[Bug 684341] New: [codecparsers vc1] many vc1 stream give corruption image when gst-vaapi is used

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=684341
  GStreamer | gst-plugins-bad | git

           Summary: [codecparsers vc1] many vc1 stream give corruption
                    image when gst-vaapi is used
    Classification: Platform
           Product: GStreamer
           Version: git
        OS/Version: All
            Status: UNCONFIRMED
          Severity: major
          Priority: Normal
         Component: gst-plugins-bad
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: halley.zhao at intel.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


when gstreamer-vaapi is used to playback some vc1 stream, many streams  result
in corruption images.

after some debug, it shows the root reason is: 
ttmbf is not set when vstransform is not set

details see below:
spec 8.3.6.2.1 Transform Type Selection
  If variable-sized transform coding is not enabled,
  then the 8x8 transform shall be used for all blocks.

I have to say the above spec isn't expressed clearly:
ttfrm is mentioned clearly, but not ttmbf.
anyway, since ttfrm is only specified when ttmbs is set,
we can deduce that ttmbf should set to 1.
it is also consistent with ffmpeg vc1 decoder and
hw behaviour (Intel GEN gfx)

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