diff --git a/Makefile b/Makefile
index 3f3189c370..350f131392 100644
--- a/Makefile
+++ b/Makefile
@@ -22,30 +22,66 @@ cgo_cflags :=
 cgo_ldflags :=
 cc :=
 
-uname_s := $(shell uname -s)
-ifeq ($(uname_s),Darwin)
+# Build platform flags
+BUILDOS ?= $(shell uname -s | tr '[:upper:]' '[:lower:]')
+BUILDARCH ?= $(shell uname -m | tr '[:upper:]' '[:lower:]')
+ifeq ($(BUILDARCH),aarch64)
+		BUILDARCH=arm64
+endif
+ifeq ($(BUILDARCH),x86_64)
+		BUILDARCH=amd64
+endif
+
+# Override these (not BUILDOS/BUILDARCH) for cross-compilation
+export GOOS ?= $(BUILDOS)
+export GOARCH ?= $(BUILDARCH)
+
+# Cross-compilation section. Currently supported:
+# darwin amd64 --> darwin arm64
+# darwin arm64 --> linux arm64
+# linux amd64 --> linux arm64
+# linux amd64 --> windows amd64
+
+ifeq ($(BUILDOS),darwin)
+	ifeq ($(GOOS),darwin)
 		cgo_ldflags += -framework CoreFoundation -framework Security
-	ifeq ($(GOARCH),arm64)
-		cgo_cflags += --target=arm64-apple-macos11
-		cgo_ldflags += --target=arm64-apple-macos11
+		ifeq ($(BUILDARCH),amd64)
+			ifeq ($(GOARCH),arm64)
+				cgo_cflags += --target=arm64-apple-macos11
+				cgo_ldflags += --target=arm64-apple-macos11
+			endif
+		endif
 	endif
-endif
 
-ifeq ($(uname_s),Linux)
-	ifeq ($(GOARCH),arm64)
-		cgo_cflags += --target=aarch64-linux-gnu
-		cgo_ldflags += --target=aarch64-linux-gnu
-		cc = clang --sysroot=/usr/aarch64-linux-gnu
+	ifeq ($(GOOS),linux)
+		ifeq ($(GOARCH),arm64)
+			LLVM_PATH ?= /opt/homebrew/opt/llvm/bin
+			SYSROOT ?= /tmp/sysroot-aarch64-linux-gnu
+			cgo_cflags += --target=aarch64-linux-gnu -Wno-error=unused-command-line-argument
+			cgo_ldflags += --target=aarch64-linux-gnu
+			cc = $(LLVM_PATH)/clang -fuse-ld=$(LLVM_PATH)/ld.lld --sysroot=$(SYSROOT)
+		endif
 	endif
 endif
 
-pkg_config_libdir :=
-ifeq ($(uname_s),Linux)
+ifeq ($(BUILDOS),linux)
+	ifeq ($(BUILDARCH),amd64)
+		ifeq ($(GOARCH),arm64)
+			ifeq ($(GOOS),linux)
+				SYSROOT ?= /usr/aarch64-linux-gnu
+				cgo_cflags += --target=aarch64-linux-gnu
+				cgo_ldflags += --target=aarch64-linux-gnu
+				cc = clang --sysroot=$(SYSROOT)
+			endif
+		endif
+	endif
+
 	ifeq ($(GOOS),windows)
 		cc = x86_64-w64-mingw32-gcc
 	endif
 endif
 
+
 .PHONY: livepeer livepeer_bench livepeer_cli livepeer_router docker
 
 livepeer:
diff --git a/install_ffmpeg.sh b/install_ffmpeg.sh
index 56ef2cf901..daaf37352d 100755
--- a/install_ffmpeg.sh
+++ b/install_ffmpeg.sh
@@ -1,56 +1,94 @@
 #!/usr/bin/env bash
 
-set -ex
+set -exuo pipefail
 
 ROOT="${1:-$HOME}"
-[[ -z "$ARCH" ]] && ARCH="$(uname -m)"
-[[ -z "$UNAME" ]] && UNAME="$(uname)"
 NPROC=${NPROC:-$(nproc)}
 EXTRA_CFLAGS=""
 EXTRA_LDFLAGS=""
 EXTRA_X264_FLAGS=""
 EXTRA_FFMPEG_FLAGS=""
+BUILD_TAGS="${BUILD_TAGS:-}"
 
-
-if [[ "$ARCH" == "arm64" && "$UNAME" == "Darwin" ]]; then
-  # Detect Apple Silicon
-  IS_ARM64=1
+# Build platform flags
+BUILDOS=$(uname -s | tr '[:upper:]' '[:lower:]')
+BUILDARCH=$(uname -m | tr '[:upper:]' '[:lower:]')
+if [[ $BUILDARCH == "aarch64" ]]; then
+  BUILDARCH=arm64
+fi
+if [[ $BUILDARCH == "x86_64" ]]; then
+  BUILDARCH=amd64
 fi
 
