anchor.diff:      /*
        *  Build flags
        */
  -    # One some ARM platforms --enable-thumb
  +    # On some ARM platforms --enable-thumb
       "--enable-shared --disable-static"
       (mkFlag true "0.6" "pic")
  +    (if (stdenv.cc.cc.isClang or false) then "--cc=clang" else null)
       (mkFlag smallBuild "0.5" "small")
       (mkFlag runtime-cpudetectBuild "0.5" "runtime-cpudetect")
       (mkFlag grayBuild "0.5" "gray")
  
positive.code:  *
   * Packages with errors:
   *   flite ilbc schroedinger
   *
   * Not packaged:
   *   aacplus avisynth cdio-paranoia crystalhd libavc1394 libiec61883
   *   libmxf libnut libquvi nvenc opencl opencore-amr openh264 oss shine twolame
   *   utvideo vo-aacenc vo-amrwbenc xvmc zvbi blackmagic-design-desktop-video
   *
   * Not supported:
   *   stagehright-h264(android only)
   *
   * Known issues:
   * 0.5     - libgsm: configure fails to find library (fix: disable for 0.5)
  
negative.code:                                        && avutilLibrary; # configure flag since 0.6
  assert avformatLibrary && reqMin "0.6" -> avcodecLibrary && avutilLibrary; # configure flag since 0.6
  assert avresampleLibrary && reqMin "0.11" -> avutilLibrary;
  assert postprocLibrary && reqMin "0.5" -> avutilLibrary;
  assert swresampleLibrary && reqMin "0.9" -> soxr != null;
  assert swscaleLibrary && reqMin "0.5" -> avutilLibrary;
  /*
   *  External libraries
   */
  #assert aacplusExtlib && reqMin "0.7" -> nonfreeLicensing;
  #assert decklinkExtlib && reqMin "2.2" -> blackmagic-design-desktop-video != null
  #                                       && !isCygwin && multithreadBuild # POSIX threads required
  #                                       && nonfreeLicensing;
  assert faacExtlib && reqMin "0.5" -> faac != null && nonfreeLicensing;
  assert fdk-aacExtlib && reqMin "1.0" -> fdk_aac != null && nonfreeLicensing;
  assert gnutls != null && reqMin "0.9" -> !opensslExtlib;
  assert libxcb-shmExtlib && reqMin "2.5" -> libxcb != null;
  assert libxcb-xfixesExtlib && reqMin "2.5" -> libxcb != null;
  assert libxcb-shapeExtlib && reqMin "2.5" -> libxcb != null;
  assert openglExtlib && reqMin "2.2" -> mesa != null;
  assert opensslExtlib && reqMin "0.9" -> gnutls == null && openssl != null && nonfreeLicensing;
  assert sambaExtlib && reqMin "2.3" -> samba != null && !isDarwin;
  assert x11grabExtlib && reqMin "0.5" -> libX11 != null && libXv != null;
  
  with stdenv.lib;
  stdenv.mkDerivation rec {
  