2 Copyright (C) 2012 Paul Davis
3 Written by Robin Gareus <robin@gareus.org>
5 This program is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 2 of the License, or
8 (at your option) any later version.
10 This program is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with this program; if not, write to the Free Software
17 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21 #include "timecode/time.h"
23 #include "ardour/audioengine.h"
24 #include "ardour/audio_port.h"
25 #include "ardour/debug.h"
26 #include "ardour/io.h"
27 #include "ardour/session.h"
28 #include "ardour/slave.h"
33 using namespace ARDOUR;
36 using namespace Timecode;
38 /* really verbose timing debug */
39 //#define LTC_GEN_FRAMEDBUG
40 //#define LTC_GEN_TXDBUG
43 #define MAX(a,b) ( (a) > (b) ? (a) : (b) )
46 #define MIN(a,b) ( (a) < (b) ? (a) : (b) )
49 /* LTC signal should have a rise time of 25 us +/- 5 us.
50 * yet with most sound-cards a square-wave of 1-2 sample
51 * introduces ringing and small oscillations.
52 * https://en.wikipedia.org/wiki/Gibbs_phenomenon
53 * A low-pass filter in libltc can reduce this at
54 * the cost of being slightly out of spec WRT to rise-time.
56 * This filter is adaptive so that fast vari-speed signals
57 * will not be affected by it.
59 #define LTC_RISE_TIME(speed) MIN (100, MAX(25, (4000000 / ((speed==0)?1:speed) / engine().frame_rate())))
62 Session::ltc_tx_initialize()
64 ltc_enc_tcformat = config.get_timecode_format();
66 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)));
67 ltc_encoder = ltc_encoder_create(nominal_frame_rate(),
68 timecode_to_frames_per_second(ltc_enc_tcformat),
71 ltc_encoder_set_bufsize(ltc_encoder, nominal_frame_rate(), 23.0);
72 ltc_encoder_set_filter(ltc_encoder, LTC_RISE_TIME(1.0));
74 /* buffersize for 1 LTC frame: (1 + sample-rate / fps) bytes
75 * usually returned by ltc_encoder_get_buffersize(encoder)
77 * since the fps can change and A3's min fps: 24000/1001 */
78 ltc_enc_buf = (ltcsnd_sample_t*) calloc((nominal_frame_rate() / 23), sizeof(ltcsnd_sample_t));
81 ltc_tx_resync_latency();
82 Xrun.connect_same_thread (*this, boost::bind (&Session::ltc_tx_reset, this));
83 engine().GraphReordered.connect_same_thread (*this, boost::bind (&Session::ltc_tx_resync_latency, this));
87 Session::ltc_tx_cleanup()
89 DEBUG_TRACE (DEBUG::LTC, "LTC TX cleanup\n");
90 if (ltc_enc_buf) free(ltc_enc_buf);
91 ltc_encoder_free(ltc_encoder);
96 Session::ltc_tx_resync_latency()
98 DEBUG_TRACE (DEBUG::LTC, "LTC TX resync latency\n");
99 if (!deletion_in_progress()) {
100 boost::shared_ptr<Port> ltcport = ltc_output_port();
102 ltcport->get_connected_latency_range(ltc_out_latency, true);
108 Session::ltc_tx_reset()
110 DEBUG_TRACE (DEBUG::LTC, "LTC TX reset\n");
111 ltc_enc_pos = -9999; // force re-start
117 ltc_encoder_reset(ltc_encoder);
121 Session::ltc_tx_recalculate_position()
125 ltc_encoder_get_timecode(ltc_encoder, &enctc);
127 a3tc.hours = enctc.hours;
128 a3tc.minutes = enctc.mins;
129 a3tc.seconds = enctc.secs;
130 a3tc.frames = enctc.frame;
131 a3tc.rate = timecode_to_frames_per_second(ltc_enc_tcformat);
132 a3tc.drop = timecode_has_drop_frames(ltc_enc_tcformat);
134 Timecode::timecode_to_sample (a3tc, ltc_enc_pos, true, false,
135 (double)frame_rate(),
136 config.get_subframes_per_frame(),
137 config.get_timecode_offset_negative(), config.get_timecode_offset()
142 Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end_frame,
143 double target_speed, double current_speed,
146 assert (nframes > 0);
150 boost::shared_ptr<Port> ltcport = ltc_output_port();
152 Buffer& buf (ltcport->get_buffer (nframes));
154 if (!ltc_encoder || !ltc_enc_buf) {
158 SyncSource sync_src = Config->get_sync_source();
159 if (engine().freewheeling() || !Config->get_send_ltc()
161 * decide which time-sources we can generated LTC from.
