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         ltc_tx_resync_latency();
  62         Xrun.connect_same_thread (*this, boost::bind (&Session::ltc_tx_reset, this));
  63         engine().GraphReordered.connect_same_thread (*this, boost::bind (&Session::ltc_tx_resync_latency, this));
  64 }
  65
  66 void
  67 Session::ltc_tx_cleanup()
  68 {
  69         DEBUG_TRACE (DEBUG::LTC, "LTC TX cleanup\n");
  70         if (ltc_enc_buf) free(ltc_enc_buf);
  71         ltc_encoder_free(ltc_encoder);
  72         ltc_encoder = NULL;
  73 }
  74
  75 void
  76 Session::ltc_tx_resync_latency()
  77 {
  78         DEBUG_TRACE (DEBUG::LTC, "LTC TX resync latency\n");
  79         if (!deletion_in_progress()) {
  80                 boost::shared_ptr<Port> ltcport = ltc_output_port();
  81                 if (ltcport) {
  82                         ltcport->get_connected_latency_range(ltc_out_latency, true);
  83                 }
  84         }
  85 }
  86
  87 void
  88 Session::ltc_tx_reset()
  89 {
  90         DEBUG_TRACE (DEBUG::LTC, "LTC TX reset\n");
  91         ltc_enc_pos = -9999; // force re-start
  92         ltc_buf_len = 0;
  93         ltc_buf_off = 0;
  94         ltc_enc_byte = 0;
  95         ltc_enc_cnt = 0;
  96 }
  97
  98 void
  99 Session::ltc_tx_recalculate_position()
 100 {
 101         SMPTETimecode enctc;
 102         Timecode::Time a3tc;
 103         ltc_encoder_get_timecode(ltc_encoder, &enctc);
 104
 105         a3tc.hours   = enctc.hours;
 106         a3tc.minutes = enctc.mins;
 107         a3tc.seconds = enctc.secs;
 108         a3tc.frames  = enctc.frame;
 109         a3tc.rate = timecode_to_frames_per_second(ltc_enc_tcformat);
 110         a3tc.drop = timecode_has_drop_frames(ltc_enc_tcformat);
 111
 112         Timecode::timecode_to_sample (a3tc, ltc_enc_pos, true, false,
 113                 double(frame_rate()),
 114                 config.get_subframes_per_frame(),
 115                 config.get_timecode_offset_negative(), config.get_timecode_offset()
 116                 );
 117 }
 118
 119 void
 120 Session::ltc_tx_send_time_code_for_cycle (framepos_t start_frame, framepos_t end_frame,
 121                                           double target_speed, double current_speed,
 122                                           pframes_t nframes)
 123 {
 124         assert (nframes > 0);
 125
 126         Sample *out;
 127         pframes_t txf = 0;
 128         boost::shared_ptr<Port> ltcport = ltc_output_port();
 129
 130         Buffer& buf (ltcport->get_buffer (nframes));
 131
 132         if (!ltc_encoder || !ltc_enc_buf) {
 133                 return;
 134         }
 135
 136         SyncSource sync_src = Config->get_sync_source();
 137         if (engine().freewheeling() || !Config->get_send_ltc()
 138             /* TODO
 139              * decide which time-sources we can generated LTC from.
 140              * Internal, JACK or sample-synced slaves should be fine.
 141              * talk to oofus.
