libs/ardour/session_ltc.cc

   1 /*
   2   Copyright (C) 2012 Paul Davis
   3   Written by Robin Gareus <robin@gareus.org>
   4
   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.
   9
  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.
  14
  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.
  18
  19 */
  20
  21 #include "timecode/time.h"
  22
  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"
  29
  30 #include "i18n.h"
  31
  32 using namespace std;
  33 using namespace ARDOUR;
  34 using namespace MIDI;
  35 using namespace PBD;
  36 using namespace Timecode;
  37
  38 /* really verbose timing debug */
  39 //#define LTC_GEN_FRAMEDBUG
  40 //#define LTC_GEN_TXDBUG
  41
  42 void
  43 Session::ltc_tx_initialize()
  44 {
  45         ltc_enc_tcformat = config.get_timecode_format();
  46
  47         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)));
  48         ltc_encoder = ltc_encoder_create(nominal_frame_rate(),
  49                         timecode_to_frames_per_second(ltc_enc_tcformat),
  50                         0);
  51
  52         ltc_encoder_set_bufsize(ltc_encoder, nominal_frame_rate(), 23.0);
  53
  54         /* buffersize for 1 LTC frame: (1 + sample-rate / fps) bytes
  55          * usually returned by ltc_encoder_get_buffersize(encoder)
  56          *
  57          * since the fps can change and A3's  min fps: 24000/1001 */
  58         ltc_enc_buf = (ltcsnd_sample_t*) calloc((nominal_frame_rate() / 23), sizeof(ltcsnd_sample_t));
  59         ltc_speed = 0;
  60         ltc_tx_reset();
  61         Xrun.connect_same_thread (*this, boost::bind (&Session::ltc_tx_reset, this));
  62         engine().GraphReordered.connect_same_thread (*this, boost::bind (&Session::ltc_tx_reset, this));
  63 }
  64
  65 void
  66 Session::ltc_tx_cleanup()
  67 {
  68         DEBUG_TRACE (DEBUG::LTC, "LTC TX cleanup\n");
  69         if (ltc_enc_buf) free(ltc_enc_buf);
  70         ltc_encoder_free(ltc_encoder);
  71         ltc_encoder = NULL;
  72 }
  73
  74 void
  75 Session::ltc_tx_reset()
  76 {
  77         DEBUG_TRACE (DEBUG::LTC, "LTC TX reset\n");
  78         ltc_enc_pos = -9999; // force re-start
  79         ltc_buf_len = 0;
  80         ltc_buf_off = 0;
  81         ltc_enc_byte = 0;
  82         ltc_enc_cnt = 0;
  83
  84         boost::shared_ptr<Port> ltcport = ltc_output_port();
  85         if (ltcport) {
  86                 ltcport->get_connected_latency_range(ltc_out_latency, true);
  87         }
  88 }
  89
  90 void
  91 Session::ltc_tx_recalculate_position()
  92 {
  93         SMPTETimecode enctc;
  94         Timecode::Time a3tc;
  95         ltc_encoder_get_timecode(ltc_encoder, &enctc);
  96
  97         a3tc.hours   = enctc.hours;
  98         a3tc.minutes = enctc.mins;
  99         a3tc.seconds = enctc.secs;
 100         a3tc.frames  = enctc.frame;
 101         a3tc.rate = timecode_to_frames_per_second(ltc_enc_tcformat);
 102         a3tc.drop = timecode_has_drop_frames(ltc_enc_tcformat);
 103
 104         Timecode::timecode_to_sample (a3tc, ltc_enc_pos, true, false,
 105                 double(frame_rate()),
 106                 config.get_subframes_per_frame(),
 107                 config.get_timecode_offset_negative(), config.get_timecode_offset()
 108                 );
 109 }
 110
 111 void
 112 Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end_frame,
 113                                           double target_speed, double current_speed,
 114                                           pframes_t nframes)
 115 {
 116         assert (nframes > 0);
 117
 118         Sample *out;
 119         pframes_t txf = 0;
 120         boost::shared_ptr<Port> ltcport = ltc_output_port();
 121
 122         Buffer& buf (ltcport->get_buffer (nframes));
 123
 124         if (!ltc_encoder || !ltc_enc_buf) {
 125                 return;
 126         }
 127
 128         SyncSource sync_src = Config->get_sync_source();
 129         if (engine().freewheeling() || !Config->get_send_ltc()
 130             /* TODO
 131              * decide which time-sources we can generated LTC from.
