Created attachment 76905 [details]
python script to listen to SAP announcements from PulseAudio.

I set up two Ubuntu machines, both with PulseAudio. 

In one machine (Ubuntu 12.04), I set it up to act as a network audio device. In the other machine (Ubuntu 12.10), I set it up to use the network audio device.

I took a tcpdump of the traffic going between the two computers. I extracted the PCM audio. I was unable to play it with the parameters from the SAP announcement, which are as follows. The garbled characters were also there in the announcement. I captured the SAP announcement using a small python script (attached).

 u]
�kapplication/sdpv=0
o=william 3572777767 0 IN IP4 192.168.1.23
s=PulseAudio RTP Stream on william-X101CH
c=IN IP4 224.0.0.56
t=3572777767 0
a=recvonly
m=audio 46194 RTP/AVP 10
a=rtpmap:10 L16/44100/2
a=type:broadcast

When I played back the audio I extracted from the tcpdump, I was able to play it like this. As you can see, the parameters are quite different from the SAP announcements.

aplay -t raw -c 2 -f S32_LE -r 44100 myrawaudio.dat

(The parameters from the SAP announcement just caused it to play white noise.)