162 * Internal, JACK or sample-synced slaves should be fine.
165 || (config.get_external_sync() && sync_src == LTC)
166 || (config.get_external_sync() && sync_src == MTC)
168 ||(config.get_external_sync() && sync_src == MIDIClock)
173 out = dynamic_cast<AudioBuffer*>(&buf)->data ();
175 /* range from libltc (38..218) || - 128.0 -> (-90..90) */
176 const float ltcvol = Config->get_ltc_output_volume()/(90.0); // pow(10, db/20.0)/(90.0);
178 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX %1 to %2 / %3 | lat: %4\n", start_frame, end_frame, nframes, ltc_out_latency.max));
180 /* all systems go. Now here's the plan:
182 * 1) check if fps has changed
183 * 2) check direction of encoding, calc speed, re-sample existing buffer
184 * 3) calculate frame and byte to send aligned to jack-period size
185 * 4) check if it's the frame/byte that is already in the queue
186 * 5) if (4) mismatch, re-calculate offset of LTC frame relative to period size
187 * 6) actual LTC audio output
188 * 6a) send remaining part of already queued frame; break on nframes
189 * 6b) encode new LTC-frame byte
195 TimecodeFormat cur_timecode = config.get_timecode_format();
196 if (cur_timecode != ltc_enc_tcformat) {
197 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)));
198 if (ltc_encoder_reinit(ltc_encoder, nominal_frame_rate(), timecode_to_frames_per_second(cur_timecode), -2)) {
199 PBD::error << _("LTC encoder: invalid framerate - LTC encoding is disabled for the remainder of this session.") << endmsg;
203 ltc_encoder_set_filter(ltc_encoder, LTC_RISE_TIME(ltc_speed));
204 ltc_enc_tcformat = cur_timecode;
208 /* LTC is max. 30 fps */
209 if (timecode_to_frames_per_second(cur_timecode) > 30) {
213 // (2) speed & direction
215 /* speed 0 aka transport stopped is interpreted as rolling forward.
216 * keep repeating current frame
218 #define SIGNUM(a) ( (a) < 0 ? -1 : 1)
219 bool speed_changed = false;
221 /* port latency compensation:
222 * The _generated timecode_ is offset by the port-latency,
223 * therefore the offset depends on the direction of transport.
225 framepos_t cycle_start_frame = (current_speed < 0) ? (start_frame - ltc_out_latency.max) : (start_frame + ltc_out_latency.max);
227 /* cycle-start may become negative due to latency compensation */
228 if (cycle_start_frame < 0) { cycle_start_frame = 0; }
230 double new_ltc_speed = (double)(labs(end_frame - start_frame) * SIGNUM(current_speed)) / (double)nframes;
231 if (nominal_frame_rate() != frame_rate()) {
232 new_ltc_speed *= (double)nominal_frame_rate() / (double)frame_rate();
235 if (SIGNUM(new_ltc_speed) != SIGNUM (ltc_speed)) {
236 DEBUG_TRACE (DEBUG::LTC, "LTC TX2: transport changed direction\n");
240 if (ltc_speed != new_ltc_speed) {
241 /* check ./libs/ardour/interpolation.cc CubicInterpolation::interpolate
242 * if target_speed != current_speed we should interpolate, too.
244 * However, currency in A3 target_speed == current_speed for each process cycle
245 * (except for the sign and if target_speed > 8.0).
246 * Besides, above speed calculation uses the difference (end_frame - start_frame).
247 * end_frame is calculated from 'frames_moved' which includes the interpolation.
250 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));
251 speed_changed = true;
252 ltc_encoder_set_filter(ltc_encoder, LTC_RISE_TIME(new_ltc_speed));
255 if (end_frame == start_frame || fabs(current_speed) < 0.1 ) {
256 DEBUG_TRACE (DEBUG::LTC, "LTC TX2: transport is not rolling or absolute-speed < 0.1\n");
257 /* keep repeating current frame
259 * an LTC generator must be able to continue generating LTC when Ardours transport is in stop
260 * some machines do odd things if LTC goes away:
261 * e.g. a tape based machine (video or audio), some think they have gone into park if LTC goes away,
262 * so unspool the tape from the playhead. That might be inconvenient.
