[FFmpeg-user] Encode lossless Dirac?

[Peter B.]

Carl Eugen Hoyos wrote:
>> but currently only supports lossy mode.
>>     
>
> Why do you think so?
> If it fails, please provide command line and complete, uncut console output.
>   
Sure.
(Sorry for not posting it in my earlier message)

[code]
ffmpeg -i input_ffv1.avi -an -vcodec libschroedinger -qscale 255
test_dirac.mkv
[/code]


I've also tried "-qscale 0.0001" as suggested in an earlier thread on
the ffmpeg-user list in July 2011 [1] by the user "charvak", since it's
still unclear to me whether a high or low qscale value triggers lossless
mode.

Then I've compared the output of "framemd5" of both Dirac encodings with
its FFv1 original (using the current git-version of ffmpeg):

[code]
ffmpeg -i dirac-x.mkv -an -f framemd5 dirac-x-checksums.txt
[/code]

The results were:
*) MD5 checksums of both Dirac encoded videos had no match with the FFv1
checksums
*) Surprisingly, 'some' of the checksums of the Dirac encodings
(q=0.0001 and q=255) matched - which would mean that they decode to
exactly same image. Although I still wouldn't consider any of these
encodings to be lossless.

Pb

== References:
[1] http://ffmpeg.org/pipermail/ffmpeg-user/2011-July/001745.html