[Bluez-devel] org.bluez.Audio

[Bluez-devel] org.bluez.Audio

[Brad Midgley]

Marcel

I rewrote the dbus proposal. If what's here looks ok we can start
thinking about the named pipe, ipc, or whatever we use for sending audio
and file descriptors around.

http://bluetooth-alsa.sourceforge.net/future.html

Brad

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Re: [Bluez-devel] org.bluez.Audio

[Jose Vasconcellos]

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Hi Brad,

I'm a little unclear on the division of work between bt.audiod and
the audio library plugins. From the diagram, it seems that bt.audiod
handles the control as well as the audio streams. Does this mean
that the the audio samples get copied from the plugins to/from
bt.audiod? I'm not sure if the extra copying and latency is a good
thing.

I think that bt.audiod should only handle the audio control portion.
The audio plugins should do direct bluetooth I/O.

Jose

Brad Midgley wrote:
> Marcel
>
> I rewrote the dbus proposal. If what's here looks ok we can start
> thinking about the named pipe, ipc, or whatever we use for sending audio
> and file descriptors around.
>
> http://bluetooth-alsa.sourceforge.net/future.html
>
> Brad
>   

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fn:Jose Vasconcellos
n:Vasconcellos;Jose
org:Vas & Mac Enterprises LLC
adr:;;P.O. Box 567;Red Bank;NJ;07701;USA
email;internet:jose@vasmac.com
title:Managing Member and CTO
tel;work:+1 732 978 4680 x102
tel;fax:+1 206 888 6951
url:http://www.vasmac.com
version:2.1
end:vcard


[-- Attachment #3: Type: text/plain, Size: 347 bytes --]

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Re: [Bluez-devel] org.bluez.Audio

[Brad Midgley]

Jose

> I think that bt.audiod should only handle the audio control portion.
> The audio plugins should do direct bluetooth I/O.

I'll update the page then. I won't rule out having bt.audiod manage a 
file descriptor for the sco channel and pass it around like Fabien did 
in his daemon. Only one app could use the sco channel at a time.

In the case of a2dp where we're already dealing with long latencies, I 
would like to have bt.audiod mix, encode, and deliver the audio. The 
challenge there is to keep the latency consistent so a video player 
could accommodate it.

Brad

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Re: [Bluez-devel] org.bluez.Audio

[Fabien Chevalier]

Hi Brad&Jose,

> 
>> I think that bt.audiod should only handle the audio control portion.
>> The audio plugins should do direct bluetooth I/O.
> 
> I'll update the page then. I won't rule out having bt.audiod manage a 
> file descriptor for the sco channel and pass it around like Fabien did 
> in his daemon. Only one app could use the sco channel at a time.

Brad, i think the 'only on sco channel at a time argument' is not very
pertinent, for two reasons:
  * First, i'm not sure there is an added value to be able to mix sound
channels to a sco headset.
  * Second, if we think this is really needed, ALSA provides all
required facilities to mix multiple streams to one (think to the dmix
plugin). For your information, dmix is now on by default since alsa
1.0.10 if i remember. Previously most cheap computers were only able to
play one PCM stream at a time. While annoying,  that didn't kill anybody
tought ;-)

> 
> In the case of a2dp where we're already dealing with long latencies, I 
> would like to have bt.audiod mix, encode, and deliver the audio. The 
> challenge there is to keep the latency consistent so a video player 
> could accommodate it.
> 
> Brad
> 




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Re: [Bluez-devel] org.bluez.Audio

[Brad Midgley]

Fabien

> Brad, i think the 'only on sco channel at a time argument' is not very
> pertinent, for two reasons:
>   * First, i'm not sure there is an added value to be able to mix sound
> channels to a sco headset.
>   * Second, if we think this is really needed, ALSA provides all
> required facilities to mix multiple streams to one (think to the dmix
> plugin). For your information, dmix is now on by default since alsa
> 1.0.10 if i remember. Previously most cheap computers were only able to
> play one PCM stream at a time. While annoying,  that didn't kill anybody
> tought ;-)

maybe the documentation could use some improvement, but I'm in agreement
with you. We should give the plugin its own file descriptor for the sco
link.

Brad

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Re: [Bluez-devel] org.bluez.Audio

[Fabien Chevalier]

Hi Brad,

>> Brad, i think the 'only on sco channel at a time argument' is not very
>> pertinent, for two reasons:
>>   * First, i'm not sure there is an added value to be able to mix sound
>> channels to a sco headset.
>>   * Second, if we think this is really needed, ALSA provides all
>> required facilities to mix multiple streams to one (think to the dmix
>> plugin). For your information, dmix is now on by default since alsa
>> 1.0.10 if i remember. Previously most cheap computers were only able to
>> play one PCM stream at a time. While annoying,  that didn't kill anybody
>> tought ;-)
> 
> maybe the documentation could use some improvement, but I'm in agreement
> with you. We should give the plugin its own file descriptor for the sco
> link.
> 
hmmm... i must have smoked the carpet again :-(
So it looks that we agree, everything's fine. ;-)

But what about A2DP ? Wouldn't it make sense to use ALSA mixing facility 
too ?

Cheers,

Fabien

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Re: [Bluez-devel] org.bluez.Audio

[Brad Midgley]

Fabien

> But what about A2DP ? Wouldn't it make sense to use ALSA mixing facility 
> too ?

dmix essentially acts as an audio server. But it's not the only one we 
should consider. I've been looking at pulseaudio to see if it fits in 
the picture at all. Seems to handle sound adapters that come and go and 
includes a sort of audio routing mechanism.

Brad

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Re: [Bluez-devel] org.bluez.Audio

[Fabien Chevalier]

Hi Brad & Marcel,

I got a number of interrogations regarding the various methods/signals
exposed here. I noticed a few things that won't work. To be able to
pinpoint these issues one by one, i think there is a need to draw some
diagrams that show the dynamic aspects of things. I'm gonna try drawing
a few of those before the end of the year : hopefully i will find some
spare time as i'm gonna be in hollidays from Xmas till new year...

Cheers,

Fabien

> Marcel
> 
> I rewrote the dbus proposal. If what's here looks ok we can start
> thinking about the named pipe, ipc, or whatever we use for sending audio
> and file descriptors around.
> 
> http://bluetooth-alsa.sourceforge.net/future.html
> 
> Brad
> 



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