[Ffmpeg-devel] swscaler integration

Luca Abeni lucabe72
Tue Mar 14 10:33:05 CET 2006

Hi all,

based on my set of patches I sent yesterday, here is a patch for using
swscaler for image rescaling.

First of all, how to compile ffmpeg with swscaler:
1) get mplayer sources, configure with --disable-fastmemcpy, and compile
(at least, compile the "postproc" subdirectory)
2) get ffmpeg from CVS, apply the set of patches I sent yesterday, and
apply this "sws.diff" patch
3) configure ffmpeg with
./configure --enable-gpl --enable-swscaler --extra-cflags="-I <path to mplayer>/postproc" --extra-ldflags="-L <path to mplayer>/postproc"
4) compile ffmpeg. It should use swscaler by default, now.

I did some quick tests with various combinations of rescaling padding,
and cropping, and everything seems to work.

1) The patches I send yesterday contain bug found by Baptiste, I'll send
an updated patchset in the next days
2) libswscale is still used as an external library. This is only my
first step, and I want to check that everything works and if I followed
the correct approach (so, feedback is welcome). As soon as I'll be sure
that I interfaced libavcodec and libswscale in the correct way, I'll
work on integrating libswscale in the ffmpeg tree
3) the conversion between pixel format names is currently done in
libavcodec (swscaler_glue.c). When integrating libswscale in ffmpeg,
I'll move such conversion in swscale::remove_dup_fourcc(). (I found some
old notes where Michael explained that. I did not fully understand the
explaination at that time, but now it's pretty clear to me)
4) the license is still GPL. When integrating libswscale in ffmpeg, I'll
mail all the people listed as authors in the headers, asking the
permission for using the non-MMX code under the LGPL license (as
suggested by Michael)
5) ffmpeg still converts to YUV420P before rescaling. After integrating
libswscale, I'll fix this.

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