Subject: [Megaco] misleading ABNF comment on stream descriptor?

From: Raphael Tryster <[email-masked]>
Date: Wed, 23 Jan 2002 10:15:34 +0200

Here is something from the archive which was never answered.  I think the
answer to Steven's question is that section 7.1.4 is right and the comment
in the ABNF is wrong, as the ASN.1 definition allows multiple stream
descriptors per media descriptor.  Will the comment in the ABNF be changed?

Raphael Tryster

From: Steven Weisz <[email-masked]>
To: "Megaco Mailing List (E-mail)" <[email-masked]>
Subject: Clarification on Media Descriptor needed.
Date: Tue, 24 Apr 2001 13:32:09 -0400
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Hi List,

I need some clarification regarding the Media Descriptor. Specifically in
section 7.1.4, paragraph 1 the protocol states:

  "The Media Descriptor specifies the parameters for all the media
   streams.  These parameters are structured into two descriptors, a
   Termination State Descriptor, which specifies the properties of a
   termination that are not stream dependent, and one or more Stream
   Descriptors each of which describes a single media stream."

This states that a Media Descriptor has one or more Stream Descriptors
associated with it. However, in the ABNF we have:

  "mediaDescriptor = MediaToken LBRKT mediaParm *(COMMA mediaParm)
                        RBRKT

   ; at-most-once per item
   ; and either streamParm or streamDescriptor but not both
   mediaParm            = (streamParm / streamDescriptor /
                           terminationStateDescriptor)"

Which to me seems to say that we have only one Stream Descriptor associated
with it (as indicated by the comment "; at-most-once per item".

Am I interpreting the ABNF correctly?

thanks,

Steven Weisz