Video and perferness

[kenny1999]

Hello
I've got two video files. They are the same contents. Also, they are exactly the same from their sizes (up to bytes), lengths (up to seconds), and resolutions etc. I've also used MediaInfo to compare if there are anything like those encoding decoding method. They are ALL the same. However, when I check their MD5/SHD1 etc, they are different. What is the most probable reason behind? Disc bad sector? Data rot? or is it more likely for the checksum to be intentionally altered by the provider? what do you think?
Thanks

[Groucho2004]

I've got two video files. They are the same contents.
However, when I check their MD5/SHD1 etc, they are different.
You have to make up your mind.

Logical fallacies aside, you should probably first let us know what evidence you have for your first statement.

[filler56789]

If the bytes which "make the difference" are outside of the container/stream headers, then yes, MediaInfo probably will say the two files "are identical".
However only you can determine the cause of the data corruption --- without more relevant information, we can only throw wild guesses (file transfer errors, bad HDD, bad luck, evil spirits, whatever).

[raffriff42]

The Frhed (http://frhed.sourceforge.net/en/) FOSS hex editor can find differences in files. Open file 1; Edit menu, Compare...

You could call fc (http://www.computerhope.com/fchlp.htm) (file compare) in binary mode. If you just want to see if two files are identical, it's faster. It will point you to the byte offset of any differences (same as Fhed), which you can then explore further with a hex viewer.
@echo off
:: fc_bin_compare.bat
:: Purpose: perform a bytewise comparison in two files
:: Usage: drag or copy-paste two files onto this BAT file.
::
if not exist "%~dpnx1" goto USAGE
if not exist "%~dpnx2" goto USAGE
@echo on
fc /b "%~dpnx1" "%~dpnx2"
@echo off
pause
goto :EOF

:USAGE
@echo Usage: drag or copy-paste two files onto this BAT file.
pause
goto :EOFTo know what the difference *means* you would need a file analyzer for the type of video you're looking at. Virtualdub and VirtualDubMod include a hex editor which can parse an AVI file. If there are more free tools like that, I'd like to know about them!

EDIT I Suppose you could demux the streams and compare them individually...