ubuntu-phone team mailing list archive

[Michael Zanetti <michael.zanetti@xxxxxxxxxxxxx>]

On 08.10.2015 14:57, Simon Fels wrote:
> On 08.10.2015 14:30, Michał Sawicz wrote:
>> W dniu 08.10.2015 o 14:00, Simon Fels pisze:
>>> A tablet stays a tablet. Having a modem included doesn't make it a
>>> phone. The Bluetooth device class is meant to stay static for one device
>>> forever. No dynamic changes. It is your first point to find out what
>>> kind of Bluetooth device you've found.
>>>
>>> Btw. that a tablet includes a GSM modem still doesn't say anything about
>>> if it also allows you to do voice calls ... If we have a "phablet"
>>> device then this needs to be categorized as a phone as it provides voice
>>> call capabilities. See
>>> https://www.bluetooth.org/en-us/specification/assigned-numbers/baseband
>>> for some more details on the major and minor device classes we're
>>> talking about here. Putting the device into the right major/minor class
>>> is crucial as some car kits doesn't allow you to pair them only with
>>> devices part of the phone device class...
>>>
>>> Also what would be the benefit of having an option for the user to
>>> override this?
>>
>> I think you just wrote what would be the benefit - some car kits only
>> connect to phone devices. What if I wanted my 3G tablet (no voice, but
>> VoIP still works!) to connect to the car?
> 
> That would a use case, yes, but still really a workaround for a corner
> case.
> 
> However that wouldn't work with our implementation playing the role of
> the audio gateway strictly requires a modem with voice call
> capabilities.. no way to inject your VoIP stack here. It also hardly
> depends on how the hardware is build. For HFP on most Android devices
> the audio is directly routed from the microphone to the BT chip without
> involving the CPU so we can gurantee you're even able to inject your
> VoIP audio data.

Hmm... wouldn't be so sure about that.. Yes, HFP's control channel is
based on AT commands, and it's also correct that most hardware wires the
sound chip with the Bluetooth chip directly, still, every Bluetooth chip
I came across so far allowed routing audio data through the HCI. AFAIK,
bypassing the HCI is the optional case here. I did see dummy AT command
layers injecting VoIP into HFP before...

Br,
Michael

Attachment: signature.asc
Description: OpenPGP digital signature