[Bug 704946] New: appsink/funnel/playbin: Buffers show up late at the appsink if their times are out of order

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=704946
  GStreamer | gst-plugins-base | git

           Summary: appsink/funnel/playbin: Buffers show up late at the
                    appsink if their times are out of order
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-base
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: self at brendanlong.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


Created an attachment (id=250222)
 --> (https://bugzilla.gnome.org/attachment.cgi?id=250222)
Example of playbin+funnel+appsink

This is causing problems for me in WebKit:
https://bugs.webkit.org/show_bug.cgi?id=103771

I'm trying to use a funnel in playbin to mix all of the text streams, then get
them out with an appsink. The problem is that the order of the buffer is fairly
random if they show up at the same time (the funnel could send multiple buffers
from one stream before the first buffer in another stream), and I don't get
buffers at my appsink until it's time to present them (meaning any buffer that
was out of order may show up too late to be displayed, because it's waiting for
another later buffer to be displayed).

An example is attached, run it on this file (download it, this issue happens
less often when streaming):

https://github.com/WebKit/webkit/raw/master/LayoutTests/media/content/counting-subtitled.m4v

Then using the attached file:

    gst-git python3 playbin-funnel.py file://$PWD/counting-subtitled.m4v

I get output like this:

Got sample at 00.33: 00.33 --> 00.67 Two
Got sample at 00.33: 00.33 --> 00.67 Deux
Got sample at 00.67: 00.67 --> 01.00 Trois
Got sample at 01.00: 01.00 --> 01.33 Quatre
Got late sample at 01.00: 00.67 --> 01.00 Three
Got sample at 01.33: 01.33 --> 01.67 Cinq
Got sample at 01.67: 01.67 --> 02.00 Six
Got sample at 02.00: 02.00 --> 02.33 Seven
Got late sample at 01.33: 01.00 --> 01.33 Four
Got late sample at 01.67: 01.33 --> 01.67 Five
Got late sample at 02.00: 01.67 --> 02.00 Six
Got sample at 02.00: 02.00 --> 02.33 Seven
Got sample at 02.33: 02.33 --> 02.67 Eight
Got sample at 02.67: 02.67 --> 03.00 Nine
Got sample at 03.00: 03.00 --> 03.33 Ten
Got sample at 03.33: 03.33 --> 03.67 Eleven
Got sample at 03.67: 03.67 --> 04.00 Twelve
Got sample at 04.00: 04.00 --> 04.33 Thirteen
Got sample at 04.33: 04.33 --> 04.67 Fourteen
Got sample at 04.67: 04.67 --> 05.00 Fifteen
Got sample at 05.00: 05.00 --> 05.33 Sixteen
Got sample at 05.33: 05.33 --> 05.67 Seventeen
Got sample at 05.67: 05.67 --> 06.00 Eighteen
Got late sample at 02.67: 02.33 --> 02.67 Huit
Got late sample at 03.00: 02.67 --> 03.00 Nine
Got late sample at 03.33: 03.00 --> 03.33 Ten
Got late sample at 03.67: 03.33 --> 03.67 Onze
Got late sample at 04.00: 03.67 --> 04.00 Douze
Got late sample at 04.33: 04.00 --> 04.33 Thirteen
Got late sample at 04.67: 04.33 --> 04.67 Quatorze
Got late sample at 05.00: 04.67 --> 05.00 Quinze
Got late sample at 05.33: 05.00 --> 05.33 Seize
Got late sample at 05.67: 05.33 --> 05.67 Seventeen
Got sample at 05.67: 05.67 --> 06.00 Dix-huit
Got sample at 06.00: 06.00 --> 06.33 Nineteen
Got sample at 06.33: 06.33 --> 06.67 Vingt
Got sample at 06.67: 06.67 --> 07.00 Vingt et un
Got sample at 07.00: 07.00 --> 07.33 Vingt-deux
Got sample at 07.33: 07.33 --> 07.67 Vingt-trois
Got late sample at 06.33: 06.00 --> 06.33 Nineteen
Got late sample at 06.67: 06.33 --> 06.67 Twenty
Got late sample at 07.00: 06.67 --> 07.00 Twenty one
Got late sample at 07.33: 07.00 --> 07.33 Twenty two
Got sample at 07.34: 07.33 --> 07.67 Twenty three
Got sample at 07.67: 07.67 --> 08.00 Twenty four
Got sample at 08.00: 08.00 --> 08.33 Twenty five
Got sample at 08.33: 08.33 --> 08.67 Twenty six
Got sample at 08.67: 08.67 --> 09.00 Twenty seven
Got sample at 09.00: 09.00 --> 09.33 Twenty eight
Got sample at 09.33: 09.33 --> 09.67 Twenty nine
Got late sample at 08.00: 07.67 --> 08.00 Vingt-quatre
Got late sample at 08.33: 08.00 --> 08.33 Vingt-cinq
Got late sample at 08.67: 08.33 --> 08.67 Vingt-six
Got late sample at 09.00: 08.67 --> 09.00 Vingt-sept
Got sample at 09.67: 09.67 --> 10.80 Thirty
Got late sample at 09.33: 09.00 --> 09.33 Vingt-huit
Got late sample at 09.67: 09.33 --> 09.67 Vingt-neuf
Got sample at 09.67: 09.67 --> 10.00 Trente
EOS

"late" in this output means "so late that the cue won't be displayed at all"
(current_time >= end_time).

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