[XviD-devel] Re: packed bitstream

ChristianHJW christian at matroska.org
Sun Jul 13 01:09:40 CEST 2003


Radek Czyz wrote:
> Hi,
> 
> I'm trying to create an mpeg4 parser (a small lib that will be able to
> analyze m4v stream or frames and give information about it - matroska
> project needs it).
> I'm trying to figure out the meaning of N-VOPs in packed bitstream..
> and I can't. What do they do? How can I tell if an N-VOP is dummy or
> real? Also, what is exactly written to the 'empty' frame after packed
> PB frame? (or maybe this is the N-VOP.. or maybe not).
> 
> Can anyone tell me please? :)
> 
> Ah, one more thing - imagine that you have a pure m4v stream with 0x7f
> frames (yes I know current encraw doesn't do that - but what if) - is
> there a way to tell if 0x7f byte was added, and remove it? Note that
> I'm not decoding everything, only startcodes and headers - and 0x7f
> looks exactly like what I would expect at the end of real frame, so I
> can't just look at the byte before a startcode... but maybe there is a
> simple way to do that?
> If I don't do that and mux such stream to a container with 0x7f
> included (it would stick to the end of previous frame), do you think
> decoders will ignore it, or activate some kind of error correction?
> 
> Thanks in advance
> Regards,
> Radek


nobody ?? sysKin's code is very important for us. Please help him ...

Christian




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