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cmp4

Detect mp4 files

I have to design a module that detects mp4 files. If will get any random file as input and it has to tell whether it is a mp4 file or not. Where can I find the specification of headers for the mp4 file? Tried googling but could not find anything except the signature. Any other tips regarding C programming for the module?

Solution

  • you can check the extension or the file signature (magic number)

    http://www.garykessler.net/library/file_sigs.html

    http://en.wikipedia.org/wiki/List_of_file_signatures

    00 00 00 18 66 74 79 70 33 67 70 35 ....ftyp 3gp5 MPEG-4 video files

    Or if you're on Unix/Linux you can parse the output of file(1) from your program.

    Edit:

    You don't need to scan the whole file to identify it, the signature will do, however, if you have to, note that MP4 is a container for other formats, which means you will probably need to know about MP4 and other formats it contains as well, there's some information here: http://en.wikipedia.org/wiki/MPEG-4_Part_14

    I'd use something like libffmpeg to do that instead.