[Live-devel] User Private Data Streams via RTSP?

[Bill Dolson]

>> We have Mpeg-2 Transport Streams which contain video, audio, and user 
>> private data (PES packets containing private data stream_type=6) under 
>> their own PID.  This data contains camera geospatial positioning and 
>> pointing data and conforms to an NGA/MISB standard.
> 
> What exactly do you mean by "private data streams"?  Are you referring 
> just to 'private data' that's contained within Transport Streams?  If 
> so, then we already support this, because - when we stream Transport 
> Stream data (either over RTP/UDP or raw-UDP) - we don't care about its 
> contents.

Ross,

The user private data streams are as described in ITU-T Rec 222.0, Annex 
H, bullet item 3, "second possibility", "private data within PES packets 
under the stream_type Table 2-34" as private_stream_1.  These are 
carried under their own PID as a separate elementary stream in the 
multiplex.

 From your comments I gather that when Live555 transmits an MPEG2 
Transport Stream you do not demux it and send the elementary streams but 
rather send it as am RTP/AVP MP2T media type ala RFC 2250.  I assume 
RTSP work with this media type?

While this would provide us with transparent transmission of our private 
data ES, we anticipate running on a very noisy channel and would like to 
have the advantages of having elementary streams on separate RTP 
sessions to make error concealment simpler.  This would involve demuxing 
the elementary streams and adding a media type and support for "data" to 
get our private data stream across.

I'd be curious as to your feelings about the need for this.  The case 
for elementary stream transmission is made pretty well here:
http://www.envivio.com/pdf/RTPvsTS-v4.pdf

Best,
Bill Dolson
RIS, Inc.