263 * If LTC keeps arriving they remain in a stop position with the tape on the playhead.
266 if (!Config->get_ltc_send_continuously()) {
267 ltc_speed = new_ltc_speed;
272 if (fabs(new_ltc_speed) > 10.0) {
273 DEBUG_TRACE (DEBUG::LTC, "LTC TX2: speed is out of bounds.\n");
278 if (ltc_speed == 0 && new_ltc_speed != 0) {
279 DEBUG_TRACE (DEBUG::LTC, "LTC TX2: transport started rolling - reset\n");
283 /* the timecode duration corresponding to the samples that are still
284 * in the buffer. Here, the speed of previous cycle is used to calculate
285 * the alignment at the beginning of this cycle later.
287 double poff = (ltc_buf_len - ltc_buf_off) * ltc_speed;
289 if (speed_changed && new_ltc_speed != 0) {
290 /* we need to re-sample the existing buffer.
291 * "make space for the en-coder to catch up to the new speed"
293 * since the LTC signal is a rectangular waveform we can simply squeeze it
294 * by removing samples or duplicating samples /here and there/.
296 * There may be a more elegant way to do this, in fact one could
297 * simply re-render the buffer using ltc_encoder_encode_byte()
298 * but that'd require some timecode offset buffer magic,
299 * which is left for later..
302 double oldbuflen = (double)(ltc_buf_len - ltc_buf_off);
303 double newbuflen = (double)(ltc_buf_len - ltc_buf_off) * fabs(ltc_speed / new_ltc_speed);
305 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: bufOld %1 bufNew %2 | diff %3\n",
306 (ltc_buf_len - ltc_buf_off), newbuflen, newbuflen - oldbuflen
309 double bufrspdiff = rint(newbuflen - oldbuflen);
311 if (abs(bufrspdiff) > newbuflen || abs(bufrspdiff) > oldbuflen) {
312 DEBUG_TRACE (DEBUG::LTC, "LTC TX2: resampling buffer would destroy information.\n");
315 } else if (bufrspdiff != 0 && newbuflen > oldbuflen) {
317 double samples_to_insert = ceil(newbuflen - oldbuflen);
318 double avg_distance = newbuflen / samples_to_insert;
319 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: resample buffer insert: %1\n", samples_to_insert));
321 for (int rp = ltc_buf_off; rp < ltc_buf_len - 1; ++rp) {
322 const int ro = rp - ltc_buf_off;
323 if (ro < (incnt*avg_distance)) continue;
324 const ltcsnd_sample_t v1 = ltc_enc_buf[rp];
325 const ltcsnd_sample_t v2 = ltc_enc_buf[rp+1];
326 if (v1 != v2 && ro < ((incnt+1)*avg_distance)) continue;
327 memmove(<c_enc_buf[rp+1], <c_enc_buf[rp], ltc_buf_len-rp);
331 } else if (bufrspdiff != 0 && newbuflen < oldbuflen) {
332 double samples_to_remove = ceil(oldbuflen - newbuflen);
333 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: resample buffer - remove: %1\n", samples_to_remove));
334 if (oldbuflen <= samples_to_remove) {
335 ltc_buf_off = ltc_buf_len= 0;
337 double avg_distance = newbuflen / samples_to_remove;
339 for (int rp = ltc_buf_off; rp < ltc_buf_len - 1; ++rp) {
340 const int ro = rp - ltc_buf_off;
341 if (ro < (rmcnt*avg_distance)) continue;
342 const ltcsnd_sample_t v1 = ltc_enc_buf[rp];
343 const ltcsnd_sample_t v2 = ltc_enc_buf[rp+1];
344 if (v1 != v2 && ro < ((rmcnt+1)*avg_distance)) continue;
345 memmove(<c_enc_buf[rp], <c_enc_buf[rp+1], ltc_buf_len-rp-1);
353 ltc_speed = new_ltc_speed;
354 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: transport speed %1.\n", ltc_speed));
356 // (3) bit/sample alignment
357 Timecode::Time tc_start;
358 framepos_t tc_sample_start;
360 /* calc timecode frame from current position - round down to nearest timecode */
361 Timecode::sample_to_timecode(cycle_start_frame, tc_start, true, false,
362 timecode_frames_per_second(),
363 timecode_drop_frames(),
364 (double)frame_rate(),
365 config.get_subframes_per_frame(),
366 config.get_timecode_offset_negative(), config.get_timecode_offset()
369 /* convert timecode back to sample-position */
370 Timecode::timecode_to_sample (tc_start, tc_sample_start, true, false,
371 (double)frame_rate(),
372 config.get_subframes_per_frame(),
373 config.get_timecode_offset_negative(), config.get_timecode_offset()
376 /* difference between current frame and TC frame in samples */
377 frameoffset_t soff = cycle_start_frame - tc_sample_start;
378 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX3: A3cycle: %1 = A3tc: %2 +off: %3\n",
379 cycle_start_frame, tc_sample_start, soff));
382 // (4) check if alignment matches
383 const double fptcf = frames_per_timecode_frame();
385 /* maximum difference of bit alignment in audio-samples.
