[gstreamer-bugs] [Bug 576739] New: A/V sync error when seeking RTSP/RTP streams

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-bad | Ver: 0.10.21
           Summary: A/V sync error when seeking RTSP/RTP streams
           Product: GStreamer
           Version: 0.10.21
          Platform: Other
        OS/Version: All
            Status: UNCONFIRMED
          Severity: critical
          Priority: Normal
         Component: gst-plugins-bad
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: javier.galvez.guerrero at gmail.com
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: 2.23/2.24
   GNOME milestone: Unspecified


Please describe the problem:
While receiving a RTSP/RTP stream, if the stream is sought the video stream is
shown properly, while there is no sound for a while (~3 seconds). Then the
buffered audio starts playing at double(?) speed till it synchronizes with the
video, which has been played smoothly all the time.

It can be depicted like this:

Video        Audio

00:00         00:00
-(playing)      - (playing)
-               -
-               -
-               -
00:23        00:23
(seek)       (seek)
01:20        (silence)
- (seamless) (silence)
-            (silence)
01:23        01:20 (not synchronized)
-                 = (x2)
-                 = (x2)
01:26        01:26 (synchronized)
-                 -
-                 -
-                 -
...               ... 

At the time of seeking (PLAY RTSP message with the proper 'ntp' parameter sent
and Reply received), at the client side this message is prompted:

GStreamer-CRITICAL **: gst_clock_set_calibration: assertion `internal <=
gst_clock_get_internal_time (clock)' failed.

Seeking the same content in a local environment works with no issues.

Steps to reproduce:
1. Set up a RTSP server (tested with VLC 0.9.4) with a VoD content.
2. Start playing the content with gstreamer.
3. Seek to any point in time of the streamed media.


Actual results:
Video is gapless but audio remains silently buffering, then plays at double
speed till it synchronizes with the video and then both audio and video
continue the playback properly.

Expected results:
Both the video and audio jump to the asked position in a synchronized way.

Does this happen every time?
NEARLY every time i tried (9 out of 10).

Other information:
I've been told that this bug has already been reported but I couldn't find it,
so I file it just in case.


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