[Mp4-tech] H264: is access unit delimiter required?

[Victor lyamtsev]

I'll read it it but that just doesn't make much sense to me... It's been my
understanding that byte stream is either "raw", or it's contained within RTP
packets as RTP payload, therefore must come with delimiters... Why different
"packaging" for RTP transport?
How's about other transports, like mpeg-ts? Should I expect to find NALU
delimiters there?
Thank you,
Victor
On 10/26/07, Gary Sullivan <garysull windows.microsoft.com> wrote:
>
>  Now you are talking about RTP.  That is a particular specialized
> environment.  I think perhaps those things are not true in the RTP
> environment.  My understanding is that RTP is unlikely to include access
> unit delimiters and will not include start codes (i.e., you'll never find
> that next_bits(24) == 0x000001).  Start codes are part of the "byte stream"
> format specified in Annex B of the video standard.  My understanding is that
> the byte stream format is not used in Annex B.  Instead, you should look up
> RFC 3984.  And study the video spec, of course.
>
> Best Regards,
>
> Gary Sullivan
>
>  ------------------------------
> *From:* Victor lyamtsev [mailto:vlyamtsev gmail.com]
> *Sent:* Friday, October 26, 2023 10:26 AM
> *To:* Gary Sullivan
> *Cc:* mp4-tech lists.mpegif.org
> *Subject:* Re: [Mp4-tech] H264: is access unit delimiter required?
>
> OK, so if I have to parse h264 stream, should I just start looking for the
> NALU delimiters in RTP payload ( if I am using RTP as transport layer),  as
> following?
> next_bits (24) == 0x000001 && next_bites(32) == 0x000001 - for NALU start
> next_bits(24) == 0x0 && next_bits(24) == 0x000001 - for NALU end
> Thanks again,
> -vl
>
> On 10/24/07, Gary Sullivan < garysull windows.microsoft.com> wrote:
> >
> >  I am almost certain that the answer would be that the answer is No.
> > Part of the motivation behind some key aspects of the design of the video
> > standard was to consider environments like RTP where some packets will be
> > lost and it is therefore beneficial to ensure that slices can be decoded
> > without dependency on a single copy of some picture header information that
> > appears only once at the beginning of each picture in the transmission
> > sequence.  If we assume that decoders include the functionality to decode
> > individual slices when some information has been lost, the access unit
> > delimiter would appear to serve no purpose in such an environment.
> >
> > Best Regards,
> >
> > Gary Sullivan
> >
> >  ------------------------------
> > *From:* Victor lyamtsev [mailto:vlyamtsev gmail.com]
> > *Sent:* Wednesday, October 24, 2023 7:32 AM
> > *To:* mp4-tech lists.mpegif.org
> > *Cc:* Gary Sullivan
> > *Subject:* Re: [Mp4-tech] H264: is access unit delimiter required?
> >
> >  Does RTP transport require it?
> > Thank you,
> > -vl
> >
> >
> > On 10/23/07, Gary Sullivan <garysull windows.microsoft.com> wrote:
> > >
> > >  Its presence is not required by the video standard.  However, its
> > > presence may be required in some application-level specifications.
> > >
> > > Best Regards,
> > >
> > > Gary Sullivan
> > >
> > >  ------------------------------
> > > *From:* mp4-tech-bounces lists.mpegif.org [mailto:mp4-tech-bounces lists.mpegif.org]
> > > *On Behalf Of *Victor lyamtsev
> > > *Sent:* Tuesday, October 23, 2023 7:31 AM
> > > *To:* mp4-tech lists.mpegif.org
> > > *Subject:* [Mp4-tech] H264: is access unit delimiter required?
> > >
> > >
> > >  Hello,
> > > Regarding parsing of H264 stream...
> > > Do I have to start from searching for Access Unit delimiter to read
> > > NAL unit? More to the point: is the Access Unit delimiter required by
> > > standard and is it common practice to use it?
> > > Thanks,
> > > -vl
> > >
> > >
> > >
> > >
> >
>
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