Yong Xin wrote:
> Hi,
>
> We have different interpretation regarding to the "c=" line definition in
> RFC 2327.
>
> Session description
> c=* (connection information - not required if included in all media)
>
> Media description
> c=* (connection information - optional if included at session-level)
>
> I think "c=" line is optional when SDP has no "m=" line, since I don't see a
> use case to present connection info when there's no media description. But
> some people think the above definition indicates the "c=" line is mandatory
> and must be present in either session or media level in any case.
>
> Could anyone tell me which interpretation is correct?
That is an interesting question. The interpretation you propose makes
more sense to me than the alternative. The question is whether the text
in RFC 4566 supports that interpretation. I think the following from
section 5.7 is the relevant text to interpret:
A session description MUST contain either at least one "c=" field in
each media description or a single "c=" field at the session level.
It MAY contain a single session-level "c=" field and additional "c="
field(s) per media description, in which case the per-media values
override the session-level settings for the respective media.
Now suppose you have a session description that has no media
descriptions. Does that 'have at least one "c=" field in each media
description'? I think so. It has one "c=" in each (in this case none)
media descriptions.
So I support you.
Paul
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