anchor.diff:  #, vo-aacenc ? null # AAC encoder
   #, vo-amrwbenc ? null # AMR-WB encoder
   , wavpack ? null # Wavpack encoder
  -, x11grabExtlib ? false, libXext ? null, libXfixes ? null # X11 grabbing (legacy)
  +, x11grabExtlib ? false
   , x264 ? null # H.264/AVC encoder
   , x265 ? null # H.265/HEVC encoder
   , xavs ? null # AVS encoder
  
positive.code: assert faacExtlib -> faac != null && nonfreeLicensing;
  assert fdkaacExtlib -> fdk_aac != null && nonfreeLicensing;
  assert gnutls != null -> !opensslExtlib;
  assert libxcbshmExtlib -> libxcb != null;
  assert libxcbxfixesExtlib -> libxcb != null;
  assert libxcbshapeExtlib -> libxcb != null;
  assert openglExtlib -> mesa != null;
  assert opensslExtlib -> gnutls == null && openssl != null && nonfreeLicensing;
  assert x11grabExtlib -> libX11 != null && libXv != null;
  
  stdenv.mkDerivation rec {
    name = "ffmpeg-full-${version}";
  
negative.code: , libvorbis ? null # Vorbis de/encoding, native encoder exists
  , libvpx ? null # VP8 & VP9 de/encoding
  , libwebp ? null # WebP encoder
  , xorg ? null
  , libxcbshmExtlib ? true # X11 grabbing shm communication
  , libxcbxfixesExtlib ? true # X11 grabbing mouse rendering
  , libxcbshapeExtlib ? true # X11 grabbing shape rendering
  , lzma ? null # xz-utils
  #, nvenc ? null # NVIDIA NVENC support
  , openal ? null # OpenAL 1.1 capture support
  