 132              * Internal, JACK or sample-synced slaves should be fine.
 133              * talk to oofus.
 134              *
 135              || (config.get_external_sync() && sync_src == LTC)
 136              || (config.get_external_sync() && sync_src == MTC)
 137             */
 138              ||(config.get_external_sync() && sync_src == MIDIClock)
 139                 ) {
 140                 return;
 141         }
 142
 143         out = dynamic_cast<AudioBuffer*>(&buf)->data ();
 144
 145         /* range from libltc (38..218) || - 128.0  -> (-90..90) */
 146         const float ltcvol = Config->get_ltc_output_volume()/(90.0); // pow(10, db/20.0)/(90.0);
 147
 148 #if 1
 149         /* TODO read layency only on demand -> ::ltc_tx_reset()
 150          * this is already prepared.
 151          *
 152          * ..but first fix jack2 issue with re-computing latency
 153          * in the correct order. Until then, querying it in the
 154          * process-callback is the only way to get the current value
 155          */
 156         ltcport->get_connected_latency_range(ltc_out_latency, true);
 157 #endif
 158         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX %1 to %2 / %3 | lat: %4\n", start_frame, end_frame, nframes, ltc_out_latency.max));
 159
 160         /* all systems go. Now here's the plan:
 161          *
 162          *  1) check if fps has changed
 163          *  2) check direction of encoding, calc speed, re-sample existing buffer
 164          *  3) calculate frame and byte to send aligned to jack-period size
 165          *  4) check if it's the frame/byte that is already in the queue
 166          *  5) if (4) mismatch, re-calculate offset of LTC frame relative to period size
 167          *  6) actual LTC audio output
 168          *  6a) send remaining part of already queued frame; break on nframes
 169          *  6b) encode new LTC-frame byte
 170          *  6c) goto 6a
 171          *  7) done
 172          */
 173
 174         // (1) check fps
 175         TimecodeFormat cur_timecode = config.get_timecode_format();
 176         if (cur_timecode != ltc_enc_tcformat) {
 177                 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)));
 178                 if (ltc_encoder_reinit(ltc_encoder, nominal_frame_rate(), timecode_to_frames_per_second(cur_timecode), 0)) {
 179                         PBD::error << _("LTC encoder: invalid framerate - LTC encoding is disabled for the remainder of this session.") << endmsg;
 180                         ltc_tx_cleanup();
 181                         return;
 182                 }
 183                 ltc_enc_tcformat = cur_timecode;
 184                 ltc_tx_reset();
 185         }
 186
 187         /* LTC is max. 30 fps */
 188         if (timecode_to_frames_per_second(cur_timecode) > 30) {
 189                 return;
 190         }
 191
 192         // (2) speed & direction
 193
 194         /* speed 0 aka transport stopped is interpreted as rolling forward.
 195          * keep repeating current frame
 196          */
 197 #define SIGNUM(a) ( (a) < 0 ? -1 : 1)
 198         bool speed_changed = false;
 199
 200         /* use port latency compensation */
 201 #if 1
 202         /* The generated timecode is offset by the port-latency,
 203          * therefore the offset depends on the direction of transport.
