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jeplerjepler
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synthio: allow increasing number of channels
12 channels works well on metro m7
1 parent e8711ee commit 02f8a45

5 files changed

Lines changed: 68 additions & 46 deletions

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‎ports/mimxrt10xx/mpconfigport.mk‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -18,6 +18,7 @@ CIRCUITPY_AUDIOIO = 0
1818
CIRCUITPY_AUDIOMIXER = 1
1919
CIRCUITPY_AUDIOMP3 = 1
2020
CIRCUITPY_AUDIOPWMIO = 1
21+
CIRCUITPY_SYNTHIO_MAX_CHANNELS = 12
2122
CIRCUITPY_BUSDEVICE = 1
2223
CIRCUITPY_COUNTIO = 0
2324
CIRCUITPY_FREQUENCYIO = 0

‎py/circuitpy_mpconfig.mk‎

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -437,6 +437,10 @@ CFLAGS += -DCIRCUITPY_SUPERVISOR=$(CIRCUITPY_SUPERVISOR)
437437
CIRCUITPY_SYNTHIO ?= $(CIRCUITPY_AUDIOCORE)
438438
CFLAGS += -DCIRCUITPY_SYNTHIO=$(CIRCUITPY_SYNTHIO)
439439

440+
CIRCUITPY_SYNTHIO_MAX_CHANNELS ?= 2
441+
CFLAGS += -DCIRCUITPY_SYNTHIO_MAX_CHANNELS=$(CIRCUITPY_SYNTHIO_MAX_CHANNELS)
442+
443+
440444
CIRCUITPY_SYS ?= 1
441445
CFLAGS += -DCIRCUITPY_SYS=$(CIRCUITPY_SYS)
442446

‎shared-bindings/audiocore/RawSample.c‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -40,7 +40,7 @@
4040
//| def __init__(
4141
//| self, buffer: ReadableBuffer, *, channel_count: int = 1, sample_rate: int = 8000
4242
//| ) -> None:
43-
//| """Create a RawSample based on the given buffer of signed values. If channel_count is more than
43+
//| """Create a RawSample based on the given buffer of values. If channel_count is more than
4444
//| 1 then each channel's samples should alternate. In other words, for a two channel buffer, the
4545
//| first sample will be for channel 1, the second sample will be for channel two, the third for
4646
//| channel 1 and so on.

‎shared-module/synthio/MidiTrack.c‎

Lines changed: 61 additions & 44 deletions
Original file line numberDiff line numberDiff line change
@@ -27,7 +27,6 @@
2727
#include "py/runtime.h"
2828
#include "shared-bindings/synthio/MidiTrack.h"
2929

30-
#define LOUDNESS 0x4000 // 0.5
3130
#define BITS_PER_SAMPLE 16
3231
#define BYTES_PER_SAMPLE (BITS_PER_SAMPLE / 8)
3332
#define SILENCE 0x80
@@ -47,36 +46,51 @@ STATIC uint8_t parse_note(const uint8_t *buffer, uint32_t len, uint32_t *pos) {
4746
return note;
4847
}
4948

50-
STATIC void terminate_span(synthio_miditrack_obj_t *self, uint16_t *dur, uint16_t *max_dur) {
49+
STATIC void terminate_span(synthio_miditrack_obj_t *self, uint16_t *dur) {
5150
if (*dur) {
5251
self->track[self->total_spans - 1].dur = *dur;
53-
if (*dur > *max_dur) {
54-
*max_dur = *dur;
55-
}
5652
*dur = 0;
5753
} else {
5854
self->total_spans--;
5955
}
6056
}
6157

