problem with mp4 (and mov?) files >= 4GB

  • Michael Anisimoff

    Yesterday I've recorded a ~7GB  H.264/aac mp4 file.

    The resulting mp4 is only readable until 4GB. Afterwards playback ist not possible. Also ffmpeg remuxing fails exactly after 4GB.

    I think one reason for the failure is that inside the moov atom of my recorded 7GB mp4 the 'stco' atom was used for storing chunk offsets.
    'stco' only allows 4byte offsets.
    For files >4GB it should instead be the 'co64' atom that allows 8byte offset values.

    Also the media data atom 'mdat' has to support 64-bit/8byte, but I havn't checked my file on that.

    This issue should be fixed in ffmpegs movenc.c since 23.January 2006

    But my recorded 7GB file still had 'stco'.
    The same should possibly apply for .mov containers, as it is the same structure & muxer (movenc.c).

    Any ideas?

  • Michael Anisimoff

    After capturing some more >4GB mp4/mov, testing the resulting files with Vega and  even looking at the underlying ffmpeg-related code in ingex I can say that I've never had the problem described above again and that all ffmpeg code is like it should be.
    The newer mp4 files are all having the right structure and they do all have the "co64" atom and the right "mdat" box.

    So, everything is fine with Ingex and the included ffmpeg libs.

    Sorry for the false alarm and any inconveniences I caused.

    I really don't know what has happened to the this first malicious file.


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