anchor.diff:      #(enableFeature (vo-aacenc != null && version3Licensing) "libvo-aacenc")
       #(enableFeature (vo-amrwbenc != null && version3Licensing) "libvo-amrwbenc")
       (enableFeature (wavpack != null) "libwavpack")
  -    (enableFeature (x11grabExtlib && gplLicensing) "x11grab")
       (enableFeature (x264 != null && gplLicensing) "libx264")
       (enableFeature (x265 != null && gplLicensing) "libx265")
       (enableFeature (xavs != null && gplLicensing) "libxavs")
  
positive.code:     (enableFeature swscaleAlphaBuild "swscale-alpha")
      (enableFeature hardcodedTablesBuild "hardcoded-tables")
      (enableFeature safeBitstreamReaderBuild "safe-bitstream-reader")
      (enableFeature memalignHackBuild "memalign-hack")
      (if multithreadBuild then (
         if isCygwin then
           "--disable-pthreads --enable-w32threads"
  
negative.code: assert libxcbshapeExtlib -> libxcb != null;
  assert openglExtlib -> mesa != null;
  assert opensslExtlib -> gnutls == null && openssl != null && nonfreeLicensing;
  assert nvenc -> nvidia-video-sdk != null && nonfreeLicensing;
  
  stdenv.mkDerivation rec {
    name = "ffmpeg-full-${version}";
    version = "3.3";
  
    src = fetchurl {
      url = "https://www.ffmpeg.org/releases/ffmpeg-${version}.tar.xz";
      sha256 = "17anx7rnbi63if1ndr61836lf76dpn47n0y424hc48bj05y7z7jr";
    };
  
    patchPhase = ''patchShebangs .
  