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Might Help with Audio Latency Issues #117

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Might Help with Audio Latency Issues #117

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6c58c96
use realtime priority for audio thread
Feb 14, 2018
b5142a5
add alsa error handling
Feb 14, 2018
caa6f1c
request as much data as we can in each callback, instead of just the …
Feb 14, 2018
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32 changes: 28 additions & 4 deletions src/apulse-stream.c
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Original file line number Diff line number Diff line change
Expand Up @@ -58,6 +58,7 @@ deh_stream_first_readwrite_callback(pa_mainloop_api *api, pa_defer_event *de, vo
pa_stream_unref(s);
}

static int xruns=0;
static
void
data_available_for_stream(pa_mainloop_api *a, pa_io_event *ioe, int fd, pa_io_event_flags_t events,
Expand Down Expand Up @@ -167,17 +168,20 @@ data_available_for_stream(pa_mainloop_api *a, pa_io_event *ioe, int fd, pa_io_ev
}

if (events & PA_IO_EVENT_OUTPUT) {
int r;

if (paused) {
// client stream is corked. Pass silence to ALSA
size_t bytecnt = MIN(buf_size, frame_count * frame_size);
memset(buf, 0, bytecnt);
snd_pcm_writei(s->ph, buf, bytecnt / frame_size);
r= snd_pcm_writei(s->ph, buf, bytecnt / frame_size);
} else {
size_t writable_size = pa_stream_writable_size(s);

// Ask client for data, but only if we are ready for at least |minreq| bytes.
if (s->write_cb && writable_size >= s->buffer_attr.minreq)
s->write_cb(s, s->buffer_attr.minreq, s->write_cb_userdata);
if (s->write_cb && writable_size >= s->buffer_attr.minreq) {
s->write_cb(s, writable_size, s->write_cb_userdata);
}

size_t bytecnt = MIN(buf_size, frame_count * frame_size);
bytecnt = ringbuffer_read(s->rb, buf, bytecnt);
Expand All @@ -188,9 +192,29 @@ data_available_for_stream(pa_mainloop_api *a, pa_io_event *ioe, int fd, pa_io_ev
// application is not ready yet, play silence
bytecnt = MIN(buf_size, frame_count * frame_size);
memset(buf, 0, bytecnt);
trace_warning("application not ready\n");
}
snd_pcm_writei(s->ph, buf, bytecnt / frame_size);
r = snd_pcm_writei(s->ph, buf, bytecnt / frame_size);
}

if (r < 0) {
switch (r) {
case -EAGAIN: // non-blocking I/O, no need to do anything
break;
case -EBADFD: // FD in wrong state
trace_warning("ALSA badfd: rv=%d\n", r);
snd_pcm_prepare(s->ph);
break;
case -EPIPE: // XRUN
xruns++;
trace_warning("ALSA xrun: rv=%d, xruns=%d\n", r, xruns);
snd_pcm_recover(s->ph, r, 1);
break;
default:
trace_warning("ALSA error: rv=%d\n", r);
snd_pcm_recover(s->ph, r, 1);
}
}
}

if (events & PA_IO_EVENT_INPUT) {
Expand Down
15 changes: 15 additions & 0 deletions src/apulse-threaded-mainloop.c
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Expand Up @@ -129,15 +129,30 @@ pa_threaded_mainloop_signal(pa_threaded_mainloop *m, int wait_for_accept)
pthread_cond_signal(&m->cond);
}

#define AUDIO_THREAD_RT_PRIORITY 60

APULSE_EXPORT
int
pa_threaded_mainloop_start(pa_threaded_mainloop *m)
{
struct sched_param rtparam;
int err;
trace_info_f("F %s m=%p\n", __func__, m);

if (m->running)
return 1;
pthread_create(&m->t, NULL, mainloop_thread, m);

memset(&rtparam, 0, sizeof(rtparam));
rtparam.sched_priority = AUDIO_THREAD_RT_PRIORITY;

if ((err = pthread_setschedparam(m->t, SCHED_FIFO, &rtparam)) != 0) {
trace_warning(
"cannot use real-time scheduling (FIFO at priority %d) "
"for audio thread (%d: %s)",
rtparam.sched_priority, err, strerror(err));
}

m->running = 1;
return 0;
}
Expand Down