[FFmpeg-user] Encode lossless Dirac?

Peter B. pb at das-werkstatt.com
Mon Nov 21 14:39:22 CET 2011

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.
(Sorry for not posting it in my earlier message)

ffmpeg -i input_ffv1.avi -an -vcodec libschroedinger -qscale 255

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

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

ffmpeg -i dirac-x.mkv -an -f framemd5 dirac-x-checksums.txt

The results were:
*) MD5 checksums of both Dirac encoded videos had no match with the FFv1
*) 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.


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

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