[AVT] RE: Doubts in draft-ietf-avt-rfc2429-bis-09.txt

["Even, Roni" <[e-mail]>]

Frederick,
Yes, The answerer May send a re-INVITE with QCIF to ensure that it will
receive QCIF and not CIF.

As for the suggestion to add offer answer, I think it may be a bit late
since it is in author48 but we intend to have a new and what we hope
last revision that will be the candidate for a proposed standard that
will clear all issues after deployment.

I suggest starting implementing based on this draft mostly since RFC2429
did not have the mechanism to specify resolution and frame rates.

Roni  

> -----Original Message-----
> From: Huve, Frederic [mailto:[e-mail]]
> Sent: Wednesday, November 29, 2006 5:58 PM
> To: Even, Roni
> Cc: AVT WG
> Subject: RE: Doubts in draft-ietf-avt-rfc2429-bis-09.txt
> 
> Roni,
> 
> Thanks for your fast and clear answer !
> 
> To complete the picture, in the depicted scenario, the answerer MAY
send
> a re-INVITE with a SDP Offer set to QCIF in order to insure that the
> initial offerer will not send CIF, is that right ?
> 
> As suggested by Desineni some times ago on the list
> (http://www1.ietf.org/mail-archive/web/avt/current/msg07267.html), it
> would be good to provide some Offer/Answer examples with Profile &
> Level, and also with Picture size and MPI.
> 
> Again thanks for you support.
> Regards,
> Frederic
> 
> [e-mail]
> 
> -----Original Message-----
> From: Even, Roni [mailto:[e-mail]]
> Sent: Wednesday, November 29, 2006 8:14 AM
> To: Huve, Frederic
> Cc: AVT WG
> Subject: RE: Doubts in draft-ietf-avt-rfc2429-bis-09.txt
> 
> Frederick,
> The picture size and MPI parameter specify receiver capability (see in
> the text from 2429bis bellow), it does not imply what will be sent
since
> asymmetry is allowed. So if the answerer specified CIF=1 it means that
> it can receive CIF at upto 30 frames per second, it must only send
QCIF
> at 15 frames per second on lower.
> So both answers are correct.
> 
> The sentence from RFC2429 means that if the offer specified QCIF=2 it
> means that it can receive SQCIF=2 or lower but not SQCIF=1. It does
not
> say what resolution and at which frame rate it will send.
> 
> 
> From 2429bis
> 
> Picture sizes and MPI:
> 
>    Supported picture sizes and their corresponding minimum picture
> interval (MPI) information for H.263 can be combined.  All picture
sizes
> can be advertised to the other party, or only a subset of it. Terminal
> announces only those picture sizes (with their MPIs) which it is
willing
> to receive.  For example, MPI=2 means that maximum(decodable) picture
> rate per second is about 15.
> 
> 
> Roni
> 
> > -----Original Message-----
> > From: Huve, Frederic [mailto:[e-mail]]
> > Sent: Tuesday, November 28, 2006 6:01 PM
> > To: Even, Roni
> > Cc: AVT WG
> > Subject: Doubts in draft-ietf-avt-rfc2429-bis-09.txt
> >
> > Roni,
> >
> > We're investigating to move from RFC 2429 support to rfc2419-bis-09
> > support and it remains one question around Offer/Answer. (I've
browsed
> 
> > the mail archive and partially found part of the response
> > http://www1.ietf.org/mail-archive/web/avt/current/msg06890.html :)
> >
> > In the following use case, what is the valid SDP Offer/Answer
scenario
> ?
> >
> > If an offerer sends a SDP offer (meaning he wants to receive QCIF
with
> 
> > MPI = 2):
> >
> > m=video 8000 RTP/AVP 96
> > a=rtpmap:96 H263-1998/90000
> > a=fmtp:96 QCIF=2
> > a=sendrecv
> >
> > The answerer sends the following SDP answer (means that he can
receive
> 
> > up to CIF with MPI = 1):
> >
> > m=video 8002 RTP/AVP 96
> > a=rtpmap:96 H263-1998/90000
> > a=fmtp:96 CIF=1
> > a=sendrecv
> >
> > IMHO this scenario is not valid because of the RFC-2429bis
statement:
> "
> > A system that declares support of a specific MPI for one of the
> > resolutions SHALL also implicitly support a lower resolution with
the
> > same MPI."
> >
> > In order to be compliant the answerer should instead responds with
the
> 
> > following SDP answer:
> >
> > m=video 8002 RTP/AVP 96
> > a=rtpmap:96 H263-1998/90000
> > a=fmtp:96 CIF=2
> > a=sendrecv
> >
> >
> > Warm thanks for your time !
> > Regards,
> > Frederic
> >
> > [e-mail]
> >
> >
> >
> >
> >
> >
>
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> 
> 
> 
> 
> 
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