[pulseaudio-discuss] bluetooth headset audio not supported by ofono

[Luiz Augusto von Dentz]

Hi Georg,

On Mon, Feb 9, 2015 at 12:42 PM, Georg Chini <georg at chini.tk> wrote:
> On 09.02.2015 11:19, Arun Raghavan wrote:
>>
>> On 9 February 2015 at 15:44, Georg Chini <georg at chini.tk> wrote:
>>>
>>> On 09.02.2015 10:55, Arun Raghavan wrote:
>>>>
>>>> On 9 February 2015 at 14:54, Georg Chini <georg at chini.tk> wrote:
>>>>>
>>>>> On 09.02.2015 10:16, Arun Raghavan wrote:
>>>>>>
>>>>>> On 9 February 2015 at 14:29, Georg Chini <georg at chini.tk> wrote:
>>>>>>>
>>>>>>> On 09.02.2015 09:28, Arun Raghavan wrote:
>>>>
>>>> [...]
>>>>>>
>>>>>> If you mean that we need to do AT command handling, we now already do
>>>>>> a bit of that in PA (we couldn't really agree upon any other place for
>>>>>> that once BlueZ dropped it). Is there much we need to support other
>>>>>> than volume commands?
>>>>>>
>>>>>> Assuming it's not too much more complex than the HSP support, we
>>>>>> should be able to manage that just fine by extending the native
>>>>>> backend.
>>>>>
>>>>>
>>>>> For audio you probably won't need much more. But if you do not
>>>>> support the telephony functions, you are in the same situation as
>>>>> ofono is with the AG role. Here ofono supports the AT commands,
>>>>> but no audio, and what use is a headset without audio?
>>>>> And if you support audio for a phone but not the telephony functions,
>>>>> what is phone audio good for where you can't make or receive a call?
>>>>
>>>> You can receive a call (you don't need the headset functions to accept
>>>> one), so we've had users using their computer, their Raspberry Pi, or
>>>> other devices for such use cases.
>>>>
>>> Really? Without using ofono? I wonder how this worked. I did already
>>> use ofono with bluez4 and it would not have worked without. Who
>>> sends the AT command to accept the call to the phone? Or do I have
>>> to pick up manually then?
>>
>> Since we didn't have a mechanism to answer the phone call, probably
>> was manual. Do note that this mode would be useful for more than
>> telephony calls (i.e. voip calls too).
>>
>>
> Sorry that I can't stop ...
> First, I can't think of a case were you need a bluetooth HF profile for
> voip.
> How should that work?
> The main difference between the implementation in Bluez4 and Bluez5
> is, that the connection management is no longer done by the Bluez
> stack but either by ofono or pulseaudio.

The connection management as per socket handling is still done by
bluetoothd, the AT command parsing is the one no longer done by BlueZ
itself.

> With Bluez 4 you could "share" the connection, meaning let Bluez
> manage the connection and then use audio from pulse and AT commands
> from ofono.

BlueZ 4 acted as a middle man only for HF role.

> Now the situation is different: Either ofono or pulse has to implement
> connection management and then pass on the unused part to the
> other application. If you don't do that you will break the other
> application.
> (See AG implementation in ofono)

If you are talking about SCO, yes that is left for oFono to deal with
thus it has some interfaces to hand over the connection to pulseaudio
via ofono backend.

> The best would be to implement the AG role in pulse (because a headset
> is mostly audio) and pass on AT handling to ofono while implementing
> the HF role in ofono (because it's mostly telephony) and pass on the
> audio to pulse. But that would imply that the developers talk to each
> other and resolve the overlap which apparently has not been the case
> until now.

It does not make sense to talk about roles here, what PulseAudio
should implement is HSP for both roles which does not require any
telephony stack since all AT commands are audio related, HFP should be
implemented by a telephony stack which optionally can hand over the
audio to pulseaudio. Depending on the platform you may or may not have
a telephony stack, Id say if you do have then HFP should be enable
otherwise use HSP.

-- 
Luiz Augusto von Dentz