I recently used a screen capture program to record a video of some actions in Firefox. When the video was complete, the Duration was incorrect. Windows Media Player doesn’t seem to mind and happily played the entire video even though the duration property was 16 seconds and the actual duration was 31 seconds.
When I moved the video over to Linux, that player refused to play past the duration property value of 16 seconds.
I tried to use EasyTag to edit the duration, but it doesn’t support editing this value.
The solution was to use ffmpeg to copy the content to a new file instead of trying to edit the original file properties:
ffmpeg -i bad-video.mp4 -vcodec copy -acodec copy good-video.mp4