This test verifies the pixdesc code by comparing the output with and
without a filter which should have no effect on the image.  Since the
available pixel formats depend on the byte order of the machine, a
simple reference checksum is not possible.

The test originally tried to solve this by generating a reference file
on the fly.  The problem with this is that the test framework expects
the reference file in the source tree, and writing to the source tree
is not allowed.

To avoid complicating the test framework, we instead provide two
reference files and select which to use based on the byte order.

Originally committed as revision 24330 to svn://svn.ffmpeg.org/ffmpeg/trunk

   Author: bcoudurier
   Date:   Sat Jul 3 03:11:04 2010 +0000

       Set graph swscale opts before parsing it, that way opts are available
       when auto-adding scalers.

It changed the swscale flags used by the auto-added scalers, and so
the output video.

Originally committed as revision 24065 to svn://svn.ffmpeg.org/ffmpeg/trunk

A patched version of ffmpeg supporting video filters is required for
getting this working; thus make lavfitest is supposed to work only in
the libavfilter repository for now.

Originally committed as revision 22586 to svn://svn.ffmpeg.org/ffmpeg/trunk