[Live-devel] Help with multicast

[Ross Finlayson]

>I have some questions about multicast that hope someone can help me with.
>
>I need to transmit a mpeg4 video using multicast and for doing that 
>I'm using the "-m" option in wis-streamer.
>Doing that and using Wireshark I can see the multicast packets but 
>if I try to watch the video connecting to the multicast address 
>using VLC I see nothing, but, if I use the RTSP option in VLC then I 
>can see the video.

So then what's the problem?  If RTSP works for you, then why not 
continue to use that?

Note that RTSP tells the client not only the multicast address and 
port number to subscribe to, but also (in the SDP description) 
important details about the codec that is being streamed.  (Note, in 
particular, the "config=" parameter, which contains important 
information for the client's MPEG-4 decoder.)

Even though VLC (apparently) allows you to subscribe to a multicast 
stream merely by specifying its address and port number, this will 
work only for certain simple codecs that are 'hard wired' into VLC. 
(However, I remind people yet again that VLC is not our software, and 
questions about VLC should be posted to a VLC mailing list.)


>With RTSP the SDP info is as following:
>
>v=0
>o=- 952047184189632 1 IN IP4 192.168.1.95
>s=RTSP/RTP stream
>i=mpeg4
>t=0 0
>a=tool:LIVE555 Streaming Media v2008.04.02
>a=type:broadcast
>a=control:*
>a=source-filter: incl IN IP4 * 192.168.1.95
>a=rtcp-unicast: reflection
>a=range:npt=0-
>a=x-qt-text-nam:RTSP/RTP stream from DaVinci EVM
>a=x-qt-text-inf:mpeg4
>m=audio 6002 RTP/AVP 96
>c=IN IP4 232.36.244.217/255
>a=rtpmap:96 L16/8000
>a=control:track1
>m=video 6000 RTP/AVP 97
>c=IN IP4 232.36.244.217/255
>a=rtpmap:97 MP4V-ES/90000
>a=fmtp:97 
>profile-level-id=1;config=000001B001000001B509000001010000012000844007A94022D0A21F
>a=control:track2
>
>And the SETUP says:
>
>Transport: 
>RTP/AVP;multicast;destination=232.36.244.217;source=192.168.1.95;port=6002-6003;ttl=255
>
>Does it mean I am really transmiting in multicast?

Yes.

>  shouldn't I be able to connect directly to the multicast address?

Yes, but the way to do this is to use RTSP (see above).
-- 

Ross Finlayson
Live Networks, Inc.
http://www.live555.com/
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