Ogg vorbis performance.

Troy Benjegerdes hozer at hozed.org
Fri Jul 18 06:40:44 CEST 2008

> It should have essentially zero overhead when properly configured, and 
> when its not doing anything fancy.  I don't think these performance 
> problems are fundamental.

Don't think, benchmark :)  There are a ton of non-obvious reasons one
approach might seem just fine but really suck. (cache alignments, tlb
misses, ctx switch overhead)

> >
> >For power and performance reasons on a cell phone, I think anything a
> >sound server does would be much better done in the kernel-level ALSA
> >drivers. The only downside I can see to this approach whether the
> >in-kernel bluetooth audio drivers are any good.
> >
> Kernel-level software resampling should be just as expensive as 
> userspace resampling...  Pulseaudio does seem to do some soft-realtime 
> stuff and adds a bit of device transparency.
> >Last I tried bluetooth-audio on my laptop I had to run a userspace
> >daemon.
> I have no idea what would happen with Alsa if you tried to transfer a 
> call between the speaker and the bluetooth set.  I think pulseaudio can 
> handle this sort of thing correctly.

All my whining aside, seamless speaker->bluetooth handoff seems to be a
'must-have' feature. Although I would like to hear a good reason why the
kernel shouldn't be in charge of that.

> >
> >Speaking of which.. do we have any way to measure the power consumption
> >of playing a reference .ogg file without special hardware? Are the
> >built-in battery charge management counters good enough?
> >
> Good question. :)  Also, pulseaudio may be preventing the sound card and 
> cpu from falling asleep, even when no sounds are being played.  From 
> what I can tell, it's been configured to never go idle.

More information about the openmoko-devel mailing list