[Mplayer-users] dirty ideas to speedup libMP3

[Felix Buenemann]

Hello Arpi,

Monday, July 23, 2001, 2:11:25 PM, you wrote:

> 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...
tested with winamp here, it still sounds ok.

> 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.
but it's not realtime then.

> A'rpi / Astral & ESP-team

-- 
Best regards,
 Felix                            mailto:atmosfear at users.sourceforge.net



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