 142              *
 143              || (config.get_external_sync() && sync_src == LTC)
 144              || (config.get_external_sync() && sync_src == MTC)
 145             */
 146              ||(config.get_external_sync() && sync_src == MIDIClock)
 147                 ) {
 148                 return;
 149         }
 150
 151         out = dynamic_cast<AudioBuffer*>(&buf)->data ();
 152
 153         /* range from libltc (38..218) || - 128.0  -> (-90..90) */
 154         const float ltcvol = Config->get_ltc_output_volume()/(90.0); // pow(10, db/20.0)/(90.0);
 155
 156         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX %1 to %2 / %3 | lat: %4\n", start_frame, end_frame, nframes, ltc_out_latency.max));
 157
 158         /* all systems go. Now here's the plan:
 159          *
 160          *  1) check if fps has changed
 161          *  2) check direction of encoding, calc speed, re-sample existing buffer
 162          *  3) calculate frame and byte to send aligned to jack-period size
 163          *  4) check if it's the frame/byte that is already in the queue
 164          *  5) if (4) mismatch, re-calculate offset of LTC frame relative to period size
 165          *  6) actual LTC audio output
 166          *  6a) send remaining part of already queued frame; break on nframes
 167          *  6b) encode new LTC-frame byte
 168          *  6c) goto 6a
 169          *  7) done
 170          */
 171
 172         // (1) check fps
 173         TimecodeFormat cur_timecode = config.get_timecode_format();
 174         if (cur_timecode != ltc_enc_tcformat) {
 175                 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)));
 176                 if (ltc_encoder_reinit(ltc_encoder, nominal_frame_rate(), timecode_to_frames_per_second(cur_timecode), 0)) {
 177                         PBD::error << _("LTC encoder: invalid framerate - LTC encoding is disabled for the remainder of this session.") << endmsg;
 178                         ltc_tx_cleanup();
 179                         return;
 180                 }
 181                 ltc_enc_tcformat = cur_timecode;
 182                 ltc_tx_reset();
 183         }
 184
 185         /* LTC is max. 30 fps */
 186         if (timecode_to_frames_per_second(cur_timecode) > 30) {
 187                 return;
 188         }
 189
 190         // (2) speed & direction
 191
 192         /* speed 0 aka transport stopped is interpreted as rolling forward.
 193          * keep repeating current frame
 194          */
 195 #define SIGNUM(a) ( (a) < 0 ? -1 : 1)
 196         bool speed_changed = false;
 197
 198         /* port latency compensation:
 199          * The _generated timecode_ is offset by the port-latency,
 200          * therefore the offset depends on the direction of transport.
 201          */
 202         framepos_t cycle_start_frame = (current_speed < 0) ? (start_frame - ltc_out_latency.max) : (start_frame + ltc_out_latency.max);
 203
 204         /* cycle-start may become negative due to latency compensation */
 205         if (cycle_start_frame < 0) { cycle_start_frame = 0; }
 206
 207         double new_ltc_speed = double(labs(end_frame - start_frame) * SIGNUM(current_speed)) / double(nframes);
 208
 209         if (SIGNUM(new_ltc_speed) != SIGNUM (ltc_speed)) {
 210                 DEBUG_TRACE (DEBUG::LTC, "LTC TX2: transport changed direction\n");
 211                 ltc_tx_reset();
 212         }
 213
 214         if (ltc_speed != new_ltc_speed) {
 215                 /* check ./libs/ardour/interpolation.cc  CubicInterpolation::interpolate
 216                  * if target_speed != current_speed we should interpolate, too.
 217                  *
 218                  * However, currency in A3 target_speed == current_speed for each process cycle
 219                  * (except for the sign and if target_speed > 8.0).
 220                  * Besides, above speed calculation uses the difference (end_frame - start_frame).
 221                  * end_frame is calculated from 'frames_moved' which includes the interpolation.
 222                  * so we're good.
 223                  */
 224                 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));
 225                 speed_changed = true;
 226         }
 227
 228         if (end_frame == start_frame || fabs(current_speed) < 0.1 ) {
 229                 DEBUG_TRACE (DEBUG::LTC, "LTC TX2: transport is not rolling or absolute-speed < 0.1\n");
 230                 /* keep repeating current frame
 231                  *
 232                  * an LTC generator must be able to continue generating LTC when Ardours transport is in stop
 233                  * some machines do odd things if LTC goes away:
 234                  * e.g. a tape based machine (video or audio), some think they have gone into park if LTC goes away,
 235                  * so unspool the tape from the playhead. That might be inconvenient.
 236                  * If LTC keeps arriving they remain in a stop position with the tape on the playhead.
 237                  */
 238                 new_ltc_speed = 0;
 239                 if (!Config->get_ltc_send_continuously()) {
 240                         ltc_speed = new_ltc_speed;
 241                         return;
 242                 }
 243         }
 244
 245         if (fabs(new_ltc_speed) > 10.0) {
 246                 DEBUG_TRACE (DEBUG::LTC, "LTC TX2: speed is out of bounds.\n");
 247                 ltc_tx_reset();
 248                 return;
 249         }
 250
 251         if (ltc_speed == 0 && new_ltc_speed != 0) {
 252                 DEBUG_TRACE (DEBUG::LTC, "LTC TX2: transport started rolling - reset\n");
 253                 ltc_tx_reset();
 254         }
 255
 256         /* the timecode duration corresponding to the samples that are still
 257          * in the buffer. Here, the speed of previous cycle is used to calculate
 258          * the alignment at the beginning of this cycle later.
