libs/ardour/ltc_slave.cc

   1 /*
   2     Copyright (C) 2012 Paul Davis
   3     Witten by 2012 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 #include <iostream>
  21 #include <errno.h>
  22 #include <sys/types.h>
  23 #include <unistd.h>
  24
  25 #include "pbd/error.h"
  26 #include "pbd/pthread_utils.h"
  27
  28 #include "ardour/debug.h"
  29 #include "ardour/slave.h"
  30 #include "ardour/session.h"
  31 #include "ardour/audioengine.h"
  32 #include "ardour/audio_port.h"
  33
  34 #include "i18n.h"
  35
  36 using namespace std;
  37 using namespace ARDOUR;
  38 using namespace MIDI;
  39 using namespace PBD;
  40 using namespace Timecode;
  41
  42 #define FLYWHEEL_TIMEOUT ( 1 * session.frame_rate() )
  43
  44 LTC_Slave::LTC_Slave (Session& s)
  45         : session (s)
  46 {
  47         frames_per_ltc_frame = session.frames_per_timecode_frame();
  48         timecode.rate = session.timecode_frames_per_second();
  49         timecode.drop  = session.timecode_drop_frames();
  50
  51         did_reset_tc_format = false;
  52         delayedlocked = 10;
  53         monotonic_cnt = 0;
  54         fps_detected=false;
  55         sync_lock_broken = false;
  56
  57         ltc_timecode = session.config.get_timecode_format();
  58         a3e_timecode = session.config.get_timecode_format();
  59         printed_timecode_warning = false;
  60         ltc_detect_fps_cnt = ltc_detect_fps_max = 0;
  61         memset(&prev_frame, 0, sizeof(LTCFrameExt));
  62
  63         decoder = ltc_decoder_create((int) frames_per_ltc_frame, 128 /*queue size*/);
  64
  65         session.config.ParameterChanged.connect_same_thread (config_connection, boost::bind (&LTC_Slave::parameter_changed, this, _1));
  66         parse_timecode_offset();
  67         reset();
  68         resync_latency();
  69         session.Xrun.connect_same_thread (port_connections, boost::bind (&LTC_Slave::resync_xrun, this));
  70         session.engine().GraphReordered.connect_same_thread (port_connections, boost::bind (&LTC_Slave::resync_latency, this));
  71 }
  72
  73 LTC_Slave::~LTC_Slave()
  74 {
  75         port_connections.drop_connections();
  76         config_connection.disconnect();
  77
  78         if (did_reset_tc_format) {
  79                 session.config.set_timecode_format (saved_tc_format);
  80         }
  81
  82         ltc_decoder_free(decoder);
  83 }
  84
  85 void
  86 LTC_Slave::parse_timecode_offset() {
  87         Timecode::Time offset_tc;
  88         Timecode::parse_timecode_format(session.config.get_slave_timecode_offset(), offset_tc);
  89         offset_tc.rate = session.timecode_frames_per_second();
  90         offset_tc.drop = session.timecode_drop_frames();
  91         session.timecode_to_sample(offset_tc, timecode_offset, false, false);
  92         timecode_negative_offset = offset_tc.negative;
  93 }
  94
  95 void
  96 LTC_Slave::parameter_changed (std::string const & p)
  97 {
  98         if (p == "slave-timecode-offset"
  99                         || p == "timecode-format"
 100                         ) {
 101                 parse_timecode_offset();
 102         }
 103 }
 104
 105 ARDOUR::framecnt_t
 106 LTC_Slave::resolution () const
 107 {
 108         return (framecnt_t) (session.frame_rate() / 1000);
 109 }
 110
 111 bool
 112 LTC_Slave::locked () const
 113 {
 114         return (delayedlocked < 5);
 115 }
 116
 117 bool
 118 LTC_Slave::ok() const
 119 {
 120         return true;
 121 }
 122
 123 void
 124 LTC_Slave::resync_xrun()
 125 {
 126         DEBUG_TRACE (DEBUG::LTC, "LTC resync_xrun()\n");
 127         engine_dll_initstate = 0;
 128         sync_lock_broken = false;
 129 }
 130
 131 void
 132 LTC_Slave::resync_latency()
 133 {
 134         DEBUG_TRACE (DEBUG::LTC, "LTC resync_latency()\n");
 135         engine_dll_initstate = 0;
 136         sync_lock_broken = false;
 137
 138         if (!session.deletion_in_progress() && session.ltc_output_io()) { /* check if Port exits */
 139                 boost::shared_ptr<Port> ltcport = session.ltc_input_port();
 140                 ltcport->get_connected_latency_range (ltc_slave_latency, false);
 141         }
 142 }
 143
 144 void
 145 LTC_Slave::reset()
 146 {
 147         DEBUG_TRACE (DEBUG::LTC, "LTC reset()\n");
 148         last_timestamp = 0;
 149         current_delta = 0;
 150         transport_direction = 0;
 151         ltc_speed = 0;
 152         engine_dll_initstate = 0;
 153         sync_lock_broken = false;
 154 }
 155
 156 void
 157 LTC_Slave::parse_ltc(const ARDOUR::pframes_t nframes, const Sample* const in, const ARDOUR::framecnt_t posinfo)
 158 {
 159         pframes_t i;
 160         unsigned char sound[8192];
 161         if (nframes > 8192) {
 162                 /* TODO warn once or wrap, loop conversion below
 163                  * does jack/A3 support > 8192 spp anyway?
