Draft: patch ffmpeg and mpv for v4l2

An experiment. 😄

This seems to work. I can watch 3840x2160@60 big buck bunny with under 10% cpu usage.

Unfortunately, the video freezes after a couple of seconds and mpv fills the terminal with:

[vo/gpu/libplacebo] vk->CreateSwapchainKHR(...): VK_ERROR_OUT_OF_HOST_MEMORY (../src/vulkan/swapchain.c:622)

Update: works fine in sway. Above error shows up in gnome only.

~/.config/mpv/mpv.conf has hwdec=v4l2request.

Also adding vo=gpu-next seems to require a bit more CPU than the default vo=gpu.

Other interesting options: gpu-api=vulkan or gpu-context=waylandvk