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Date:      Sat, 8 Jun 2013 23:55:13 -0700
From:      Adrian Chadd <adrian@freebsd.org>
To:        Iain Hibbert <plunky@ogmig.net>
Cc:        freebsd-bluetooth@freebsd.org
Subject:   Re: What's it going to take to get basic A2DP support into -HEAD?
Message-ID:  <CAJ-Vmom7X4BACQ8x_B6u=Zef7TAa8Gn4HdiB77pWU36hNJVQaA@mail.gmail.com>
In-Reply-To: <alpine.NEB.2.00.1306090731410.584@galant.ogmig.net>
References:  <CAJ-VmokxtmkqXBPXfvKzRJ2qxGUe5qN0D-pvsJP-7djDdVE4ag@mail.gmail.com> <alpine.NEB.2.00.1306090731410.584@galant.ogmig.net>

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On 8 June 2013 23:48, Iain Hibbert <plunky@ogmig.net> wrote:
> On Sat, 8 Jun 2013, Adrian Chadd wrote:
>
>> So, given that these headphones pair, what would it take to write up a
>> basic A2DP profile with the minimum-supported codec, and then route
>> audio to it?
>
> it is probably a couple of weeks work; the specification document is not
> that thick..

Yeah, I see that. And lots of the codec types are optional, right?

>> Would it be something done in-kernel? Or would we just expose the
>> audio to userland and do the (re) encoding there?
>
> imo this is likely the best approach
>
> NetBSD has a simple "pseudo audio device" driver[1], which is like a pty
> but for audio devices.. I would use that (or something like, since I don't
> know how similar the FreeBSD kernel audio interface is to the NetBSD one)
> and provide a userland program to just route the audio back into a RFCOMM
> socket after conversion.
>
>> What about supporting data sources that will happily supply a
>> supported bitrate/encoding type? (eg, if a player wants to spit out
>> MPEG encoded audio; why decode and re-encode it?)
>
> your Bluetooth interface can be whatever you need, and you can transcode
> or feed whatever the kernel will accept (PCM in the case of pad(4) on
> NetBSD)
>
>> I'm happy to hack on code. I just don't know anything about the
>> bluetooth stack here. :-)
>
> just deal with an RFCOMM socket, is my advice..  (in part, because I am a
> NetBSD developer.. and our Bluetooth stack is somewhat different, but the
> socket interface is compatible :)

It's not a bad idea to begin with. I just have no idea where to begin
there. I'll keep on reading, see if I can muster the energy to write
some bluetooth socket code.

Thanks,



Adrian



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