[opus] Question for members on using OPUS with Bluetooth

[Timothy B. Terriberry]

Robert Bean wrote:
> This is my first post to the OPUS group but I would like to find out if
> anyone is using OPUS over Bluetooth?  If so, I have some follow-up
> questions on the implementation strategies that have been used.

I know some people have looked at it (see, e.g., 
<http://stackoverflow.com/questions/19567435/can-any-other-codec-be-used-instead-of-sbc-in-bluez-bluetooth-stack>), 
and I believe a couple of companies make wireless products using either 
Opus or (old versions of) CELT, though I don't have handy references.

> Is anyone using OPUS over A2DP?  Is it possible for off-the-shelf OPUS
> bluetooth devices manufactured by different companies to be compatible
> with each other?  If so, which A2DP Audio Codec ID is being used?  For
> this, do you use the 'Non-A2DP' ID, or is there an OPUS ID?

The place to find codec IDs for A2DP is 
<https://www.bluetooth.org/en-us/specification/assigned-numbers/audio-video> 
(the list in the spec will never be updated, even in future revisions of 
the spec, according to Section 4.2).

I don't know of anyone who has written down a spec for the Codec 
Specific Information Element or Media Packet Header Requirements, but I 
don't think those would be hard to do.

That page also quotes the relevant text from the spec on the process for 
upgrading a codec from "Vendor Specific" to "Optional", which does not 
seem that difficult (basically, you have to convince one other party to 
implement it, write up a test plan for a test that would demonstrate the 
two of you interoperate, and then do the test for the Architecture 
Review Board.

But until someone does that, I think you are stuck using the Non-A2DP ID.

> I'm not sure if this topic is better addressed with the Bluetooth SIG

Probably a good idea to raise it there, too. I don't know anything about 
Bluetooth beyond what can be learned in 5 minutes reading the specs.