 164                  */
 165                 return;
 166         }
 167
 168         for (i = 0; i < nframes; i++) {
 169                 const int snd=(int)rint((127.0*in[i])+128.0);
 170                 sound[i] = (unsigned char) (snd&0xff);
 171         }
 172         ltc_decoder_write(decoder, sound, nframes, posinfo);
 173         return;
 174 }
 175
 176 bool
 177 LTC_Slave::equal_ltc_frame_time(LTCFrame *a, LTCFrame *b) {
 178         if (       a->frame_units != b->frame_units
 179                 || a->frame_tens  != b->frame_tens
 180                 || a->dfbit       != b->dfbit
 181                 || a->secs_units  != b->secs_units
 182                 || a->secs_tens   != b->secs_tens
 183                 || a->mins_units  != b->mins_units
 184                 || a->mins_tens   != b->mins_tens
 185                 || a->hours_units != b->hours_units
 186                 || a->hours_tens  != b->hours_tens
 187              ) {
 188                 return false;
 189         }
 190         return true;
 191 }
 192
 193 bool
 194 LTC_Slave::detect_discontinuity(LTCFrameExt *frame, int fps, bool fuzzy) {
 195         bool discontinuity_detected = false;
 196
 197         if (fuzzy && (
 198                   ( frame->reverse && prev_frame.ltc.frame_units == 0)
 199                 ||(!frame->reverse && frame->ltc.frame_units == 0)
 200                 )) {
 201                 memcpy(&prev_frame, frame, sizeof(LTCFrameExt));
 202                 return false;
 203         }
 204
 205         if (frame->reverse) {
 206                 ltc_frame_decrement(&prev_frame.ltc, fps, LTC_TV_525_60, 0);
 207         } else {
 208                 ltc_frame_increment(&prev_frame.ltc, fps, LTC_TV_525_60, 0);
 209         }
 210         if (!equal_ltc_frame_time(&prev_frame.ltc, &frame->ltc)) {
 211                 discontinuity_detected = true;
 212         }
 213
 214     memcpy(&prev_frame, frame, sizeof(LTCFrameExt));
 215     return discontinuity_detected;
 216 }
 217
 218 bool
 219 LTC_Slave::detect_ltc_fps(int frameno, bool df)
 220 {
 221         bool fps_changed = false;
 222         double detected_fps = 0;
 223         if (frameno > ltc_detect_fps_max)
 224         {
 225                 ltc_detect_fps_max = frameno;
 226         }
 227         ltc_detect_fps_cnt++;
 228
 229         if (ltc_detect_fps_cnt > 40) {
 230                 if (ltc_detect_fps_cnt > ltc_detect_fps_max) {
 231                         detected_fps = ltc_detect_fps_max + 1;
 232                         if (df) {
 233                                 /* LTC df -> indicates fractional framerate */
 234                                 if (Config->get_timecode_source_2997()) {
 235                                         detected_fps = detected_fps * 999.0 / 1000.0;
 236                                 } else {
 237                                         detected_fps = detected_fps * 1000.0 / 1001.0;
 238                                 }
 239                         }
 240
 241                         if (timecode.rate != detected_fps || timecode.drop != df) {
 242                                 DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC detected FPS: %1%2\n", detected_fps, df?"df":"ndf"));
 243                         } else {
 244                                 detected_fps = 0; /* no cange */
 245                         }
 246                 }
 247                 ltc_detect_fps_cnt = ltc_detect_fps_max = 0;
 248         }
 249
 250         /* when changed */
 251         if (detected_fps != 0 && (detected_fps != timecode.rate || df != timecode.drop)) {
 252                 timecode.rate = detected_fps;
 253                 timecode.drop = df;
 254                 frames_per_ltc_frame = double(session.frame_rate()) / timecode.rate;
 255                 DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC reset to FPS: %1%2 ; audio-frames per LTC: %3\n",
 256                                 detected_fps, df?"df":"ndf", frames_per_ltc_frame));
 257                 fps_changed=true;
 258         }
 259
