_reset();
                        poff = 0;
                } else if (bufrspdiff != 0 && newbuflen > oldbuflen) {
                        int incnt = 0;
                        double samples_to_insert = ceil(newbuflen - oldbuflen);
                        double avg_distance = newbuflen / samples_to_insert;
-                       DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: resample buffer insert: %1\n", samples_to_insert));
+                       DEBUG_TRACE (DEBUG::TXLTC, string_compose("2: resample buffer insert: %1\n", samples_to_insert));
 
                        for (int rp = ltc_buf_off; rp < ltc_buf_len - 1; ++rp) {
                                const int ro = rp - ltc_buf_off;
@@ -381,7 +403,7 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
                        }
                } else if (bufrspdiff != 0 && newbuflen < oldbuflen) {
                        double samples_to_remove = ceil(oldbuflen - newbuflen);
-                       DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: resample buffer - remove: %1\n", samples_to_remove));
+                       DEBUG_TRACE (DEBUG::TXLTC, string_compose("2: resample buffer - remove: %1\n", samples_to_remove));
                        if (oldbuflen <= samples_to_remove) {
                                ltc_buf_off = ltc_buf_len= 0;
                        } else {
@@ -401,41 +423,41 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
                }
        }
 
-       ltc_prev_cycle = start_frame;
+       ltc_prev_cycle = start_sample;
        ltc_speed = new_ltc_speed;
-       DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: transport speed %1.\n", ltc_speed));
+       DEBUG_TRACE (DEBUG::TXLTC, string_compose("2: transport speed %1.\n", ltc_speed));
 
        // (3) bit/sample alignment
        Timecode::Time tc_start;
-       framepos_t tc_sample_start;
+       samplepos_t tc_sample_start;
 
        /* calc timecode frame from current position - round down to nearest timecode */
-       Timecode::sample_to_timecode(cycle_start_frame, tc_start, true, false,
+       Timecode::sample_to_timecode(cycle_start_sample, tc_start, true, false,
                        timecode_frames_per_second(),
                        timecode_drop_frames(),
-                       (double)frame_rate(),
+                       (double)sample_rate(),
                        config.get_subframes_per_frame(),
                        ltc_timecode_negative_offset, ltc_timecode_offset
                        );
 
        /* convert timecode back to sample-position */
        Timecode::timecode_to_sample (tc_start, tc_sample_start, true, false,
-               (double)frame_rate(),
+               (double)sample_rate(),
                config.get_subframes_per_frame(),
                ltc_timecode_negative_offset, ltc_timecode_offset
                );
 
-       /* difference between current frame and TC frame in samples */
-       frameoffset_t soff = cycle_start_frame - tc_sample_start;
+       /* difference between current sample and TC sample in samples */
+       sampleoffset_t soff = cycle_start_sample - tc_sample_start;
        if (current_speed == 0) {
                soff = 0;
        }
-       DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX3: A3cycle: %1 = A3tc: %2 +off: %3\n",
-                               cycle_start_frame, tc_sample_start, soff));
+       DEBUG_TRACE (DEBUG::TXLTC, string_compose("3: A3cycle: %1 = A3tc: %2 +off: %3\n",
+                               cycle_start_sample, tc_sample_start, soff));
 
 
        // (4) check if alignment matches
-       const double fptcf = frames_per_timecode_frame();
+       const double fptcf = samples_per_timecode_frame();
 
        /* maximum difference of bit alignment in audio-samples.
         *
@@ -449,11 +471,11 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
         */
        double maxdiff;
 
-       if (config.get_external_sync() && slave()) {
-               maxdiff = slave()->resolution();
+       if (transport_master_is_external()) {
+               maxdiff = transport_master()->resolution();
        } else {
                maxdiff = ceil(fabs(ltc_speed))*2.0;
-               if (nominal_frame_rate() != frame_rate()) {
+               if (nominal_sample_rate() != sample_rate()) {
                        maxdiff *= 3.0;
                }
                if (ltc_enc_tcformat == Timecode::timecode_23976 || ltc_enc_tcformat == Timecode::timecode_24976) {
@@ -461,31 +483,32 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
                }
        }
 
-       DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: enc: %1 + %2 - %3 || buf-bytes: %4 enc-byte: %5\n",
+       DEBUG_TRACE (DEBUG::TXLTC, string_compose("4: enc: %1 + %2 - %3 || buf-bytes: %4 enc-byte: %5\n",
                                ltc_enc_pos, ltc_enc_cnt, poff, (ltc_buf_len - ltc_buf_off), poff, ltc_enc_byte));
 
