Re: [AVT] Reminder: WG Last Call: draft-ietf-avt-text-red-02.txt

[Colin Perkins <csp at csperkins.org>]

On 11 Apr 2004, at 06:46, Gunnar Hellstrom wrote:
> There has been a good discussion in the avt list about the use of the
> a=fmtp parameter for text-red. The discussion has been linked to the
> parallell work with real time text transmission in RFC2793bis, but is 
> valid
> for text-red and should possibly influence the text-red draft slightly.
>
> Here are my review of text-red-02 including the result of the 
> discussion on
> a=fmtp:
>
> 1. In section 4, there is this sentence:
> "Any dynamic payload type in the list MUST NOT include its content-
>    type only the payload type number."
> The "type only" comes out a bit strange. I suggest rewording to what 
> you
> shall do:
> "Any dynamic payload type in the list MUST be represented by its 
> payload
> type number and not by its content-type."
okay

> 2. The offer-answer aspects of the a=fmtp parameter
> In a separate mail in the avt thread discussing a=fmtp for RFC2198, I 
> enter
> offer-answer considerations for the a=fmtp parameter and suggest that 
> this
> sentence is included in the sdp mapping section of text-red spec:
>
> "In an offer/answer situation, the fmtp parameter in the answer MAY
> describe a different number of redundant levels than in the offer. The
> session SHOULD use the highest number of redundant levels described."
I don't think this is appropriate due to the problem of asymmetric loss 
we've previously discussed. I would suggest that the "text/red" 
registration remain silent about this issue, and that we consider 
offer/answer considerations for redundant audio when RFC 2198 is 
revised for Draft Standard. This will ensure that we have consistent 
specifications for all uses of the format.

--
Colin Perkins
http://csperkins.org/


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