 259          */
 260         double poff = (ltc_buf_len - ltc_buf_off) * ltc_speed;
 261
 262         if (speed_changed && new_ltc_speed != 0) {
 263                 /* we need to re-sample the existing buffer.
 264                  * "make space for the en-coder to catch up to the new speed"
 265                  *
 266                  * since the LTC signal is a rectangular waveform we can simply squeeze it
 267                  * by removing samples or duplicating samples /here and there/.
 268                  *
 269                  * There may be a more elegant way to do this, in fact one could
 270                  * simply re-render the buffer using ltc_encoder_encode_byte()
 271                  * but that'd require some timecode offset buffer magic,
 272                  * which is left for later..
 273                  */
 274
 275                 double oldbuflen = double(ltc_buf_len - ltc_buf_off);
 276                 double newbuflen = double(ltc_buf_len - ltc_buf_off) * fabs(ltc_speed / new_ltc_speed);
 277
 278                 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: bufOld %1 bufNew %2 | diff %3\n",
 279                                         (ltc_buf_len - ltc_buf_off), newbuflen, newbuflen - oldbuflen
 280                                         ));
 281
 282                 double bufrspdiff = rint(newbuflen - oldbuflen);
 283
 284                 if (abs(bufrspdiff) > newbuflen || abs(bufrspdiff) > oldbuflen) {
 285                         DEBUG_TRACE (DEBUG::LTC, "LTC TX2: resampling buffer would destroy information.\n");
 286                         ltc_tx_reset();
 287                         poff = 0;
 288                 } else if (bufrspdiff != 0 && newbuflen > oldbuflen) {
 289                         int incnt = 0;
 290                         double samples_to_insert = ceil(newbuflen - oldbuflen);
 291                         double avg_distance = newbuflen / samples_to_insert;
 292                         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: resample buffer insert: %1\n", samples_to_insert));
 293
 294                         for (int rp = ltc_buf_off; rp < ltc_buf_len - 1; ++rp) {
 295                                 const int ro = rp - ltc_buf_off;
 296                                 if (ro < (incnt*avg_distance)) continue;
 297                                 const ltcsnd_sample_t v1 = ltc_enc_buf[rp];
 298                                 const ltcsnd_sample_t v2 = ltc_enc_buf[rp+1];
 299                                 if (v1 != v2 && ro < ((incnt+1)*avg_distance)) continue;
 300                                 memmove(&ltc_enc_buf[rp+1], &ltc_enc_buf[rp], ltc_buf_len-rp);
 301                                 incnt++;
 302                                 ltc_buf_len++;
 303                         }
 304                 } else if (bufrspdiff != 0 && newbuflen < oldbuflen) {
 305                         double samples_to_remove = ceil(oldbuflen - newbuflen);
 306                         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: resample buffer - remove: %1\n", samples_to_remove));
 307                         if (oldbuflen <= samples_to_remove) {
 308                                 ltc_buf_off = ltc_buf_len= 0;
 309                         } else {
 310                                 double avg_distance = newbuflen / samples_to_remove;
 311                                 int rmcnt = 0;
 312                                 for (int rp = ltc_buf_off; rp < ltc_buf_len - 1; ++rp) {
 313                                         const int ro = rp - ltc_buf_off;
 314                                         if (ro < (rmcnt*avg_distance)) continue;
 315                                         const ltcsnd_sample_t v1 = ltc_enc_buf[rp];
 316                                         const ltcsnd_sample_t v2 = ltc_enc_buf[rp+1];
 317                                         if (v1 != v2 && ro < ((rmcnt+1)*avg_distance)) continue;
 318                                         memmove(&ltc_enc_buf[rp], &ltc_enc_buf[rp+1], ltc_buf_len-rp-1);
 319                                         ltc_buf_len--;
 320                                         rmcnt++;
 321                                 }
 322                         }
 323                 }
 324         }
 325
 326         ltc_speed = new_ltc_speed;
 327         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX2: transport speed %1.\n", ltc_speed));
 328
 329         // (3) bit/sample alignment
 330         Timecode::Time tc_start;
 331         framepos_t tc_sample_start;
 332
 333         /* calc timecode frame from current position - round down to nearest timecode */
 334         sample_to_timecode(cycle_start_frame, tc_start, true, false);
 335
 336         /* convert timecode back to sample-position */
 337         Timecode::timecode_to_sample (tc_start, tc_sample_start, true, false,
 338                 double(frame_rate()),
 339                 config.get_subframes_per_frame(),
 340                 config.get_timecode_offset_negative(), config.get_timecode_offset()
 341                 );
 342
 343         /* difference between current frame and TC frame in samples */
 344         frameoffset_t soff = cycle_start_frame - tc_sample_start;
 345         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX3: A3cycle: %1 = A3tc: %2 +off: %3\n",
 346                                 cycle_start_frame, tc_sample_start, soff));
 347
 348
 349         // (4) check if alignment matches
 350         const double fptcf = frames_per_timecode_frame();
 351
 352         /* maximum difference of bit alignment in audio-samples.