-       DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: enc-pos: %1  | d: %2\n",
+       DEBUG_TRACE (DEBUG::TXLTC, string_compose("4: enc-pos: %1  | d: %2\n",
                                ltc_enc_pos + ltc_enc_cnt - poff,
-                               rint(ltc_enc_pos + ltc_enc_cnt - poff) - cycle_start_frame
+                               rint(ltc_enc_pos + ltc_enc_cnt - poff) - cycle_start_sample
                                ));
 
+       const samplecnt_t wrap24h = 86400. * sample_rate();
        if (ltc_enc_pos < 0
-                       || (ltc_speed != 0 && fabs(ceil(ltc_enc_pos + ltc_enc_cnt - poff) - cycle_start_frame) > maxdiff)
+                       || (ltc_speed != 0 && fabs(fmod(ceil(ltc_enc_pos + ltc_enc_cnt - poff), wrap24h) - (cycle_start_sample % wrap24h)) > maxdiff)
                        ) {
 
                // (5) re-align
                ltc_tx_reset();
 
-               /* set frame to encode */
+               /* set sample to encode */
                SMPTETimecode tc;
-               tc.hours = tc_start.hours;
+               tc.hours = tc_start.hours % 24;
                tc.mins = tc_start.minutes;
                tc.secs = tc_start.seconds;
                tc.frame = tc_start.frames;
                ltc_encoder_set_timecode(ltc_encoder, &tc);
 
-               /* workaround for libltc recognizing 29.97 and 30000/1001 as drop-frame TC.
-                * In A3 30000/1001 or 30 fps can be drop-frame.
+               /* workaround for libltc recognizing 29.97 and 30000/1001 as drop-sample TC.
+                * In A3 30000/1001 or 30 fps can be drop-sample.
                 */
                LTCFrame ltcframe;
                ltc_encoder_get_frame(ltc_encoder, &ltcframe);
@@ -493,7 +516,7 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
                ltc_encoder_set_frame(ltc_encoder, &ltcframe);
 
 
-               DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: now: %1 trs: %2 toff %3\n", cycle_start_frame, tc_sample_start, soff));
+               DEBUG_TRACE (DEBUG::TXLTC, string_compose("4: now: %1 trs: %2 toff %3\n", cycle_start_sample, tc_sample_start, soff));
 
                int32_t cyc_off;
                if (soff < 0 || soff >= fptcf) {
@@ -524,7 +547,7 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
                        }
                }
 
-               DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX5 restart encoder: soff %1 byte %2 cycoff %3\n",
+               DEBUG_TRACE (DEBUG::TXLTC, string_compose("5 restart encoder: soff %1 byte %2 cycoff %3\n",
                                        soff, ltc_enc_byte, cyc_off));
 
                if ( (ltc_speed < 0 && ltc_enc_byte !=9 ) || (ltc_speed >= 0 && ltc_enc_byte !=0 ) ) {
@@ -541,16 +564,16 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
                        return;
                }
 
-               ltc_enc_pos = tc_sample_start;
+               ltc_enc_pos = tc_sample_start % wrap24h;
 
-               DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX5 restart @ %1 + %2 - %3 |  byte %4\n",
+               DEBUG_TRACE (DEBUG::TXLTC, string_compose("5 restart @ %1 + %2 - %3 |  byte %4\n",
                                        ltc_enc_pos, ltc_enc_cnt, cyc_off, ltc_enc_byte));
        }
        else if (ltc_speed != 0 && (fptcf / ltc_speed / 80) > 3 ) {
                /* reduce (low freq) jitter.
                 * The granularity of the LTC encoder speed is 1 byte =
-                * (frames-per-timecode-frame / 10) audio-samples.
-                * Thus, tiny speed changes [as produced by some slaves]
+                * (samples-per-timecode-sample / 10) audio-samples.
+                * Thus, tiny speed changes [as produced by some transport masters]
                 * may not have any effect in the cycle when they occur,
                 * but they will add up over time.
                 *
@@ -559,19 +582,19 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
                 *
                 * However, for very fast speeds - when 1 LTC bit is
                 * <= 3 audio-sample - adjusting speed may lead to
-                * invalid frames.
+                * invalid samples.
                 *
                 * To do better than this, resampling (or a rewrite of the
                 * encoder) is required.
                 */
-               ltc_speed -= ((ltc_enc_pos + ltc_enc_cnt - poff) - cycle_start_frame) / engine().sample_rate();
+               ltc_speed -= fmod(((ltc_enc_pos + ltc_enc_cnt - poff) - cycle_start_sample), wrap24h) / engine().sample_rate();
        }
 
