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ALSA code: Fixed corrupted sample at the end of a read 

The last sample may get corrupted. It seems that this depends on the
card that is used. To fix this, the snd_pcm_avail is checked and
one sample less than available is read using snd_pcm_readi. This
sample remains in RX buffer until next read. Then it is not corrupted.
This commit is contained in:
Andreas Eversberg 2016-07-02 08:04:43 +02:00
parent 4719be95bd
commit f3fd01ebcd
1 changed files with 18 additions and 3 deletions
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21
src/common/sound_alsa.c
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@ -154,6 +154,10 @@ void *sound_open(const char *device, int samplerate)
goto error;
}
/* trigger capturing */
int16_t buff[2];
snd_pcm_readi(sound->chandle, buff, 1);
return sound;
error:
@ -207,13 +211,24 @@ int sound_read(void *inst, int16_t *samples_left, int16_t *samples_right, int nu
{
sound_t *sound = (sound_t *)inst;
int16_t buff[num << 1];
int rc;
int in, rc;
int i, ii;
/* get samples in rx buffer */
in = snd_pcm_avail(sound->chandle);
/* if less than 2 frames available, try next time */
if (in < 2)
return 0;
/* read one frame less than in buffer, because snd_pcm_readi() seems
* to corrupt last frame */
in--;
if (in > num)
in = num;
if (sound->cchannels == 2)
rc = snd_pcm_readi(sound->chandle, buff, num);
rc = snd_pcm_readi(sound->chandle, buff, in);
else
rc = snd_pcm_readi(sound->chandle, samples_left, num);
rc = snd_pcm_readi(sound->chandle, samples_left, in);
if (rc < 0) {
if (errno == EAGAIN)