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pq_alsa.c: handle output buffer underrun 

On some systems the ALSA output buffer is pretty big, and
if the audio samples are not being passed into the buffer
quickly enough, it becomes starved for data, resulting
in an error called underrun.

Previously, when it happenned, GAPK used to stop processing
with the following message (where X is a random number):

[+] PQ: Adding ALSA output (dev='default', blk_len=320)
[!] pq_execute(): abort, item returned -1
[+] Processed X frames

According to the ALSA documentation, the pcm_handle
changes its state when the problem happens, and should
be recovered using the snd_pcm_prepare() call. This change
actually does that.
This commit is contained in:
Vadim Yanitskiy 2017-09-02 21:34:02 +07:00 committed by Harald Welte
parent 6c42261cd2
commit 83aa99e7a9
1 changed files with 8 additions and 0 deletions
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8
src/pq_alsa.c
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@ -57,7 +57,15 @@ pq_cb_alsa_output(void *_state, uint8_t *out, const uint8_t *in, unsigned int in
struct pq_state_alsa *state = _state;
unsigned int num_samples = in_len/2;
int rv;
rv = snd_pcm_writei(state->pcm_handle, in, num_samples);
if (rv == -EPIPE) {
/* Recover from buffer underrun */
snd_pcm_prepare(state->pcm_handle);
/* Send a new sample again */
rv = snd_pcm_writei(state->pcm_handle, in, num_samples);
}
return rv == num_samples ? 0 : -1;
}