[MPlayer-dev-eng] [BUG] surround audio plugin broken

[Arpi]

Hi,

> > maybe we should change all codecs to output in their native formats only,
> > and left all kind of downsampling, float2int etc to libaf.
> > this way we lose conversions helped by the codecs (examples: liba52's
> > float2int, channels downsampling, mp3lib's half or quarter freq decoding,
> > mono decoding of stereo sterams, stereo decoding of mono streams).
> 
> This seems like something of a negative to me, especially with ac3
> decoding...but I'm not sure how it works now. If there are only 2
> output channels but the stream is 5.1 ac3, does liba52 really decode
> all the channels and then downmix them, or can it just skip the
> surround stuff and decode only l/r for better performance? If it can't
> do that, it seems like a really desirable feature, especially since
> ac3 decoding is so damn slow to begin with.

liba52 is very clever...
it downmixes channels in freq space (with coeffs) and the imdct only
the requested number of channels.

also it can add a given bias value to the pcm values (while doint the imdct)
helping the float2int process (there are integeronly tricks to convert an
ieee float in a given range to integer)


A'rpi / Astral & ESP-team

--
Developer of MPlayer, the Movie Player for Linux - http://www.MPlayerHQ.hu