[Mp4-tech] Ask for help in streaming H264 bitstream using RTP

[Herbert Thoma]

Felix schrieb:
> Hi All:
>    
>     I am trying to stream from a H264 bytestream file(a sequence of
> NALUs in Annex B format).

A H.264 bytestream is not very well suited for streaming. It usually
contains no timing information. A H.264 bitstream can contain timing
information in so called picture timing SEI messages, but these SEI
messages are not mandatory.
You might consider using a file format that contains timing information,
e.g. the ISO file format (ISO/IEC 14496-12 + ISO/IEC 14496-15 for AVC).
>     I come across some problems that you might help with.
>     Some similar problems might have alreday been discussed on the
> maillist before, but I sitll can not figure out the solution when
> streaming a H264 bitstream file:
>    
>    1.How to calculate the presentationTime for each frame:
>    
>      The first frame's presentationTime is get from the wallclock by
> "gettimeofday()", what about the following frames?
>      
>    2.How to calculate the DurationTime?
>    
>      DurationTime is usede to calculate the nextTime to send packet, how
> to calculate it if I am streaming from a H264 bytestream file, rather
> than from a live encoder? Is the DurationTime the reciprocal of Frame Rate?

The duration time of one AU is the reciprocal of the frame rate only
if the bitstream is a constant frame rate bitstream.
>    3.How to judge the current NALU Ends one AccessUnit in the function
> currentNALUnitEndsAccessUnit()?
>    
>      I found some clues in H264's standand document's section 7.4.1.2.4,
> is it the right place?

Yes, the section 7.4.1.2.4 "Detection of the first VCL NAL unit of a primary
coded picture" is the right place. However, your server needs to parse the
H.264 bistream to the slice header level to access the needed information.
IMHO one of the following requirements has to be fulfilled to be able to
stream from a H.264 bytestream:
- you need to know that the bitstream is fixed frame rate and you need to
  know that frame rate
or
- the bitstream contains picture timing SEI messages
Regards,
 Herbert.
>    Any help will be apprecaiated!
>    Thanks.
>    
> B.R.
> Felix.Xu
> 
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-- 
!!! Please note new phone and fax numbers !!!
Herbert Thoma
Head of Video Group
Multimedia Realtime Systems Department
Fraunhofer IIS
Am Wolfsmantel 33, 91058 Erlangen, Germany
Phone: +49-9131-776-6130
Fax:   +49-9131-776-6099
email: tma iis.fhg.de
www: http://www.iis.fhg.de/