-if [[ "$ARCH" == "x86_64" && "$UNAME" == "Linux" && "${GOARCH:-}" == "arm64" ]]; then
-  echo "cross-compiling linux-arm64"
-  export CC="clang --sysroot=/usr/aarch64-linux-gnu"
+# Override these for cross-compilation
+export GOOS="${GOOS:-$BUILDOS}"
+export GOARCH="${GOARCH:-$BUILDARCH}"
+
+echo "BUILDOS: $BUILDOS"
+echo "BUILDARCH: $BUILDARCH"
+echo "GOOS: $GOOS"
+echo "GOARCH: $GOARCH"
+
+SYSROOT="${SYSROOT:-}"
+function check_sysroot() {
+  if ! stat $SYSROOT > /dev/null; then
+    echo "cross-compilation sysroot not found at $SYSROOT, try setting SYSROOT to the correct path"
+    exit 1
+  fi
+}
+
+if [[ "$BUILDARCH" == "amd64" && "$BUILDOS" == "linux" && "$GOARCH" == "arm64" && "$GOOS" == "linux" ]]; then
+  SYSROOT="${SYSROOT:-/usr/aarch64-linux-gnu}"
+  check_sysroot
+  echo "cross-compiling linux-amd64 --> linux-arm64"
+  export CC="clang --sysroot=$SYSROOT"
   EXTRA_CFLAGS="--target=aarch64-linux-gnu -I/usr/local/cuda_arm64/include $EXTRA_CFLAGS"
   EXTRA_LDFLAGS="--target=aarch64-linux-gnu -L/usr/local/cuda_arm64/lib64 $EXTRA_LDFLAGS"
-  EXTRA_FFMPEG_FLAGS="$EXTRA_FFMPEG_FLAGS --arch=aarch64 --enable-cross-compile --cc=clang --sysroot=/usr/aarch64-linux-gnu"
+  EXTRA_FFMPEG_FLAGS="$EXTRA_FFMPEG_FLAGS --arch=aarch64 --enable-cross-compile --cc=clang --sysroot=$SYSROOT"
+  HOST_OS="--host=aarch64-linux-gnu"
+fi
+
+if [[ "$BUILDARCH" == "arm64" && "$BUILDOS" == "darwin" && "$GOARCH" == "arm64" && "$GOOS" == "linux" ]]; then
+  SYSROOT="${SYSROOT:-/tmp/sysroot-aarch64-linux-gnu}"
+  check_sysroot
+  echo "cross-compiling darwin-arm64 --> linux-arm64"
+  LLVM_PATH="${LLVM_PATH:-/opt/homebrew/opt/llvm/bin}"
+  if [[ ! -f "$LLVM_PATH/ld.lld" ]]; then
+    echo "llvm linker not found at '$LLVM_PATH/ld.lld'. try 'brew install llvm' or set LLVM_PATH to your LLVM bin directory"
+    exit 1
+  fi
+  export CC="$LLVM_PATH/clang --sysroot=$SYSROOT"
+  EXTRA_CFLAGS="--target=aarch64-linux-gnu $EXTRA_CFLAGS"
+  EXTRA_LDFLAGS="--target=aarch64-linux-gnu -fuse-ld=$LLVM_PATH/ld.lld $EXTRA_LDFLAGS"
+  EXTRA_FFMPEG_FLAGS="$EXTRA_FFMPEG_FLAGS --arch=aarch64 --enable-cross-compile --cc=$LLVM_PATH/clang --sysroot=$SYSROOT --target-os=linux"
+  EXTRA_X264_FLAGS="$EXTRA_X264_FLAGS --sysroot=$SYSROOT"
   HOST_OS="--host=aarch64-linux-gnu"
-  IS_ARM64=1
 fi
 
-if [[ "$ARCH" == "x86_64" && "$UNAME" == "Linux" && "${GOOS:-}" == "windows" ]]; then
-  echo "cross-compiling windows-amd64"
-  EXTRA_CFLAGS="-L/usr/x86_64-w64-mingw32/lib -I/usr/x86_64-w64-mingw32/include  $EXTRA_CFLAGS"
-  EXTRA_LDFLAGS="-L/usr/x86_64-w64-mingw32/lib $EXTRA_LDFLAGS"
-  EXTRA_FFMPEG_FLAGS="$EXTRA_FFMPEG_FLAGS --arch=x86_64 --enable-cross-compile --cross-prefix=x86_64-w64-mingw32- --target-os=mingw64 --sysroot=/usr/x86_64-w64-mingw32"
-  EXTRA_X264_FLAGS="$EXTRA_X264_FLAGS --cross-prefix=x86_64-w64-mingw32- --sysroot=/usr/x86_64-w64-mingw32"
+if [[ "$BUILDARCH" == "amd64" && "$BUILDOS" == "linux" && "$GOARCH" == "amd64" && "$GOOS" == "windows" ]]; then
+  echo "cross-compiling linux-amd64 --> windows-amd64"
+  SYSROOT="${SYSROOT:-/usr/x86_64-w64-mingw32}"
+  check_sysroot
+  EXTRA_CFLAGS="-L$SYSROOT/lib -I$SYSROOT/include  $EXTRA_CFLAGS"
+  EXTRA_LDFLAGS="-L$SYSROOT/lib $EXTRA_LDFLAGS"
+  EXTRA_FFMPEG_FLAGS="$EXTRA_FFMPEG_FLAGS --arch=x86_64 --enable-cross-compile --cross-prefix=x86_64-w64-mingw32- --target-os=mingw64 --sysroot=$SYSROOT"
+  EXTRA_X264_FLAGS="$EXTRA_X264_FLAGS --cross-prefix=x86_64-w64-mingw32- --sysroot=$SYSROOT"
   HOST_OS="--host=mingw64"
   # Workaround for https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=967969
   export PKG_CONFIG_LIBDIR="/usr/local/x86_64-w64-mingw32/lib/pkgconfig"
   EXTRA_FFMPEG_FLAGS="$EXTRA_FFMPEG_FLAGS --pkg-config=$(which pkg-config)"
 fi
 
