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nRF: PWMAudioOut: fix half-speed playback of stereo samples #2364

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Merged
merged 1 commit into from
Dec 9, 2019
Merged

nRF: PWMAudioOut: fix half-speed playback of stereo samples #2364

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16 changes: 10 additions & 6 deletions ports/nrf/common-hal/audiopwmio/PWMAudioOut.c
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Original file line number Diff line number Diff line change
Expand Up @@ -97,27 +97,28 @@ STATIC void fill_buffers(audiopwmio_pwmaudioout_obj_t *self, int buf) {
common_hal_audiopwmio_pwmaudioout_stop(self);
return;
}
uint32_t num_samples = buffer_length / self->bytes_per_sample / self->spacing;
uint32_t num_samples = buffer_length / self->bytes_per_sample / self->sample_channel_count;
uint16_t *end_dev_buffer = dev_buffer + 2 * num_samples;

if (self->bytes_per_sample == 1) {
uint8_t offset = self->signed_to_unsigned ? 0x80 : 0;
uint16_t scale = self->scale;
for (uint32_t i=0; i<buffer_length/self->spacing; i++) {
while (dev_buffer < end_dev_buffer) {
uint8_t rawval = (*buffer++ + offset);
uint16_t val = (uint16_t)(((uint32_t)rawval * (uint32_t)scale) >> 8);
*dev_buffer++ = val;
if (self->spacing == 1)
if (self->sample_channel_count == 1)
*dev_buffer++ = val;
}
} else {
uint16_t offset = self->signed_to_unsigned ? 0x8000 : 0;
uint16_t scale = self->scale;
uint16_t *buffer16 = (uint16_t*)buffer;
for (uint32_t i=0; i<buffer_length/2/self->spacing; i++) {
while (dev_buffer < end_dev_buffer) {
uint16_t rawval = (*buffer16++ + offset);
uint16_t val = (uint16_t)((rawval * (uint32_t)scale) >> 16);
*dev_buffer++ = val;
if (self->spacing == 1)
if (self->sample_channel_count == 1)
*dev_buffer++ = val;
}
}
Expand Down Expand Up @@ -231,9 +232,12 @@ void common_hal_audiopwmio_pwmaudioout_play(audiopwmio_pwmaudioout_obj_t* self,
self->bytes_per_sample = audiosample_bits_per_sample(sample) / 8;

uint32_t max_buffer_length;
uint8_t spacing;
audiosample_get_buffer_structure(sample, /* single channel */ false,
&self->single_buffer, &self->signed_to_unsigned, &max_buffer_length,
&self->spacing);
&spacing);
self->sample_channel_count = audiosample_channel_count(sample);

if (max_buffer_length > UINT16_MAX) {
mp_raise_ValueError_varg(translate("Buffer length %d too big. It must be less than %d"), max_buffer_length, UINT16_MAX);
}
Expand Down
2 changes: 1 addition & 1 deletion ports/nrf/common-hal/audiopwmio/PWMAudioOut.h
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Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,7 @@ typedef struct {

uint8_t left_channel_number;
uint8_t right_channel_number;
uint8_t spacing;
uint8_t sample_channel_count;
uint8_t bytes_per_sample;

bool playing;
Expand Down