Support seeking as defined by the rfc

a PLAY with Range alone while in PLAY status should be interpreted
as an enqueue
a PAUSE followed by a PLAY with Range is the proper way to ask to
seek to a point.

See rfc2326

Originally committed as revision 19143 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/rtsp.c

@@ -1599,6 +1599,9 @@ static int rtsp_read_seek(AVFormatContext *s, int stream_index,
     case RTSP_STATE_IDLE:
         break;
     case RTSP_STATE_PLAYING:
+        if (rtsp_read_pause(s) != 0)
+            return -1;
+        rt->state = RTSP_STATE_SEEKING;
         if (rtsp_read_play(s) != 0)
             return -1;
         break;

libavformat/rtsp.h

@@ -151,6 +151,7 @@ enum RTSPClientState {
     RTSP_STATE_IDLE,    /**< not initialized */
     RTSP_STATE_PLAYING, /**< initialized and receiving data */
     RTSP_STATE_PAUSED,  /**< initialized, but not receiving data */
+    RTSP_STATE_SEEKING, /**< initialized, requesting a seek */
 };
 
 /**