**Dirac patch for ffmpeg
**Tested with ffmpeg svn revision 8950
**Original Author: Andrew Kennedy (dirac_dev@users.sourceforge.net)
**Additional Contributors:
  Anuradha Suraparaju (asuraparaju@users.sourceforge.net)
  Bernhard Rosenkraenzer (bero@users.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 0.7.0 from
   http://sourceforge.net/projects/dirac/

2. Unpack the Dirac source
   tar xvzf dirac-0.7.0.tar.gz

3. Build and Install

   cd dirac-0.7.0
   ./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 svn revision 8950

   svn checkout -r 8950 svn://svn.mplayerhq.hu/ffmpeg/trunk ffmpeg_trunk_rev_8950

4. Apply the patch

   cd ffmpeg_trunk_rev_8950
   patch -p1 < ffmpegsvn_trunk_revision_8950-dirac-0.7.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)

Constant quality encoding example:
ffmpeg -s 720x576 -i input_file.yuv -vcodec dirac -strict -2 -qscale 15 dirac_output.drc

Constant bitrate encoding example:
ffmpeg -s 720x576 -i input_file.yuv -b 1500000-vcodec dirac -strict -2 dirac_output.drc
The encoder will attempt tp keep the bitrate constant at 1500000 bps.

Currently, the output from the encoder is exactly as it is written to the .drc 
encoded file. The -qscale flag controls the quality of the Dirac encoder
output. The bit rate is not constant when this option is choses.  A qscale of 1 
maps to dirac quality factor 10 and 30 maps to quality factor 1). The -b flag
controls the bitrate (in bps) of Dirac encoder output. The Dirac encoder 
attempts to keep the output bitrate constant at the value specified.

(decoding)
ffmpeg -i input.drc 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