How can I validate a video file from a script?

Question

I have a server with lots of video files. After a restore, I noticed that the checksum of a couple of files changed. Since I don\'t have checksums for all files, I wanted write

Answer 1

Short of watching all the videos, there's no "perfect" way to do this.

Video files are quite robust - as an experiment I took a random MPEG-4 video file, opened it in a hex-editor and started changing bytes.. mplayer and Quicktime still played it back without errors.

I had to delete thousands of bytes before getting any error from mplayer:

...
[mpeg4 @ 0x6762b0]marker does not match f_code
[mpeg4 @ 0x6762b0]marker does not match f_code
[mpeg4 @ 0x6762b0]concealing 852 DC, 852 AC, 852 MV errors
[mpeg4 @ 0x6762b0]header damaged:  0.055  16/ 16 15%  1%  3.5% 0 0 
Error while decoding frame!

It wouldn't be difficult to write a script that runs mplayer on each video, and checks the output for error messages/warnings, but unless the changed bytes are in the file header, or a lot of data was changed, you'll never find them all