[asterisk-dev] New codec support in Asterisk 10

[Simon Perreault]

On 2011-10-14 13:15, Tilghman Lesher wrote:
> On Fri, Oct 14, 2011 at 11:53 AM, Jason Parker <jparker at digium.com> wrote:
>> In Asterisk 10, we've changed the way codecs are defined, to expand the number
>> of codecs that we can support.  However, due to protocol limitations, many
>> channel drivers (pretty much everything but chan_sip) can only support a limited
>> number of codecs.  As an example, chan_iax2 uses a 32-bit bitfield on the wire,
>> which means the codec list on each side can never change.
> 
> One small correction:  chan_iax2 uses a 64-bit bitfield on the wire,
> with approximately
> 30 of those bits unallocated.  (Testlaw can be removed; it's just a
> duplicate of ulaw.)

(just trolling a little bit)

So chan_iax2 doesn't follow the RFC?

   While IAX is very effective, addressing many of today's
   communications needs, it does have a few limitations.  For instance,
   IAX uses a point-to-point codec negotiation mechanism that limits
   extensibility because every IAX node in a call path must support
   every used codec to some degree.  In addition, the codec definition
   is controlled by an internally defined 32-bit mask, so the codecs
   must be defined in the protocol, and the maximum number of
   simultaneous codecs is, therefore, limited.

http://tools.ietf.org/html/rfc5456#section-1.2

Simon
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