- if (timecode.drop) {
- // The drop frame format was created to better approximate the 30000/1001 = 29.97002997002997....
- // framerate of NTSC color TV. The used frame rate of drop frame is 29.97, which drifts by about
- // 0.108 frame per hour, or about 1.3 frames per 12 hours. This is not perfect, but a lot better
- // than using 30 non drop, which will drift with about 1.8 frame per minute.
- // Using 29.97, drop frame real time can be accurate only every 10th minute (10 minutes of 29.97 fps
- // is exactly 17982 frames). One minute is 1798.2 frames, but we count 30 frames per second
- // (30 * 60 = 1800). This means that at the first minute boundary (at the end of 0:0:59:29) we
- // are 1.8 frames too late relative to real time. By dropping 2 frames (jumping to 0:1:0:2) we are
- // approx. 0.2 frames too early. This adds up with 0.2 too early for each minute until we are 1.8
- // frames too early at 0:9:0:2 (9 * 0.2 = 1.8). The 10th minute brings us 1.8 frames later again
- // (at end of 0:9:59:29), which sums up to 0 (we are back to zero at 0:10:0:0 :-).
- //
- // In table form:
- //
- // Timecode value frames offset subframes offset seconds (rounded) 44100 sample (rounded)
- // 0:00:00:00 0.0 0 0.000 0 (accurate)
- // 0:00:59:29 1.8 144 60.027 2647177
- // 0:01:00:02 -0.2 -16 60.060 2648648
- // 0:01:59:29 1.6 128 120.020 5292883
- // 0:02:00:02 -0.4 -32 120.053 5294354
- // 0:02:59:29 1.4 112 180.013 7938588
- // 0:03:00:02 -0.6 -48 180.047 7940060
- // 0:03:59:29 1.2 96 240.007 10584294
- // 0:04:00:02 -0.8 -64 240.040 10585766
- // 0:04:59:29 1.0 80 300.000 13230000
- // 0:05:00:02 -1.0 -80 300.033 13231471
- // 0:05:59:29 0.8 64 359.993 15875706
- // 0:06:00:02 -1.2 -96 360.027 15877177
- // 0:06:59:29 0.6 48 419.987 18521411
- // 0:07:00:02 -1.4 -112 420.020 18522883
- // 0:07:59:29 0.4 32 478.980 21167117
- // 0:08:00:02 -1.6 -128 480.013 21168589
- // 0:08:59:29 0.2 16 539.973 23812823
- // 0:09:00:02 -1.8 -144 540.007 23814294
- // 0:09:59:29 0.0+ 0+ 599.967 26458529
- // 0:10:00:00 0.0 0 600.000 26460000 (accurate)
- //
- // Per Sigmond <per@sigmond.no>
-
- // Samples inside time dividable by 10 minutes (real time accurate)
- framecnt_t base_samples = (framecnt_t) (((timecode.hours * 107892) + ((timecode.minutes / 10) * 17982)) * _frames_per_timecode_frame);
-
- // Samples inside time exceeding the nearest 10 minutes (always offset, see above)
- int32_t exceeding_df_minutes = timecode.minutes % 10;
- int32_t exceeding_df_seconds = (exceeding_df_minutes * 60) + timecode.seconds;
- int32_t exceeding_df_frames = (30 * exceeding_df_seconds) + timecode.frames - (2 * exceeding_df_minutes);
- framecnt_t exceeding_samples = (framecnt_t) rint(exceeding_df_frames * _frames_per_timecode_frame);
- sample = base_samples + exceeding_samples;
- } else {
- /*
- Non drop is easy.. just note the use of
- rint(timecode.rate) * _frames_per_timecode_frame
- (frames per Timecode second), which is larger than
- frame_rate() in the non-integer Timecode rate case.
- */
-
- sample = (framecnt_t)rint((((timecode.hours * 60 * 60) + (timecode.minutes * 60) + timecode.seconds) * (rint(timecode.rate) * _frames_per_timecode_frame)) + (timecode.frames * _frames_per_timecode_frame));
- }
-
- if (use_subframes) {
- sample += (int32_t) (((double)timecode.subframes * _frames_per_timecode_frame) / config.get_subframes_per_frame());
- }
-
- if (use_offset) {
- if (config.get_timecode_offset_negative()) {
- if (sample >= config.get_timecode_offset()) {
- sample -= config.get_timecode_offset();
- } else {
- /* Prevent song-time from becoming negative */
- sample = 0;
- }
- } else {
- if (timecode.negative) {
- if (sample <= config.get_timecode_offset()) {
- sample = config.get_timecode_offset() - sample;
- } else {
- sample = 0;
- }
- } else {
- sample += config.get_timecode_offset();
- }
- }
- }