[FFmpeg-devel] Consultant for seeking improvements (in mov demuxer)

Reimar Döffinger Reimar.Doeffinger at gmx.de
Sun Sep 2 10:30:20 CEST 2012

On 1 Sep 2012, at 22:02, Beni Weine <onlineweinies at bluewin.ch> wrote:
> Hi,
> Our organization is willing to fund improvements on the seeking capabilities for mp4 files. 
> We are particularly interested in a byte-wise seeking mechanism, which is currently not implemented in libavformat/mov.c.Meaning, calling avformat_seek_file with AVSEEK_FLAG_BYTE does not work with mp4 (it does work with MPEG-2, libavformat/mpegts.c contains read_seek2). 
> Why bytes-wise seeking? Long story... The video recording system delivers a mp4 file (segmented, without hint tracks) plus a time index file (proprietary) which includes a timestamp and the corresponding byte position in the H.264 data (I-frame).

I'm not sure that makes sense within the FFmpeg framework.
The purpose of byte-wise seeking is to be able to do without an index, but for mov demuxing is never possible without index.
That would make bytewise seeking into something silly like looking up the byte offset in the index (with the additional issue of deciding which stream to use, as mov can be non-interleaved), and then find the timestamp and do the actual seeking by that.
Not saying that such a feature could not be acceptable, but it would be very silly for anything but your special use-case. So I kind of think it might make more sense if just had some tool that could do the offset to timestamp lookup in the mov index for you. (I am not interested in doing consulting work though)

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