What does this mean in the converged world where a phone is also a desktop?
On Thu, Oct 8, 2015 at 10:30 AM, Simon Fels <[email protected]> wrote: > On 08.10.2015 15:08, Michael Zanetti wrote: > >> >> >> 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... >> > > On Android devices that is the regular case. The audio data is passed to > the BT chip over a PCM line rather than through HCI. That still doesn't say > it's not possible to do it but that is a way nobody tested yet and proved > it works. > > In our current setup we're using the PCM line approach which also saves us > from burning CPU cycles on this rather than letting the BT chip which is > optimised for this doing that. > > The next bigger point is how HFP is currently implemented. With the shift > to BlueZ 5 the implementation moved into ofono as that is the natural place > where you want to do AT command processing. The current implementation > expects a voice call capable modem to be present before we even even allow > the HFP AG profile to be connected. As there can be only one provider in > the system for a profile we would have to integrate what VoIP solution we > want to use over HFP into ofono to let it expose a modem which we can use > as control interface ... However that doesn't say that we can add another > provider for the HFP profile which becomes active in scenarios where we > don't have a GSM modem but then has to implement the whole profile support > on its own with the point of proper audio routing still being sorted. > > > regards, > Simon > > -- > Mailing list: https://launchpad.net/~ubuntu-phone > Post to : [email protected] > Unsubscribe : https://launchpad.net/~ubuntu-phone > More help : https://help.launchpad.net/ListHelp >
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