[asterisk-dev] how does a channel driver know the result of codec negotiation ?

[Kevin P. Fleming]

Luigi Rizzo wrote:

> Anyways, what would be wrong with the obvious solution of notify
> the caller's channel driver once the remote party reports supported
> formats ?  I don't know exactly if we already have a suitable
> callback in struct ast_channel_tech but given the abundance of
> entries there i suppose one more wouldn't harm too much.

There are multiple potential issues that get involved here.

The first is that you say when 'THE remote party'... but there could be
many remote parties, since an outbound dial operation can call multiple
endpoints. If we ever decide to support SIP forking, then it gets worse,
because dialing a single SIP endpoint could result in more than one
temporary dialog (until one of them answers).

The next issue is one of 'control', or handling preferences, especially
when there are multiple Asterisk servers in the chain of the call. If
party A places a call through one server, then through another server,
then to party B, how is this 'format list' going to get communicated all
the way back to party A, or should that even happen?

These issues are hard to deal with well and provide an understandable
solution to the end users, and they aren't even involving the technical
(implementation) aspects yet. It's just not an easy problem to solve.

-- 
Kevin P. Fleming
Director of Software Technologies
Digium, Inc. - "The Genuine Asterisk Experience" (TM)