Comment 33 for bug 1767312

Verified on bionic (fresh install and fully updated) that the bug is still present, and that the workaround in comment #16 works. It just took me a while to remember you need to:
  1. Install ubuntu-restricted-addons; and
  2. Use Xorg (because if you're in a Wayland session you hit bug 1720820 instead).

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OpenGL vendor string: X.Org
OpenGL renderer string: AMD Radeon R6 Graphics (CARRIZO, DRM 3.23.0, 4.15.0-46-generic, LLVM 7.0.0)
OpenGL core profile version string: 4.5 (Core Profile) Mesa 18.2.2
OpenGL core profile shading language version string: 4.50
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile

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00:01.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI] Wani [Radeon R5/R6/R7 Graphics] (rev c6)
        Subsystem: Hewlett-Packard Company Carrizo
        Kernel driver in use: amdgpu
        Kernel modules: amdgpu

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libva info: VA-API version 1.1.0
libva info: va_getDriverName() returns 0
libva info: Trying to open /usr/lib/x86_64-linux-gnu/dri/radeonsi_drv_video.so
libva info: Found init function __vaDriverInit_1_1
libva info: va_openDriver() returns 0
vainfo: VA-API version: 1.1 (libva 2.1.0)
vainfo: Driver version: Mesa Gallium driver 18.2.2 for AMD Radeon R6 Graphics (CARRIZO, DRM 3.23.0, 4.15.0-46-generic, LLVM 7.0.0)
vainfo: Supported profile and entrypoints
      VAProfileMPEG2Simple : VAEntrypointVLD
      VAProfileMPEG2Main : VAEntrypointVLD
      VAProfileVC1Simple : VAEntrypointVLD
      VAProfileVC1Main : VAEntrypointVLD
      VAProfileVC1Advanced : VAEntrypointVLD
      VAProfileH264ConstrainedBaseline: VAEntrypointVLD
      VAProfileH264ConstrainedBaseline: VAEntrypointEncSlice
      VAProfileH264Main : VAEntrypointVLD
      VAProfileH264Main : VAEntrypointEncSlice
      VAProfileH264High : VAEntrypointVLD
      VAProfileH264High : VAEntrypointEncSlice
      VAProfileHEVCMain : VAEntrypointVLD
      VAProfileJPEGBaseline : VAEntrypointVLD
      VAProfileNone : VAEntrypointVideoProc