 260         /* poll and check session TC */
 261         TimecodeFormat tc_format = apparent_timecode_format();
 262         TimecodeFormat cur_timecode = session.config.get_timecode_format();
 263
 264         if (Config->get_timecode_sync_frame_rate()) {
 265                 /* enforce time-code */
 266                 if (!did_reset_tc_format) {
 267                         saved_tc_format = cur_timecode;
 268                         did_reset_tc_format = true;
 269                 }
 270                 if (cur_timecode != tc_format) {
 271                         if (ceil(Timecode::timecode_to_frames_per_second(cur_timecode)) != ceil(Timecode::timecode_to_frames_per_second(tc_format))) {
 272                                 warning << string_compose(_("Session framerate adjusted from %1 to LTC's %2."),
 273                                                 Timecode::timecode_format_name(cur_timecode),
 274                                                 Timecode::timecode_format_name(tc_format))
 275                                         << endmsg;
 276                         }
 277                         session.config.set_timecode_format (tc_format);
 278                 }
 279         } else {
 280                 /* only warn about TC mismatch */
 281                 if (ltc_timecode != tc_format) printed_timecode_warning = false;
 282                 if (a3e_timecode != cur_timecode) printed_timecode_warning = false;
 283
 284                 if (cur_timecode != tc_format && ! printed_timecode_warning) {
 285                         if (ceil(Timecode::timecode_to_frames_per_second(cur_timecode)) != ceil(Timecode::timecode_to_frames_per_second(tc_format))) {
 286                                 warning << string_compose(_("Session and LTC framerate mismatch: LTC:%1 Session:%2."),
 287                                                 Timecode::timecode_format_name(tc_format),
 288                                                 Timecode::timecode_format_name(cur_timecode))
 289                                         << endmsg;
 290                         }
 291                         printed_timecode_warning = true;
 292                 }
 293         }
 294         ltc_timecode = tc_format;
 295         a3e_timecode = cur_timecode;
 296
 297         return fps_changed;
 298 }
 299
 300 void
 301 LTC_Slave::process_ltc(framepos_t const /*now*/)
 302 {
 303         LTCFrameExt frame;
 304         enum LTC_TV_STANDARD tv_standard = LTC_TV_625_50;
 305         while (ltc_decoder_read(decoder, &frame)) {
 306                 SMPTETimecode stime;
 307
 308                 ltc_frame_to_time(&stime, &frame.ltc, 0);
 309                 timecode.negative  = false;
 310                 timecode.subframes  = 0;
 311
 312                 /* set timecode.rate and timecode.drop: */
 313                 bool ltc_is_static = equal_ltc_frame_time(&prev_frame.ltc, &frame.ltc);
 314
 315                 if (detect_discontinuity(&frame, ceil(timecode.rate), !fps_detected)) {
 316                         if (fps_detected) { ltc_detect_fps_cnt = ltc_detect_fps_max = 0; }
 317                         fps_detected=false;
 318                 }
 319
 320                 if (!ltc_is_static && detect_ltc_fps(stime.frame, (frame.ltc.dfbit)? true : false)) {
 321                         reset();
 322                         fps_detected=true;
 323                 }
 324
 325 #if 0 // Devel/Debug
 326                 fprintf(stdout, "LTC %02d:%02d:%02d%c%02d | %8lld %8lld%s\n",
 327                         stime.hours,
 328                         stime.mins,
 329                         stime.secs,
 330                         (frame.ltc.dfbit) ? '.' : ':',
 331                         stime.frame,
 332                         frame.off_start,
 333                         frame.off_end,
 334                         frame.reverse ? " R" : "  "
 335                         );
 336 #endif
 337
 338                 /* when a full LTC frame is decoded, the timecode the LTC frame
 339                  * is referring has just passed.
