[FFmpeg-devel] [PATCH] h264 bitstream filter

Benoit Fouet benoit.fouet
Thu Aug 30 11:17:35 CEST 2007

M?ns Rullg?rd wrote:
> Benoit Fouet wrote:
>> Hi,
>> here is a patch to convert from avc in mp4 container to elementary stream.
>> be fair, this is my first try :-P
>> things i don't really know:
>>  - whether sps and pps have to be written for each elementary stream
>> NALU or not
> That question doesn't really make sense, SPS and PPS being NAL units of
> their own.  I guess what you meant to ask was at which points the SPS and
> PPS should be inserted into the stream.

yes, indeed.

>   They should be present before
> any IDR picture (NAL unit type 5), after any optional AUD or SEI NAL units.

is there a function accessible to the bitstream filter than can get me
the NALU type ? or do i have to do it on my own in the filter ?

>>  - whether bistream filter is fed with NALU or not (that's to say: do we
>> have to parse input buffer)
> The mp4 container already has the data split as NAL units, so there's
> nothing to parse.


>   In fact, you can't in general find the NAL unit
> boundaries in raw RBSP data, hence the need for Annex B format or a
> container like mp4 to provide framing.

thanks for the explanation

i also think that i can "construct" the sps/pps NALU only once, instead
of doing it every time, but i don't know how to do it, as bsfs don't
have a cleanup function...

Purple Labs S.A.

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