387 * if transport and LTC generator differs more than this, the LTC
388 * generator will be re-initialized
390 * due to rounding error and variations in LTC-bit duration depending
391 * on the speed, it can be off by +- ltc_speed audio-samples.
392 * When the playback speed changes, it can actually reach +- 2 * ltc_speed
393 * in the cycle _after_ the speed changed. The average delta however is 0.
397 if (config.get_external_sync() && slave()) {
398 maxdiff = slave()->resolution();
400 maxdiff = ceil(fabs(ltc_speed))*2.0;
403 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: enc: %1 + %2 - %3 || buf-bytes: %4 enc-byte: %5\n",
404 ltc_enc_pos, ltc_enc_cnt, poff, (ltc_buf_len - ltc_buf_off), poff, ltc_enc_byte));
406 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: enc-pos: %1 | d: %2\n",
407 ltc_enc_pos + ltc_enc_cnt - poff,
408 rint(ltc_enc_pos + ltc_enc_cnt - poff) - cycle_start_frame
412 || (ltc_speed != 0 && fabs(ceil(ltc_enc_pos + ltc_enc_cnt - poff) - cycle_start_frame) > maxdiff)
418 /* set frame to encode */
420 tc.hours = tc_start.hours;
421 tc.mins = tc_start.minutes;
422 tc.secs = tc_start.seconds;
423 tc.frame = tc_start.frames;
424 ltc_encoder_set_timecode(ltc_encoder, &tc);
426 /* workaround for libltc recognizing 29.97 and 30000/1001 as drop-frame TC.
427 * In A3 30000/1001 or 30 fps can be drop-frame.
430 ltc_encoder_get_frame(ltc_encoder, <cframe);
431 ltcframe.dfbit = timecode_has_drop_frames(cur_timecode)?1:0;
432 ltc_encoder_set_frame(ltc_encoder, <cframe);
435 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: now: %1 trs: %2 toff %3\n", cycle_start_frame, tc_sample_start, soff));
438 if (soff < 0 || soff >= fptcf) {
439 /* session framerate change between (2) and now */
444 if (ltc_speed < 0 ) {
445 /* calculate the byte that starts at or after the current position */
446 ltc_enc_byte = floor((10.0 * soff) / (fptcf));
447 ltc_enc_cnt = ltc_enc_byte * fptcf / 10.0;
449 /* calculate difference between the current position and the byte to send */
450 cyc_off = soff- ceil(ltc_enc_cnt);
453 /* calculate the byte that starts at or after the current position */
454 ltc_enc_byte = ceil((10.0 * soff) / fptcf);
455 ltc_enc_cnt = ltc_enc_byte * fptcf / 10.0;
457 /* calculate difference between the current position and the byte to send */
458 cyc_off = ceil(ltc_enc_cnt) - soff;
460 if (ltc_enc_byte == 10) {
462 ltc_encoder_inc_timecode(ltc_encoder);
466 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX5 restart encoder: soff %1 byte %2 cycoff %3\n",
467 soff, ltc_enc_byte, cyc_off));
469 if (cyc_off > 0 && cyc_off <= nframes) {
470 /* offset in this cycle */
471 txf= rint(cyc_off / fabs(ltc_speed));
472 memset(out, 0, cyc_off * sizeof(Sample));
474 /* resync next cycle */
475 memset(out, 0, nframes * sizeof(Sample));
479 ltc_enc_pos = tc_sample_start;
481 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX5 restart @ %1 + %2 - %3 | byte %4\n",
482 ltc_enc_pos, ltc_enc_cnt, cyc_off, ltc_enc_byte));
484 else if (ltc_speed != 0 && (fptcf / ltc_speed / 80) > 3 ) {
485 /* reduce (low freq) jitter.
