[Mplayer-dev-eng] Fwd: Re: mspeg4 decoder optimization

Arpi arpi at thot.banki.hu
Sun Jul 8 14:21:07 CEST 2001


here is gerard's mail about ffmpeg-mplayer code sync.

ehh. again the fuckin' licensing stuff...

--------- Forwarded message ---------
From: "Gérard" Lantau <glantau at yahoo.fr>
To: arpi at thot.banki.hu
Subject: Re: mspeg4 decoder optimization


> I've made some small changes on libavcodec to fit our needs:
> - added #ifdef USE_LIBAVCODEC define to your common.h to avoid conflict
> - removed some #include's from libavcodec, to get it compilable under bsd.
> - addedd new function to get decoder by name (instead by id).
> Later we can share code in CVS.

Can I get them from the mplayer CVS server ?

Currently, you can use the mplayer CVS and generate patches with it once you
think they are OK and send them to me.

About libavcodec optimisation : 

- I won't accept code covered by the GPL license because libavcodec is about to
change license (LGPL or MPL, I don't know yet). That's why I do not use the
very good MMX/SSE code from libmpeg2. 

- I prefer C optimisations (for example, in motion estimation averaging, pixels
could be handled 4 by 4 in a totally portable way) before mmx ones.

- for MMX, I prefer to use inline asm. As you said, it allows to use the C
compiler to do some stuff (and in upcoming gcc 3.0, you will be able to use
native vector types and builtins to have an ever more readable/portable code).

- If possible, the mmx code should be dynamically choosen according to the CPU
type (I am about to add this feature in ffmpeg).

- I HATE floats, so don't use them (not a problem in video, but may be one in
audio).

Gerard.


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