 340                  * So we send the _next_ timecode which
 341                  * is expected to start at the end of the current frame
 342                  */
 343                 int fps_i = ceil(timecode.rate);
 344
 345                 switch(fps_i) {
 346                         case 30:
 347                                 if (timecode.drop) {
 348                                         tv_standard = LTC_TV_525_60;
 349                                 } else {
 350                                         tv_standard = LTC_TV_1125_60;
 351                                 }
 352                                 break;
 353                         case 25:
 354                                 tv_standard = LTC_TV_625_50;
 355                                 break;
 356                         default:
 357                                 tv_standard = LTC_TV_FILM_24; /* == LTC_TV_1125_60 == no offset, 24,30fps BGF */
 358                                 break;
 359                 }
 360
 361                 if (!frame.reverse) {
 362                         ltc_frame_increment(&frame.ltc, fps_i, tv_standard, 0);
 363                         ltc_frame_to_time(&stime, &frame.ltc, 0);
 364                         transport_direction = 1;
 365                         frame.off_start -= ltc_frame_alignment(session.frames_per_timecode_frame(), tv_standard);
 366                         frame.off_end -= ltc_frame_alignment(session.frames_per_timecode_frame(), tv_standard);
 367                 } else {
 368                         ltc_frame_decrement(&frame.ltc, fps_i, tv_standard, 0);
 369                         int off = frame.off_end - frame.off_start;
 370                         frame.off_start += off - ltc_frame_alignment(session.frames_per_timecode_frame(), tv_standard);
 371                         frame.off_end += off - ltc_frame_alignment(session.frames_per_timecode_frame(), tv_standard);
 372                         transport_direction = -1;
 373                 }
 374
 375                 timecode.hours   = stime.hours;
 376                 timecode.minutes = stime.mins;
 377                 timecode.seconds = stime.secs;
 378                 timecode.frames  = stime.frame;
 379
 380                 /* map LTC timecode to session TC setting */
 381                 framepos_t ltc_frame; ///< audio-frame corresponding to LTC frame
 382                 Timecode::timecode_to_sample (timecode, ltc_frame, true, false,
 383                         double(session.frame_rate()),
 384                         session.config.get_subframes_per_frame(),
 385                         timecode_negative_offset, timecode_offset
 386                         );
 387
 388                 ltc_frame += ltc_slave_latency.max + session.worst_playback_latency();
 389
 390                 framepos_t cur_timestamp = frame.off_end + 1;
 391                 DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC F: %1 LF: %2  N: %3 L: %4\n", ltc_frame, last_ltc_frame, cur_timestamp, last_timestamp));
 392                 if (frame.off_end + 1 <= last_timestamp || last_timestamp == 0) {
 393                         DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC speed: UNCHANGED: %1\n", ltc_speed));
 394                 } else {
 395                         ltc_speed = double(ltc_frame - last_ltc_frame) / double(cur_timestamp - last_timestamp);
 396                         DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC speed: %1\n", ltc_speed));
 397                 }
 398
 399                 if (fabs(ltc_speed) > 10.0) {
 400                         ltc_speed = 0;
 401                 }
 402
 403                 last_timestamp = frame.off_end + 1;
 404                 last_ltc_frame = ltc_frame;
 405         } /* end foreach decoded LTC frame */
 406 }
 407
 408 void
 409 LTC_Slave::init_engine_dll (framepos_t pos, int32_t inc)
 410 {
 411         double omega = 2.0 * M_PI * double(inc) / double(session.frame_rate());
 412         b = 1.4142135623730950488 * omega;
 413         c = omega * omega;
 414
 415         e2 = double(ltc_speed * inc);
 416         t0 = double(pos);
 417         t1 = t0 + e2;
 418         DEBUG_TRACE (DEBUG::LTC, string_compose ("[re-]init Engine DLL %1 %2 %3\n", t0, t1, e2));
 419 }
 420
 421 /* main entry point from session_process.cc
 422  * called from process callback context
