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a more-likely-to-be-correct version of swing quantization.

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This needs to be converted to fixed point, still.
This commit is contained in:
Paul Davis 2015-06-26 22:15:51 -04:00
parent 490138e2bf
commit 8803cd664c
1 changed files with 76 additions and 30 deletions
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106
libs/ardour/quantize.cc
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@ -52,6 +52,63 @@ Quantize::~Quantize ()
{
}
static double
swing_position (double pos, double grid, double swing, double offset)
{
/* beats start out numbered at zero.
*
* every other position on the start-quantize-grid is
* optionally swung, meaning that its position is moved
* somewhere between its natural position and 2/3 of
* the way to the next start-quantize-grid position.
*
* so, if the _start grid is 0.5, the beat at 0 isn't
* swung, but something at 0.5 is, the beat at 1 isn't
* swung, but something at 1.5 is.
*
* if the start grid is 1.0, the beat at 0 isn't swung,
* but the beat at 1.0 is. the beat at 2.0 isn't swung,
* but the beat at 3.0 is. and so on.
*
* so the criterion for a position being swung is
* whether or not ((possible_grid_position / grid) % 2) != 0
*/
const bool swing_quantize_grid_position = pos > 0.0 && fmod ((pos/grid), 2.0) != 0;
const bool swing_previous_grid_position = pos > grid && fmod ((pos-grid)/grid, 2.0) != 0;
/* one of these will not be subject to swing */
double swung_pos = pos;
double swung_previous_grid_position;
if (pos > grid) {
swung_previous_grid_position = pos - grid;
} else {
swung_previous_grid_position = 0.0;
}
if (swing_previous_grid_position) {
swung_previous_grid_position = swung_previous_grid_position + (2.0/3.0 * swing * grid);
}
if (swing_quantize_grid_position) {
swung_pos = swung_pos + (2.0/3.0 * swing * grid);
}
/* now correct for start-of-model offset */
pos += offset;
if (fabs (pos - swung_pos) > fabs (pos - swung_previous_grid_position)) {
pos = swung_previous_grid_position;
} else {
pos = swung_pos;
}
return pos;
}
Command*
Quantize::operator () (boost::shared_ptr<MidiModel> model,
Evoral::Beats position,
@ -66,47 +123,38 @@ Quantize::operator () (boost::shared_ptr<MidiModel> model,
const double round_pos = round(position.to_double() / _start_grid) * _start_grid;
const double offset = round_pos - position.to_double();
bool even;
MidiModel::NoteDiffCommand* cmd = new MidiModel::NoteDiffCommand (model, "quantize");
for (std::vector<Evoral::Sequence<Evoral::Beats>::Notes>::iterator s = seqs.begin(); s != seqs.end(); ++s) {
even = false;
;
/* TODO 'swing' probably requires a 2nd iteration:
* first quantize notes to the grid, then apply beat shift
*/
for (Evoral::Sequence<MidiModel::TimeType>::Notes::iterator i = (*s).begin(); i != (*s).end(); ++i) {
double new_start = round (((*i)->time().to_double() - offset) / _start_grid) * _start_grid + offset;
double new_end = round (((*i)->end_time().to_double() - offset) / _end_grid) * _end_grid + offset;
/* compute new start + end points WITHOUT the offset
* caused by the start of the model (see above).
*
* these versions of new_start and new_end are
* guaranteed to precisely align with the quantize grid(s).
*/
double new_start = round (((*i)->time().to_double() - offset) / _start_grid) * _start_grid;
double new_end = round (((*i)->end_time().to_double() - offset) / _end_grid) * _end_grid;
if (_swing > 0.0 && even) {
if (_swing) {
double next_grid = new_start + _start_grid;
new_start = swing_position (new_start, _start_grid, _swing, offset);
new_end = swing_position (new_end, _end_grid, _swing, offset);
} else {
/* find a spot 2/3 (* swing factor) of the way between the grid point
we would put this note at, and the nominal position of the next note.
*/
new_start = new_start + (2.0/3.0 * _swing * (next_grid - new_start));
new_end = new_end + (2.0/3.0 * _swing * (next_grid - new_start));
} else if (_swing < 0.0 && even) {
double prev_grid = new_start - _start_grid;
/* find a spot 2/3 (* swing factor) of the way between the grid point
we would put this note at, and the nominal position of the previous note.
*/
new_start = new_start - (2.0/3.0 * _swing * (new_start - prev_grid));
new_end = new_end - (2.0/3.0 * _swing * (new_start - prev_grid));
/* now correct for start-of-model offset */
new_start += offset;
new_end += offset;
}
double delta = new_start - (*i)->time().to_double();
if (fabs (delta) >= _threshold) {
if (_snap_start) {
delta *= _strength;
@ -128,8 +176,6 @@ Quantize::operator () (boost::shared_ptr<MidiModel> model,
cmd->change ((*i), MidiModel::NoteDiffCommand::Length, new_dur);
}
}
even = !even;
}
}