The string in the below line should be "video".          else if(g_strrstr (gst_structure_get_name (str), "vedio"))       {                       t_pad = gst_element_get_static_pad (multiudpsink2, "sink");              g_print("rtp catch vedio\n");         } Its always better to check the return values, and print the appropriate error messages. Say for in your example you can check if the "t_pad" is created or its NULL. So that you can trace easily. <div class="gmail_quote">2009/6/3 xuxin04072129 <<a href="mailto:xuxin04072129@126.com">xuxin04072129@126.com</a>> <blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> <div> hi all    I come across a problem when sending out vedio through rtp protocol.Last time i ask the same question here and Wim Taymans told me that i had connected to the pad-added signal twice.I should thank him first .Later  I re-write the code , but i get error as flows        Error: internal data flow error. I am new to gstreamer , can anyone help me to check my code and give me some suggestions . Thank you very much. the following is my code /******************************************************  #include <gst/gsth> #include <glib.h> #include <unistd.h> #include <stdlib.h> GstElement *multiudpsink1, *multiudpsink2; static gboolean bus_call (GstBus     *bus,           GstMessage *msg,           gpointer    data) {   GMainLoop *loop = (GMainLoop *) data;   switch (GST_MESSAGE_TYPE (msg)) {     case GST_MESSAGE_EOS:       g_print ("End of stream\n");       g_main_loop_quit (loop);       break;     case GST_MESSAGE_ERROR: {       gchar *debug;       GError *error;       gst_message_parse_error (msg, &error, &debug);       g_free (debug);       g_printerr ("Error: %s\n", error->message);       g_error_free (error);       g_main_loop_quit (loop);       break;     }     default:       break;   }   return TRUE; } // I have rewrite this function static void on_pad_added(GstElement *element, GstPad *pad, gpointer data) {     GstCaps *caps;     GstStructure *str;     GstPad *t_pad;         caps=gst_pad_get_caps(pad);     str=gst_caps_get_structure(caps,0);         //          if (g_strrstr (gst_structure_get_name (str), "audio"))          {                          t_pad = gst_element_get_static_pad (multiudpsink1, "sink");              g_print("rtp catch audio\n");          }          else if(g_strrstr (gst_structure_get_name (str), "vedio"))       {                       t_pad = gst_element_get_static_pad (multiudpsink2, "sink");              g_print("rtp catch vedio\n");         }         else         {             gst_caps_unref (caps);             return;         }                 if (GST_PAD_IS_LINKED (t_pad))       {           gst_caps_unref (caps);             g_object_unref (t_pad);             return;       }       //       else       {           //           gst_pad_link (pad, t_pad);           g_print("Dynamic pad created, linking rtpbin/udp\n");                               gst_caps_unref (caps);                      g_object_unref (t_pad);             return;       }     } int main(int argc, char **argv) {     GMainLoop *loop;     GstBus *bus;     GstPad *pad;     GstCaps *videocap, *audiocap;     GstElement *pipeline, *gstrtpbin, *udpsrc1, *udpsrc2;                 gst_init(&argc, &argv);     loop = g_main_loop_new(NULL, FALSE);         pipeline = gst_pipeline_new("server");     gstrtpbin = gst_element_factory_make("gstrtpbin", "gst_rtpbin");     udpsrc1 = gst_element_factory_make("udpsrc", "udpsrc1");     udpsrc2 = gst_element_factory_make("udpsrc", "udpsrc2");     multiudpsink1 = gst_element_factory_make("multiudpsink", "multiudpsink1");     multiudpsink2 = gst_element_factory_make("multiudpsink", "multiudpsink2");                bus = gst_pipeline_get_bus(GST_PIPELINE(pipeline));     gst_bus_add_watch(bus, bus_call, loop);     gst_object_unref(bus);         videocap = gst_caps_new_simple("application/x-rtp",         "media", G_TYPE_STRING, "video",         "clock-rate", G_TYPE_INT, 90000,         "encoding-name", G_TYPE_STRING, "H264", NULL);             audiocap = gst_caps_new_simple("application/x-rtp",         "media", G_TYPE_STRING, "audio",         "clock-rate", G_TYPE_INT, 8000,         "encoding-name", G_TYPE_STRING, "PCMA", NULL);         g_object_set(G_OBJECT(udpsrc1), "caps", videocap, NULL);     g_object_set(G_OBJECT(udpsrc2), "caps", audiocap, NULL);     g_object_set(G_OBJECT(udpsrc1), "port", 5000, NULL);     g_object_set(G_OBJECT(udpsrc2), "port", 5002, NULL);     g_object_set(G_OBJECT(multiudpsink1), "clients","<a href="http://172.21.29.169:5000" target="_blank">172.21.29.169:5000</a>,<a href="http://172.21.29.168:5000" target="_blank">172.21.29.168:5000</a>", NULL);     g_object_set(G_OBJECT(multiudpsink2), "clients","<a href="http://172.21.29.169:5002" target="_blank">172.21.29.169:5002</a>,<a href="http://172.21.29.168:5002" target="_blank">172.21.29.168:5002</a>", NULL);     g_object_set(G_OBJECT(multiudpsink1), "sync",FALSE, NULL);     g_object_set(G_OBJECT(multiudpsink2), "sync",FALSE, NULL);         gst_caps_unref(videocap);     gst_caps_unref(audiocap);             gst_bin_add_many(GST_BIN(pipeline), udpsrc1, udpsrc2, gstrtpbin, multiudpsink1, multiudpsink2, NULL);         pad = gst_element_get_request_pad(gstrtpbin, "recv_rtp_sink_0");     gst_pad_link(gst_element_get_pad(udpsrc1, "src"), pad);         pad = gst_element_get_request_pad(gstrtpbin, "recv_rtp_sink_1");     gst_pad_link(gst_element_get_pad(udpsrc2, "src"), pad);         g_signal_connect(gstrtpbin, "pad-added", G_CALLBACK(on_pad_added),NULL);            gst_element_set_state(pipeline, GST_STATE_PLAYING);         g_print("Running...\n");     g_main_loop_run(loop);         /* Out of the main loop, clean up nicely */     g_print("Returned, stopping playback\n");     gst_element_set_state(pipeline, GST_STATE_NULL);         g_print("Deleting pipeline\n");     gst_object_unref(GST_OBJECT(pipeline));         return 0; } </div> <hr> <a href="http://qiye.163.com/?ft=2" target="_blank">��ȫ��Ƴ��ҵ��</a> ------------------------------------------------------------------------------ OpenSolaris 2009.06 is a cutting edge operating system for enterprises looking to deploy the next generation of Solaris that includes the latest innovations from Sun and the OpenSource community. Download a copy and enjoy capabilities such as Networking, Storage and Virtualization. Go to: <a href="http://p.sf.net/sfu/opensolaris-get" target="_blank">http://p.sf.net/sfu/opensolaris-get</a> _______________________________________________ gstreamer-devel mailing list <a href="mailto:gstreamer-devel@lists.sourceforge.net">gstreamer-devel@lists.sourceforge.net</a> <a href="https://lists.sourceforge.net/lists/listinfo/gstreamer-devel" target="_blank">https://lists.sourceforge.net/lists/listinfo/gstreamer-devel</a> </blockquote></div>