The DRM renderer does this for the out-of-tree v4l2m2m patches to ensure
we get NV12 buffers, but it ends up clobbering our own preference for
DRM_PRIME frames in the process.
This case basically works like a degenerate case of a DRM hwaccel
without DRM master where we just provide EGL export functionality
except that we don't even need a DRM FD in this case.
There are patches floating around the FFmpeg list for this:
https://patchwork.ffmpeg.org/project/ffmpeg/list/?series=12604
SpacemiT K1's BSP has a version of FFmpeg that contains both
v4l2m2m and their own *_stcodec decoders. Not only is their
V4L2 driver for their mvx decoder seemingly totally broken
(output buffers are all zeros), but it doesn't have any of
the DRM_PRIME support work that is maintained out of tree.
The result is we use a broken copyback decoder instead of
a (mostly) working zero-copy decoder because we didn't
include any logic to rank non-hwaccel decoders by pixfmt
like we have with device type for hwaccel decoders.
There are at least 2 out-of-tree OMX decoder implementations
that both lack AV_CODEC_CAP_HARDWARE, so they trick us into
thinking that neither of them is hardware accelerated.
Fixes false decoder warnings when linked against the patched
FFmpeg builds shipping on VisionFive 2 and LicheePi 4A SBCs.
Vulkan H.264/HEVC video decoding isn't supported with Fedora's Mesa binaries due to
patent issues, so only the VAAPI/DRM-PRIME import path was tested locally with ANV.
HDR video is getting tonemapped to my SDR monitor reasonably, so HDR output probably
works with GameScope but I haven't confirmed yet.
See #1117
Using the stream resolution instead of the test frame resolution was causing all non-720p streams to fail on the VisionFive 2 board with the wave5 driver.
It also likely fixes a similar interoperability issue with the qcom-venus driver that was reported in #1042
This avoids having to maintain a hardcoded list of all known H.264/HEVC/AV1 decoders
and ensures new/unknown decoders will just work automatically (assuming we have
a renderer that can process their output pixel format).
