[asterisk-dev] SIP: handling multiple m=video or m= audio lines

[Kevin P. Fleming]

Vadim Lebedev wrote:

> I think it would be good occasion to implement better handling of fmtp
> attributes for streams
> handled in transparent way.  I mean that if endpoint A  calling endpoint
> B has a fmtp attribute in video stream descriptor it should be fowarded
> to B by asterisk.
> Today it is scrapped.

No, it is not 'scrapped'. Asterisk is not a proxy, and for that reason
there is *zero* expectation that an incoming channel's media format
parameters are going to somehow magically be carried over to an outgoing
channel. The outgoing channel might not even have a way to express those
parameters, or the outgoing channel could *change* after the initial
connection (due to transfers or other call control activities) in which
case the media format parameters may or may not be appropriate at all.

While I certainly understand the desire for this to happen, doing it
properly (without causing new breakage) will require the efforts we
discussed at last year's AstriDevCon, ensuring that Asterisk can at
least properly parse and understand the format parameters to the best of
its ability, so that it can match them up and determine when sets of
parameters are 'compatible'. Just passing through the fmtp attributes
does not provide any real solution except for some very small cases.

-- 
Kevin P. Fleming
Digium, Inc. | Director of Software Technologies
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
skype: kpfleming | jabber: kpfleming at digium.com
Check us out at www.digium.com & www.asterisk.org