[itu-sg16] FW: [T16AVD] Request for input to the "Multiple video streams FECC AHG"

Paul E. Jones paulej at packetizer.com
Mon Sep 28 12:04:24 EDT 2009


FYI

 

From: stephen botzko [mailto:stephen.botzko at gmail.com] 
Sent: Friday, September 25, 2009 3:31 PM
To: t09sg16avd at lists.itu.int
Subject: [T16AVD] Request for input to the "Multiple video streams FECC AHG"

 

 I would remind you all of the following item in the Q1/16 Experts Meeting
Report (24-25 June 2009):
>>>


2.3  H.281 and changes for supporting multiple video streams


Q1-I08 was presented and a short discussion followed. The group noted the
limitations and considerations raised by the contribution. It was noted
that, if the solution would involve enhancements to both H.281 and H.224, it
would be desirable to consent those recommendations at the same time.
Because of the absence of several experts, the proponent himself and not
being able to fully discuss this topic, Q1 experts agreed to create an
Ad-hoc group (chaired by S. Botzko) to progress this work through electronic
correspondence in the interim period. The contributor was asked to submit a
contribution to the next meeting of SG16 to allow a continuation of the
discussion. Experts interested in participating in this work are encouraged
to contact the Rapporteur and/or the AHG Chair.

>>>

Feedback on these approaches would be appreciated - please reply to this
email.  If desired, contact me directly and I will set up a meeting.
Alternatively, interested parties can communicate through email.

At this point I see three possible ways to progress the work:

(1) Use the Q1-I08 contribution (June 2009 meeting) as the basis
This contribution proposes "channeling" the existing H.281 messages, so that
the video channel can be carried in the new messages.  Backwards
compatibility is provided since the existing messages are still used for the
main video channel.  Existing H.281 clients would not be able to control the
second (or third) channels. 

(2) Use the C-0399 contribution (April 2008 meeting) as the basis
This contribution proposes adding a second H.224 CME client id for the
second video channel.  Backwards compatibility is provided since the
existing client ID is still used for the main video channel.  Existing H.281
clients would not be able to control the second (or third) channels. 

(3) Revise H.281 Video Source Capability to include a channel number (Figure
10/H.281)
There is no contribution (yet) for this approach.  This idea proposes
specifying the channel number within the existing H.281 Video Source
Capability for sources 6-15. The channel is transmitted in ASCII in the
existing camera name.  Backwards compatibility is provided since existing
clients can decode this message.  This idea allows existing H.281 clients to
control the cameras for both video channels - it is the only current
proposal which does this.  The syntax of only one message in H.281 is
slightly adjusted.

The existing video source capability for these sources looks like this:


8

7

6

5

4

3

2

1



4-bits encoded Video Source


Reserved

Motion
video

Normal resolution still
image

Double resolution still
image


Up to 16 ASCII encoded characters


All zeros octet


Pan

Tilt

Zoom

Focus

Reserved


The revision is to set the Reserved Bit if the Video Source is sending on a
secondary video channel.  If the reserved bit is set, the first character of
the source name is a channel number (in ASCII), the second character is a
space.  The remaining 14 characters have the existing meaning.  This is
backwards compatible, since if the reserved bit is ignored the message can
be decoded properly by existing receivers.  An alternative is to leave the
reserved bit alone - since use of these extended sources is rare, this might
be sufficient.



All three approaches share a common issue.  H.323 and H.320 video channel
numbering is not preserved end-to-end.  Therefore, sometimes the user may
discover that they are moving the camera for the "wrong" video stream.  One
solution is bind the channels to H.239 role labels, which are preserved.
For instance, use channel 0 for main, channel 1 for presentation, and
channel 2 for live.  Expanding beyond 2 channels could be done by adding new
role labels to H.239.

Stephen Botzko
Chair - Multiple video streams FECC AHG
Polycom
+1 978 292 5395

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