 204          */
 205         framepos_t cycle_start_frame = (current_speed < 0) ? (start_frame + ltc_out_latency.max) : (start_frame - ltc_out_latency.max);
 206 #else
 207         /* This comes in handy when testing sync - record output on an A3 track
 208          * see also http://tracker.ardour.org/view.php?id=5073
 209          */
 210         framepos_t cycle_start_frame = start_frame;
 211 #endif
 212
 213         /* cycle-start may become negative due to latency compensation */
 214         if (cycle_start_frame < 0) { cycle_start_frame = 0; }
 215
 216         double new_ltc_speed = double(labs(end_frame - start_frame) * SIGNUM(current_speed)) / double(nframes);
 217
 218         if (SIGNUM(new_ltc_speed) != SIGNUM (ltc_speed)) {
 219                 DEBUG_TRACE (DEBUG::LTC, "LTC TX2: transport changed direction\n");
 220                 ltc_tx_reset();
 221         }
 222
 223         if (ltc_speed != new_ltc_speed) {
 224                 /* check ./libs/ardour/interpolation.cc  CubicInterpolation::interpolate
 225                  * if target_speed != current_speed we should interpolate, too.
 226                  *
 227                  * However, currency in A3 target_speed == current_speed for each process cycle
 228                  * (except for the sign and if target_speed > 8.0).
 229                  * Besides, above speed calculation uses the difference (end_frame - start_frame).
 230                  * end_frame is calculated from 'frames_moved' which includes the interpolation.
 231                  * so we're good.
 232                  */
 233                 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));
 234                 speed_changed = true;
 235         }
 236
 237         if (end_frame == start_frame || fabs(current_speed) < 0.1 ) {
 238                 DEBUG_TRACE (DEBUG::LTC, "LTC TX2: transport is not rolling or absolute-speed < 0.1\n");
 239                 /* keep repeating current frame
 240                  *
 241                  * an LTC generator must be able to continue generating LTC when Ardours transport is in stop
 242                  * some machines do odd things if LTC goes away:
 243                  * e.g. a tape based machine (video or audio), some think they have gone into park if LTC goes away,
 244                  * so unspool the tape from the playhead. That might be inconvenient.
 245                  * If LTC keeps arriving they remain in a stop position with the tape on the playhead.
 246                  */
 247                 new_ltc_speed = 0;
 248                 if (!Config->get_ltc_send_continuously()) {
 249                         ltc_speed = new_ltc_speed;
 250                         return;
 251                 }
 252         }
 253
 254         if (fabs(new_ltc_speed) > 10.0) {
 255                 DEBUG_TRACE (DEBUG::LTC, "LTC TX2: speed is out of bounds.\n");
 256                 ltc_tx_reset();
 257                 return;
 258         }
 259
 260         if (ltc_speed == 0 && new_ltc_speed != 0) {
 261                 DEBUG_TRACE (DEBUG::LTC, "LTC TX2: transport started rolling - reset\n");
 262                 ltc_tx_reset();
 263         }
 264
 265         /* the timecode duration corresponding to the samples that are still
 266          * in the buffer. Here, the speed of previous cycle is used to calculate
 267          * the alignment at the beginning of this cycle later.
 268          */
 269         double poff = (ltc_buf_len - ltc_buf_off) * ltc_speed;
 270
 271         if (speed_changed && new_ltc_speed != 0) {
 272                 /* we need to re-sample the existing buffer.
 273                  * "make space for the en-coder to catch up to the new speed"
 274                  *
 275                  * since the LTC signal is a rectangular waveform we can simply squeeze it
 276                  * by removing samples or duplicating samples /here and there/.
 277                  *
 278                  * There may be a more elegant way to do this, in fact one could
 279                  * simply re-render the buffer using ltc_encoder_encode_byte()
 280                  * but that'd require some timecode offset buffer magic,
 281                  * which is left for later..
