[asterisk-dev] Adding Audio/Video/Text Format to IAX2: Formal Procedure?

[Matt Fredrickson]

Greetings Alexander,

On Fri, Mar 10, 2017 at 12:22 PM, Alexander Traud
<pabstraud at compuserve.com> wrote:
> Thanks to a user of one of my audio transcoding modules, I noticed that my modules work in chan_sip and res_pjsip but not in the channel driver for IAX2 of Asterisk 13. He changed:
> - include/asterisk/format_compatibility.h
> - channels/iax2/format_compatibility.c
> - main/format_compatibility.c
>
> However, I asked that question already in <http://gerrit.asterisk.org/3244> and was told "New [formats] shouldn't be added to [format_compatibility.*]." I cannot double-check, because I do not use IAX2.
>
> Furthermore, I saw the IANA registration: <http://www.iana.org/assignments/iax-parameters#iax-parameters-15>. Was 0x00002000 re-assigned from AMR to Siren7? I am a bit confused.

That's what it looks like.  At the very least, there's a discrepancy
between Asterisk's implementation and the protocol document.  I'm
guessing AMR might have been dropped due to lack of considerable
"in-the-wild" interop use cases.

> Does IAX2 do any magic and loads formats without ID dynamically? I do not find the source code for that. Or should I register a new format via some formal procedure with IANA first (and then submit a patch for all three format_compatibility.* files)?

If I remember correctly, it does not have a dynamic payload type
mapping (similar to SDP's dynamic payload type mappings) and is stuck
with pre-defined static mappings right now.  Doing anything else would
call for a protocol revision.  If you try to allow= a format that IAX2
doesn't have protocol compatibility for, it should remove the format
from the allowed codec list for the IAX2 endpoint.

Since I'm guessing most of the people that are interested in IAX2 as a
protocol are on this list or are involved with Asterisk, my suggestion
is to propose something on the -dev list or on gerrit, and we can
discuss it there first.

---
Matthew Fredrickson
Digium, Inc. | Engineering Manager
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA