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5th September 2013, 08:25 | #1 | Link |
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Join Date: Jun 2006
Posts: 111
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How to tell if a mp4 file has metadata at the begining or not?
As I'm working with files for the web, I sometimes need to know if the mp4 files I recieve have their metadata at the begining. Mediainfo does not seems to provide such informations.
What tool can I use to check that? (Linux or OSX) Thank you. |
5th September 2013, 18:08 | #3 | Link |
Software Developer
Join Date: Jun 2005
Location: Last House on Slunk Street
Posts: 13,248
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Parsing MP4 files is not that complicated. You always have "boxes" (aka "atoms"), each of which starts with an 8 Byte header (4 Byte size field + 4 Byte name in ASCII).
Boxes may also contain other boxes, but you don't need to care here. Just do the following in a loop: Read the 8 Byte header, then check the name and finally skip over exactly size-8 Bytes to the next box. Either you will encounter the "moov" box before the "mdat" box - or the other way around. All the meta-data and all the fancy tables are stored within the "moov" box.
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5th September 2013, 19:02 | #4 | Link |
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Join Date: Aug 2010
Location: Paris
Posts: 52
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MP4Box from the gpac package can do that.
Code:
MP4Box -info -v file.mp4 |
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