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hold accumulator phase across span

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this fixes grunk in held notes
This commit is contained in:
Jeff Epler 2023-03-31 10:51:03 -05:00
parent 02f8a45dfa
commit 7f73ff1b2d
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GPG Key ID: D5BF15AB975AB4DE
2 changed files with 9 additions and 4 deletions
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12
shared-module/synthio/MidiTrack.c
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@ -204,16 +204,20 @@ audioio_get_buffer_result_t synthio_miditrack_get_buffer(synthio_miditrack_obj_t
if (active_channels) {
int16_t loudness = 0x3fff / (1 + active_channels);
for (int chan = 0; chan < CIRCUITPY_SYNTHIO_MAX_CHANNELS; chan++) {
uint8_t octave = span.note[chan] / 12;
uint16_t base_freq = notes[span.note[chan] % 12];
if (span.note[chan] == SILENCE) {
self->accum[chan] = 0;
continue;
}
uint8_t octave = span.note[chan] / 12;
uint16_t base_freq = notes[span.note[chan] % 12];
uint32_t accum = self->accum[chan];
uint32_t rate = base_freq * 2;
for (uint16_t i = 0; i < span.dur; i++) {
int16_t semiperiod =
((base_freq * i * 2) / sample_rate) >> (10 - octave);
accum += rate;
int16_t semiperiod = (accum / sample_rate) >> (10 - octave);
self->buffer[i] += semiperiod % 2 ? loudness : -loudness;
}
self->accum[chan] = accum;
}
}

1
shared-module/synthio/MidiTrack.h
View File

@ -44,6 +44,7 @@ typedef struct {
synthio_midi_span_t *track;
uint16_t next_span;
uint16_t total_spans;
uint32_t accum[CIRCUITPY_SYNTHIO_MAX_CHANNELS];
} synthio_miditrack_obj_t;