alsa virtual sound card (with networked output)

alsa virtual sound card (with networked output)

[Metyl Methylius]

Hello everyone,

I was wondering if its possible to just create a "virtual" sound card
using alsa which will just sent its audio stream to other computer
(using TCP/IP or UDP for example). On the other end there would be
some kind of server (or just nc -u -l -p 31337 | aplay ). I want to do
it on alsa layer because other aps using alsa will get immediate
support.

It should be something like described in

http://alsa.opensrc.org/index.php/Network

but with transparent support for all alsa based applications. I dont
care about syncronization or transmission delay. Any pointers as how
this could be done in alsa ?

metyl

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Re: alsa virtual sound card (with networked output)

[Colin Guthrie]

'Twas brillig, and Metyl Methylius at 11/01/11 14:51 did gyre and gimble:
> Hello everyone,
> 
> I was wondering if its possible to just create a "virtual" sound card
> using alsa which will just sent its audio stream to other computer
> (using TCP/IP or UDP for example). On the other end there would be
> some kind of server (or just nc -u -l -p 31337 | aplay ). I want to do
> it on alsa layer because other aps using alsa will get immediate
> support.
> 
> It should be something like described in
> 
> http://alsa.opensrc.org/index.php/Network
> 
> but with transparent support for all alsa based applications. I dont
> care about syncronization or transmission delay. Any pointers as how
> this could be done in alsa ?

Any particular reason you cannot use PulseAudio? It support usage from
existing ALSA apps and also works automatically with SSH by
piggy-backing connection settings on X11 root windows which are
accessable when the remote connection has X11 forwarding enabled.

> This mess was sent using 100% recycled electrons. If you want to get
> rid of this mess just turn off your computer,

:)

-- 

Colin Guthrie
gmane(at)colin.guthr.ie
http://colin.guthr.ie/

Day Job:
  Tribalogic Limited [http://www.tribalogic.net/]
Open Source:
  Mageia Contributor [http://www.mageia.org/]
  PulseAudio Hacker [http://www.pulseaudio.org/]
  Trac Hacker [http://trac.edgewall.org/]

Re: alsa virtual sound card (with networked output)

[Jaroslav Kysela]

On Tue, 11 Jan 2011, Metyl Methylius wrote:

> Hello everyone,
>
> I was wondering if its possible to just create a "virtual" sound card
> using alsa which will just sent its audio stream to other computer
> (using TCP/IP or UDP for example). On the other end there would be
> some kind of server (or just nc -u -l -p 31337 | aplay ). I want to do
> it on alsa layer because other aps using alsa will get immediate
> support.
>
> It should be something like described in
>
> http://alsa.opensrc.org/index.php/Network
>
> but with transparent support for all alsa based applications. I dont
> care about syncronization or transmission delay. Any pointers as how
> this could be done in alsa ?

I plan to add network support to the alsaloop utility (in the current 
repository of the alsa-utils package) using the snd-aloop loopback kernel
module on the playback (producer) side. This solution would be 100% 
transparent for all current ALSA apps. But I don't have any estimate when 
I start the work on this. Any volunteer? I think that it would be best to 
use the RTP UDP streaming.

 						Jaroslav

-----
Jaroslav Kysela <perex@perex.cz>
Linux Kernel Sound Maintainer
ALSA Project, Red Hat, Inc.

Re: alsa virtual sound card (with networked output)

[Metyl Methylius]

The main reason I can't use pulseaudio it's because it won't even
compile on the embedded platform i'm running (openwrt). Also
pulseaudio it's overcomplicated for such a straightforward task. I was
hoping that a simpler solution would exist.

