[asterisk-dev] SDP negotation problem

[Kevin P. Fleming]

Salvatore Frandina wrote:
> The thing is strange for me...If my application offers a specific
> payload type to Asterisk it SHOULD use the same type.
> Why should "my application" be adapt to Asterisk? Because is it no
> famous (VLC)?

It SHOULD, but it is not required to. Any SIP/SDP-supporting application
is free to choose the payload numbers for dynamic payload types as it
sees fit, and all applications must be able to send payloads to other
endpoints using the payload numbers that that endpoint selected, in all
cases.

The same situation would occur if Asterisk was sending the INVITE to
*your* application; Asterisk might choose 103 as the payload number for
H.263, but your application would respond with 96 because it only
supports 96 (based on your previous comments). This is perfectly valid
and acceptable, and yet your application will not work properly, because
it would send packets to Asterisk using payload number 96 when Asterisk
is expecting them to be 103.

The simple answer is: your application *MUST* respect the payload
numbers selected by the other endpoint, whether they match the ones you
offered or not.

-- 
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