Andrea, could you add that to the hardware performance section in Latex for the Manual if you have time?
To add Vulkan to the manual, I would need some clarification.
Decoding:
1- Is the “vulkan” setting in Preferences --> performance only valid for amdgpu?
It should work for other Vulkan drivers exposing those Vulkan video extensions. Notably new Nvidia with proprietary drivers, and somewhere at Mesa3d's freedesktop MergeRequests I saw patch for Nouveau's NVK driver (decode only for now).
2- Is there a need for libplacebo and certain environmental variables? Which ones?
as far as I understand - libplacebo may only be needed for ffv1 de/en coding via Vulkan, but mostly because it pulls shader compiler as dependency.. Vulkan SDK must be new enough so ffmpeg-8.0 build will recognize decoding extensions, they were added in late 2023, see Phoronix or Khronos websites.
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Vulkan 1.3.274 moves the Vulkan encode work out of BETA and moves h264 and h265 into KHR extensions.
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Some hardware should work without any variables, my RX 550 need RADV_PERFTEST=video_decode.
3- Is there anything else about vulkan that should be included in the manual?
FFV1 decoding might be slower than software, depending on how fast your GPU is?
Encoding:
4- Are presets with Vulkan hardware agnostic? (Apart from Intel with problems in ANV).
In theory ... Whole point of Vulkan was having some cross-platform, cross-vendor solution for video decode/encode (it may even work inside qemu VM, if it was compiled with Vulkan passthru support? vaapi support was developed but not accepted upstream)
5- Is there a need for libplacebo and certain environmental variables? Which ones?
libplacebo for now enables ffv1 Vulkan encoding. I am not sure how many amdgpu supported GPUs were enabled by default in recent mesa, I think your still need RADV_PERFTEST=video_encode ? So depending on Mesa driver version and gpu, I'd say?
6- Is there anything else about vulkan that should be included in the manual?
Not much, for me it was fastest *decode* method for HDR 4K HEVC test file (using X11 direct) but I guess this heavily depend on GPU.