[gstreamer-bugs] [Bug 576381] New: [basesink] QoS: emergency rendering not always done

[GStreamer (bugzilla.gnome.org)]

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  GStreamer | gstreamer (core) | Ver: git
           Summary: [basesink] QoS: emergency rendering not always done
           Product: GStreamer
           Version: git
          Platform: Other
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gstreamer (core)
        AssignedTo: gstreamer-bugs at lists.sourceforge.net
        ReportedBy: t.i.m at zen.co.uk
         QAContact: gstreamer-bugs at lists.sourceforge.net
     GNOME version: Unspecified
   GNOME milestone: Unspecified


Consider a situation where a video decoder is very very slow, *much* slower
than the desired framerate. The decoder supports QoS, yet still only the very
first frame is ever rendered; no 'emergency renderings' are done, because all
buffers but the very first are late and the code in gst_base_sink_is_too_late()
goes like this:

     /* !!emergency!!, if we did not receive anything valid for more than a 
      * second, render it anyway so the user sees something */
     if (priv->last_in_time && start - priv->last_in_time > GST_SECOND) {
      late = FALSE;
      GST_DEBUG_OBJECT (basesink,
          "**emergency** last buffer at %" GST_TIME_FORMAT " > GST_SECOND",
          GST_TIME_ARGS (priv->last_in_time));
    }

The problem is the priv->last_in_time != 0 check here. priv->last_in_time is
updated whenever a frame/buffer is actually rendered (normal or emergency), so
if only the very first frame with a timestamp of 0 ever got rendered, no
emergency renderings will be done ever again, unless a buffer actually arrives
in time, which would set last_in_time to something non-0.

I think this should be:

     /* !!emergency!!, if we did not receive anything valid for more than a 
      * second, render it anyway so the user sees something */
-    if (priv->last_in_time && start - priv->last_in_time > GST_SECOND) {
+    if (priv->last_in_time != -1 && start - priv->last_in_time > GST_SECOND) {

instead (or maybe the last_in_time check should just be dropped at all?).

I will attach two logs that demonstrate the problem.


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