Russell Sears wrote:
Flemming Richter Mikkelsen wrote:
On 2008-07-13, Russell Sears <[EMAIL PROTECTED]> wrote:
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.
Thanks!
-Rusty
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 :)
I use my Freerunner as a mediaplayer. I installed mplayer and stored
my ogg vorbis files on the micro SD card. They are encoded with high,
but floating bitrate.
I got no problems when playing.
Also, please note that ogg vorbis is extremely flexible and you can
select any bitrate for playback without the need for reencode.
There is now a bug for this, number 1614.
I'm beginning to agree with Sören; I think it's resampling or doing
software mixing in the pulseaudio layer. Getting pulseaudio to perform
passthrough will probably help.
Also, I'm attempting to build all the packages from scratch, and figure
out who links to which vorbis decoder, and with which compilation
options. Hopefully, we can save some cycles there too.
-Rusty
I uploaded a fix to the bug tracker. It bypasses PulseAudio and uses
ALSA. Any idea why that helps? In principle, ALSA and PulseAudio
should have to perform the same computations to play the sound back
(alsa contains a software resampler...) I haven't been able to find any
obviously mistakes in the configuration files.
Also, are there any bad implications to bypassing pulseaudio? I haven't
noticed any. I'd like to get ogg vorbis (and anything else that outputs
16bit/44.1kHz) fixed in the official image...
-Rusty