486 * The granularity of the LTC encoder speed is 1 byte =
487 * (frames-per-timecode-frame / 10) audio-samples.
488 * Thus, tiny speed changes [as produced by the slave]
489 * may not have any effect in the cycle when they occur,
490 * but they will add up over time.
492 * This is a linear approx to compensate for this drift
493 * and prempt re-sync when the drift builds up.
495 * However, for very fast speeds - when 1 LTC bit is
496 * <= 3 audio-sample - adjusting speed may lead to
499 * To do better than this, resampling (or a rewrite of the
500 * encoder) is required.
502 ltc_speed -= ((ltc_enc_pos + ltc_enc_cnt - poff) - cycle_start_frame) / engine().frame_rate();
506 // (6) encode and output
508 #ifdef LTC_GEN_TXDBUG
509 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.1 @%1 [ %2 / %3 ]\n", txf, ltc_buf_off, ltc_buf_len));
511 // (6a) send remaining buffer
512 while ((ltc_buf_off < ltc_buf_len) && (txf < nframes)) {
513 const float v1 = ltc_enc_buf[ltc_buf_off++] - 128.0;
514 const Sample val = (Sample) (v1*ltcvol);
517 #ifdef LTC_GEN_TXDBUG
518 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.2 @%1 [ %2 / %3 ]\n", txf, ltc_buf_off, ltc_buf_len));
521 if (txf >= nframes) {
522 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX7 enc: %1 [ %2 / %3 ] byte: %4 spd %5 fpp %6 || nf: %7\n",
523 ltc_enc_pos, ltc_buf_off, ltc_buf_len, ltc_enc_byte, ltc_speed, nframes, txf));
530 // (6b) encode LTC, bump timecode
533 ltc_enc_byte = (ltc_enc_byte + 9)%10;
534 if (ltc_enc_byte == 9) {
535 ltc_encoder_dec_timecode(ltc_encoder);
536 ltc_tx_recalculate_position();
541 if (ltc_encoder_encode_byte(ltc_encoder, ltc_enc_byte, (ltc_speed==0)?1.0:(1.0/ltc_speed))) {
542 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.3 encoder error byte %1\n", ltc_enc_byte));
543 ltc_encoder_buffer_flush(ltc_encoder);
547 int enc_frames = ltc_encoder_get_buffer(ltc_encoder, &(ltc_enc_buf[ltc_buf_len]));
548 #ifdef LTC_GEN_FRAMEDBUG
549 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));
551 if (enc_frames <=0) {
552 DEBUG_TRACE (DEBUG::LTC, "LTC TX6.3 encoder empty buffer.\n");
553 ltc_encoder_buffer_flush(ltc_encoder);
558 ltc_buf_len += enc_frames;
560 ltc_enc_cnt -= fptcf/10.0;
562 ltc_enc_cnt += fptcf/10.0;
564 if (ltc_speed >= 0) {
565 ltc_enc_byte = (ltc_enc_byte + 1)%10;
566 if (ltc_enc_byte == 0 && ltc_speed != 0) {
567 ltc_encoder_inc_timecode(ltc_encoder);
568 #if 0 /* force fixed parity -- scope debug */
570 ltc_encoder_get_frame(ltc_encoder, &f);
571 f.biphase_mark_phase_correction=0;
572 ltc_encoder_set_frame(ltc_encoder, &f);
574 ltc_tx_recalculate_position();
576 } else if (ltc_enc_byte == 0) {
580 #ifdef LTC_GEN_FRAMEDBUG
581 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));
585 dynamic_cast<AudioBuffer*>(&buf)->set_written (true);