{
  lib,
  gccStdenv,
  stdenv,
  fetchurl,
  cmake,
  nasm,
  fetchpatch2,

  # NUMA support enabled by default on NUMA platforms:
  numaSupport ? (
    stdenv.hostPlatform.isLinux && (stdenv.hostPlatform.isx86 || stdenv.hostPlatform.isAarch64)
  ),
  numactl,

  # Multi bit-depth support (8bit+10bit+12bit):
  multibitdepthSupport ? (
    stdenv.hostPlatform.is64bit && !(stdenv.hostPlatform.isAarch64 && stdenv.hostPlatform.isLinux)
  ),

  # Other options:
  cliSupport ? true, # Build standalone CLI application
  custatsSupport ? false, # Internal profiling of encoder work
  debugSupport ? false, # Run-time sanity checks (debugging)
  ppaSupport ? false, # PPA profiling instrumentation
  unittestsSupport ? stdenv.hostPlatform.isx86_64, # Unit tests - only testing x64 assembly
  vtuneSupport ? false, # Vtune profiling instrumentation
  werrorSupport ? false, # Warnings as errors
  # NEON support is always enabled for aarch64
  # this flag is only needed for armv7.
  neonSupport ? false, # force enable the NEON fpu support for arm v7 CPUs
}:

let
  mkFlag = optSet: flag: if optSet then "-D${flag}=ON" else "-D${flag}=OFF";

  isCross = stdenv.buildPlatform != stdenv.hostPlatform;
in

stdenv.mkDerivation rec {
  pname = "x265";
  version = "4.1";

  outputs = [
    "out"
    "dev"
  ];

  # Check that x265Version.txt contains the expected version number
  # whether we fetch a source tarball or a tag from the git repo
  src = fetchurl {
    url = "https://bitbucket.org/multicoreware/x265_git/downloads/x265_${version}.tar.gz";
    hash = "sha256-oxaZxqiYBrdLAVHl5qffZd5LSQUEgv5ev4pDedevjyk=";
  };

  patches = [
    ./darwin-__rdtsc.patch
  ]
  # TODO: remove after update to version 4.2
  ++ lib.optionals (stdenv.hostPlatform.isAarch32 && stdenv.hostPlatform.isLinux) [
    (fetchpatch2 {
      url = "https://bitbucket.org/multicoreware/x265_git/commits/ddb1933598736394b646cb0f78da4a4201ffc656/raw";
      hash = "sha256-ZH+jbVtfNJ+CwRUEgsnzyPVzajR/+4nDnUDz5RONO6c=";
      stripLen = 1;
    })
  ];

  sourceRoot = "x265_${version}/source";

  postPatch = ''
    substituteInPlace cmake/Version.cmake \
      --replace-fail "unknown" "${version}" \
      --replace-fail "0.0" "${version}"
  ''
  # There is broken and complicated logic when setting X265_LATEST_TAG for
  # mingwW64 builds. This bypasses the logic by setting it at the end of the
  # file
  + lib.optionalString stdenv.hostPlatform.isMinGW ''
    echo 'set(X265_LATEST_TAG "${version}")' >> ./cmake/Version.cmake
  '';

  nativeBuildInputs = [
    cmake
    nasm
  ]
  ++ lib.optionals (numaSupport) [ numactl ];

  cmakeFlags = [
    "-DENABLE_ALPHA=ON"
    "-DENABLE_MULTIVIEW=ON"
    "-DENABLE_SCC_EXT=ON"
    "-Wno-dev"
    (mkFlag custatsSupport "DETAILED_CU_STATS")
    (mkFlag debugSupport "CHECKED_BUILD")
    (mkFlag ppaSupport "ENABLE_PPA")
    (mkFlag vtuneSupport "ENABLE_VTUNE")
    (mkFlag werrorSupport "WARNINGS_AS_ERRORS")
  ]
  # Clang does not support the endfunc directive so use GCC.
  ++ lib.optional (
    stdenv.cc.isClang && !stdenv.targetPlatform.isDarwin && !stdenv.targetPlatform.isFreeBSD
  ) "-DCMAKE_ASM_COMPILER=${gccStdenv.cc}/bin/${gccStdenv.cc.targetPrefix}gcc"
  # Neon support
  ++ lib.optionals (neonSupport && stdenv.hostPlatform.isAarch32) [
    "-DENABLE_NEON=ON"
    "-DCPU_HAS_NEON=ON"
    "-DENABLE_ASSEMBLY=ON"
  ];

  cmakeStaticLibFlags = [
    "-DHIGH_BIT_DEPTH=ON"
    "-DENABLE_CLI=OFF"
    "-DENABLE_SHARED=OFF"
    "-DEXPORT_C_API=OFF"
  ]
  ++ lib.optionals stdenv.hostPlatform.isPower [
    "-DENABLE_ALTIVEC=OFF" # https://bitbucket.org/multicoreware/x265_git/issues/320/fail-to-build-on-power8-le
  ]
  ++ lib.optionals isCross [
    (mkFlag stdenv.hostPlatform.isAarch32 "CROSS_COMPILE_ARM")
    (mkFlag stdenv.hostPlatform.isAarch64 "CROSS_COMPILE_ARM64")
  ];

  preConfigure =
    lib.optionalString multibitdepthSupport ''
      cmake -B build-10bits $cmakeFlags "''${cmakeFlagsArray[@]}" $cmakeStaticLibFlags
      cmake -B build-12bits $cmakeFlags "''${cmakeFlagsArray[@]}" $cmakeStaticLibFlags -DMAIN12=ON
      cmakeFlagsArray+=(
        -DEXTRA_LIB="x265-10.a;x265-12.a"
        -DEXTRA_LINK_FLAGS=-L.
        -DLINKED_10BIT=ON
        -DLINKED_12BIT=ON
      )
    ''
    + ''
      cmakeFlagsArray+=(
        -DGIT_ARCHETYPE=1 # https://bugs.gentoo.org/814116
        ${mkFlag (!stdenv.hostPlatform.isStatic) "ENABLE_SHARED"}
        -DHIGH_BIT_DEPTH=OFF
        -DENABLE_HDR10_PLUS=ON
        ${mkFlag cliSupport "ENABLE_CLI"}
        ${mkFlag unittestsSupport "ENABLE_TESTS"}
      )
    '';

  # Builds 10bits and 12bits static libs on the side if multi bit-depth is wanted
  # (we are in x265_<version>/source/build)
  preBuild = lib.optionalString multibitdepthSupport ''
    make -C ../build-10bits -j $NIX_BUILD_CORES
    make -C ../build-12bits -j $NIX_BUILD_CORES
    ln -s ../build-10bits/libx265.a ./libx265-10.a
    ln -s ../build-12bits/libx265.a ./libx265-12.a
  '';

  doCheck = unittestsSupport;

  checkPhase = ''
    runHook preCheck

    ./test/TestBench

    runHook postCheck
  '';

  postInstall = ''
    rm -f ${placeholder "out"}/lib/*.a
  ''
  # For mingw, libs are located in $out/bin not $out/lib
  + lib.optionalString stdenv.hostPlatform.isMinGW ''
    ln -s $out/bin/*.dll $out/lib
  '';

  meta = {
    description = "Library for encoding H.265/HEVC video streams";
    mainProgram = "x265";
    homepage = "https://www.x265.org";
    changelog = "https://x265.readthedocs.io/en/master/releasenotes.html#version-${
      lib.strings.replaceStrings [ "." ] [ "-" ] version
    }";
    license = lib.licenses.gpl2Plus;
    maintainers = with lib.maintainers; [ codyopel ];
    platforms = lib.platforms.all;
  };
}