[gstreamer-bugs] [Bug 442557] New: [videorate] doesn't handle latency queries

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gst-plugins-base | Ver: HEAD CVS
           Summary: [videorate] doesn't handle latency queries
           Product: GStreamer
           Version: HEAD CVS
          Platform: Other
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-base
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: bilboed at bilboed.com
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


videorate should handle latency queries since it's delaying the output of the
video frames (it needs to have 2 buffers before knowing which ones to output
with which timestamps).

The hard part is figuring out exactly what value should be added to the
upstream latency.

It should at least be the duration of one output frame (ie 1/output_framerate
seconds), but that might not be enough.

If you have an constant input framerate which is lower, then you should be
adding the duration of one of the input framerate (ie 1/input_framerate
seconds).

The really tricky part is for non-constant incoming framerates (a webcam for
example, or an rtp source which can have frame dropped). Then you have no way
of knowing how much latency is introduced.


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