 
        // (6) encode and output
        while (1) {
 #ifdef LTC_GEN_TXDBUG
-               DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.1 @%1  [ %2 / %3 ]\n", txf, ltc_buf_off, ltc_buf_len));
+               DEBUG_TRACE (DEBUG::TXLTC, string_compose("6.1 @%1  [ %2 / %3 ]\n", txf, ltc_buf_off, ltc_buf_len));
 #endif
                // (6a) send remaining buffer
                while ((ltc_buf_off < ltc_buf_len) && (txf < nframes)) {
@@ -580,11 +603,11 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
                        out[txf++] = val;
                }
 #ifdef LTC_GEN_TXDBUG
-               DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.2 @%1  [ %2 / %3 ]\n", txf, ltc_buf_off, ltc_buf_len));
+               DEBUG_TRACE (DEBUG::TXLTC, string_compose("6.2 @%1  [ %2 / %3 ]\n", txf, ltc_buf_off, ltc_buf_len));
 #endif
 
                if (txf >= nframes) {
-                       DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX7 enc: %1 [ %2 / %3 ] byte: %4 spd %5 fpp %6 || nf: %7\n",
+                       DEBUG_TRACE (DEBUG::TXLTC, string_compose("7 enc: %1 [ %2 / %3 ] byte: %4 spd %5 fpp %6 || nf: %7\n",
                                                ltc_enc_pos, ltc_buf_off, ltc_buf_len, ltc_enc_byte, ltc_speed, nframes, txf));
                        break;
                }
@@ -603,35 +626,35 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
                        }
                }
 
-               int enc_frames;
+               int enc_samples;
 
                if (restarting) {
-                       /* write zero bytes -- don't touch encoder until we're at a frame-boundary
+                       /* write zero bytes -- don't touch encoder until we're at a sample-boundary
                         * otherwise the biphase polarity may be inverted.
                         */
-                       enc_frames = fptcf / 10.0;
-                       memset(&ltc_enc_buf[ltc_buf_len], 127, enc_frames * sizeof(ltcsnd_sample_t));
+                       enc_samples = fptcf / 10.0;
+                       memset(&ltc_enc_buf[ltc_buf_len], 127, enc_samples * sizeof(ltcsnd_sample_t));
                } else {
                        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));
+                               DEBUG_TRACE (DEBUG::TXLTC, string_compose("6.3 encoder error byte %1\n", ltc_enc_byte));
                                ltc_encoder_buffer_flush(ltc_encoder);
                                ltc_tx_reset();
                                return;
                        }
-                       enc_frames = ltc_encoder_get_buffer(ltc_encoder, &(ltc_enc_buf[ltc_buf_len]));
+                       enc_samples = 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 for LTC-byte %2 at spd %3\n", enc_frames, ltc_enc_byte, ltc_speed));
+               DEBUG_TRACE (DEBUG::TXLTC, string_compose("6.3 encoded %1 bytes for LTC-byte %2 at spd %3\n", enc_samples, ltc_enc_byte, ltc_speed));
 #endif
-               if (enc_frames <=0) {
-                       DEBUG_TRACE (DEBUG::LTC, "LTC TX6.3 encoder empty buffer.\n");
+               if (enc_samples <=0) {
+                       DEBUG_TRACE (DEBUG::TXLTC, "6.3 encoder empty buffer.\n");
                        ltc_encoder_buffer_flush(ltc_encoder);
                        ltc_tx_reset();
                        return;
                }
 
-               ltc_buf_len += enc_frames;
+               ltc_buf_len += enc_samples;
                if (ltc_speed < 0)
                        ltc_enc_cnt -= fptcf/10.0;
                else
@@ -655,7 +678,7 @@ Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end
                        }
                }
 #ifdef LTC_GEN_FRAMEDBUG
-               DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.4 enc-pos: %1 + %2 [ %4 / %5 ] spd %6\n", ltc_enc_pos, ltc_enc_cnt, ltc_buf_off, ltc_buf_len, ltc_speed));
+               DEBUG_TRACE (DEBUG::TXLTC, string_compose("6.4 enc-pos: %1 + %2 [ %4 / %5 ] spd %6\n", ltc_enc_pos, ltc_enc_cnt, ltc_buf_off, ltc_buf_len, ltc_speed));
 #endif
        }