[Ffmpeg-devel] Re: idct_mmi.c license in FFmpeg

leon l.vanstuivenberg
Mon Sep 4 18:44:04 CEST 2006

Hello Diego,

> I'm reviewing licensing in FFmpeg and stumbled over the file idct_mmi.c
> that you contributed to FFmpeg way back in September 2002.
> Unfortunately there is no clear license statement in the code.
> The copyright header at the top of the file says
> /*
>   Originally provided by Intel at AP-922
>   http://developer.intel.com/vtune/cbts/strmsimd/922down.htm
>   (See more app notes at http://developer.intel.com/vtune/cbts/strmsimd/appnotes.htm)
>   but in a limited edition.
>   column code adapted from peter gubanov
>   Copyright (c) 2000-2001 Peter Gubanov <peter at elecard.net.ru>
>   http://www.elecard.com/peter/idct.shtml
>   Rounding trick Copyright (c) 2000 Michel Lespinasse <walken at zoy.org>
>   mmi port by leonvs at iae.nl
> */
> Are you the (sole) author of that code?  Can it be used under the LGPL?

It's probably safe to say i'm the (sole) author of this particular 
formulation of the idct algorithm in MMI instructions. The particular 
formulation of the idct algorithm and the partial implementation in MMX 
are (c) by intel (see ap-922)(to the degree that's even possible of 
course), and Peter added the column code in MMX (afaik). Michel's 
rounding trick actually is probably no longer used, but i couldn't find 
what the trick exactly was at that time.
For safety (IANAL) i just included the copyright statements of the 
original mmx version in this mmi version.

If it's up to me, LGPL is fine.


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