[Bug 693000] New: codecparsers: mpeg2: fix default quantizer matrix for intra blocks

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=693000
  GStreamer | gst-plugins-bad | git

           Summary: codecparsers: mpeg2: fix default quantizer matrix for
                    intra  blocks
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-bad
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: gb.devel at gmail.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


Created an attachment (id=234969)
 View: https://bugzilla.gnome.org/attachment.cgi?id=234969
 Review: https://bugzilla.gnome.org/review?bug=693000&attachment=234969

codecparsers: mpeg2: fix default quantizer matrix for intra  blocks

Quantizer matrices are encoded in zigzag scan order in the bitstream, but they
are stored in raster scan order when they are parsed. So, default matrices
shall also be prepared in raster scan order if the sequence_header() does not
provide any. Otherwise, we had a mismatch between explicit matrices stored in
raster scan order vs. default matrices that were prepared in zigzag scan order.

There are two ways to fix this issue:
(i) Specify that matrices are stored in zigzag-scan order ;
(ii) Specify that matrices are stored in raster scan order.

The attached patch implements (ii). Some people would prefer (i) because there
is some existing practice, based on incorrect/unspecified behaviour... For
sure, the current codecparser is a mix of (i) [default matrix] and (ii)
[parsed].

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