hi all :          First, thanks to all who helped to solve my problem. Now the "Sender" works fine. I've attached my sample-application for Sender . Now  I want to implement a "Server" ,which receive udp packets from "Sender" and forward these packets to Receiver. I have used the following commends to build a Server.But when I send the video again, I should restart the Server. I want the Server to work all the time, and i don't have to restart it each time I send the video.          Any suggestions?          regards xuxin Server commends:       gst-launch -v gstrtpbin name=rtpbin latency=200 \ udpsrc caps="application/x-rtp,media=(string)video,clock-rate=(int)90000,encoding-name=(string)H264" port=5000 ! rtpbin.recv_rtp_sink_0 \ rtpbin. ! udpsink port=5000 host=172.21.29.177 sync=false ts-offset=0 \ udpsrc caps="application/x-rtp,media=(string)audio,clock-rate=(int)8000,encoding-name=(string)PCMA" port=5002 ! rtpbin.recv_rtp_sink_1 \ rtpbin. ! udpsink port=5002 host=172.21.29.177 sync=false ts-offset=0 ########################### Sender: #include <gst/gst.h> #include <glib.h> #include <unistd.h> #include <stdlib.h> #define SOURCE  "/home/xuxin/desktop/g_p/test/a.avi" #define DEST_HOST  "172.21.29.169" #define VIDEO_PORT 5000 #define AUDIO_PORT 5002 // global declaration GstElement *pipeline,*udpsink0,*udpsink1; GstElement *audio_bin,*video_bin; // gboolean res;//element link GstPadLinkReturn lres;//pad link //bus 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; } static void on_pad_added_rtpbin(GstElement *element, GstPad *pad, gpointer data) {     GstCaps *caps=NULL;     GstStructure *str=NULL;     GstPad *t_pad=NULL;          const gchar* media_type=NULL;     gint clock_rate;     gboolean judgment;     const gchar* encoding_name=NULL;     const gchar* name=NULL;     g_print("**************enter into rtpbin callback ****************\n");     g_assert(pad!=NULL);     caps=gst_pad_get_caps(pad);     g_assert(caps!=NULL);     str=gst_caps_get_structure(caps,0);     g_assert(str!=NULL);          media_type=gst_structure_get_string(str,"media");     g_assert(media_type!=NULL);     g_print("the media type is %s\n",media_type);     //**************test*****************************     name=gst_structure_get_name(str);     g_print("the caps is %s\n",name);     judgment=gst_structure_get_int(str,"clock-rate",&clock_rate);     g_print("clock_rate is :%d\n",clock_rate);     encoding_name=gst_structure_get_string(str,"encoding-name");     g_assert(encoding_name!=NULL);     g_print("the encoding_name is %s\n",encoding_name);     //***********************************************                    //media type audio or video          if (g_strrstr (media_type, "video"))          {                           g_print("rtp catch audio\n");             t_pad = gst_element_get_static_pad (udpsink0, "sink");             g_assert(t_pad!=NULL);                    g_print("get the pad of udpsink0\n");                 lres=gst_pad_link (pad, t_pad);           g_assert (lres == GST_PAD_LINK_OK);           g_print("Dynamic pad created, linking rtpbin/udp1\n");          }          else if(g_strrstr (media_type, "audio"))       {                     g_print("rtp catch video\n");             t_pad = gst_element_get_static_pad (udpsink1, "sink");             g_assert(t_pad!=NULL);                g_print("get the pad of udpsink1\n");             lres=gst_pad_link (pad, t_pad);           g_assert (lres == GST_PAD_LINK_OK);           g_print("Dynamic pad created, linking rtpbin/udp0\n");                          }         else         {             gst_caps_unref (caps);             return;         }      } static void on_pad_added_decodebin(GstElement *decodebin,GstPad *pad,gboolean last,gpointer data) {     GstCaps *caps=NULL;       GstStructure *str=NULL;       GstPad *t_pad=NULL;          const gchar* media_type=NULL;     g_print("**************** enter into the decodebin signal callback **********\n");          g_assert(pad!=NULL);          caps = gst_pad_get_caps (pad);     g_assert(caps!=NULL);       str = gst_caps_get_structure (caps, 0);       g_assert(str!=NULL);              media_type=gst_structure_get_name (str);       g_assert(media_type!=NULL);     g_print("the media type is %s\n",media_type);       //check media type audio or video          if (g_strrstr (media_type, "audio"))          {                           g_print("catch audio in decodebin\n");             t_pad = gst_element_get_static_pad (audio_bin, "sink");             g_assert(t_pad!=NULL);             lres=gst_pad_link (pad, t_pad);           g_assert (lres == GST_PAD_LINK_OK);           g_print("Dynamic pad created, linking decoderbin/queue2\n");                                    }          else if(g_strrstr (media_type, "video"))       {                     g_print("catch video in decodebin\n");             t_pad = gst_element_get_static_pad (video_bin, "sink");             g_assert(t_pad!