 282                  */
 283
 284                 double oldbuflen = double(ltc_buf_len - ltc_buf_off);
 285                 double newbuflen = double(ltc_buf_len - ltc_buf_off) * fabs(ltc_speed / new_ltc_speed);
 286
 287                 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: bufOld %1 bufNew %2 | diff %3\n",
 288                                         (ltc_buf_len - ltc_buf_off), newbuflen, newbuflen - oldbuflen
 289                                         ));
 290
 291                 double bufrspdiff = rint(newbuflen - oldbuflen);
 292
 293                 if (abs(bufrspdiff) > newbuflen || abs(bufrspdiff) > oldbuflen) {
 294                         DEBUG_TRACE (DEBUG::LTC, "LTC TX2: resampling buffer would destroy information.\n");
 295                         ltc_tx_reset();
 296                         poff = 0;
 297                 } else if (bufrspdiff != 0 && newbuflen > oldbuflen) {
 298                         int incnt = 0;
 299                         double samples_to_insert = ceil(newbuflen - oldbuflen);
 300                         double avg_distance = newbuflen / samples_to_insert;
 301                         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: resample buffer insert: %1\n", samples_to_insert));
 302
 303                         for (int rp = ltc_buf_off; rp < ltc_buf_len - 1; ++rp) {
 304                                 const int ro = rp - ltc_buf_off;
 305                                 if (ro < (incnt*avg_distance)) continue;
 306                                 const ltcsnd_sample_t v1 = ltc_enc_buf[rp];
 307                                 const ltcsnd_sample_t v2 = ltc_enc_buf[rp+1];
 308                                 if (v1 != v2 && ro < ((incnt+1)*avg_distance)) continue;
 309                                 memmove(&ltc_enc_buf[rp+1], &ltc_enc_buf[rp], ltc_buf_len-rp);
 310                                 incnt++;
 311                                 ltc_buf_len++;
 312                         }
 313                 } else if (bufrspdiff != 0 && newbuflen < oldbuflen) {
 314                         double samples_to_remove = ceil(oldbuflen - newbuflen);
 315                         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: resample buffer - remove: %1\n", samples_to_remove));
 316                         if (oldbuflen <= samples_to_remove) {
 317                                 ltc_buf_off = ltc_buf_len= 0;
 318                         } else {
 319                                 double avg_distance = newbuflen / samples_to_remove;
 320                                 int rmcnt = 0;
 321                                 for (int rp = ltc_buf_off; rp < ltc_buf_len - 1; ++rp) {
 322                                         const int ro = rp - ltc_buf_off;
 323                                         if (ro < (rmcnt*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 < ((rmcnt+1)*avg_distance)) continue;
 327                                         memmove(&ltc_enc_buf[rp], &ltc_enc_buf[rp+1], ltc_buf_len-rp-1);
 328                                         ltc_buf_len--;
 329                                         rmcnt++;
 330                                 }
 331                         }
 332                 }
 333         }
 334
 335         ltc_speed = new_ltc_speed;
 336         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: transport speed %1.\n", ltc_speed));
 337
 338         // (3) bit/sample alignment
 339         Timecode::Time tc_start;
 340         framepos_t tc_sample_start;
 341
 342         /* calc timecode frame from current position - round down to nearest timecode */
 343         sample_to_timecode(cycle_start_frame, tc_start, true, false);
 344
 345         /* convert timecode back to sample-position */
 346         Timecode::timecode_to_sample (tc_start, tc_sample_start, true, false,
 347                 double(frame_rate()),
 348                 config.get_subframes_per_frame(),
 349                 config.get_timecode_offset_negative(), config.get_timecode_offset()
 350                 );
 351
 352         /* difference between current frame and TC frame in samples */
 353         frameoffset_t soff = cycle_start_frame - tc_sample_start;
 354         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX3: A3cycle: %1 = A3tc: %2 +off: %3\n",
 355                                 cycle_start_frame, tc_sample_start, soff));
 356
 357
 358         // (4) check if alignment matches
 359         const double fptcf = frames_per_timecode_frame();
 360
 361         /* maximum difference of bit alignment in audio-samples.
 362          *
 363          * if transport and LTC generator differs more than this, the LTC
 364          * generator will be re-initialized
 365          *
 366          * due to rounding error and variations in LTC-bit duration depending
 367          * on the speed, it can be off by +- ltc_speed audio-samples.
