[pulseaudio-discuss] Controlling where module-rtp-send sends multicast packets?

Jon Smirl jonsmirl at gmail.com
Fri Feb 15 06:04:19 PST 2008

On 2/15/08, Matthew Patterson <matt at v8zman.com> wrote:
> Hello all,
>  I just discovered PulseAudio about 2 weeks ago and was struck by how
>  applicable it could be in creating a whole home audio solution where
>  each room can subscribe to the same or a different audio stream as
>  another room. To create this I setup 4 mpd instances, each talking to a
>  different rtp-send module. Then on the playback side there are 4
>  rtp-recv modules that can connect to each of the multicast streams. I
>  have all of this functioning and have written a small python app to
>  configure the modules via the unix socket cli connection. All of this is
>  implemented on one machine so I have the rtp-send modules looping back
>  the data.

I'm working on dedicated hardware for a Linux based multi-room audio
solution. We're still doing the low level stuff like Ethernet and ALSA
drivers. It will be about six months before the hardware is ready. The
project is hacker friendly and has a RSS feed so that you can follow
the project.


We use powerline networking so that all of the traffic stays off the
home network. It can also be controlled by IR remotes or powerline
based wall switches. Integrated digital 100W amp with no internal
DA/AD losses.

We originally tried to build the net using wireless but there are a
lot of hidden reliability problems with wireless. We wasted six months
chasing wireless and then gave up.

A decent base for building building a multi-room system today is an
Efika. The MPC5200 on the Efika has a floating point unit. Without the
FPU you end up having to rewrite things in fixed/asm all of the time.
For example ReplayGain support in mpd uses float.

You can also use x86 boxes but they are more expensive and usually
have fans. All of the MPC5200 boards are fanless.

>  Now for my question: This implementation obviously spews a lot of
>  multicast traffic onto my network. I didn't think this would be a
>  problem, but my router/ap/switch seems to crap out when it gets hammered
>  with all the traffic. Is there any way that I can specify which
>  interface pulesaudio sends its multicast packets on? Or even more
>  ideally, can I disable all outgoing multicast traffic and just have the
>  local loopback happening?
>  I have attempted to configure the kernel routing tables on my ubuntu
>  (7.10) install, but with no change. I still see all the multicast
>  packets going out the interface (using ethereal on another machine to
>  check).
>  I have pulseaudio version 0.9.9 that I compiled myself.
>  Thank you to the authors of this awesome software package!
>  Matt
>  P.S. If anyone is interested in my little whole home audio project I am
>  perfectly happy to share my rather hackish python/php code and maybe get
>  a little help.
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Jon Smirl
jonsmirl at gmail.com

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