[alsa-devel] [REGRESSION bisected] Sound goes too fast due to commit 7b3a177b0

[Éric Piel]

On 14/04/10 08:08, Takashi Iwai wrote:
> At Tue, 13 Apr 2010 23:54:26 +0200,
> Éric Piel wrote:
>>
>> Hello,
>>
>> Since 2.6.34-rc*, I have a regression on alsa which prevents the sound
>> to be played correctly. When playing, the music goes too fast, skipping
>> some parts. Typically, it's very easy to reproduce by doing:
>> time mplayer -endpos 30 sound-file-which-lasts-more-than-thirty-sec.mp3
>>
>> If the wall clock is less than 30s, you have the bug. With my intel-hda
>> (AD1981), it's reliably reproducible: it gives ~27s, instead of the
>> normal ~31s.
>>
>> After bisection, it turns out that it is commit
>> 7b3a177b0d4f92b3431b8dca777313a07533a710, aka "ALSA: pcm_lib: fix
>> "something must be really wrong" condition" which caused this
>> regression. Reverting it on top of 2.6.34-rc3+ fixes the problem.
> 
> What happens if you pass position_fix=1 option to snd-hda-intel?
Oh! Very good remark...
I've just noticed that I had an option already on the module:
bdl_pos_adj=0. It seems it's not needed anymore to get my card working
fine. If I remove every option (leaving bdl_pos_adj to the default value
1), it works fine. If I put bdl_pos_adj=0 and position_fix=1, it works
fine again.

I don't fully grasp the meaning of bdl_pos_adj, so I don't know if it's
a bug to not play correctly when forcing it to 0. Is it?

I'll ask to another reporter who had the same problem if bdl_pos_adj is
also set to 0...

> Is it via PulseAudio or other backend?
This happens both with pulseaudio, oss and alsa (in which case it plays
the 30s clip in 12s).

Eric