Why udpsrc can't get the IPTV stream(UDP package)?

[tanzhichaoanuo]

Hello everyone:
I want to receive and play the IPV muticast stream(H264 TS stream *based on
rtp*.) with udpsrc,When I use 
*"tcpdump -i eth0" *,I get the following infor :
09:11:55.138926 IP 61.181.150.102.12502 > 225.1.2.2.8034: UDP, length 1348 
09:11:55.142901 IP 61.181.150.102.12502 > 225.1.2.2.8034: UDP, length 1348 
09:11:55.146890 IP 61.181.150.102.12502 > 225.1.2.2.8034: UDP, length 1348 
09:11:55.150871 IP 61.181.150.102.12502 > 225.1.2.2.8034: UDP, length 1348 
09:11:55.154911 IP 61.181.150.102.12502 > 225.1.2.2.8034: UDP, length 1348 
09:11:55.160492 IP 61.181.150.102.12502 > 225.1.2.2.8034: UDP, length 1348 
09:11:55.164337 IP 61.181.150.102.12502 > 225.1.2.2.8034: UDP, length 1348 

But When I use ：

gst-launch -v gstrtpbin name=rtpbin udpsrc caps="application/x-rtp, \ 
media=(string)video, clock-rate=(int)90000, encoding-name=(string)MP2T-ES, \
ssrc=(guint)1253787951, payload=(int)33, clock-base=(guint)3847989125, \
seqnum-base=(guint)25200" multicast-group=225.1.2.10 port=8050 ! \
rtpbin.recv_rtp_sink_0 rtpbin. ! rtpmp2tdepay ! mpegtsdemux name=d ! queue \
! ffdec_h264 ! ffmpegcolorspace ! videoscale ! queue ! xvimagesink

Setting pipeline to PAUSED ...
Pipeline is live and does not need PREROLL ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock
*---------Stop here,can't get anything.*

*But VLC on windows can receive an play the stream.*

      According to Wim Taymans‘s  suggestion in the forum,*I use the only
Command:*
"gst-launch-0.10 udpsrc  multicast-group=225.1.2.2  port=8034 ... ! fakesink
-v "

*to test the udpsrc plugin*,I still can't get anything,and still stop at:

Setting pipeline to PAUSED ...
Pipeline is live and does not need PREROLL ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock

    *So which reasons will result udpsrc can't get anything but tcpdump or
VLC can ? *
    And if the  length  of UDP layer in the stream package *was 1328 (not
1348*),then I can get and play the stream with udpsrc,Why will this ?
  
     More detailed information can find at the following link:
http://gstreamer-devel.966125.n4.nabble.com/How-to-play-IPTV-streamer-by-udpsrc-td4632303.html#a4632425
  
         Thanks very much.

                                                                                              
Regards. zhichao.
 

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