 353          *
 354          * if transport and LTC generator differs more than this, the LTC
 355          * generator will be re-initialized
 356          *
 357          * due to rounding error and variations in LTC-bit duration depending
 358          * on the speed, it can be off by +- ltc_speed audio-samples.
 359          * When the playback speed changes, it can actually reach +- 2 * ltc_speed
 360          * in the cycle _after_ the speed changed. The average delta however is 0.
 361          */
 362         double maxdiff;
 363
 364         if (config.get_external_sync() && slave()) {
 365                 maxdiff = slave()->resolution();
 366         } else {
 367                 maxdiff = ceil(fabs(ltc_speed))*2.0;
 368         }
 369
 370         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: enc: %1 + %2 - %3 || buf-bytes: %4 enc-byte: %5\n",
 371                                 ltc_enc_pos, ltc_enc_cnt, poff, (ltc_buf_len - ltc_buf_off), poff, ltc_enc_byte));
 372
 373         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: enc-pos: %1  | d: %2\n",
 374                                 ltc_enc_pos + ltc_enc_cnt - poff,
 375                                 rint(ltc_enc_pos + ltc_enc_cnt - poff) - cycle_start_frame
 376                                 ));
 377
 378         if (ltc_speed != 0 && fabs(ceil(ltc_enc_pos + ltc_enc_cnt - poff) - cycle_start_frame) > maxdiff) {
 379
 380                 // (5) re-align
 381                 ltc_tx_reset();
 382
 383                 /* set frame to encode */
 384                 SMPTETimecode tc;
 385                 tc.hours = tc_start.hours;
 386                 tc.mins = tc_start.minutes;
 387                 tc.secs = tc_start.seconds;
 388                 tc.frame = tc_start.frames;
 389                 ltc_encoder_set_timecode(ltc_encoder, &tc);
 390
 391                 /* workaround for libltc recognizing 29.97 and 30000/1001 as drop-frame TC.
 392                  * In A3 30000/1001 or 30 fps can be drop-frame.
 393                  */
 394                 LTCFrame ltcframe;
 395                 ltc_encoder_get_frame(ltc_encoder, &ltcframe);
 396                 ltcframe.dfbit = timecode_has_drop_frames(cur_timecode)?1:0;
 397                 ltc_encoder_set_frame(ltc_encoder, &ltcframe);
 398
 399
 400                 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX4: now: %1 trs: %2 toff %3\n", cycle_start_frame, tc_sample_start, soff));
 401
 402                 uint32_t cyc_off;
 403                 if (soff < 0 || soff >= fptcf) {
 404                         /* session framerate change between (2) and now */
 405                         ltc_tx_reset();
 406                         return;
 407                 }
 408
 409                 if (ltc_speed < 0 ) {
 410                         /* calculate the byte that starts at or after the current position */
 411                         ltc_enc_byte = floor((10.0 * soff) / (fptcf));
 412                         ltc_enc_cnt = double(ltc_enc_byte * fptcf / 10.0);
 413
 414                         /* calculate difference between the current position and the byte to send */
 415                         cyc_off = soff- ceil(ltc_enc_cnt);
 416
 417                 } else {
 418                         /* calculate the byte that starts at or after the current position */
 419                         ltc_enc_byte = ceil((10.0 * soff) / fptcf);
 420                         ltc_enc_cnt = double(ltc_enc_byte * fptcf / 10.0);
 421
 422                         /* calculate difference between the current position and the byte to send */
 423                         cyc_off = ceil(ltc_enc_cnt) - soff;
 424
 425                         if (ltc_enc_byte == 10) {
 426                                 ltc_enc_byte = 0;
 427                                 ltc_encoder_inc_timecode(ltc_encoder);
 428                         }
 429                 }
 430
 431                 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX5 restart encoder: soff %1 byte %2 cycoff %3\n",
 432                                         soff, ltc_enc_byte, cyc_off));
 433
 434                 if (cyc_off > 0 && cyc_off <= nframes) {
 435                         /* offset in this cycle */
