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

[D Richard Felker III]

On Mon, Jan 06, 2003 at 11:49:56AM +0800, Anders Johansson wrote:
> > > 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.
> 
> This coild be solved by making the ac3 decoder become  part of libaf :).

:)))

A long while back I suggested that the video encoders should all just
be filters that would output "encoded video frame" mpi formats so that
they could be used for sending video to hardware decoder display
devices as well as for mencoder, and there's a natural analogy for
video decoders and audio encoders and decoders as well. Unfortunately
Arpi thought it was rather bloated overkill, and I sorta agreed. :)
Who knows though, maybe it's a possibility...

> > > the best would be if codecs could support multiple output formats, rates,
> > > channels, and libaf could handle the handshaking between the selected (by
> > > user) filters, codec and ao. then auto-insert converters where it's needed.
> > > but it requires ig api changes and will result in many problems, see -vop :)
> > 
> > I agree. I was hoping the af layer would be just like the vf layer to
> > begin with, and somehow it didn't quite turn out that way... :( It
> > should still be possible to improve it in that direction though.
> 
> What is required in terms of API changes to achive this?

I'm probably not the person to ask, I *still* don't understand all the
stuff about how video filters are supposed to handshake even after
writing a few of them. :)

Rich