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Adding USB-audio feedback and mute command to usb_sound_card.c #53

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Adding USB-audio feedback and mute command to usb_sound_card.c #53

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18d01f3
Adding USB-audio feedback and mute command to usb_sound_card.c
sh1ura Jan 1, 2025
9f05e1e
Update usb_sound_card.c
sh1ura Jan 7, 2025
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50 changes: 50 additions & 0 deletions apps/usb_sound_card/usb_sound_card.c
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,11 @@
// todo forget why this is using core 1 for sound: presumably not necessary
// todo noop when muted

// modification for USB-sound rate feedback and mute
#define USB_FEEDBACK 1 // USB-audio rate feedback using buffer status
#define MUTE_CMD 1 // mute command
////////////////////////////////////////

CU_REGISTER_DEBUG_PINS(audio_timing)

// ---- select at most one ---
Expand All @@ -40,7 +45,12 @@ static char *descriptor_strings[] =
#undef AUDIO_SAMPLE_FREQ
#define AUDIO_SAMPLE_FREQ(frq) (uint8_t)(frq), (uint8_t)((frq >> 8)), (uint8_t)((frq >> 16))

#if USB_FEEDBACK
// when USB-audio feedback applies, it receives upto 49 samples in each packet
#define AUDIO_MAX_PACKET_SIZE(freq) (uint8_t)(((freq + 1999) / 1000) * 4)
#else
#define AUDIO_MAX_PACKET_SIZE(freq) (uint8_t)(((freq + 999) / 1000) * 4)
#endif
#define FEATURE_MUTE_CONTROL 1u
#define FEATURE_VOLUME_CONTROL 2u

Expand Down Expand Up @@ -256,6 +266,22 @@ static struct {

static struct audio_buffer_pool *producer_pool;

#if USB_FEEDBACK
#define BUFFER_NUM 16 // number of buffer

//for USB-audio rate feedback, number of vacant buffers is used
static int countFreeBuffers(void) {
int i = 0;

audio_buffer_t *audio_buffer = producer_pool->free_list;
while(audio_buffer != NULL) {
audio_buffer = audio_buffer->next;
i++;
}
return i;
}
#endif

static void _as_audio_packet(struct usb_endpoint *ep) {
assert(ep->current_transfer);
struct usb_buffer *usb_buffer = usb_current_out_packet_buffer(ep);
Expand All @@ -268,6 +294,11 @@ static void _as_audio_packet(struct usb_endpoint *ep) {
assert(audio_buffer->sample_count);
assert(audio_buffer->max_sample_count >= audio_buffer->sample_count);
uint16_t vol_mul = audio_state.vol_mul;
#if MUTE_CMD
if(audio_state.mute) {
vol_mul = 1;
}
#endif
int16_t *out = (int16_t *) audio_buffer->buffer->bytes;
int16_t *in = (int16_t *) usb_buffer->data;
for (int i = 0; i < audio_buffer->sample_count * 2; i++) {
Expand All @@ -288,8 +319,14 @@ static void _as_sync_packet(struct usb_endpoint *ep) {
assert(buffer->data_max >= 3);
buffer->data_len = 3;

#if USB_FEEDBACK
// calc rate adjustment value between -40 to 40
int feedbackvalue = (countFreeBuffers() - BUFFER_NUM / 2) * (2 * 40 / BUFFER_NUM);
uint feedback = ((audio_state.freq + feedbackvalue) << 14u) / 1000u;
#else
// todo lie thru our teeth for now
uint feedback = (audio_state.freq << 14u) / 1000u;
#endif

buffer->data[0] = feedback;
buffer->data[1] = feedback >> 8u;
Expand Down Expand Up @@ -613,7 +650,13 @@ int main(void) {
.sample_stride = 4
};

#if USB_FEEDBACK
// when USB-audio feedback applies, it receives upto 49 samples in each packet
producer_pool = audio_new_producer_pool(&producer_format, BUFFER_NUM,
AUDIO_MAX_PACKET_SIZE(AUDIO_FREQ_MAX) / 4);
#else
producer_pool = audio_new_producer_pool(&producer_format, 8, 48); // todo correct size
#endif
bool __unused ok;
struct audio_i2s_config config = {
.data_pin = PICO_AUDIO_I2S_DATA_PIN,
Expand All @@ -628,7 +671,14 @@ int main(void) {
panic("PicoAudio: Unable to open audio device.\n");
}

#if USB_FEEDBACK
// It is not clear what is meant by the number "96" but I fixed it as well as producer_pool.
// ok = audio_i2s_connect_extra(producer_pool, false, 2, 96, NULL);
ok = audio_i2s_connect_extra(producer_pool, false, 2,
AUDIO_MAX_PACKET_SIZE(AUDIO_FREQ_MAX) / 2, NULL);
#else
ok = audio_i2s_connect_extra(producer_pool, false, 2, 96, NULL);
#endif
assert(ok);
usb_sound_card_init();

Expand Down