anchor.diff:   *   libvpx(stable 1.3.0) openal openjpeg pulseaudio rtmpdump samba vid-stab
    *   wavpack x265 xavs
    *
  + * Need fixes to support AArch64:
  + *   libmfx(intel-media-sdk) nvenc
  + *
    * Not supported:
    *   stagefright-h264(android only)
    *
  
positive.code:     (enableFeature (if isLinux then libdc1394 != null && libraw1394 != null else false) "libdc1394")
      (enableFeature (libiconv != null) "iconv")
      #(enableFeature (if isLinux then libiec61883 != null && libavc1394 != null && libraw1394 != null else false) "libiec61883")
      (enableFeature (if isLinux then libmfx != null else false) "libmfx")
      (enableFeature (libmodplug != null) "libmodplug")
      (enableFeature (libmysofa != null) "libmysofa")
      #(enableFeature (libnut != null) "libnut")
  
negative.code:  */
  
  let
    inherit (stdenv) isCygwin isDarwin isFreeBSD isLinux isAarch64;
    inherit (stdenv.lib) optional optionals optionalString enableFeature;
  in
  
  