**Dirac patch for ffmpeg
**Tested with ffmpeg svn revision 10630
**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 0.8.0 from
   http://sourceforge.net/projects/dirac/

2. Unpack the Dirac source
   tar xvzf dirac-0.8.0.tar.gz

3. Build and Install

   cd dirac-0.8.0
   ./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 10630

   svn checkout -r 10630 svn://svn.mplayerhq.hu/ffmpeg/trunk ffmpeg_trunk_rev_10630

4. Apply the patch

   cd ffmpeg_trunk_rev_10630
   patch -p1 < ffmpegsvn_trunk_revision_10630-dirac-0.8.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.

Interlaced encoding example:
ffmpeg -s 720x576 -i input_file.yuv -flags ilme -vcodec dirac -strict -2 dirac_output.drc

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