diff options
| author | Devin J. Pohly <djpohly@gmail.com> | 2014-05-14 02:47:32 -0400 |
|---|---|---|
| committer | Devin J. Pohly <djpohly@gmail.com> | 2014-05-14 02:54:01 -0400 |
| commit | d067e27762e6ee69dabc9d48a80828b6287511c1 (patch) | |
| tree | 2e04fc1abf6c7613ca4c6e7bf387b56eb593ac01 /libs | |
| parent | 2f6065b32c26dba0f7ea5da5c980d0406c36cc55 (diff) | |
fix accumulated rounding error in BBT grid
Though current_frame is an integral type (framepos_t), it was being
added to as if it were floating-point, leading to an ever-increasing
rounding error when creating the grid for bars/beats/ticks.
Diffstat (limited to 'libs')
| -rw-r--r-- | libs/ardour/tempo.cc | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/libs/ardour/tempo.cc b/libs/ardour/tempo.cc index 0bb2fea0cf..a2a400ad32 100644 --- a/libs/ardour/tempo.cc +++ b/libs/ardour/tempo.cc @@ -884,6 +884,7 @@ TempoMap::_extend_map (TempoSection* tempo, MeterSection* meter, TempoSection* ts; MeterSection* ms; double beat_frames; + double current_frame_exact; framepos_t bar_start_frame; DEBUG_TRACE (DEBUG::TempoMath, string_compose ("Extend map to %1 from %2 = %3\n", end, current, current_frame)); @@ -895,11 +896,13 @@ TempoMap::_extend_map (TempoSection* tempo, MeterSection* meter, } beat_frames = meter->frames_per_grid (*tempo,_frame_rate); + current_frame_exact = current_frame; while (current_frame < end) { current.beats++; - current_frame += beat_frames; + current_frame_exact += beat_frames; + current_frame = llrint(current_frame_exact); if (current.beats > meter->divisions_per_bar()) { current.bars++; @@ -942,7 +945,8 @@ TempoMap::_extend_map (TempoSection* tempo, MeterSection* meter, tempo->start(), current_frame, tempo->bar_offset())); /* back up to previous beat */ - current_frame -= beat_frames; + current_frame_exact -= beat_frames; + current_frame = llrint(current_frame_exact); /* set tempo section location * based on offset from last @@ -963,7 +967,8 @@ TempoMap::_extend_map (TempoSection* tempo, MeterSection* meter, double offset_within_old_beat = (tempo->frame() - current_frame) / beat_frames; - current_frame += (offset_within_old_beat * beat_frames) + ((1.0 - offset_within_old_beat) * next_beat_frames); + current_frame_exact += (offset_within_old_beat * beat_frames) + ((1.0 - offset_within_old_beat) * next_beat_frames); + current_frame = llrint(current_frame_exact); /* next metric doesn't have to * match this precisely to |