Re: [asterisk-users] Different codecs for reading and writing

[Tim Panton]

On 1 Aug 2009, at 22:26, Alex Balashov wrote:

Elliot Murdock wrote:

Thank you...do you know if IAX can do this?

The reason for doing is this is to get over the adsl upload/download

feasible for the upload direction, which has much more limited
bandwidth.  Accordingly, it would be possible to use G729 for upload,
but keep the higher quality codec, G711, for download.

discrepancy. While G711 gives terrific quality, it is not always that

its formal protocol mechanics.

However, poking around the various configuration options for IAX peers

to do that with IAX, either.  It's not really something 99.9% of VoIP
users want to do.  :-)

I do not know a great deal about IAX so I will defer to the experts for the definitive word on whether it is possible from the point of view of on voip-info.org and a few other places suggests that there is no option

The protocol expects the 2 ends to agree a single symmetrical codec



'the right thing' issues a warning and uses what it was given.




(in codec.conf )

should be fine with that.

see http://www.voip-info.org/wiki/view/Asterisk+config+codecs.conf

Tim.


Tim Panton - Web/VoIP consultant and implementor
www.westhawk.co.uk

I think you will find that it may work with Asterisk's IAX implementation. as part of the connection setup, but it doesn't define what actually happens if the codec specified in the first (full frame) voice packet isn't what was agreed. I have a vague memory that if the codec is one that is allowed, asterisk does But, as Alex says, there is no clear way to define this in the config files. You would probably do better to use Speex in both directions, but set the encoding quality parameters to be different at the 2 ends. The speex decoder should at the far end

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