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Send silence when no audio is coming through from Shairport Sync. Thi…
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…s eliminates (?) xrun errors. Clean up a few imprefections.
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@mikebrady
mikebrady committed Oct 2, 2023
1 parent 29a5589 commit dc197ae
Showing 1 changed file with 71 additions and 50 deletions.
121 changes: 71 additions & 50 deletions audio_pw.c
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@

// This uses ideas from the tone generator sample code at:
// https://github.com/PipeWire/pipewire/blob/master/src/examples/audio-src.c
// Thanks to the Wim Taymans.
// Thanks to Wim Taymans.

#include "audio.h"
#include "common.h"
Expand All @@ -39,7 +39,7 @@
#include <pipewire/pipewire.h>
#include <spa/param/audio/format-utils.h>

// note -- these are hacked and hardwired into this code.
// note -- these are hardwired into this code.
#define DEFAULT_FORMAT SPA_AUDIO_FORMAT_S16_LE
#define DEFAULT_RATE 44100
#define DEFAULT_CHANNELS 2
Expand All @@ -52,8 +52,7 @@ static pthread_mutex_t buffer_mutex = PTHREAD_MUTEX_INITIALIZER;
static char *audio_lmb, *audio_umb, *audio_toq, *audio_eoq;
static size_t audio_size = buffer_allocation;
static size_t audio_occupancy;

uint64_t starting_time;
static int enable_fill;

struct timing_data {
int pw_time_is_valid; // set when the pw_time has been set
Expand All @@ -72,17 +71,17 @@ struct data {
};

// the pipewire global data structure
struct data data = {
0,
};
struct data data = {NULL, NULL};

/*
static void on_state_changed(__attribute__((unused)) void *userdata, enum pw_stream_state old,
enum pw_stream_state state,
__attribute__((unused)) const char *error) {
// struct pw_data *pw = userdata;
debug(3, "pw: stream state changed %s -> %s", pw_stream_state_as_string(old),
pw_stream_state_as_string(state));
}
*/

static void on_process(void *userdata) {

Expand All @@ -91,52 +90,63 @@ static void on_process(void *userdata) {

pthread_mutex_lock(&buffer_mutex);

if (audio_occupancy > 0) {
if ((audio_occupancy > 0) || (enable_fill)) {

// get a buffer to see how big it can be
struct pw_buffer *b = pw_stream_dequeue_buffer(data->stream);
if (b == NULL) {
pw_log_warn("out of buffers: %m");
return;
die("PipeWire failue -- out of buffers!");
}
struct spa_buffer *buf = b->buffer;
uint8_t *dest = buf->datas[0].data;
if (dest == NULL) // the first data block does not contain a data pointer
return;

int stride = sizeof(int16_t) * DEFAULT_CHANNELS;
int max_possible_frames = SPA_MIN(b->requested, buf->datas[0].maxsize / stride);

size_t bytes_we_can_transfer = max_possible_frames * stride;

if (bytes_we_can_transfer > audio_occupancy)
bytes_we_can_transfer = audio_occupancy;

n_frames = bytes_we_can_transfer / stride;

size_t bytes_to_end_of_buffer = (size_t)(audio_umb - audio_toq); // must be zero or positive

if (bytes_we_can_transfer <= bytes_to_end_of_buffer) {
// the bytes are all in a row in the audio buffer
memcpy(dest, audio_toq, bytes_we_can_transfer);
audio_toq += bytes_we_can_transfer;
} else {
// the bytes are in two places in the audio buffer
size_t first_portion_to_write = audio_umb - audio_toq;
if (first_portion_to_write != 0)
memcpy(dest, audio_toq, first_portion_to_write);
uint8_t *new_dest = dest + first_portion_to_write;
memcpy(new_dest, audio_lmb, bytes_we_can_transfer - first_portion_to_write);
audio_toq = audio_lmb + bytes_we_can_transfer - first_portion_to_write;
}

buf->datas[0].chunk->offset = 0;
buf->datas[0].chunk->stride = stride;
buf->datas[0].chunk->size = n_frames * stride;
pw_stream_queue_buffer(data->stream, b);
debug(3, "Queueing %d frames for output.", n_frames);

audio_occupancy -= bytes_we_can_transfer;
if (dest != NULL) {
int stride = sizeof(int16_t) * DEFAULT_CHANNELS;

