[asterisk-users] Inefficient Codec Translation

[Steve Davies]

2008/9/3 Jim Boykin <boykinjim at gmail.com>:
> Brent/Steve, Thanks for the answer. Point here is that asterisk
> already knows about first leg and the codec so shouldn't it select the
> best codec for second leg to match first leg. Instead asterisk is
> selecting first codec in order.
>
> To illustrate, if the first leg was ilbc and second leg supports both
> g729/ilbc, I will assume that asterisk will select ilbc but that does
> not seems to be the case.
>
> Jim
>

Perhaps Asterisk needs a "notranscode" pseudo-codec, which tries to
use any existing codec that it has a handle on before then continuing
through the preferred list. This would be ignored if * could not
identify any existing codec, or if the existing codec was not at least
listed as valid later in the list.

It certainly has no such feature at present, and generally IIRC you
will get the first matchable codec as listed on the caller's end.

In fact the current behaviour makes perfect sense as it results in
last-minute transcoding, and utilises the fact that Asterisk may know
better about the capabilities of an onward link than the originator's
phone! By specifying g729/ilbc, you are saying that g729 is better on
that link, so Asterisk tries to be helpful - If ilbc is better,
specify ilbc/g729 instead :)

Just my 2p.
Steve