[FFmpeg-devel] [PATCH] activate ac3 decoder

[Guillaume POIRIER]

Hi,

On 8/7/07, Justin Ruggles <justinruggles at bellsouth.net> wrote:
> Diego Biurrun wrote:
> > On Sat, Aug 04, 2007 at 09:36:05PM -0400, Justin Ruggles wrote:
> >> --- configure        (revision 9911)
> >> +++ configure        (working copy)
> >> @@ -1594,6 +1595,9 @@
> >>
> >> +# disable the native AC-3 decoder if liba52 is enabled
> >> +enabled liba52 && disable ac3_decoder
> >
> > Possibly we should remove liba52 support, same as we did for
> > libdca/libdts.
>
> Right now it's a bit slower.  For straight channel-for-channel decoding
> it's about 3%-per-channel slower on my machine.  With downmixing 5.1 to
> stereo it's closer to 30% slower.  I'm working on better downmixing
> though.  Basically I need to work out how to downmix before the IMDCT,
> not after.  I've got papers on the subject, but I need to delve into the
> math to implement it properly.

Does it take advantage of existing DSP functions of FFmpeg?
Does it take advantage of SIMD-optimized code?

What's the slowest part of AC3 decoding currently?

Guillaume
-- 
A soldier will fight long and hard for a bit of colored ribbon.
 -- Napoleon Bonaparte