[Libav-user] parsing in-memory MP4 fragment

"René J.V. Bertin" rjvbertin at gmail.com
Sun Oct 21 14:19:51 CEST 2012

Hello list,

I'm working on a QuickTime importer plugin to read video recordings in a proprietary format by Brigade Electronics ('VOD' files, nothing to do with video on demand). These files contain 1s MP4 fragments interspersed with other data. FFmpeg succeeds in extracting these fragments and from the original combining them into a transcoded video file, even better so when I concatenate the fragments first.

Looking at the code of the Perian importer component, it is clear that it will be possible to use libavformat to retrieve the relevant info for the individual frames in the MP4 fragments, and construct a so-called QuickTime reference movie (i.e. a movie that contains something like a track with pointers to the frames in the original file). However, the Perian code is conceived for standard video containers, not for the kind of stream I'm working with.

My question therefore is: is it possible to hand off an MP4 sequence that resides in a memory buffer to libavformat, and retrieve the offsets and byte lengths of the individual frames making up that fragment. Alternatively, is there a file (pointer) based approach where I can specify the offset in the file where the MP4 data starts? I'm completely new to the FFmeg project, so a few pointers to relevant examples or tutorials would be appreciated greatly!

Thanks in advance,

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