[FFmpeg-trac] #3871(avcodec:new): FFmpeg MD5 output different with same data #2

FFmpeg trac at avcodec.org
Wed Aug 20 21:45:40 CEST 2014

#3871: FFmpeg MD5 output different with same data #2
             Reporter:  ahthovaikied  |                    Owner:
                 Type:  defect        |                   Status:  new
             Priority:  normal        |                Component:  avcodec
              Version:  2.2.4         |               Resolution:
             Keywords:  md5 aac h264  |               Blocked By:
             Blocking:                |  Reproduced by developer:  0
Analyzed by developer:  0             |

Comment (by ahthovaikied):

 Replying to [comment:3 cehoyos]:
 > Additionally please note that your command line can be considered
 ambiguous for the given input sample (there is not much indication which
 audio stream is the ''best'' one to quote the documentation), so I don't
 think there is any reason to expect identical md5 output for different
 FFmpeg versions.
 You are right, so I added '-map' switches when relevant in my tests below
 to remove the ambiguity (although I seriously doubt the code in any
 version would do other than taking the first audio stream).

 Replying to [comment:1 kurosu]:
 > You can replace alternatively -c:a copy by -an and -c:v copy by -vn to
 narrow down whether audio or video causes different MD5.
 Here are the results of my tests:
 * When taking all streams, md5 do not match:
 $ ./ffmpeg_2.2.7 -loglevel quiet -i ../ref.mkv -map v -map a -c:v copy
 -c:a copy -f md5 -
 $ ./ffmpeg_git_master -loglevel quiet -i ../ref.mkv -map v -map a -c:v
 copy -c:a copy -f md5 -

 * When taking only the video stream, md5 match:
 $ ./ffmpeg_2.2.7 -loglevel quiet -i ../ref.mkv -c:v copy -an -f md5 -
 $ ./ffmpeg_git_master -loglevel quiet -i ../ref.mkv -c:v copy -an -f md5 -

 * When taking only audio streams, md5 match:
 $ ./ffmpeg_2.2.7 -loglevel quiet -i ../ref.mkv -map a -vn -c:a copy -f md5
 $ ./ffmpeg_git_master -loglevel quiet -i ../ref.mkv -map a -vn -c:a copy
 -f md5 -

 What can I conclude? It seems the problem is occurring only when feeding
 the MD5 calculation with all streams...

Ticket URL: <https://trac.ffmpeg.org/ticket/3871#comment:4>
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