[pulseaudio-discuss] Receiving RTP streams with pulseaudio

[Maarten Bosmans]

2011/5/18 Colin Guthrie <gmane at colin.guthr.ie>:
> 'Twas brillig, and Rémi Denis-Courmont at 18/05/11 07:37 did gyre and
> gimble:
>> 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.
>
> Many thanks for the info Rémi :)
>
>> By default, PulseAudio uses a proprietary non-standard SAP group, namely
>> 224.0.0.56. This cannot interoperate with VLC.
>
> Interesting. I see from the history:

Then there is also http://www.pulseaudio.org/ticket/436
Can we decide now what to change the default to?

> commit e1887b552ceb324f70732c85c7458119e03718b7
> Author: Lennart Poettering <lennart at poettering.net>
> Date:   Sun Apr 16 11:13:20 2006 +0000
>
>    change default mcast address once again, to make sure our traffic
> doesn't leave the network by default
>
>
> Previously the address was 224.0.1.3
>
>
> The change before that is:
>
> commit c999fe40b841b035c7d0c873b4a4875e12e9c9a4
> Author: Lennart Poettering <lennart at poettering.net>
> Date:   Sun Apr 16 09:15:51 2006 +0000
>
>    * deal properly with underruns, overflows and packet losses
>    * change default mcast address
>    * detect RTP loops
>
> Which had the address as 224.0.1.2. This was the address used when the
> module was committed.
>
>
> This default can be overridden in the module-rtp-recv module with the
> sap_address= argument. And with the module-rtp-send module with the
> destination= argument.
>
>
> Hope that helps.
>
> If you have any recommendations for the defaults, please feel free to
> suggest them, but I guess the intention was to keep the traffic in house
> by default. We should likely expose via paprefs the ability to choose a
> public mutlicast group or something. WDYT?
>
> Col
>
>
>
>
>
>
> --
>
> Colin Guthrie
> gmane(at)colin.guthr.ie
> http://colin.guthr.ie/
>
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