rtspsrc: Consistently set seqnums on events

Set udpsrc seqnums on all events sent to the udpsrc's, and before
forwarding events out of rtspsrc set the latest seek seqnum on them if
any.

Also produce a consistent seqnum in rtspsrc from the very beginning.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3409>

subprojects/gst-plugins-good/gst/rtsp/gstrtspsrc.c

@@ -2779,8 +2779,7 @@ gst_rtspsrc_set_state (GstRTSPSrc * src, GstState state)
 }
 
 static void
-gst_rtspsrc_flush (GstRTSPSrc * src, gboolean flush, gboolean playing,
+gst_rtspsrc_flush (GstRTSPSrc * src, gboolean flush, gboolean playing)
-    guint32 seqnum)
 {
   GstEvent *event;
   gint cmd;
@@ -2788,13 +2787,11 @@ gst_rtspsrc_flush (GstRTSPSrc * src, gboolean flush, gboolean playing,
 
   if (flush) {
     event = gst_event_new_flush_start ();
-    gst_event_set_seqnum (event, seqnum);
     GST_DEBUG_OBJECT (src, "start flush");
     cmd = CMD_WAIT;
     state = GST_STATE_PAUSED;
   } else {
     event = gst_event_new_flush_stop (TRUE);
-    gst_event_set_seqnum (event, seqnum);
     GST_DEBUG_OBJECT (src, "stop flush; playing %d", playing);
     cmd = CMD_LOOP;
     if (playing)
@@ -2927,7 +2924,7 @@ gst_rtspsrc_perform_seek (GstRTSPSrc * src, GstEvent * event)
    * blocking in preroll). */
   if (flush) {
     GST_DEBUG_OBJECT (src, "starting flush");
-    gst_rtspsrc_flush (src, TRUE, FALSE, gst_event_get_seqnum (event));
+    gst_rtspsrc_flush (src, TRUE, FALSE);
   } else {
     if (src->task) {
       gst_task_pause (src->task);
@@ -2977,7 +2974,7 @@ gst_rtspsrc_perform_seek (GstRTSPSrc * src, GstEvent * event)
   if (flush) {
     /* if we started flush, we stop now */
     GST_DEBUG_OBJECT (src, "stopping flush");
-    gst_rtspsrc_flush (src, FALSE, playing, gst_event_get_seqnum (event));
+    gst_rtspsrc_flush (src, FALSE, playing);
   }
 
   /* now we did the seek and can activate the new segment values */
@@ -3131,15 +3128,13 @@ gst_rtspsrc_update_src_event (GstRTSPSrc * self, GstRTSPStream * stream,
       event = gst_event_new_stream_start (stream_id);
       gst_rtspsrc_stream_start_event_add_group_id (self, event);
       g_free (stream_id);
+
+      gst_event_set_seqnum (event, self->seek_seqnum);
       break;
     }
-    case GST_EVENT_SEGMENT:
+    default:
-      if (self->seek_seqnum != GST_SEQNUM_INVALID) {
       event = gst_event_make_writable (event);
       gst_event_set_seqnum (event, self->seek_seqnum);
-      }
-      break;
-    default:
       break;
   }
 
@@ -5196,8 +5191,8 @@ gst_rtspsrc_stream_push_event (GstRTSPSrc * src, GstRTSPStream * stream,
   if (stream->udpsrc[0]) {
     GstEvent *sent_event;
 
-    if (GST_EVENT_TYPE (event) == GST_EVENT_EOS) {
+    if (stream->segment_seqnum[0] != GST_SEQNUM_INVALID) {
-      sent_event = gst_event_new_eos ();
+      sent_event = gst_event_copy (event);
       gst_event_set_seqnum (sent_event, stream->segment_seqnum[0]);
     } else {
       sent_event = gst_event_ref (event);
@@ -5205,32 +5200,38 @@ gst_rtspsrc_stream_push_event (GstRTSPSrc * src, GstRTSPStream * stream,
 
     res = gst_element_send_event (stream->udpsrc[0], sent_event);
   } else if (stream->channelpad[0]) {
-    gst_event_ref (event);
+    GstEvent *sent_event;
+
+    sent_event = gst_event_copy (event);
+    gst_event_set_seqnum (sent_event, src->seek_seqnum);
+
     if (GST_PAD_IS_SRC (stream->channelpad[0]))
-      res = gst_pad_push_event (stream->channelpad[0], event);
+      res = gst_pad_push_event (stream->channelpad[0], sent_event);
     else
-      res = gst_pad_send_event (stream->channelpad[0], event);
+      res = gst_pad_send_event (stream->channelpad[0], sent_event);
   }
 
   if (stream->udpsrc[1]) {
     GstEvent *sent_event;
 
-    if (GST_EVENT_TYPE (event) == GST_EVENT_EOS) {
-      sent_event = gst_event_new_eos ();
     if (stream->segment_seqnum[1] != GST_SEQNUM_INVALID) {
+      sent_event = gst_event_copy (event);
       gst_event_set_seqnum (sent_event, stream->segment_seqnum[1]);
-      }
     } else {
       sent_event = gst_event_ref (event);
     }
 
     res &= gst_element_send_event (stream->udpsrc[1], sent_event);
   } else if (stream->channelpad[1]) {
-    gst_event_ref (event);
+    GstEvent *sent_event;
+
+    sent_event = gst_event_copy (event);
+    gst_event_set_seqnum (sent_event, src->seek_seqnum);
+
     if (GST_PAD_IS_SRC (stream->channelpad[1]))
-      res &= gst_pad_push_event (stream->channelpad[1], event);
+      res &= gst_pad_push_event (stream->channelpad[1], sent_event);
     else
-      res &= gst_pad_send_event (stream->channelpad[1], event);
+      res &= gst_pad_send_event (stream->channelpad[1], sent_event);
   }
 
 done:
@@ -9460,6 +9461,7 @@ gst_rtspsrc_change_state (GstElement * element, GstStateChange transition)
         goto start_failed;
       break;
     case GST_STATE_CHANGE_READY_TO_PAUSED:
+      rtspsrc->seek_seqnum = gst_util_seqnum_next ();
       /* init some state */
       rtspsrc->cur_protocols = rtspsrc->protocols;
       /* first attempt, don't ignore timeouts */