[Ffmpeg-devel] [PATCH] Vorbis decoder

Rich Felker dalias
Thu May 12 11:25:01 CEST 2005

On Thu, May 12, 2005 at 10:10:10AM +0200, Balatoni Denes wrote:
> Hi!
> So I uploaded it here:
> http://people.inf.elte.hu/isten/vorbis/vorbis.diff
> It is under the LGPL license, although not stated in the diff (but hopefully 
> obvious, as it's a patch to libavcodec).
> I know a fixed point implementation would be great but:
> 1.) on pentium III (and athlon-xp) upwards it's definietly slower

I don't believe float is ever faster than a _proper_ int
implementation, except maybe on broken intel crap (i.e. P4).
In any case, the performance on systems where it's using 0.05% cpu
already doesn't really matter...where it matters is on systems where
it's using 10-100% cpu.

> 2.) lavc currently has wrapper for libvorbis only, which is floating point 

Well, you can drop in libvorbisidec (tremor) which is fixed point, at
least with minimal modification..

> 3.) lavc's fft based imdct is floating point

Volunteers to fix? :(

> 4.) embedded platforms are also memory constrained - I didn't say, but this 
> decoder also uses more memory than libvorbis

I didn't say embedded necessarily. In any case I don't think the
memory usage is a problem, but if it is we should find a fix. Large
memory usage by the audio codec is one of the #1 performance problems
in movie playing, because it kills the cache coherency for video

> 5.) I have little time


> Constructive comments welcome, I say apply it, or I have just waisted one week

Definitely not a waste. I agree we should apply it now/soon, but I
think there are a lot of improvements that could be made too.


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