[gstreamer-bugs] [Bug 631633] New: [oggdemux] fix seeking with negative rate with skeleton

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=631633
  GStreamer | gst-plugins-base | git

           Summary: [oggdemux] fix seeking with negative rate with
                    skeleton
    Classification: Desktop
           Product: GStreamer
           Version: git
        OS/Version: All
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-base
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: gemont at igalia.com
         QAContact: gstreamer-bugs at lists.sourceforge.net
      GNOME target: ---
     GNOME version: ---


Files with a skeleton, or other files with a stream that ends before the end of
the chain would start playing from the end of the chain when trying to seek
with
a negative rate at a position between the end of any stream and the end of the
chain.

Way to reproduce:
 1. Load an ogg version of Monty's "A Digital Media Primer For Geeks" as
distributed on xiph's site[1] with the seek example from tests/examples/seek.
 2. Try seeking with a negative rate

Expected result: Monty speaks backwards from the selected time in the video (by
default, where the video was being played previously)

What happens: playback starts from the end of the video.

With the attached patch applied, we get the expected result.


I didn't do measurement, but I believe this bug also slows down seeking, since
the demuxer spends time looking for a keyframe that doesn't exist.

Explanations on the code are in the commit message and in comments, in the
attached patch.


[1] http://downloads.xiph.org/video/A_Digital_Media_Primer_For_Geeks-360p.ogv

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