From: Timur Tabi <timur@freescale.com>
To: alsa-devel@alsa-project.org
Subject: Question about snd_pcm_update_hw_ptr_post()
Date: Mon, 03 Mar 2008 14:42:45 -0600 [thread overview]
Message-ID: <47CC62C5.5010308@freescale.com> (raw)
Can someone explain to me this snippet from snd_pcm_update_hw_ptr_post():
if (avail >= runtime->stop_threshold) {
if (substream->runtime->status->state == SNDRV_PCM_STATE_DRAINING)
snd_pcm_drain_done(substream);
else
xrun(substream);
return -EPIPE;
}
During playback, avail = snd_pcm_playback_avail(). Does this mean that avail is
number of frames available in the playback DMA buffer for new data?
If so, why is avail >= runtime->stop_threshold considered an underrun condition?
Does ALSA try to keep the amount of available data to a minimum?
If so, how can I adjust runtime->stop_threshold? I'd like to see what happens
if I make stop_threshold equal to the size of my DMA buffer.
--
Timur Tabi
Linux kernel developer at Freescale
next reply other threads:[~2008-03-03 20:42 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-03-03 20:42 Timur Tabi [this message]
2008-03-04 7:27 ` Question about snd_pcm_update_hw_ptr_post() Clemens Ladisch
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