[Bug 679664] New: [matroska demux] wrong time stamp given if divx/xvid encoded in mkv container
GStreamer (bugzilla.gnome.org)
bugzilla at gnome.org
Tue Jul 10 00:04:00 PDT 2012
https://bugzilla.gnome.org/show_bug.cgi?id=679664
GStreamer | gst-plugins-good | 0.10.29
Summary: [matroska demux] wrong time stamp given if divx/xvid
encoded in mkv container
Classification: Platform
Product: GStreamer
Version: 0.10.29
OS/Version: Linux
Status: UNCONFIRMED
Severity: normal
Priority: Normal
Component: gst-plugins-good
AssignedTo: gstreamer-bugs at lists.freedesktop.org
ReportedBy: bcxa.sz at gmail.com
QAContact: gstreamer-bugs at lists.freedesktop.org
GNOME version: ---
I have one stream whose codec is xvid encoded, which have B picture inside.
I looked at the way of gstreamer native mkv demux to give time stamp:
buffer time = (cluster_time + time) * demux->time_scale;
So the gstreamer native mkv demux will not consider the display order of
frames.
So in I P B B case (decoding order):
the P timestamp can be 2 second, and B time stamp can be 3 second, even though
the B should be displayed before the P.
And if downstream element think coming buffer time stamp is display time
information, then it will be wrong.
So here the 1st question: whether the buffer time stamp from demux element is
decoding time stamp or presentation time stamp?
I backed to ffmpeg to see how ffmpeg handle the divx in mkv container: I saw it
will detect the frame type and only take B frame's decoding time (the same way
as gstreamer native mkv demux caculate from cluster time and block time) as
presentation time. For P and I frame, invalid time stamp is given.
Here the 2nd question: whether gstreamer native mkv demux should adopt the same
strategy as ffmpeg? detect frame type and give correct PTS as buffer time
stamp?
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