anchor.diff:    buildInputs = [zlib openssl libre librem pkgconfig
       cairo mpg123 gstreamer gst-ffmpeg gst-plugins-base gst-plugins-bad gst-plugins-good
       alsaLib SDL libv4l celt libsndfile srtp ffmpeg gsm speex portaudio spandsp libuuid
  -    ccache
  +    ccache libvpx
       ];
     makeFlags = [
       "LIBRE_MK=${libre}/share/re/re.mk"
  
positive.code: {stdenv, fetchurl, zlib, openssl, libre, librem, pkgconfig
  , cairo, mpg123, gstreamer, gst-ffmpeg, gst-plugins-base, gst-plugins-bad
  , gst-plugins-good, alsaLib, SDL, libv4l, celt, libsndfile, srtp, ffmpeg
  , gsm, speex, portaudio, spandsp, libuuid, ccache
  }:
  stdenv.mkDerivation rec {
    version = "0.5.1";
  
negative.code:     "USE_VIDEO=1"
      "CCACHE_DISABLE=1"
  
      "USE_ALSA=1" "USE_AMR=1" "USE_CAIRO=1" "USE_CELT=1"
      "USE_CONS=1" "USE_EVDEV=1" "USE_FFMPEG=1"  "USE_GSM=1" "USE_GST=1"
      "USE_L16=1" "USE_MPG123=1" "USE_OSS=1" "USE_PLC=1" "USE_VPX=1"
      "USE_PORTAUDIO=1" "USE_SDL=1" "USE_SNDFILE=1" "USE_SPEEX=1"
      "USE_SPEEX_AEC=1" "USE_SPEEX_PP=1" "USE_SPEEX_RESAMP=1" "USE_SRTP=1"
      "USE_STDIO=1" "USE_SYSLOG=1" "USE_UUID=1" "USE_V4L2=1" "USE_X11=1"
  
      "USE_BV32=" "USE_COREAUDIO=" "USE_G711=1" "USE_G722=1" "USE_G722_1="
      "USE_ILBC=" "USE_OPUS=" "USE_SILK="
    ]
    ++ stdenv.lib.optional (stdenv.cc.cc != null) "SYSROOT_ALT=${stdenv.cc.cc}"
    ++ stdenv.lib.optional (stdenv.cc.libc != null) "SYSROOT=${stdenv.cc.libc}"
    ;
  
    NIX_CFLAGS_COMPILE='' -I${librem}/include/rem -I${gsm}/include/gsm
      -DHAVE_INTTYPES_H -D__GLIBC__
      -D__need_timeval -D__need_timespec -D__need_time_t '';
    meta = {
      homepage = "http://www.creytiv.com/baresip.html";
  