[Bug 110257] Major artifacts in mpeg2 vaapi hw decoding

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=110257

            Bug ID: 110257
           Summary: Major artifacts in mpeg2 vaapi hw decoding
           Product: Mesa
           Version: unspecified
          Hardware: All
                OS: All
            Status: NEW
          Severity: major
          Priority: medium
         Component: Drivers/Gallium/radeonsi
          Assignee: dri-devel at lists.freedesktop.org
          Reporter: 67b0226d at casix.org
        QA Contact: dri-devel at lists.freedesktop.org

Created attachment 143787
  --> https://bugs.freedesktop.org/attachment.cgi?id=143787&action=edit
hardware-decoded screenshot

Hi,

on latest Mesa I still get tons of artifacts when decoding MPEG2 on my AMD card
via VAAPI, to the point where it is not usable for video decoding at all to be
honest.
I've attached sample screenshots to show the problem - one software-decoded and
one hardware-decoded via libva in mpv.
The sample video is taken from https://www.w6rz.net/1080p25.zip but the
artifacts are visible more or less on any MPEG2 video including DVDs.

There is this older bug report:
https://bugs.freedesktop.org/show_bug.cgi?id=93760 but I'm not sure it's
related because I do not get any assertion failure and it vaguely reads like it
has been fixed?

For clarification, I see no artifacts with VDPAU.

Tested with Mesa-19.1.0-devel (git-bea540173c), libva 2.5.0-pre1
(git-c98b06d2b8), FFmpeg N-93467-g54655623a8
VAAPI driver string: Mesa Gallium driver 19.1.0-devel for Radeon RX 580 Series
(POLARIS10, DRM 3.27.0, 4.20.13-arch1-1-ARCH, LLVM 7.0.1)

I verified this with mpv, gstreamer and Kodi.
mpv seems to have disabled mpeg2 hw decoding by default due to this problem:
https://github.com/mpv-player/mpv/commit/3dd59dbe
In Kodi we cannot go this route because we want to support low-end hardware
that might have trouble decoding 1080p in software out-of-the-box.
I want to avoid having to blacklist the radeon vaapi driver for mpeg2 if
possible.

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