allanger/ardour
1
0
Fork 0
Code Issues Pull Requests 1 Actions Packages Projects Releases Activity

tempo twisting: various fixes and improvements to core logic

Browse Source
This commit is contained in:
Paul Davis
2023-03-17 18:30:20 -06:00
parent 0cf199ac48
commit 393929a55b
1 changed files with 45 additions and 28 deletions
Download Patch File Download Diff File Expand all files Collapse all files

73
libs/temporal/tempo.cc
View File

@@ -3330,10 +3330,20 @@ TempoMap::stretch_tempo_end (TempoPoint* ts, samplepos_t sample, samplepos_t end
void
TempoMap::twist_tempi (TempoPoint& prev, TempoPoint& focus, TempoPoint& next, double tempo_value)
{
if (tempo_value < 4.0 || tempo_value > 800) {
/* Check if the new tempo value is within an acceptable range */
if (tempo_value < 4.0 || tempo_value > 400) {
return;
}
/* Our job here is to reposition @param focus without altering the
* tempos or positions of @param prev and @param next. We are
* "twisting" the tempo section before and after focus
*
* Start by saving the current state of prev and focus in case we need
* to bail out because change is impossible.
*/
TempoPoint old_prev (prev);
TempoPoint old_focus (focus);
@@ -3350,63 +3360,70 @@ TempoMap::twist_tempi (TempoPoint& prev, TempoPoint& focus, TempoPoint& next, do
/* set focus start & end tempos appropriately */
focus.set_note_types_per_minute (tempo_value);
focus.set_end_npm (next.note_types_per_minute());
/* recompute focus omega */
focus.compute_omega_beats_from_next_tempo (next);
/* Now iteratively adjust focus.end_superclocks_per_quarter_note() so
* that next.sclock() remains within 1 sample of its actual position
/* Now iteratively adjust focus.superclocks_per_quarter_note() (the
* section's starting tempo) so that next.sclock() remains within 1
* sample of its current position
*/
superclock_t err = focus.superclock_at (next.beats()) - next.sclock();
const superclock_t one_sample = superclock_ticks_per_second() / TEMPORAL_SAMPLE_RATE;
Beats b (next.beats() - focus.beats());
double end_scpqn = focus.end_superclocks_per_quarter_note();
double new_end_npm;
const Beats b (next.beats() - focus.beats());
const double end_scpqn = focus.end_superclocks_per_quarter_note();
double scpqn = focus.superclocks_per_quarter_note ();
double new_npm;
int cnt = 0;
while (std::abs(err) >= one_sample) {
if (err > 0) {
/* estimated > actual: speed end tempo up a little aka
reduce scpqn
*/
end_scpqn *= 0.99;
scpqn *= 0.99;
} else {
/* estimated < actual: reduce end tempo a little, aka
increase scpqn
*/
end_scpqn *= 1.01;
scpqn *= 1.01;
}
if (end_scpqn < 1.0) {
goto no_can_do;
if (scpqn < 1.0) {
/* mathematically too small, bail out */
prev = old_prev;
focus = old_focus;
return;
}
/* recompute omega with this new end_scpqn value, and then
* recompute the error in predicted position of next and its
* actual position.
/* Convert scpqn to notes-per-minute */
new_npm = ((superclock_ticks_per_second() * 60.0) / scpqn) * (focus.note_type() / 4.0);
/* limit range of possible discovered tempo */
if (new_npm < 4.0 && new_npm > 400) {
/* too low of a tempo for our taste, bail out */
prev = old_prev;
focus = old_focus;
return;
}
/* set the (initial) tempo, recompute omega and then compute
* the (new) error (distance between the predicted position of
* the next marker and its actual (fixed) position.
*/
focus.set_note_types_per_minute (new_npm);
focus.compute_omega_beats_from_quarter_duration (b, end_scpqn);
err = focus.superclock_at (next.beats()) - next.sclock();
++cnt;
}
new_end_npm = ((superclock_ticks_per_second() * 60.0) / end_scpqn) * (focus.note_type() / 4.0);
/* limit range of possible discovered tempo */
if (new_end_npm > 4.0 && new_end_npm < 800) {
focus.set_end_npm (new_end_npm);
return;
}
no_can_do:
prev = old_prev;
focus = old_focus;
return;
std::cerr << "that took " << cnt << " iterations to get to < 1 sample\n";
}
void