[asterisk-dev] Advanced Codec Negotiation: Asymmetric Codecs

[Michael Maier]

On Mon, Jun 15, 2020 at 19:56 Joshua Elson wrote:
> So I am the one responsible for this situation, if I recall the discussion
> a few years back. We actually have had to support several phones - Yealink
> being the most distinctly memorable - that support asymmetric codecs on a
> single call leg, and from our reading, it's legal in the RFC. In some very
> high throughput cases, it was preferable to reduce overall transcoding use
> in our infrastructure when you did the math on having a few thousand of
> these phones in the same situation.
> 
> That being said, it's conceivable we could live without that option now,
> and some phone vendors do still not properly implement the RFC standard
> around this, but we do still run in production with asymmetric codecs on a
> single call leg for a slight majority of our devices.

Sorry, I couldn't find any absolutely necessary reason why there must be asymmetric codecs. For me it sounds more like 
it's just happening at the moment, but it could work all the same using symmetric codecs.
At the moment, I can't see any reason why the 2 legs from a phone must use different codecs. I would be happy to learn 
such a use case which implies necessarily asymmetric codecs.


Thanks
Michael