[pulseaudio-discuss] Bluetooth - A2DP only? Recommended headsets? Jack?

[Lennart Poettering]

On Sat, 15.08.09 13:01, Ng Oon-Ee (ngoonee at gmail.com) wrote:

> 
> On Sat, 2009-08-15 at 02:35 +0200, Lennart Poettering wrote:
> > On Fri, 14.08.09 11:33, Ng Oon-Ee (ngoonee at gmail.com) wrote:
> > 
> > > > There's an ALSA module for BT. It works for basic stuff, but I'd guess
> > > > the PA plugin for ALSA plus PA's native BT support actually works
> > > > better. It's mostly about the timing. 
> > >
> > > Okay, good to hear. I'm thinking of ALSA as just 'the stuff between
> > > Pulse and system' nowadays, but may try that out just for novelty
> > > value.
> > 
> > Of course, I should probably mention that you most likely won't have
> > much fun with running JACK on that faked device (not that that would
> > make much sense anyway, though ...). BT and JACK doesn't really fit
> > together.
> 
> So the best way still seems to be JACK->Pulse->headset? All hail
> Pulse!

No. PA does not allow you to connect the JACK and the BT sinks/sources
directly. Sorry.

Also, this doesn't make much sense anyway. JACK is for audio
production. A2DP/BT is certainly completely unsuitable for audio
production. It's a spec that is amazingly simple-minded -- it lacks
any kind of timing synchronization. i.e. you just spit out your
packets at the frequency that makes sense to you and the device needs
to keep up with this. The better devices (s9) slave themselves to that
rate and resample as necessary, the not so good devices (FreePulse)
simply read the data into a jitter buffer and when after a while the
buffer gets too full or too empty they simply skip or drop out. 

Also, because there is no timing sync we have no clue how long the
data actually takes to be played, so getting things lip-sync is black
magic.

And then, what A2DP calls "hifi" is not comparable to real "hifi" at
all. SBC does not compare to CD audio.

> > Yes the fact that S9 is in-ear makes it a problematic choice. I am not
> > that fond of that either. But then again, it has relatively good
> > quality and the A2DP is much nicer implemented than the Logitech, and
> > it is both A2DP and HSP/HFP.
> 
> So, just to conclude, in general any A2DP compliant headphone should
> function, at least?

Good question. I only made sure the code works fine with the headsets
I personally possess. As I heard it seems to work fine on many
headsets, but then again we also have at least one report in the BTS
where things don't work (though I assume that is more related to the
faulty dongle than to a faulty headset):

http://pulseaudio.org/ticket/612

I am pretty sure the Nokians have done a bit more testing with various
headsets, they might know better. Given that the amount of patches
regarding the BT stuff coming from them is not as big as it used to be
I'd interpolate that PA's BT support is pretty good now... ;-)

Lennart

-- 
Lennart Poettering                        Red Hat, Inc.
lennart [at] poettering [dot] net
http://0pointer.net/lennart/           GnuPG 0x1A015CC4