[MPlayer-dev-eng] AC3-surround patch

[Stephen Davies]

On Tue, 27 Nov 2001, Felix Buenemann wrote:

> I get heavy distortions on the Canyon trailer for example. When I do a 
> -dumpaudio and play with a52dec -o oss6 stream.dump it is fine, so stuff in 
> libac3 is buggy.

I can hear some clipping on the audio peaks towards the end of the Canyon
vob.  This could be my fault - I'll investigate.

Its also possible that mixing the centre and LFE channels to the front is
causing the SBLive headroom to be exceeded.  Can you test with just
fx8:Front L, fx9:Front R, fx10:Rear L, fx11:Rear R and see how it sounds?


> 
> Do you use a CPU with SSE support?

No - I've an Athlon.  Yours?  This could make a difference due to
mmx/imdct_kni.c vs mmx/imdct_3dnow.c if you have more than just a couple
of clipped spots.

> >   emu-dspmgr -a"fx8:Front L"
> >   emu-dspmgr -a"fx9:Front R"
> >   emu-dspmgr -a"fx10:Rear L"
> >   emu-dspmgr -a"fx11:Rear R"
> >   emu-dspmgr -a"fx12:Analog Center"
> >   emu-dspmgr -a"fx13:Analog LFE"
> >
> > This will map all the outputs to the right places.

> Either you have both front and rear speaker swapped ot it should be:
> --setup script for my sb live! value --
> #!/bin/sh
> emu-dspmgr -x -z
> emu-dspmgr -y
> emu-config -a
> # Front L
> emu-dspmgr -a"fx8:Front R"
> # Front R
> emu-dspmgr -a"fx9:Front L"
> # Rear L
> emu-dspmgr -a"fx10:Rear R"
> # Rear R
> emu-dspmgr -a"fx11:Rear L"
> # Center
> emu-dspmgr -a"fx12:Analog Center"
> # LFE
> emu-dspmgr -a"fx13:Analog LFE"
> --end of script--
> 
> I tested speaker order with the ac3test.ac3 extracted from AC3TEST.vob.

Thought I had the channels the right way round but didn't really have a
suitable test file.  I got ac3test and will investigate.

> this won't work, you have to use my above config, as there is no output named 
> "Front", my emu-dspmgr -o shows me:

Well - on my version of emu-dspmgr, ":Front" is interpretted to send to
both Front L and Front R.  In practice it definitely works for me.

> > There is an emu-script provided with the emu10k1 driver that can help get
> > this stuff configured for you.
> what's the name?

emu-script.  It installs it into /usr/local/etc/

<snip>

> Isit ok to apply patch to cvs?

I just want to understand your probs first.

I haven't changed anything in the old code path - so for ordinary stereo
mix the patch will make no change.  Users will have to select >2channel
mix so can always fall back to the old code.

Steve