[Openal-devel] Default buffer size

[Chris Robinson]

Lately I've been wondering if the default buffer size for OpenAL Soft 
<http://kcat.strangesoft.net/openal.html> should be reduced. Currently the 
default is 8192 frames, which I more or less haphazardly chose as it didn't 
seem to have a noticeable lag to me and didn't have problems with skipping, 
but I've been getting more reports, mainly in Windows/DSound for some odd 
reason, that there is a noticeable delay. Setting the value to 4096 seems to 
solve it.

I've played around with the setting a bit, and 4096 doesn't seem to cause me 
any problems (but then, I have an AMD Athlon X2 4200+). My main hesitation 
about lowering the default buffer size to 4096, or lower, comes from the 
effects on low-end systems, which I obviously don't have. I want to make sure 
that turning it down like that won't reintroduce skipping or noise that was 
prevelant in the SI.

So, this is pretty much a callout to anyone with an older system (1GHz single 
core, or lesser, would be ideal). If anyone can test OpenAL Soft on it with 
various buffer sizes and backends (and in the case of ALSA, mmap on and off), 
with a real-world app, I'd be most appreciative. Free, hopefully 
low-requirement, games that use OpenAL include:
Warsow <http://www.warsow.net>
Tremulous <http://www.tremulous.net/>
Thunder & Lightning <http://tnlgame.net/>
SuperTuxKart <http://supertuxkart.sourceforge.net/>
plus more listed at <http://openal.org/titles.html>.

If anyone tests it out, please make sure you have the latest OpenAL Soft 
version (at least 1.4, preferably GIT/SVN) and remember to say what CPU and 
OS you have, as well as the actual settings. You can use the OpenAL Soft 
configuration utility <http://www.anduin.net/~angasule/> or simply look in 
the source archive for alsoftrc.sample which has information on how to set 
it.

Note that if you have PulseAudio, I strongly recommend turning it off. The 
extra software mixing, volume control, and bugs it has, can likely increase 
the lag and hide potential skipping.

Thanks!