[pulseaudio-discuss] Receiving RTP streams with pulseaudio

[Rémi Denis-Courmont]

On Tue, 17 May 2011 21:51:35 +0200, Michael Trunner <michael at trunner.de>
wrote:
> I'm trying to setup Pulseaudio to receive RTP/Multicast steams. Sender
> should be vlc, (and receiver should be pulseaudio). I activated
> module-rtp-recv (and module-rtp-send) with papref, but I can't get it
> work. Can some one explain me what I have to do? Or how to debug it.

First you need to make sure that VLC uses an RTP payload format that
PulseAudio understands, typically L16/44100/2 (signed big endian 16-bits
stereo at 44100 Hz). By default, VLC will not decode the audio. Also make
sure SAP is enabled.

For example:
# IP=224.0.0.42
# vlc --sout-keep --no-sout-video --no-sout-spu \
      --sout
"#transcode{acodec=s16b,samplerate=44100}:gather:rtp{sap,dst=$IP}"

Then you need to configure PulseAudio to use the standard SAP address as
specified in IETF RFC2974 §3, corresponding to the multicast scope that VLC
is configured to use, in particular:
- 224.2.127.254 (SAP.MCAST.NET) for global IPv4,
- ff0e::2:7ffe for global IPv6,
- 224.0.0.255 for link-local IPv4,
- ff02::2:7ffe for link-local IPv6.

By default, PulseAudio uses a proprietary non-standard SAP group, namely
224.0.0.56. This cannot interoperate with VLC.

-- 
Rémi Denis-Courmont
http://www.remlab.net/