[pulseaudio-discuss] regression with tsched=0 and small fragments?

[Lennart Poettering]

On Wed, 28.10.09 18:14, pl bossart (bossart.nospam at gmail.com) wrote:

> Hi all,
> I have lost the afternoon chasing an audio quality issue with PA
> configured with tsched=0 and small fragments (<30ms). I am doing this
> on purpose to profile the behavior of PulseAudio with lots of wakeups
> and samples provided in chunks at once.
> With the latest 0.9.19 version I have cracking noise but no reports of
> underflows, it works fine maybe once in 20 trials. With 0.9.15, no
> issue at all, I can even go down to fragments of 2ms without any
> issue. This is on a Atom board with classic HDAudio. I have no problem
> at all in both cases with aplay -Dhw. What I noticed though is that
> aplay seems to select a period size and buffer size that are multiples
> of 128 bytes. For example a period of 5ms at 48kHz is actually
> configured as 5.33ms and 256 frames; I suspect an alignement issue
> that would cause these noises.
> 
> I have an intuition that the regression was introduced by the ALSA
> configuration rewrite
> SHA:557c4295107dc7374c850b0bd5331dd35e8fdd0f ,
> but before I go on with a dichotomy and try to fix the issue I wanted
> to check if others faced the same problem.

I wonder if the issues raised by Alexandre Savard on the ML here
recently might actually be the same issue.

If you compare the output of snd_pcm_dump() for 0.9.15 and 0.9.19 on
your card, is there any obvious difference?

(snd_pcm_dump() is called as part of the normal setup these days and
dumped to stderr when debug logging is on. the snd_pcm_dump() output
looks like this: http://fpaste.org/X9Vh/)

Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/           GnuPG 0x1A015CC4