ardour/livetrax
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fix accumulated rounding error in BBT grid

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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.
This commit is contained in:
Devin J. Pohly 2014-05-14 02:47:32 -04:00 committed by Paul Davis
parent e7b3020294
commit 0aa2ed582a
1 changed files with 8 additions and 3 deletions
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11
libs/ardour/tempo.cc
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@ -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