mp4v2 muxer unreliable
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#58 mp4v2 muxer unreliable
Scenario: Cutting (audio/video = COPY) a HDTV recording .ts file 1280x720, Codec: H264 - MPEG-4 AVC (part 10) (h264) with avidemux 2.6.10 and 2.6.911 in up-to-date windows7 x64
If I save the cut .ts to mp4 multiple times (like test1.mp4, test2.mp4) and compare the md5 checksums of the files, they are all identical.
But: saving to mp4v2 (no matter if "Optimize for Streaming" is on or off) while the filesizes are identical, the checksums are not - never!
Every mp4v2 created from the same ts with the same settings in the same session has a different checksum.
While on short glance the videos all play in vlc, who knows what problems are inside of those files that will lead to trouble when played back on a different device, encoded to a different format, etc.
It might be normal. I did not check yet, but each mp4 file is supposed to have a uniq ID
It can be generated from a random number. That might be what is happening
To finally conclude this topic:
Encoding the same video with identical settings to mp4 multiple times does always result in identical files, but encoding to mp4v2 or mkv adds unique elements (creation and modification time, I think) to the container every time, so while the content is identical, the containers and therefore the checksums are not.
How can I check if two videos are identical then - use ffmpeg to get the checksum of the videostream only, without the container (source https://stackoverflow.com/questions/25774996/how-to-compare-show-the-difference-between-2-videos-in-ffmpeg):
ffmpeg -loglevel error -i video.mp4 -map 0:v -f md5 -So this isn't a bug, report can be closed.