This is a thumbnail extractor using the ffmpeg libraries that will eventually
support extracting thumbnails from both image and video files. Compiling
the ffmpeg libraries requires at least GNU make version 3.81.

A local ffmpeg tree is used, because
(1) there are no recent official releases of the ffmpeg libs,
(2) mainline ffmpeg is not reentrant,
(3) security issues can be handled locally.

Originally:
svn export -r 13836 --ignore-externals svn://svn.mplayerhq.hu/ffmpeg/trunk ffmpeg
svn export -r 27100 svn://svn.mplayerhq.hu/mplayer/trunk/libswscale ffmpeg/libswscale
sync with ffmpeg:
FFREV=14311
SWSREV=27332
cd /tmp
svn co -r $FFREV --ignore-externals svn://svn.mplayerhq.hu/ffmpeg/trunk ffmpeg
svn co -r $SWSREV svn://svn.mplayerhq.hu/mplayer/trunk/libswscale ffmpeg/libswscale
cd Extractor/src/plugins/thumbnailffmpeg
# copy, rsync skips .svn dirs
rsync -aC ffmpeg /tmp/
cd /tmp/ffmpeg
svn update
<resolve conflicts>
cd Extractor/src/plugins/thumbnailffmpeg
rsync -aC /tmp/ffmpeg .
# check for deletions
diff -qr . /tmp/ffmpeg -x .svn
<svn delete ...>
# check for additions
<svn status, svn add>

update ffmpeg_distfiles.am:
svn list -R src/plugins/ffmpeg | \
  sed '/\/$/d' | \
  sed '$!s/$/ \\/g' | \
  sed 's/^/ffmpeg\//' | \
  grep -v "no-indent" | \
  sed '1 i EXTRA_DIST = \\' > src/plugins/ffmpeg_distfiles.am

Plan: test & enable ffmpeg decoders one by one
tests:
- multithreading test
- zzuf test
- random input test
(- valgrind)

At least, the following should be eventually enabled:
if ! ./configure			\
	--prefix=/tmp/FF		\
	--disable-mmx			\
	--disable-altivec		\
	--enable-shared			\
	--enable-swscale		\
	--enable-gpl			\
	--disable-vhook			\
	--disable-postproc		\
	--disable-network		\
	--disable-ffmpeg		\
	--disable-ffserver		\
	--disable-ffplay		\
	--disable-devices		\
	--disable-protocols		\
	--disable-bsfs			\
	--disable-parsers		\
	--disable-muxers		\
	--disable-demuxers		\
	--disable-encoders		\
	--disable-decoders		\
	--enable-parser=h263		\
	--enable-parser=h264		\
	--enable-parser=mjpeg		\
	--enable-parser=mpeg4video	\
	--enable-parser=mpegvideo	\
	--enable-encoder=png		\
	--enable-encoder=mjpeg		\
	--enable-decoder=bmp		\
	--enable-decoder=pcx		\
	--enable-decoder=png		\
	--enable-decoder=mjpeg		\
	--enable-decoder=mjpegb		\
	--enable-decoder=targa		\
	--enable-decoder=tiff		\
	--enable-decoder=flashsv	\
	--enable-decoder=h263		\
	--enable-decoder=flv		\
	--enable-decoder=h264		\
	--enable-decoder=mpeg1video	\
	--enable-decoder=mpeg2video	\
	--enable-decoder=mpegvideo	\
	--enable-decoder=mpeg4		\
	--enable-decoder=vp6		\
	--enable-decoder=vp6a		\
	--enable-decoder=vp6f		\
	--enable-demuxer=asf		\
	--enable-demuxer=avi		\
	--enable-demuxer=flv		\
	--enable-demuxer=mjpeg		\
	--enable-demuxer=mpegps		\
	--enable-demuxer=mpegts		\
	--enable-demuxer=mpegvideo	\
	--enable-demuxer=mov		\
	--enable-demuxer=ogg		\
	--enable-demuxer=rm

