[Ffmpeg-devel] I want to know what data set to AVCodecContext for H.264

Michael Niedermayer michaelni
Sat Jun 25 16:01:48 CEST 2005


On Saturday 25 June 2005 11:54, bond wrote:
> its indeed often the case that mpeg-4 part2 encoders outputting to .avi
> place the vol together with the i-frames, because avi seems to require this

wrong, avi doesnt require it, its just the way divx did it and everyone not 
wanting to break compatibility did it that way too

> when placing mpeg-4 part2 in .mp4 you are not allowed to place the vol
> together with the video data (i-frames), 

hmm, could you quote the relevant part of the spec which forbids that, note 
though iam not saying its not true just that iam curious, as such a 
restriction would be very silly

> but it has to be stored only once 
> on a seperated place from the video data. ffmpeg doesnt do this, which is
> also one of the problems with its .mp4 muxing

this is not true, ffmpeg does store the global headers like VOL at the correct 
place when encoding mpeg4 it just doesnt support extracting these headers 
during stream copy, so .mp4->.mp4 or mpeg4 encoding should be fine avi->.mp4 
and mpeg4-es -> .mp4 are not


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