 423  * so it is OK to use get_buffer()
 424  */
 425 bool
 426 LTC_Slave::speed_and_position (double& speed, framepos_t& pos)
 427 {
 428         bool engine_init_called = false;
 429         framepos_t now = session.engine().sample_time_at_cycle_start();
 430         framepos_t sess_pos = session.transport_frame(); // corresponds to now
 431         framecnt_t nframes = session.engine().samples_per_cycle();
 432
 433         Sample* in;
 434
 435         boost::shared_ptr<Port> ltcport = session.ltc_input_port();
 436
 437         in = (Sample*) AudioEngine::instance()->port_engine().get_buffer (ltcport->port_handle(), nframes);
 438
 439         frameoffset_t skip = now - (monotonic_cnt + nframes);
 440         monotonic_cnt = now;
 441         DEBUG_TRACE (DEBUG::LTC, string_compose ("speed_and_position - TID:%1 | latency: %2 | skip %3\n", pthread_name(), ltc_slave_latency.max, skip));
 442
 443         if (last_timestamp == 0) {
 444                 engine_dll_initstate = 0;
 445                 if (delayedlocked < 10) ++delayedlocked;
 446         }
 447         else if (engine_dll_initstate != transport_direction && ltc_speed != 0) {
 448                 engine_dll_initstate = transport_direction;
 449                 init_engine_dll(last_ltc_frame + rint(ltc_speed * double(2 * nframes + now - last_timestamp)),
 450                                 session.engine().samples_per_cycle());
 451                 engine_init_called = true;
 452         }
 453
 454         if (in) {
 455                 DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC Process eng-tme: %1 eng-pos: %2\n", now, sess_pos));
 456                 /* when the jack-graph changes and if ardour performs
 457                  * locates, the audioengine is stopped (skipping frames) while
 458                  * jack [time] moves along.
 459                  */
 460                 if (skip > 0) {
 461                         DEBUG_TRACE (DEBUG::LTC, string_compose("engine skipped %1 frames. Feeding silence to LTC parser.\n", skip));
 462                         if (skip >= 8192) skip = 8192;
 463                         unsigned char sound[8192];
 464                         memset(sound, 0, sizeof(char) * skip);
 465                         ltc_decoder_write(decoder, sound, nframes, now);
 466                 } else if (skip != 0) {
 467                         /* this should never happen. it may if monotonic_cnt, now overflow on 64bit */
 468                         DEBUG_TRACE (DEBUG::LTC, string_compose("engine skipped %1 frames\n", skip));
 469                         reset();
 470                 }
 471
 472                 parse_ltc(nframes, in, now);
 473                 process_ltc(now);
 474         }
 475
 476         if (last_timestamp == 0) {
 477                 DEBUG_TRACE (DEBUG::LTC, "last timestamp == 0\n");
 478                 speed = 0;
 479                 pos = session.transport_frame();
 480                 return true;
 481         } else if (ltc_speed != 0) {
 482                 if (delayedlocked > 1) delayedlocked--;
 483                 else if (current_delta == 0) delayedlocked = 0;
 484         }
 485
 486         if (abs(now - last_timestamp) > FLYWHEEL_TIMEOUT) {
 487                 DEBUG_TRACE (DEBUG::LTC, "flywheel timeout\n");
 488                 reset();
 489                 speed = 0;
 490                 pos = session.transport_frame();
 491                 return true;
 492         }
 493
 494         /* it take 2 cycles from naught to rolling.
 495          * during these to initial cycles the speed == 0
 496          *
 497          * the first cycle:
 498          * DEBUG::Slave: slave stopped, move to NNN
 499          * DEBUG::Transport: Request forced locate to NNN
 500          * DEBUG::Slave: slave state 0 @ NNN speed 0 cur delta VERY-LARGE-DELTA avg delta 1800
 501          * DEBUG::Slave: silent motion
 502          * DEBUG::Transport: realtime stop @ NNN
 503          * DEBUG::Transport: Butler transport work, todo = PostTransportStop,PostTransportLocate,PostTransportClearSubstate
 504          *
 505          * [engine skips frames to locate, jack time keeps rolling on]
 506          *
 507          * the second cycle:
 508          *
 509          * DEBUG::LTC: [re-]init Engine DLL
 510          * DEBUG::Slave: slave stopped, move to NNN+
 511          * ...
