Hi Pali,
On 1/8/20 3:25 PM, Pali Rohár wrote:
Hello!
Somehow this went straight to my Junk folder, so I didn't see this
message at all until now.
Audio application (e.g. pulseaudio) really do not want to handle two
separate services to monitor and process HSP/HFP devices. >
For audio application are HSP and HFP devices equivalent, they provide
same features: SCO socket, API for controlling microphone and speaker
gain; plus optionally specify used codec.
So having two separate services which fully divided for audio
application purpose does not make sense.
So it is possible that both HSP and HFP audio cards would be available
via one audio API? Because I do not see how it could be done via design
like dundee.
One API sure. Maybe on multiple services. Honestly, I don't see why
this would be such a burden for PA to watch 2 dbus services instead of
1. From oFono perspective it would make more sense to keep the HSP part
a separate daemon. I could be convinced otherwise if it is indeed a big
burden for PA...
You can then implement the same API interfaces for setting up the HSP audio
stream as oFono does today (i.e. https://git.kernel.org/pub/scm/network/ofono/ofono.git/tree/doc/handsfree-audio-api.txt),
This API is unusable for both HSP and HFP audio streams. In pulseaudio
it is somehow used, but it is not suitable.
Funny. "It is used but not suitable"?
Main objection for handsfree-audio-api.txt is that it does not provide
information about locally used codec and somehow mixes air codec and
local codec. In my hsphfpd.txt I used term "AgentCodec" for bluetooth
local codec and term "AirCodec" for bluetooth air codec format.
Okay. But, just FYI, at the time there was no hw that could do such
on-the-fly conversions, so this use case wasn't considered/implemented.
There's really no reason why we couldn't extend our APIs to handle this.
Another objection against handsfree-audio-api.txt API is that it is
bound to HF codecs (via number) and does not support for pass e.g. CSR
codecs.
True. In retrospect we probably should have used strings. But it was
assumed that vendor extensions would go via the Bluetooth SIG Assigned
Numbers facility. Anyhow, we can always add a 'Register2' method that
could take codecs as a string array or a combination of strings & ints.
And if Register2 was used, then use 'NewConnection2' with a signature
that supports passing in vendor codecs and whatever else that might be
needed.
What is completely missing in that API is controlling volume level.
It is there on the CallVolume interface
And also API does not provide socket MTU information or ability to
change/specify which codec would be used.
There was no need, we automatically defaulted to using Wide band if
available. Third party codecs are a new use case (for oFono HFP), so
would require an API extension.
Non-audio APIs which are needed to export (for both HSP and HFP profiles):
* battery level (0% - 100%)
* power source (external, battery, unknown)
* ability to send "our laptop" battery level and power source to remote device
* send text message to embedded display
* process button press event (exported via linux kernel uinput)
I think all of these are feasible to support under the current oFono
structure, either via plugins or API extensions.
Regards,
-Denis
