Ogg vorbis performance.

Russell Sears sears at cs.berkeley.edu
Sun Jul 13 09:34:48 CEST 2008

Sören Apel wrote:
> Heya,
> On Sat, 2008-07-12 at 14:27 -0700, Russell Sears wrote:
>> I've noticed that my freerunner is *almost* fast enough to play my ogg 
>> vorbis files; running a second app, or even gpsd causes the media player 
>> to skip, then to go silent.
> Yep.
>> What's been done to get ogg vorbis to perform well so far?  ogg123, 
>> oggdec seem to be able to decode in roughly 2/3's realtime, which is 
>> similar to the CPU usage of openmoko-mediaplayer.
> If I remember correctly it was a problem with the sample rate/sample
> format,
> meaning that resampling had to take place - which eats CPU like candy.

Ouch.  What sample rate does the hardware provide, and does pulseaudio 
or gstreamer do the resampling?  Also, decoding to /dev/null is slow... 
  That shouldn't resample should it?

I've noticed that things I've encoded more recently seem to be less 
likely to play (perhaps I changed an encoding setting at some point...), 
but that it varies from track to track...  I'll time some files, and see 
if I can find a pattern.



>> I noticed that gstreamer is using libvorbisi (tremor) since there is no 
>> floating point unit.  It looks like there are three ways to make it go 
>> faster:
>>   - Tremolo, which is ARM specific, and claims 15-20% better performance
>>   - _LOW_ACCURACY_ mode
>>   - The "low-mem" branch of tremor
>> Which of these have been tried so far?
> None, as I didn't find the time unfortunately. 
> You're more than welcome to try these :)
>  -Soeren

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