**Dirac patch for ffmpeg
**Tested with ffmpeg cvs version dated 06-08-2005
**Author: dirac_dev@sourceforge.net

Dirac is an open-source video codec currently under development. Both the 
encoder and decoder have been integrated with ffmpeg. This patch is only a 
basic integration such that only the salient paremeters are currently passed 
from ffmpeg to Dirac. As Dirac develops, especially with the integration of
a formalised bit-stream syntax,  then more complex screnarios can be dealt with.
Encoded Dirac files, with the right patch, can be played back using MPlayer.

Please feel free to modify/add-to the code. 

These are the instructions for enabling Dirac support in ffmpeg source
code.

1. Download Dirac 0.5.4 from
   http://sourceforge.net/projects/dirac/

2. Unpack the Dirac source
   tar xvzf dirac-0.5.4.tar.gz

3. Build and Install

   cd dirac-0.5.4
   ./configure 
   make
   make install

   The last step installs the Dirac share encoder and decoder libraries in
   /usr/local/lib (which is the default install point).
   
3. Download ffmpeg cvs version dated 06-08-2005

   http://www2.mplayerhq.hu/MPlayer/cvs/FFMpeg-20050806.tar.bz2
   (NOTE that the patch also works with CVS snapshot up until 16-08-2005.
    However, CVS snapshots were not available for dates past 6-Aug-2005 on
	the FFmpeg server at the time this note was written).
	
4. Unpack the source
   tar xjvf FFMpeg-20050806.tar.bz2

5. Apply the patch

   cd FFMpeg-20050806.tar.bz2
   patch -p1 < FFMpeg-20050806-dirac-0.5.x.patch

6. Build and Install
   
   ./configure --enable-dirac
   make 
   make install

The option '--enable-dirac' must be used during configuration in order to 
pick-up the Dirac code during building. pkg-config is used to determine if
dirac is available. Note that on some systems pkg-config is not available by
default and will have to be installed.


Sample Usage: (encoding)
ffmpeg -s 720x576 -i input_file.yuv -vcodec dirac -qscale 15 -f rawvideo dirac_output.drc

Currently, the output from the encoder is exactly as it is written to the .drc 
encoded file ( hence the '-f rawvideo' output). Dirac bit-rate is controlled by 
a quality-factor (currently a basic intepretation from qscale. A qscale of
1 maps to dirac uality factor 10 and 30 maps to quality factor 1)

(decoding)
ffmpeg -i input.drc -f rawvideo output.yuv

Dirac can also be invoked via ffmpeg using transcode after applying the 
transcode patch.
transcode -i input.avi -x raw -i raw_input.avi -y ffmpeg -F dirac,null -o dirac_output.avi