[FFmpeg-devel] Cleanup libswscale and reimplement GPL code under LGPL

Michael Niedermayer michaelni
Mon Apr 7 17:43:44 CEST 2008

On Mon, Apr 07, 2008 at 04:30:51PM +0100, M?ns Rullg?rd wrote:
> Luca Abeni wrote:
> > Hi Ramiro,
> >
> > Ramiro Polla wrote:
> >>> IMO rewriting the SIMD code because of GPL makes no sense, why would you
> >>> want to do that? The code can be used without SIMD, is it so bad that
> >>> non free software will be a little slower?
> >>> Also i will not review any rewritten SIMD code.
> >>
> >> Ok, but what about the rest of the project? Instead of rewriting SIMD
> >> code, cleanly #ifdef'ing it so that swscaler can be the default scaler,
> >
> > I think the SIMD code is already #ifdef'ed (I do not know if it is
> > cleanly #ifdef'ed or not, this depends on how you define "cleanly" :).
> > Compiling only the non-SIMD code is quite easy.
> >
> > The problem is that the non-SIMD code (which is mainly LGPLed) depends
> > on some conversion tables which are generated by GPLed code. So,
> > libswscale depends on "--enable-gpl". To make the LGPLed code really
> > useful without "--enable-gpl", you have to re-implement the lookup tables
> > generator and release it under LGPL.
> Could these tables be hardcoded?  Tables of numbers are generally not
> subject to copyright law, since they contain no creative element as such.

They depend on user specified contrast/saturation/brightness. If you ignore
these then yes they could be hardcoded. I guess that would be enough for a
LGPL version, especially considering that IIRC theres no way for the user
to set these contrast/saturation/brightness from ffmpeg/ffplay.

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates
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