anchor.diff:      ++ optional (!isAarch64 && libvmaf != null && version3Licensing) libvmaf
       ++ optionals isLinux [ alsa-lib libraw1394 libv4l vulkan-loader glslang ]
       ++ optional (isLinux && !isAarch64 && libmfx != null) libmfx
  -    ++ optional nvenc nv-codec-headers
  +    ++ optional (nvdec || nvenc) nv-codec-headers
       ++ optionals stdenv.isDarwin [ Cocoa CoreServices CoreAudio AVFoundation
                                      MediaToolbox VideoDecodeAcceleration
                                      libiconv ];
  
positive.code: , libXext ? null # Xlib support
  , libxml2 ? null # libxml2 support, for IMF and DASH demuxers
  , xz ? null # xz-utils
  , nvenc ? !stdenv.isDarwin && !stdenv.isAarch64, nv-codec-headers ? null # NVIDIA NVENC support
  , openal ? null # OpenAL 1.1 capture support
  #, opencl ? null # OpenCL code
  , opencore-amr ? null # AMR-NB de/encoder & AMR-WB decoder
  
negative.code:     (enableFeature libxcbshapeExtlib "libxcb-shape")
      (enableFeature (libxml2 != null) "libxml2")
      (enableFeature (xz != null) "lzma")
      (enableFeature nvdec "cuvid")
      (enableFeature nvdec "nvdec")
      (enableFeature nvenc "nvenc")
      (enableFeature (openal != null) "openal")
      #(enableFeature opencl "opencl")
  