RE: [AVT] Interop issue with H263-1998

["Even, Roni" <roni.even at polycom.co.il>]

Guido,
I have to agree that systems that tried to use the payload type H263-1998 before RFC 4629 may send any annexes available in H.263+, not all of them since that may be not feasible. So it was really un-specified before RFC 4629. 

The big motivation for RFC 4629 was because the video conferencing manufacturers, who were the major users of H.263+ were trying to support SIP (Moving from H.263) and ran into SDP problems.

When writing the draft, the assumption was that there were no real implementations using H.263-1998 but mostly H263 or H263-200 with profile and level optional options.

Roni 

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> -----Original Message-----
> From: Franceschini Guido [mailto:guido.franceschini at telecomitalia.it]
> Sent: Tuesday, August 21, 2007 6:49 PM
> To: avt at ietf.org
> Cc: Paltro Pier Carlo
> Subject: [AVT] Interop issue with H263-1998
> 
> Dear all,
> 
> I have an issue with the definition of the H263-1998 media type.
> In the RFC 2429, no optional parameters are defined, implying that any
> valid H263+ stream could be streamed.
> In the RFC 4629, that obsoletes 2429, various optional parameters are
> specified, which allow specifying the (decoder) support to the various
> annexes.
> 
> What confuses me is the following statement in RFC 4629, concerning H263-
> 1998
> 
>    Interoperability considerations:
> 
>       These are receiver options; current implementations will not send
>       any optional parameters in their SDP.  They will ignore the
>       optional parameters and will *** encode the H.263 stream without any
> ***
>       of the annexes.  Most decoders support at least QCIF and CIF fixed
>       resolutions, and they are expected to be available almost in every
>       H.263-based video application.
> 
> Indeed my understanding would be quite different, and I would have written
> instead:
> 
>       These are receiver options; current implementations will not send
>       any optional parameters in their SDP.  They will ignore the
>       optional parameters and will *** encode the H.263+ stream with
> possibly all ***
>       of the annexes.  Most decoders support at least QCIF and CIF fixed
>       resolutions, and they are expected to be available almost in every
>       H.263-based video application.
> 
> 
> Any clarification would be welcomed
> 
> Best regards
> Guido Franceschini
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