62-
STATIC void add_span(synthio_miditrack_obj_t *self, uint8_t note1, uint8_t note2) {
63-
synthio_midi_span_t span = { 0, {note1, note2} };
58+
STATIC void add_span(synthio_miditrack_obj_t *self, const synthio_midi_span_t *span) {
6459
self->track = m_realloc(self->track,
6560
(self->total_spans + 1) * sizeof(synthio_midi_span_t));
66-
self->track[self->total_spans++] = span;
61+
self->track[self->total_spans++] = *span;
62+
}
63+
64+
STATIC int find_channel_with_note(const synthio_midi_span_t *span, uint8_t note) {
65+
for (int i = 0; i < CIRCUITPY_SYNTHIO_MAX_CHANNELS; i++) {
66+
if (span->note[i] == note) {
67+
return i;
68+
}
69+
}
70+
return -1;
71+
}
72+
73+
STATIC void change_span_note(synthio_miditrack_obj_t *self, uint8_t old_note, uint8_t new_note, uint16_t *dur) {
74+
synthio_midi_span_t span = self->track[self->total_spans - 1];
75+
int channel = find_channel_with_note(&span, old_note);
76+
if (channel != -1) {
77+
terminate_span(self, dur);
78+
span.note[channel] = new_note;
79+
add_span(self, &span);
80+
}
6781
}
6882

6983
void common_hal_synthio_miditrack_construct(synthio_miditrack_obj_t *self,
7084
const uint8_t *buffer, uint32_t len, uint32_t tempo, uint32_t sample_rate) {
7185

72-
synthio_midi_span_t initial = { 0, {SILENCE, SILENCE} };
86+
synthio_midi_span_t initial = { 0, {[0 ... (CIRCUITPY_SYNTHIO_MAX_CHANNELS - 1)] = SILENCE} };
7387
self->sample_rate = sample_rate;
7488
self->track = m_malloc(sizeof(synthio_midi_span_t), false);
7589
self->next_span = 0;
7690
self->total_spans = 1;
7791
*self->track = initial;
7892

79-
uint16_t dur = 0, max_dur = 0;
93+
uint16_t dur = 0;
8094
uint32_t pos = 0;
8195
while (pos < len) {
8296
uint8_t c;
@@ -91,37 +105,19 @@ void common_hal_synthio_miditrack_construct(synthio_miditrack_obj_t *self,
91105
raise_midi_stream_error(pos);
92106
}
93107

108+
// dur is carried over here so that if a note on/off message doesn't actually produce a change, the
109+
// underlying "span" is extended. Otherwise, it is zeroed out in the call to `terminate_span`.
94110
dur += delta * sample_rate / tempo;
95111

96112
switch (buffer[pos++] >> 4) {
97113
case 8: { // Note Off
98114
uint8_t note = parse_note(buffer, len, &pos);
99-
100-
// Ignore if not a note which is playing
101-
synthio_midi_span_t last_span = self->track[self->total_spans - 1];
102-
if (last_span.note[0] == note || last_span.note[1] == note) {
103-
terminate_span(self, &dur, &max_dur);
104-
if (last_span.note[0] == note) {
105-
add_span(self, last_span.note[1], SILENCE);
106-
} else {
107-
add_span(self, last_span.note[0], SILENCE);
108-
}
109-
}
115+
change_span_note(self, note, SILENCE, &dur);
110116
break;
111117
}
112118
case 9: { // Note On
113119
uint8_t note = parse_note(buffer, len, &pos);
114-
115-
// Ignore if two notes are already playing
116-
synthio_midi_span_t last_span = self->track[self->total_spans - 1];
117-
if (last_span.note[1] == SILENCE) {
118-
terminate_span(self, &dur, &max_dur);
119-
if (last_span.note[0] == SILENCE) {
120-
add_span(self, note, SILENCE);
121-
} else {
122-
add_span(self, last_span.note[0], note);
123-
}
124-
}
120+
change_span_note(self, SILENCE, note, &dur);
125121
break;
126122
}
127123
case 10:
@@ -142,8 +138,12 @@ void common_hal_synthio_miditrack_construct(synthio_miditrack_obj_t *self,
142138
raise_midi_stream_error(pos);
143139
}
144140
}
145-
terminate_span(self, &dur, &max_dur);
141+
terminate_span(self, &dur);
146142

