Specifying a revision for ffmpeg has no influence on the libswscale. This will be
the current head of libswscale which might conflict with ffmpeg's HEAD. The
suggested revision to use is 29968, which must be forced by removing libswscale and
checking out: svn co -r 29968 svn://svn.ffmpeg.org/mplayer/trunk/libswscale libswscale