// note: the requested field is the number of frames, not bytes, requested
int max_possible_frames = SPA_MIN(b->requested, buf->datas[0].maxsize / stride);

size_t bytes_we_can_transfer = max_possible_frames * stride;

if (audio_occupancy > 0) {
// if (enable_fill == 1)) {
// debug(1, "got audio -- disable_fill");
// }
enable_fill = 0;

if (bytes_we_can_transfer > audio_occupancy)
bytes_we_can_transfer = audio_occupancy;

n_frames = bytes_we_can_transfer / stride;

size_t bytes_to_end_of_buffer = (size_t)(audio_umb - audio_toq); // must be zero or positive
if (bytes_we_can_transfer <= bytes_to_end_of_buffer) {
// the bytes are all in a row in the audio buffer
memcpy(dest, audio_toq, bytes_we_can_transfer);
audio_toq += bytes_we_can_transfer;
} else {
// the bytes are in two places in the audio buffer
size_t first_portion_to_write = audio_umb - audio_toq;
if (first_portion_to_write != 0)
memcpy(dest, audio_toq, first_portion_to_write);
uint8_t *new_dest = dest + first_portion_to_write;
memcpy(new_dest, audio_lmb, bytes_we_can_transfer - first_portion_to_write);
audio_toq = audio_lmb + bytes_we_can_transfer - first_portion_to_write;
}
audio_occupancy -= bytes_we_can_transfer;

} else {
debug(3, "send silence");
// this should really be dithered silence
memset(dest, 0, bytes_we_can_transfer);
n_frames = max_possible_frames;
}
buf->datas[0].chunk->offset = 0;
buf->datas[0].chunk->stride = stride;
buf->datas[0].chunk->size = n_frames * stride;
pw_stream_queue_buffer(data->stream, b);
debug(3, "Queueing %d frames for output.", n_frames);
} // (else the first data block does not contain a data pointer)
}
pthread_mutex_unlock(&buffer_mutex);

Expand All @@ -150,8 +160,9 @@ static void on_process(void *userdata) {
__sync_synchronize();
}

static const struct pw_stream_events stream_events = {
PW_VERSION_STREAM_EVENTS, .process = on_process, .state_changed = on_state_changed};
static const struct pw_stream_events stream_events = {PW_VERSION_STREAM_EVENTS,
.process = on_process};
// PW_VERSION_STREAM_EVENTS, .process = on_process, .state_changed = on_state_changed};

static void deinit(void) {
pw_thread_loop_stop(data.loop);
Expand All @@ -173,7 +184,6 @@ static int init(__attribute__((unused)) int argc, __attribute__((unused)) char *
config.audio_backend_latency_offset = 0;

// get settings from settings file

// do the "general" audio options. Note, these options are in the "general" stanza!
parse_general_audio_options();

Expand All @@ -188,10 +198,12 @@ static int init(__attribute__((unused)) int argc, __attribute__((unused)) char *
// allocate space for the audio buffer
audio_lmb = malloc(audio_size);
if (audio_lmb == NULL)
die("Can't allocate %d bytes for pulseaudio buffer.", audio_size);
die("Can't allocate %d bytes for PipeWire buffer.", audio_size);
audio_toq = audio_eoq = audio_lmb;
audio_umb = audio_lmb + audio_size;
audio_occupancy = 0;
// debug(1, "init enable_fill");
enable_fill = 1;

const struct spa_pod *params[1];
uint8_t buffer[1024];
Expand Down Expand Up @@ -233,7 +245,8 @@ static int init(__attribute__((unused)) int argc, __attribute__((unused)) char *
}

static void start(__attribute__((unused)) int sample_rate,
__attribute__((unused)) int sample_format) {}
__attribute__((unused)) int sample_format) {
}

static int play(__attribute__((unused)) void *buf, int samples,
__attribute__((unused)) int sample_type, __attribute__((unused)) uint32_t timestamp,
Expand Down Expand Up @@ -322,6 +335,10 @@ static void flush(void) {
audio_toq = audio_eoq = audio_lmb;
audio_umb = audio_lmb + audio_size;
audio_occupancy = 0;
// if (enable_fill == 0) {
// debug(1, "flush enable_fill");
// }
enable_fill = 1;
pthread_mutex_unlock(&buffer_mutex);
}

Expand All @@ -330,6 +347,10 @@ static void stop(void) {
audio_toq = audio_eoq = audio_lmb;
audio_umb = audio_lmb + audio_size;
audio_occupancy = 0;
// if (enable_fill == 0) {
// debug(1, "stop enable_fill");
// }
enable_fill = 1;
pthread_mutex_unlock(&buffer_mutex);
}

Expand Down

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