143+
uint16_t max_dur = 0;
144+
for (int i = 0; i < self->total_spans; i++) {
145+
max_dur = MAX(self->track[i].dur, max_dur);
146+
}
147147
self->buffer_length = max_dur * BYTES_PER_SAMPLE;
148148
self->buffer = m_malloc(self->buffer_length, false);
149149
}
@@ -177,6 +177,16 @@ void synthio_miditrack_reset_buffer(synthio_miditrack_obj_t *self,
177177
STATIC const uint16_t notes[] = {8372, 8870, 9397, 9956, 10548, 11175, 11840,
178178
12544, 13290, 14080, 14917, 15804}; // 9th octave
179179

180+
static int count_active_channels(synthio_midi_span_t *span) {
181+
int result = 0;
182+
for (int i = 0; i < CIRCUITPY_SYNTHIO_MAX_CHANNELS; i++) {
183+
if (span->note[i] != SILENCE) {
184+
result += 1;
185+
}
186+
}
187+
return result;
188+
}
189+
180190
audioio_get_buffer_result_t synthio_miditrack_get_buffer(synthio_miditrack_obj_t *self,
181191
bool single_channel_output, uint8_t channel, uint8_t **buffer, uint32_t *buffer_length) {
182192

@@ -187,19 +197,26 @@ audioio_get_buffer_result_t synthio_miditrack_get_buffer(synthio_miditrack_obj_t
187197

188198
synthio_midi_span_t span = self->track[self->next_span++];
189199
*buffer_length = span.dur * BYTES_PER_SAMPLE;
190-
uint8_t octave1 = span.note[0] / 12; // 0..10
191-
uint8_t octave2 = span.note[1] / 12; // 0..10
192-
int32_t base_freq1 = notes[span.note[0] % 12];
193-
int32_t base_freq2 = notes[span.note[1] % 12];
194-
int32_t sample_rate = self->sample_rate;
200+
memset(self->buffer, 0, *buffer_length);
195201

196-
for (uint16_t i = 0; i < span.dur; i++) {
197-
int16_t semiperiod1 = span.note[0] == SILENCE ? 0 :
198-
((base_freq1 * i * 2) / sample_rate) >> (10 - octave1);
199-
int16_t semiperiod2 = span.note[1] == SILENCE ? semiperiod1 :
200-
((base_freq2 * i * 2) / sample_rate) >> (10 - octave2);
201-
self->buffer[i] = ((semiperiod1 % 2 + semiperiod2 % 2) - 1) * LOUDNESS;
202+
int32_t sample_rate = self->sample_rate;
203+
int active_channels = count_active_channels(&span);
204+
if (active_channels) {
205+
int16_t loudness = 0x3fff / (1 + active_channels);
206+
for (int chan = 0; chan < CIRCUITPY_SYNTHIO_MAX_CHANNELS; chan++) {
207+
uint8_t octave = span.note[chan] / 12;
208+
uint16_t base_freq = notes[span.note[chan] % 12];
209+
if (span.note[chan] == SILENCE) {
210+
continue;
211+
}
212+
for (uint16_t i = 0; i < span.dur; i++) {
213+
int16_t semiperiod =
214+
((base_freq * i * 2) / sample_rate) >> (10 - octave);
215+
self->buffer[i] += semiperiod % 2 ? loudness : -loudness;
216+
}
217+
}
202218
}
219+
203220
*buffer = (uint8_t *)self->buffer;
204221

205222
return self->next_span >= self->total_spans ?

‎shared-module/synthio/MidiTrack.h‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -33,7 +33,7 @@
3333

3434
typedef struct {
3535
uint16_t dur;
36-
uint8_t note[2];
36+
uint8_t note[CIRCUITPY_SYNTHIO_MAX_CHANNELS];
3737
} synthio_midi_span_t;
3838

3939
typedef struct {

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