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There's a 50-minute long webm video file which stops playing after about 8th minute. As I don't require the beginning of the video, I decided to split it and get last 30 minutes of it.

For that, I have installed ffmpeg and I am using the following command as suggested in here,

ffmpeg -ss 00:20:00 -t 00:50:00 -i a.webm -acodec copy -vcodec copy b.webm

When I do this, however, I am getting the following error messages:

Truncating packet of size 591111 to 13231
[matroska,webm @ 00000225a4ac8c00] Element at 0xb966ccb ending at 0x11ee2070 exceeds containing master element ending at 0xbc386e8
    Last message repeated 1 times
[matroska,webm @ 00000225a4ac8c00] Length 5 indicated by an EBML number's first byte 0x09 at pos 200544103 (0xbf40f67) exceeds max length 4.
[matroska,webm @ 00000225a4ac8c00] Element at 0xc4e9b68 ending at 0xc4eb1e3 exceeds containing master element ending at 0xc4e9bb9

Does it mean that I can't split the file until I fix it? And if so, can you guide me in fixing it given the error stack?

gdrt
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  • Try to use VLC to play the file. Check that in *Preferences > Input / Codecs*, that the "Damaged or incomplete AVI file" is not set to "Never fix". I hope that this parameter also applies to webm. – harrymc Dec 24 '19 at 18:32
  • It was set to "Ask for action". So, I took a backup of the file and then set the option to "Always fix", but nothing happened. – gdrt Dec 24 '19 at 23:23
  • There exist video recovery tools, but they are not free. – harrymc Dec 25 '19 at 16:45
  • Okay :( Do you have any recommendations specifically for webm format by any chance? – gdrt Dec 26 '19 at 10:43
  • Many recovery products will work on webm as well, but they are mostly on Windows. – harrymc Dec 26 '19 at 11:07
  • I actually use Windows – gdrt Dec 27 '19 at 00:26
  • Where did you get this webm file? If downloaded, where from? – harrymc Dec 27 '19 at 07:18
  • It's a cam record, recorded on Ubuntu. Was able to play the whole of it on both Ubuntu and then after copying it on Windows. But something happened half a year ago and now it stops playing after couple of minutes. – gdrt Dec 27 '19 at 11:46
  • Try to run `chkdsk` to check for disk corruption. Be careful with running `chkdsk /f` that can destroy files. – harrymc Dec 27 '19 at 11:49

1 Answers1

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Try dumping out the video and audio separately to isolate the problem. This may reveal that you have no video or no audio at a certain point.

Convert Video to Still Images

.\ffmpeg.exe -ss 00:20:00 -t 00:50:00 -i a.webm -an -f image2 filename%03d.jpg

Extract Audio

.\ffmpeg.exe -ss 00:20:00 -t 00:50:00 -i a.webm audio.mp3
HackSlash
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