Can I test my understanding of the testMPEG4VideoStreamer multicast sample application and ask a question on the server media session reference count ?
testMPEG4VideoStreamer creates an RTSP server to stream test.m4e and reports 'Play using this stream using the URL ...'. The URL is of the form RTSP://<Source_IP_Addr>:8554/testStream, which is a unicast address. When connecting using VLC the RTSP SETUP response provides the multicast address with the line: Transport: RTP/AVP;multicast;destination=<Source Specific Multicast Address>;source=<Source_IP_Addr>;port=1234-1235;ttl=1 Using wireshark I can see the image data is being sent from the source address to the multicast address. The FAQ mentions that the testMPEG4VideoStreamer program incorporates an RTSP server to provide the SDP description - is this why the RTP multicast stream is accessed using the RTSP unicast address ? VLC instructions (http://www.videolan.org/doc/play-howto/en/ch04.html) suggest an RTP multicast stream can be received using rtp://@<multicast_addr>:1234/, however VLC does not display a video stream when this address is used - is this because it cannot decode the stream as it doesn't have the information required ? I am extending a program (a camera application running on Embedded Linux and using live555 to server the video streams) that we have been using to provide multiple unicast streams (MPEG4, H.264, JPEG (sorry - its for Onvif standard compliance)) at different resolutions. The aim is to allow some of the streams to be multicast streams (either SSM or non-SSM) and the rest unicast. I am testing this on a LAN with simple unmanaged switches and have set ttl to 1 to avoid issues with routers. On start-up the camera joins the multicast group(s) (one for every stream that is set to use multicast) with an IGMP v2 Membership Report (0x16); When each VLC client connects the PC it is running on joins the multicast group for the stream requested (if it is not already a member) with an IGMP v2 Membership Report (0x16); Each connection to RTSP://<Source_IP_Addr>:8554/streamN produces the RTSP Options, Describe, Setup, Play sequence; Each connection causes that stream's ServerMediaSession reference count to increase; When each connection is closed that stream's ServerMediaSession reference count decreases; When all connections from one PC are closed we get an RTSP Teardown followed by an IGMP v2 Leave Group (0x17) (from the PC); When the program on the camera stops the live555 event thread / closes the RTSP server we get an IGMP v2 Leave Group (0x17) (from the camera). Each stream's ServerMediaSession reference count (from sms->referenceCount(), where sms was created with ServerMediaSession *sms = ServerMediaSession::createNew(...) ) increments with each new multicast connection. Is this a count of the number of clients not a count of the number of streams being sent ? Many thanks, Piers Hawksley _______________________________________________ live-devel mailing list live-devel@lists.live555.com http://lists.live555.com/mailman/listinfo/live-devel