=NULL);             lres=gst_pad_link (pad, t_pad);           g_assert (lres == GST_PAD_LINK_OK);           g_print("Dynamic pad created, linking decoderbin/queue1\n");                                   }         else         {             g_print("have not get suitable type\n");             gst_caps_unref (caps);             return;         }      } int main(int argc, char **argv) {     GMainLoop *loop;     GstBus *bus;          //pad of rtpbin     GstPad *sink_pad;         GstPad *bin_pad;              GstPad *videopad_src,*videopad_sink;     GstPad *audiopad_src,*audiopad_sink;     //declare elements     GstElement  *filesrc,*decodebin,*gstrtpbin;     //element for video     GstElement *queue1,*x264enc,*rtph264pay;     //element for audio     GstElement *queue2,*audioresample,*audioconvert,*alawenc,*rtppcmapay;          gst_init(&argc, &argv);     loop = g_main_loop_new(NULL, FALSE);          //generate elements     pipeline = gst_pipeline_new("server");     filesrc=gst_element_factory_make("filesrc", "filesrc");     decodebin=gst_element_factory_make("decodebin", "decodebin");     gstrtpbin = gst_element_factory_make("gstrtpbin", "gstrtpbin");     //for video     queue1=gst_element_factory_make("queue", "queue1");     x264enc=gst_element_factory_make("x264enc", "x264enc");     rtph264pay=gst_element_factory_make("rtph264pay", "rtph264pay");     udpsink0=gst_element_factory_make("udpsink", "udpsink0");     //for audio     queue2 = gst_element_factory_make("queue", "queue2");     audioresample = gst_element_factory_make("audioresample", "audioresample");     audioconvert = gst_element_factory_make("audioconvert", "audioconvert");     alawenc = gst_element_factory_make("alawenc", "alawenc");         rtppcmapay = gst_element_factory_make("rtppcmapay", "rtppcmapay");     udpsink1=gst_element_factory_make("udpsink", "udpsink1");          bus = gst_pipeline_get_bus(GST_PIPELINE(pipeline));     gst_bus_add_watch(bus, bus_call, loop);     gst_object_unref(bus);          //set properties of elements     g_object_set(G_OBJECT(filesrc), "location",SOURCE, NULL);         g_object_set(G_OBJECT(udpsink0), "host",DEST_HOST,"port",VIDEO_PORT, NULL);     g_object_set(G_OBJECT(udpsink1), "host",DEST_HOST,"port",AUDIO_PORT, NULL);     //g_object_set(G_OBJECT(udpsink0), "sync",FALSE,NULL);     //g_object_set(G_OBJECT(udpsink1), "sync",FALSE,NULL);         //g_object_set(G_OBJECT(udpsink0), "async", FALSE,NULL);     //g_object_set(G_OBJECT(udpsink1), "async", FALSE,NULL);          //create video_bin     video_bin = gst_bin_new ("videobin");     gst_bin_add_many (GST_BIN (video_bin),queue1,x264enc,rtph264pay,NULL);     res=gst_element_link_many(queue1,x264enc,rtph264pay,NULL);     g_assert (res == TRUE);     //add pad to video_bin     videopad_sink = gst_element_get_static_pad (queue1, "sink");     videopad_src= gst_element_get_static_pad (rtph264pay, "src");         gst_element_add_pad (video_bin,gst_ghost_pad_new ("sink", videopad_sink));     gst_element_add_pad (video_bin,gst_ghost_pad_new ("src",videopad_src));       gst_object_unref (videopad_sink);       gst_object_unref (videopad_src);              //create audio_bin       audio_bin = gst_bin_new ("audiobin");     gst_bin_add_many (GST_BIN (audio_bin),queue2,audioresample,audioconvert,alawenc,rtppcmapay,NULL);     res=gst_element_link_many(queue2,audioresample,audioconvert,alawenc,rtppcmapay,NULL);     g_assert (res == TRUE);     //add pad to audio_bin     audiopad_sink = gst_element_get_static_pad (queue2, "sink");     audiopad_src= gst_element_get_static_pad (rtppcmapay, "src");         res=gst_element_add_pad (audio_bin,gst_ghost_pad_new ("sink", audiopad_sink));     g_assert (res == TRUE);     res=gst_element_add_pad (audio_bin,gst_ghost_pad_new ("src", audiopad_src));     g_assert (res == TRUE);       gst_object_unref (audiopad_sink);       gst_object_unref (audiopad_src);          //add elements into pipeline     gst_bin_add_many(GST_BIN(pipeline),             filesrc,decodebin,audio_bin,video_bin,gstrtpbin,udpsink0,udpsink1,NULL);          //static link filesrc and decoderbin     res=gst_element_link(filesrc,decodebin);         g_assert (res == TRUE);              //get request pad from gstrtpbin and connect with video_bin     bin_pad=gst_element_get_pad(video_bin, "src");     g_assert(bin_pad!=NULL);         sink_pad = gst_element_get_request_pad(gstrtpbin, "recv_rtp_sink_0");     g_assert(sink_pad!=NULL);         lres=gst_pad_link(bin_pad, sink_pad);     g_assert (lres == GST_PAD_LINK_OK);               //get request pad from gstrtpbin and connect with audio_bin     bin_pad=gst_element_get_pad(audio_bin, "src");     g_assert(bin_pad!=NULL);     sink_pad = gst_element_get_request_pad(gstrtpbin, "recv_rtp_sink_1");     g_assert(sink_pad!=NULL);     lres=gst_pad_link(bin_pad, sink_pad);     g_assert (lres == GST_PAD_LINK_OK);     //signal link     g_signal_connect(decodebin, "new-decoded-pad", G_CALLBACK(on_pad_added_decodebin),NULL);              g_signal_connect(gstrtpbin, "pad-added", G_CALLBACK(on_pad_added_rtpbin),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; }  <hr/> <a href="http://qiye.163.com/?ft=2">��ȫ��Ƴ��ҵ��</a>