 512          *
 513          * we need to seek two cycles ahead: 2 * nframes
 514          */
 515         if (engine_dll_initstate == 0) {
 516                 DEBUG_TRACE (DEBUG::LTC, "engine DLL not initialized. ltc_speed\n");
 517                 speed = 0;
 518                 pos = last_ltc_frame + rint(ltc_speed * double(2 * nframes + now - last_timestamp));
 519                 return true;
 520         }
 521
 522         /* interpolate position according to speed and time since last LTC-frame*/
 523         double speed_flt = ltc_speed;
 524         double elapsed = (now - last_timestamp) * speed_flt;
 525
 526         if (!engine_init_called) {
 527                 const double e = elapsed + double (last_ltc_frame - sess_pos);
 528                 t0 = t1;
 529                 t1 += b * e + e2;
 530                 e2 += c * e;
 531                 speed_flt = (t1 - t0) / double(session.engine().samples_per_cycle());
 532                 DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC engine DLL t0:%1 t1:%2 err:%3 spd:%4 ddt:%5\n", t0, t1, e, speed_flt, e2 - session.engine().samples_per_cycle() ));
 533         } else {
 534                 DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC adjusting elapsed (no DLL) from %1 by %2\n", elapsed, (2 * nframes * ltc_speed)));
 535                 speed_flt = 0;
 536                 elapsed += 2.0 * nframes * ltc_speed; /* see note above */
 537         }
 538
 539         pos = last_ltc_frame + rint(elapsed);
 540         speed = speed_flt;
 541         current_delta = (pos - sess_pos);
 542
 543         if (((pos < 0) || (labs(current_delta) > 2 * session.frame_rate()))) {
 544                 DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC large drift: %1\n", current_delta));
 545                 reset();
 546                 speed = 0;
 547                 pos = session.transport_frame();
 548                 return true;
 549         }
 550
 551         DEBUG_TRACE (DEBUG::LTC, string_compose ("LTCsync spd: %1 pos: %2 | last-pos: %3 elapsed: %4 delta: %5\n",
 552                                                  speed, pos, last_ltc_frame, elapsed, current_delta));
 553
 554         /* provide a .1% deadzone to lock the speed */
 555         if (fabs(speed - 1.0) <= 0.001) {
 556                 speed = 1.0;
 557         }
 558
 559         if (speed != 0 && delayedlocked == 0 && fabsf(speed) != 1.0) {
 560                 sync_lock_broken = true;
 561                 DEBUG_TRACE (DEBUG::LTC, string_compose ("LTC speed not locked %1 %2\n", speed, ltc_speed));
 562         }
 563
 564         return true;
 565 }
 566
 567 Timecode::TimecodeFormat
 568 LTC_Slave::apparent_timecode_format () const
 569 {
 570         if      (timecode.rate == 24 && !timecode.drop)
 571                 return timecode_24;
 572         else if (timecode.rate == 25 && !timecode.drop)
 573                 return timecode_25;
 574         else if (rint(timecode.rate * 100) == 2997 && !timecode.drop)
 575                 return (Config->get_timecode_source_2997() ? timecode_2997000 : timecode_2997);
 576         else if (rint(timecode.rate * 100) == 2997 &&  timecode.drop)
 577                 return (Config->get_timecode_source_2997() ? timecode_2997000drop : timecode_2997drop);
 578         else if (timecode.rate == 30 &&  timecode.drop)
 579                 return timecode_2997drop; // timecode_30drop; // LTC counting to 30 frames w/DF *means* 29.97 df
 580         else if (timecode.rate == 30 && !timecode.drop)
 581                 return timecode_30;
 582
 583         /* XXX - unknown timecode format */
 584         return session.config.get_timecode_format();
 585 }
 586
 587 std::string
 588 LTC_Slave::approximate_current_position() const
 589 {
 590         if (last_timestamp == 0) {
 591                 return " --:--:--:--";
 592         }
 593         return Timecode::timecode_format_time(timecode);
 594 }
 595
 596 std::string
 597 LTC_Slave::approximate_current_delta() const
 598 {
 599         char delta[80];
 600         if (last_timestamp == 0 || engine_dll_initstate == 0) {
 601                 snprintf(delta, sizeof(delta), "\u2012\u2012\u2012\u2012");
 602         } else if ((monotonic_cnt - last_timestamp) > 2 * frames_per_ltc_frame) {
 603                 snprintf(delta, sizeof(delta), "%s", _("flywheel"));
 604         } else {
 605                 snprintf(delta, sizeof(delta), "\u0394<span foreground=\"%s\" face=\"monospace\" >%s%s%lld</span>sm",
 606                                 sync_lock_broken ? "red" : "green",
 607                                 LEADINGZERO(llabs(current_delta)), PLUSMINUS(-current_delta), llabs(current_delta));
 608         }
 609         return std::string(delta);
 610 }