anchor.diff:        "--enable-ffmpeg"
         "--disable-ffplay"
         (ifMinVer "0.6" "--enable-ffprobe")
  -      (if reqMin "4" then null else "--disable-ffserver")
  +      (ifVerOlder "4" "--disable-ffserver")
       # Libraries
         (ifMinVer "0.6" "--enable-avcodec")
         (ifMinVer "0.6" "--enable-avdevice")
  
positive.code:     # Build flags
        "--enable-shared"
        (ifMinVer "0.6" "--enable-pic")
        (ifMinVer "4.0" (enableFeature (srt != null) "libsrt"))
        (enableFeature runtimeCpuDetectBuild "runtime-cpudetect")
        "--enable-hardcoded-tables"
      ] ++
  
negative.code: { lib, stdenv, buildPackages, fetchurl, pkg-config, addOpenGLRunpath, perl, texinfo, yasm
  , alsa-lib, bzip2, fontconfig, freetype, gnutls, libiconv, lame, libass, libogg
  , libssh, libtheora, libva, libdrm, libvorbis, xz, soxr
  , x264, x265, xvidcore, zimg, zlib, libopus, speex, nv-codec-headers, dav1d
  , vpxSupport ? !stdenv.isAarch32, libvpx
  , srtSupport ? true, srt
  , vaapiSupport ? ((stdenv.isLinux || stdenv.isFreeBSD) && !stdenv.isAarch32)
  , openglSupport ? false, libGLU, libGL
  , libmfxSupport ? false, intel-media-sdk
  , libaomSupport ? false, libaom
  