[Bug 685279] New: DVD still frames need a way to never be dropped by QOS

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=685279
  GStreamer | gstreamer (core) | git

           Summary: DVD still frames need a way to never be dropped by QOS
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: Normal
         Component: gstreamer (core)
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: thaytan at mad.scientist.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


If playback is running late (because things are slow coming off the disc, or
any of the usual CPU-busy reasons) then DVD still frames can get dropped - and
the presentation will pause and show whichever was the last frame to make it to
the DVD SPU, making menus look weird (button highlights on some random intro
frame).

To fix it, I think we need a buffer flag 'GST_BUFFER_FLAG_NOT_DROPPABLE' that
can be set on a frame by the MPEG decoder. I think (from memory, may be wrong)
it is required that all still frames be an I frame followed by an END packet,
so an MPEG decoder could store a ref to the most recent keyframe, and output
the frame when seeing an inbound still frame event, setting the NOT_DROPPABLE
flag. I think it would have to do this unconditionally though, as downstream
elements (might have dropped the frame).

Alternatively, the MPEG decoder could always set the NOT_DROPPABLE frame on
outbound keyframes.

Comments?

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