Re: Determinate EDR speed

["Gix, Brian" <brian.gix@intel.com>]

Hi Pali,

On Fri, 2019-10-11 at 20:35 +0200, Pali Rohár wrote:
> Currently bluez API, method Acquire() already inform called application
> what is socket MTU for input and output. So from this information it is
> possible to detect if device supports EDR 3 or not.
> 
> But it is too late to have this information. I need to send SBC
> parameters to bluez first when doing A2DP negotiation, this is early
> steps before Acquire() is called.

This seems to be the kind of information which is fixed, for the life of the pairing.

What if you assumed the lower speed the first time you connected, determined the
speed during the first streaming, and then either immediately renegotiate (caching the identifying information
of the SNK), or just cache the information for future connections.

Or the reverse, and assume fast, but immediately adjust down if you aren't getting what you hoped for.

In any case, this would be a "Device Setup" glitch which you could note as a routine part of pairing in the
documentation.

> 
> Therefore I'm asking for some way how to get information if device
> supports EDR 2 or EDR 3. This is basically requirement for proper
> implementation of SBC in high quality mode. So if there are not such API
> yet, could it be exported from kernel to userspace and bluetoothd
> daemon?
> 
> See these two articles for more details about SBC and its high quality:
> 
> https://habr.com/en/post/456182/
> http://soundexpert.org/articles/-/blogs/audio-quality-of-sbc-xq-bluetooth-audio-codec
> 
> > > Is there any bluez API for it?
> > >