rtp sout: fix RTSP track numbering in SDP

Add a helper to get the right values from the RTSP code

modules/stream_out/rtp.c

@@ -833,11 +833,12 @@ char *SDPGenerate( const sout_stream_t *p_stream, const char *rtsp_url )
 
         if( rtsp_url != NULL )
         {
-            assert( strlen( rtsp_url ) > 0 );
-            bool addslash = ( rtsp_url[strlen( rtsp_url ) - 1] != '/' );
-            sdp_AddAttribute ( &psz_sdp, "control",
-                               addslash ? "%s/trackID=%u" : "%strackID=%u",
-                               rtsp_url, i );
+            char *track_url = RtspAppendTrackPath( id->rtsp_id, rtsp_url );
+            if( track_url != NULL )
+            {
+                sdp_AddAttribute ( &psz_sdp, "control", "%s", track_url );
+                free( track_url );
+            }
         }
         else
         {

modules/stream_out/rtp.h

@@ -34,6 +34,8 @@ rtsp_stream_id_t *RtspAddId( rtsp_stream_t *rtsp, sout_stream_id_t *sid,
                              unsigned loport, unsigned hiport );
 void RtspDelId( rtsp_stream_t *rtsp, rtsp_stream_id_t * );
 
+char *RtspAppendTrackPath( rtsp_stream_id_t *id, const char *base );
+
 char *SDPGenerate( const sout_stream_t *p_stream, const char *rtsp_url );
 
 uint32_t rtp_compute_ts( const sout_stream_id_t *id, int64_t i_pts );

modules/stream_out/rtsp.c

@@ -179,6 +179,19 @@ struct rtsp_strack_t
 };
 
 
+char *RtspAppendTrackPath( rtsp_stream_id_t *id, const char *base )
+{
+    assert( ( strlen( base ) > 0 && base[strlen( base ) - 1] == '/' )
+            ^ ( id->stream->track_sep[0] == '/' ) );
+
+    char *url;
+    if( asprintf( &url, "%s%strackID=%u", base, id->stream->track_sep,
+                  id->track_id ) == -1 )
+        url = NULL;
+    return url;
+}
+
+
 rtsp_stream_id_t *RtspAddId( rtsp_stream_t *rtsp, sout_stream_id_t *sid,
                              uint32_t ssrc,
                              /* Multicast stuff - TODO: cleanup */