 368          * When the playback speed changes, it can actually reach +- 2 * ltc_speed
 369          * in the cycle _after_ the speed changed. The average delta however is 0.
 370          */
 371         double maxdiff;
 372
 373         if (config.get_external_sync() && slave()) {
 374                 maxdiff = slave()->resolution();
 375         } else {
 376                 maxdiff = ceil(fabs(ltc_speed))*2.0;
 377         }
 378
 379         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: enc: %1 + %2 - %3 || buf-bytes: %4 enc-byte: %5\n",
 380                                 ltc_enc_pos, ltc_enc_cnt, poff, (ltc_buf_len - ltc_buf_off), poff, ltc_enc_byte));
 381
 382         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: enc-pos: %1  | d: %2\n",
 383                                 ltc_enc_pos + ltc_enc_cnt - poff,
 384                                 rint(ltc_enc_pos + ltc_enc_cnt - poff) - cycle_start_frame
 385                                 ));
 386
 387         if (ltc_speed != 0 && fabs(ceil(ltc_enc_pos + ltc_enc_cnt - poff) - cycle_start_frame) > maxdiff) {
 388
 389                 // (5) re-align
 390                 ltc_tx_reset();
 391
 392                 /* set frame to encode */
 393                 SMPTETimecode tc;
 394                 tc.hours = tc_start.hours;
 395                 tc.mins = tc_start.minutes;
 396                 tc.secs = tc_start.seconds;
 397                 tc.frame = tc_start.frames;
 398                 ltc_encoder_set_timecode(ltc_encoder, &tc);
 399
 400                 /* workaround for libltc recognizing 29.97 and 30000/1001 as drop-frame TC.
 401                  * In A3 30000/1001 or 30 fps can be drop-frame.
 402                  */
 403                 LTCFrame ltcframe;
 404                 ltc_encoder_get_frame(ltc_encoder, &ltcframe);
 405                 ltcframe.dfbit = timecode_has_drop_frames(cur_timecode)?1:0;
 406                 ltc_encoder_set_frame(ltc_encoder, &ltcframe);
 407
 408
 409                 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: now: %1 trs: %2 toff %3\n", cycle_start_frame, tc_sample_start, soff));
 410
 411                 uint32_t cyc_off;
 412                 if (soff < 0 || soff >= fptcf) {
 413                         /* session framerate change between (2) and now */
 414                         ltc_tx_reset();
 415                         return;
 416                 }
 417
 418                 if (ltc_speed < 0 ) {
 419                         /* calculate the byte that starts at or after the current position */
 420                         ltc_enc_byte = floor((10.0 * soff) / (fptcf));
 421                         ltc_enc_cnt = double(ltc_enc_byte * fptcf / 10.0);
 422
 423                         /* calculate difference between the current position and the byte to send */
 424                         cyc_off = soff- ceil(ltc_enc_cnt);
 425
 426                 } else {
 427                         /* calculate the byte that starts at or after the current position */
 428                         ltc_enc_byte = ceil((10.0 * soff) / fptcf);
 429                         ltc_enc_cnt = double(ltc_enc_byte * fptcf / 10.0);
 430
 431                         /* calculate difference between the current position and the byte to send */
 432                         cyc_off = ceil(ltc_enc_cnt) - soff;
 433
 434                         if (ltc_enc_byte == 10) {
 435                                 ltc_enc_byte = 0;
 436                                 ltc_encoder_inc_timecode(ltc_encoder);
 437                         }
 438                 }
 439
 440                 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX5 restart encoder: soff %1 byte %2 cycoff %3\n",
 441                                         soff, ltc_enc_byte, cyc_off));
 442
 443                 if (cyc_off > 0 && cyc_off <= nframes) {
 444                         /* offset in this cycle */
 445                         txf= rint(cyc_off / fabs(ltc_speed));
 446                         memset(out, 0, cyc_off * sizeof(Sample));
 447                 } else {
