[FFmpeg-devel] [RFC] special "broken DV" demuxer

Reimar Döffinger Reimar.Doeffinger
Wed Mar 11 22:33:03 CET 2009

On Wed, Mar 11, 2009 at 01:13:18PM -0700, Baptiste Coudurier wrote:
> I believe the adequate solution would be to indentify what exactly _is_
> needed to be able to demux/decode and check for this information.

A valid combination of 1 bit dsf and 5 bits of stype. About 1 out of 6
random bit combinations are valid.
For a reliable autodetection with that that supports any start offset
means checking every byte if it is a valid stype, which with a
probability of 1/6. Then you need to read the dsf, unfortunately from a
different byte, to get the frame size.
Then you need to check the dsf and stype of at least several next frames
to see if they match to get sufficient reliability.
Obviously that either involves a lot of seeking or buffering in memory,
nor is it possible to support e.g. extracting the DV part from broken
AVI or MOV files like that.

More information about the ffmpeg-devel mailing list