[MPlayer-dev-eng] AC3-surround patch

[Felix Buenemann]

On Tuesday, 27. November 2001 20:52, you wrote:
> 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.
>
yes, it's towards the end.

> 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?
sounds the same, because I can't remap LFE, it is always mapped to lef front 
speaker, can't change that (doesn't matter what I ntry to map it to).

Btw. distortions are also on the rear channels if I heard right.

>
> > 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.
yea, I should try recompile without sse support then.

> > 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"
this line is now: Front instead of 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.
>
ok, I see.

[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.
>
Btw. just checked on laptop in 2 channel mode, and there I get no distortion 
at the end of the Canyon clip (laptop is also SSE cpu).

> Steve
>

-- 
Best Regards,
	Atmos
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