[Mplayer-users] dirty ideas to speedup libMP3

[Arpi]

Hi,

> >
> >It should be possible to downmix the audio (to mono, perhaps?)
> >I remember winamp (I know, I know...) having settings where you could
> >downmix to 1/2 or 1/4 bitrate if you had a slow-ass computer...
> 
> Yes, but does it work on non-decoded data, i.e. is it really _faster_ 
> then? Because mpg123 gets _slower_ by this...

I'm not an mp3 expert, but AFAIK it uses huffman to code quantized values.
So you have to decode every bit of the file to get quants, you can't
skip or speedup this part.
(huffman is prefixed coding, so you have to decode a symbol to get position
of the next)

The only thing you can trick with, is the sampling rate.
If you decode 44khz samples to 22khz, you can skip quantized values of
high frequenzies. But the audio will be ugly...

Btw divx decoding eats >10 times more decoding than mp3, so you should
focus on that. Maybe transcoding to mpeg1 before playing the movie? This way
it gets about 2-4 times bigger but playable realtime even on p166mmx.


A'rpi / Astral & ESP-team

--
mailto:arpi at thot.banki.hu
http://esp-team.scene.hu

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