MP4 video plays past it's length?

Question

I have a video file. MP4.

It was originally 25GB and 10 hours long.

But then I tried to trim it with movie maker.

I did what I needed and then I published the video.

No, I didn't save over the original video. I made a new copy. But somehow windows movie maker messed up my original copy.

Because now, the file details of my original copy say that it's 7 hours long, but it's still 25GB.

The same size as the 10 hour video, but 3 hours shorter. That can't be right.

So I let the video play all night long. I woke up this morning and it played all the way through to ten hours.

So what I don't understand is why is any video player I try to use (windows media player, VLC) saying it's 7 hours long but then it plays the full 10 hours? Is there any way I can fix this?

When I put the video in movie maker again, it only gives me the 7 hours of the video instead of the full 10.

And when I watch it in a video player, it only lets me seek to 7 hours but then continues to play after that.

Answer 1

If you have the hard drive space to spare, you can try remultiplexing the video (and audio) parts into another container. The container (e.g. MP4) is what tells the player how long the video content is – and if that's garbled, then you'll see a wrong video length.

You can download ffmpeg and from a command line run:

ffmpeg -i input.mp4 -c copy output.mp4

That way, the container will be rewritten, and this should fix the displayed duration too. Note that this does not alter the video or audio parts, it'll just copy the streams. So this is faster than re-encoding, but still might take a bit of time for a 25 GB file.

Answer 2

try re-render the whole entire 7 hour video. That happened to me once and after rendering the video again, it went to the normal length of 13 min instead of 16 min for me. Probably a computer error while you left the computer on to render the video.