[alsa-devel] Driver recovers from underrun in plain ALSA mode, but not in OSS emulation

Takashi Iwai tiwai at suse.de
Tue Mar 4 11:38:19 CET 2008

At Fri, 29 Feb 2008 17:56:43 -0600,
Timur Tabi wrote:
> I'm stress-testing my sound driver using mplayer to see how it handles underrun
> during jumps in CPU loads.  That is, I start playing a movie, and then I cause
> the CPU to jump to 100%, and then I drop the CPU back to normal.  During the
> times when the CPU is at 100%, I get underruns and other problems.  That's normal.
> When I tell mplayer to use the ALSA API, my driver recovers nicely from an
> underrun situation when the CPU load drops back to normal.  However, if I tell
> mplayer to use the OSS API (i.e. ALSA's OSS emulation), it does not recover from
> an underrun situation.  The audio and video playback remains distorted.  I need
> to tell mplayer to pause and resume to get it to recover.
> Is this normal for ALSA drivers?  Before I try to debug this problem the hard
> way, I want to know if this could be the result of a common programming mistake
> in my driver or something like similar.

No, it's not normal.

The question is whether OSS emulation really notices the underrun.
More likely, it's caused by the difference of parameters.


More information about the Alsa-devel mailing list