 448                         /* resync next cycle */
 449                         memset(out, 0, nframes * sizeof(Sample));
 450                         return;
 451                 }
 452
 453                 ltc_enc_pos = tc_sample_start;
 454
 455                 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX5 restart @ %1 + %2 - %3 |  byte %4\n",
 456                                         ltc_enc_pos, ltc_enc_cnt, cyc_off, ltc_enc_byte));
 457         }
 458
 459
 460         // (6) encode and output
 461         while (1) {
 462 #ifdef LTC_GEN_TXDBUG
 463                 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.1 @%1  [ %2 / %3 ]\n", txf, ltc_buf_off, ltc_buf_len));
 464 #endif
 465                 // (6a) send remaining buffer
 466                 while ((ltc_buf_off < ltc_buf_len) && (txf < nframes)) {
 467                         const float v1 = ltc_enc_buf[ltc_buf_off++] - 128.0;
 468                         const Sample val = (Sample) (v1*ltcvol);
 469                         out[txf++] = val;
 470                 }
 471 #ifdef LTC_GEN_TXDBUG
 472                 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.2 @%1  [ %2 / %3 ]\n", txf, ltc_buf_off, ltc_buf_len));
 473 #endif
 474
 475                 if (txf >= nframes) {
 476                         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX7 enc: %1 [ %2 / %3 ] byte: %4 spd %5 fpp %6 || nf: %7\n",
 477                                                 ltc_enc_pos, ltc_buf_off, ltc_buf_len, ltc_enc_byte, ltc_speed, nframes, txf));
 478                         break;
 479                 }
 480
 481                 ltc_buf_len = 0;
 482                 ltc_buf_off = 0;
 483
 484                 // (6b) encode LTC, bump timecode
 485
 486                 if (ltc_speed < 0) {
 487                         ltc_enc_byte = (ltc_enc_byte + 9)%10;
 488                         if (ltc_enc_byte == 9) {
 489                                 ltc_encoder_dec_timecode(ltc_encoder);
 490                                 ltc_tx_recalculate_position();
 491                                 ltc_enc_cnt = fptcf;
 492                         }
 493                 }
 494
 495                 if (ltc_encoder_encode_byte(ltc_encoder, ltc_enc_byte, (ltc_speed==0)?1.0:(1.0/ltc_speed))) {
 496                         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.3 encoder error byte %1\n", ltc_enc_byte));
 497                         ltc_encoder_buffer_flush(ltc_encoder);
 498                         ltc_tx_reset();
 499                         return;
 500                 }
 501                 int enc_frames = ltc_encoder_get_buffer(ltc_encoder, &(ltc_enc_buf[ltc_buf_len]));
 502 #ifdef LTC_GEN_FRAMEDBUG
 503                 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));
 504 #endif
 505                 if (enc_frames <=0) {
 506                         DEBUG_TRACE (DEBUG::LTC, "LTC TX6.3 encoder empty buffer.\n");
 507                         ltc_encoder_buffer_flush(ltc_encoder);
 508                         ltc_tx_reset();
 509                         return;
 510                 }
 511
 512                 ltc_buf_len += enc_frames;
 513                 if (ltc_speed < 0)
 514                         ltc_enc_cnt -= fptcf/10.0;
 515                 else
 516                         ltc_enc_cnt += fptcf/10.0;
 517
 518                 if (ltc_speed >= 0) {
 519                         ltc_enc_byte = (ltc_enc_byte + 1)%10;
 520                         if (ltc_enc_byte == 0 && ltc_speed != 0) {
 521                                 ltc_encoder_inc_timecode(ltc_encoder);
 522                                 ltc_tx_recalculate_position();
 523                                 ltc_enc_cnt = 0;
 524                         } else if (ltc_enc_byte == 0) {
 525                                 ltc_enc_cnt = 0;
 526                         }
 527                 }
 528 #ifdef LTC_GEN_FRAMEDBUG
 529                 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));
 530 #endif
 531         }
 532
 533         dynamic_cast<AudioBuffer*>(&buf)->set_written (true);
 534         return;
 535 }