anchor.diff:      #"--${boolEn (twolame != null)}-libtwolame"
       /**/"--disable-libtwolame"
       "--${boolEn (v4l_lib != null)}-libv4l2"
  -    "--${boolEn (v4l_lib != null)}-v4l2_m2m"
  +    (deprfflag "--${boolEn (v4l_lib != null)}-v4l2_m2m" null "3.4")
  +    (fflag "--${boolEn (v4l_lib != null)}-v4l2-m2m" "3.5")
       "--${boolEn (vid-stab != null)}-libvidstab"
       /**/"--disable-libvmaf"
       "--${boolEn (vo-amrwbenc != null)}-libvo-amrwbenc"
  
positive.code:     /*
       *  Hardware accelerators
       */
      (fflag "--disable-amf" "3.5")  # macOS
      "--disable-audiotoolbox"  # macOS
      "--${boolEn (
        nvidia-cuda-toolkit != null
  
negative.code:       sha256 = "5a77278a63741efa74e26bf197b9bb09ac6381b9757391b922407210f0f991c0";
      };
      "9.9" = { # Git
        version = "2017.12.15";
        rev = "3c6dc270355f27645cf931fae1ed2dc1405507f8";
        sha256 = "64f9b15adaf585ddca918db9bb6e202ccc795c56579ce70b2f9fe075d5c043fa";
      };
    };
    source = sources."${channel}";
  