 436                         txf= rint(cyc_off / fabs(ltc_speed));
 437                         memset(out, 0, cyc_off * sizeof(Sample));
 438                 } else {
 439                         /* resync next cycle */
 440                         memset(out, 0, nframes * sizeof(Sample));
 441                         return;
 442                 }
 443
 444                 ltc_enc_pos = tc_sample_start;
 445
 446                 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX5 restart @ %1 + %2 - %3 |  byte %4\n",
 447                                         ltc_enc_pos, ltc_enc_cnt, cyc_off, ltc_enc_byte));
 448         }
 449
 450
 451         // (6) encode and output
 452         while (1) {
 453 #ifdef LTC_GEN_TXDBUG
 454                 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.1 @%1  [ %2 / %3 ]\n", txf, ltc_buf_off, ltc_buf_len));
 455 #endif
 456                 // (6a) send remaining buffer
 457                 while ((ltc_buf_off < ltc_buf_len) && (txf < nframes)) {
 458                         const float v1 = ltc_enc_buf[ltc_buf_off++] - 128.0;
 459                         const Sample val = (Sample) (v1*ltcvol);
 460                         out[txf++] = val;
 461                 }
 462 #ifdef LTC_GEN_TXDBUG
 463                 DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.2 @%1  [ %2 / %3 ]\n", txf, ltc_buf_off, ltc_buf_len));
 464 #endif
 465
 466                 if (txf >= nframes) {
 467                         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX7 enc: %1 [ %2 / %3 ] byte: %4 spd %5 fpp %6 || nf: %7\n",
 468                                                 ltc_enc_pos, ltc_buf_off, ltc_buf_len, ltc_enc_byte, ltc_speed, nframes, txf));
 469                         break;
 470                 }
 471
 472                 ltc_buf_len = 0;
 473                 ltc_buf_off = 0;
 474
 475                 // (6b) encode LTC, bump timecode
 476
 477                 if (ltc_speed < 0) {
 478                         ltc_enc_byte = (ltc_enc_byte + 9)%10;
 479                         if (ltc_enc_byte == 9) {
 480                                 ltc_encoder_dec_timecode(ltc_encoder);
 481                                 ltc_tx_recalculate_position();
 482                                 ltc_enc_cnt = fptcf;
 483                         }
 484                 }
 485
 486                 if (ltc_encoder_encode_byte(ltc_encoder, ltc_enc_byte, (ltc_speed==0)?1.0:(1.0/ltc_speed))) {
 487                         DEBUG_TRACE (DEBUG::LTC, string_compose("LTC TX6.3 encoder error byte %1\n", ltc_enc_byte));
 488                         ltc_encoder_buffer_flush(ltc_encoder);
 489                         ltc_tx_reset();
 490                         return;
 491                 }
 492                 int enc_frames = ltc_encoder_get_buffer(ltc_encoder, &(ltc_enc_buf[ltc_buf_len]));
 493 #ifdef LTC_GEN_FRAMEDBUG
 494                 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));
 495 #endif
 496                 if (enc_frames <=0) {
 497                         DEBUG_TRACE (DEBUG::LTC, "LTC TX6.3 encoder empty buffer.\n");
 498                         ltc_encoder_buffer_flush(ltc_encoder);
 499                         ltc_tx_reset();
 500                         return;
 501                 }
 502
 503                 ltc_buf_len += enc_frames;
 504                 if (ltc_speed < 0)
 505                         ltc_enc_cnt -= fptcf/10.0;
 506                 else
 507                         ltc_enc_cnt += fptcf/10.0;
 508
 509                 if (ltc_speed >= 0) {
 510                         ltc_enc_byte = (ltc_enc_byte + 1)%10;
 511                         if (ltc_enc_byte == 0 && ltc_speed != 0) {
 512                                 ltc_encoder_inc_timecode(ltc_encoder);
 513                                 ltc_tx_recalculate_position();
 514                                 ltc_enc_cnt = 0;
 515                         } else if (ltc_enc_byte == 0) {
 516                                 ltc_enc_cnt = 0;
 517                         }
 518                 }
 519 #ifdef LTC_GEN_FRAMEDBUG
 520                 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));
 521 #endif
 522         }
 523
 524         dynamic_cast<AudioBuffer*>(&buf)->set_written (true);
 525         return;
 526 }