Metyl

On Tue, Jan 11, 2011 at 4:35 PM, Colin Guthrie <gmane@colin.guthr.ie> wrote:
> 'Twas brillig, and Metyl Methylius at 11/01/11 14:51 did gyre and gimble:
>> Hello everyone,
>>
>> I was wondering if its possible to just create a "virtual" sound card
>> using alsa which will just sent its audio stream to other computer
>> (using TCP/IP or UDP for example). On the other end there would be
>> some kind of server (or just nc -u -l -p 31337 | aplay ). I want to do
>> it on alsa layer because other aps using alsa will get immediate
>> support.
>>
>> It should be something like described in
>>
>> http://alsa.opensrc.org/index.php/Network
>>
>> but with transparent support for all alsa based applications. I dont
>> care about syncronization or transmission delay. Any pointers as how
>> this could be done in alsa ?
>
> Any particular reason you cannot use PulseAudio? It support usage from
> existing ALSA apps and also works automatically with SSH by
> piggy-backing connection settings on X11 root windows which are
> accessable when the remote connection has X11 forwarding enabled.
>
>> This mess was sent using 100% recycled electrons. If you want to get
>> rid of this mess just turn off your computer,
>
> :)
>
> --
>
> Colin Guthrie
> gmane(at)colin.guthr.ie
> http://colin.guthr.ie/
>
> Day Job:
>  Tribalogic Limited [http://www.tribalogic.net/]
> Open Source:
>  Mageia Contributor [http://www.mageia.org/]
>  PulseAudio Hacker [http://www.pulseaudio.org/]
>  Trac Hacker [http://trac.edgewall.org/]
>
> _______________________________________________
> Alsa-devel mailing list
> Alsa-devel@alsa-project.org
> http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
>



-- 
This mess was sent using 100% recycled electrons. If you want to get
rid of this mess just turn off your computer,

Re: alsa virtual sound card (with networked output)

[Metyl Methylius]

On Tue, Jan 11, 2011 at 5:33 PM, Jaroslav Kysela <perex@perex.cz> wrote:
> On Tue, 11 Jan 2011, Metyl Methylius wrote:
>
>> Hello everyone,
>>
>> I was wondering if its possible to just create a "virtual" sound card
>> using alsa which will just sent its audio stream to other computer
>> (using TCP/IP or UDP for example). On the other end there would be
>> some kind of server (or just nc -u -l -p 31337 | aplay ). I want to do
>> it on alsa layer because other aps using alsa will get immediate
>> support.
>>
>> It should be something like described in
>>
>> http://alsa.opensrc.org/index.php/Network
>>
>> but with transparent support for all alsa based applications. I dont
>> care about syncronization or transmission delay. Any pointers as how
>> this could be done in alsa ?
>
> I plan to add network support to the alsaloop utility (in the current
> repository of the alsa-utils package) using the snd-aloop loopback kernel
> module on the playback (producer) side. This solution would be 100%
> transparent for all current ALSA apps. But I don't have any estimate when I
> start the work on this. Any volunteer? I think that it would be best to use
> the RTP UDP streaming.
>

That sounds very interesting. Still there is minor problem with RTP as
I've found in rfc3551 that at least there defined RAW audio encodings - L8
and L16 - supports only 8 and 16-bit wide samples (how to support 24
or 32-bit audio ?).
Which RTP library do you plan to use unless you wanted to integrate
RTP code directly into alsaloop ?

metyl

Re: alsa virtual sound card (with networked output)

[Jassi Brar]

On Tue, Jan 11, 2011 at 11:51 PM, Metyl Methylius <the.metyl@gmail.com> wrote:
> Hello everyone,
>
> I was wondering if its possible to just create a "virtual" sound card
> using alsa which will just sent its audio stream to other computer
> (using TCP/IP or UDP for example). On the other end there would be
> some kind of server (or just nc -u -l -p 31337 | aplay ). I want to do
> it on alsa layer because other aps using alsa will get immediate
> support.
>
> It should be something like described in
>
> http://alsa.opensrc.org/index.php/Network
>
> but with transparent support for all alsa based applications. I dont
> care about syncronization or transmission delay. Any pointers as how
> this could be done in alsa ?

If anything in kernel space, I'd suggest we have Audio-Over-Ethernet(AOE).
Audio-Over-IP(AOIP) isn't much useful for commercial application requiring
low-latencies, besides that can be done from User-Space like PulseAudio.