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

[Georg Chini]

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:
>>> On 4 February 2015 at 14:10, David Henningsson
>>> <david.henningsson at canonical.com> wrote:
>>>>
>>>> On 2015-02-03 15:04, Tanu Kaskinen wrote:
>>>>> On Mon, 2015-02-02 at 16:49 +0100, Georg Chini wrote:
>>>>>> I think the release notes for 6.0 should be revised to account for
>>>>>> that.
>>>>>
>>>>> Indeed. Before I update the notes, though, I want to get a decision on
>>>>> whether we will release with your patch to use both backends
>>>>> side-by-side (probably implies another rc before final release), or will
>>>>> we postpone that to the next release. Either is fine by me, but I'd vote
>>>>> for releasing with your patch.
>>>>
>>>> Hmm. I'm not totally sure about the differences between HF and AG so take
>>>> this with a grain of salt, but...
>>>>
>>>> It seems to me that it's not extremely unlikely that either of us will
>>>> step
>>>> into the other domain in the future, i e, bluez 5 might implement AG
>>>> audio
>>>> or PulseAudio might implement a native support for HF.
>>>>
>>>> Also, if the AG plugin of Bluez 5 supports RFCOMM/AT commands then we're
>>>> already partially overlapping, because that's what we use to set/get
>>>> headset
>>>> volume and mic gain. If we enable both backends, will that then send AT
>>>> commands from both backends when we try to set the volume, or...?
>>>>
>>>> Hence, instead of removing all backend switching code, maybe we should
>>>> instead add a switching mode "both" which does what you say. Or
>>>> potentially
>>>> replace "auto" with "both", if "auto" now makes no sense.
>>>>
>>>> Finally, I remember Arun had a strong preference for not enabling the
>>>> ofono
>>>> backend by default, so Arun, could you elaborate upon whether that still
>>>> makes sense given this new information?
>>> The reason I was against a "both" mode is that it seems odd to me from
>>> a system integration perspective. The current situation seems to be
>>> either you have oFono as a part of your system and you're using it for
>>> modem management, some amount of BT audio management, and so forth.
>>> Else, you're using PulseAudio for the BT audio management (the stuff
>>> that BlueZ used to do but dropped in 5.x).
>>
>> That is not really correct. Even if you use ofono, you still need pulseaudio
>> for the BT audio, otherwise it just won't work. ofono will only manage
>> the connection for you.
> I think you might've misunderstood me. With oFono, you need PulseAudio
> for Bluetooth audio. As I wrote below, I don't think it makes sense
> that we mandate the opposite dependency. That is to say, it does not
> make sense to make oFono a dependency of PulseAudio for the use-cases
> that we supported with BlueZ 4.0.
>
>>> It seems odd to me to have a "both" mode -- I'd like to add back the
>>> features we supported before the BlueZ 5.x migration caused us to
>>> regress. Once Wim's HSP work is out, that basically leaves the HF role
>>> (PA on your acting as a headset). If I understand correctly, that will
>>> overlap with oFono (if oFono wasn't bringing a telephony stack along
>>> with it, I wouldn't be objecting to just using it as our external dep
>>> that provides these features)..
>>
>> But that is the point of the HF role. If pulseaudio was going to support
>> the HF role, it would also need to implement an (external) handler for
>> RFCOMM. So you would need to duplicate the ofono functionality in
>> some way or do the integration the other way round.
> 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?


>>> So to my mind, having a both mode does not seem too useful from a
>>> system integration point of view -- either we have oFono provide these
>>> and other services, system-wide, or we're having PA manage whatever
>>> (sub?)set of features we want to.
>>
>> I think the idea of having ofono manage the HF role and using pulseaudio
>> for the AG is from the practical (user) perspective at the moment as near
>> as you can get to the bluez4 situation. With both backends I finally can
>> connect my mobile and my headset which was not possible for bluez5
>> before.
> Yes, it is not a great thing that we had to regress on this
> functionality, but I think we're making progress towards restoring
> that via the native backend now.
>
> -- Arun
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