anchor.diff:      (enableFeature (postprocSupport && (vp9DecoderSupport || vp9EncoderSupport)) "vp9-postproc")
       (enableFeature multithreadSupport "multithread")
       (enableFeature internalStatsSupport "internal-stats")
  -    (enableFeature memTrackerSupport "mem-tracker")
  +    #(enableFeature memTrackerSupport "mem-tracker")
       (enableFeature spatialResamplingSupport "spatial-resampling")
       (enableFeature realtimeOnlySupport "realtime-only")
       (enableFeature ontheflyBitpackingSupport "onthefly-bitpacking")
  
positive.code: 
  stdenv.mkDerivation rec {
    name = "libvpx-${version}";
    version = "1.4.0";
  
    src = fetchFromGitHub {
      owner = "webmproject";
      repo = "libvpx";
      rev = "v${version}";
      sha256 = "1y8cf2q5ij8z8ab5j36m18rbs62aah6sw6shzbs3jr70ja0z6n8s";
    };
  
    patchPhase = ''patchShebangs .'';
  
negative.code:     "--as=yasm"
      # Limit default decoder max to WHXGA
      (if sizeLimitSupport then "--size-limit=5120x3200" else null)
      #(enableFeature fastUnalignedSupport "fast-unaligned")
      "--disable-codec-srcs"
      (enableFeature debugLibsSupport "debug-libs")
      (enableFeature isMips "dequant-tokens")
  