-if [[ "$ARCH" == "x86_64" && "$UNAME" == "Darwin" && "${GOARCH:-}" == "arm64" ]]; then
-  echo "cross-compiling darwin-arm64"
+if [[ "$BUILDARCH" == "amd64" && "$BUILDOS" == "darwin" && "$GOARCH" == "arm64" && "$GOOS" == "darwin" ]]; then
+  echo "cross-compiling darwin-amd64 --> darwin-arm64"
   EXTRA_CFLAGS="$EXTRA_CFLAGS --target=arm64-apple-macos11"
   EXTRA_LDFLAGS="$EXTRA_LDFLAGS --target=arm64-apple-macos11"
   HOST_OS="--host=aarch64-darwin"
   EXTRA_FFMPEG_FLAGS="$EXTRA_FFMPEG_FLAGS --arch=aarch64 --enable-cross-compile"
-  IS_ARM64=1
 fi
-echo "Arch $ARCH ${IS_ARM64:+(ARM64)}"
 
 # Windows (MSYS2) needs a few tweaks
-if [[ "$UNAME" == *"MSYS"* ]]; then
+if [[ "$BUILDOS" == *"MSYS"* ]]; then
   ROOT="/build"
   export PATH="$PATH:/usr/bin:/mingw64/bin"
   export C_INCLUDE_PATH="${C_INCLUDE_PATH:-}:/mingw64/lib"
@@ -72,7 +110,7 @@ export PKG_CONFIG_PATH="${PKG_CONFIG_PATH:-}:$ROOT/compiled/lib/pkgconfig"
 mkdir -p "$ROOT/"
 
 # NVENC only works on Windows/Linux
-if [[ "$UNAME" != "Darwin" ]]; then
+if [[ "$GOOS" != "Darwin" ]]; then
   if [[ ! -e "$ROOT/nv-codec-headers" ]]; then
     git clone https://git.videolan.org/git/ffmpeg/nv-codec-headers.git "$ROOT/nv-codec-headers"
     cd $ROOT/nv-codec-headers
@@ -82,7 +120,7 @@ if [[ "$UNAME" != "Darwin" ]]; then
   fi
 fi
 
-if [[ "$UNAME" != *"MSYS"* && ! $IS_ARM64 ]]; then
+if [[ "$GOOS" != "windows" && "$GOARCH" == "amd64" ]]; then
   if [[ ! -e "$ROOT/nasm-2.14.02" ]]; then
     # sudo apt-get -y install asciidoc xmlto # this fails :(
     cd "$ROOT"
@@ -101,7 +139,7 @@ fi
 if [[ ! -e "$ROOT/x264" ]]; then
   git clone http://git.videolan.org/git/x264.git "$ROOT/x264"
   cd "$ROOT/x264"
-  if [[ $IS_ARM64 ]]; then
+  if [[ $GOARCH == "arm64" ]]; then
     # newer git master, compiles on Apple Silicon
     git checkout 66a5bc1bd1563d8227d5d18440b525a09bcf17ca
   else
@@ -113,7 +151,7 @@ if [[ ! -e "$ROOT/x264" ]]; then
   make -j$NPROC install-lib-static
 fi
 
-if [[ "$UNAME" == "Linux" && "${BUILD_TAGS}" == *"debug-video"* ]]; then
+if [[ "$GOOS" == "linux" && "$BUILD_TAGS" == *"debug-video"* ]]; then
   sudo apt-get install -y libnuma-dev cmake
   if [[ ! -e "$ROOT/x265" ]]; then
     git clone https://bitbucket.org/multicoreware/x265_git.git "$ROOT/x265"
@@ -140,9 +178,9 @@ EXTRA_FFMPEG_LDFLAGS="$EXTRA_LDFLAGS"
 # all flags which should be present for production build, but should be replaced/removed for debug build
 DEV_FFMPEG_FLAGS="--disable-programs"
 
-if [[ "$UNAME" == "Darwin" ]]; then
+if [[ "$BUILDOS" == "darwin" && "$GOOS" == "darwin" ]]; then
   EXTRA_FFMPEG_LDFLAGS="$EXTRA_FFMPEG_LDFLAGS -framework CoreFoundation -framework Security"
-elif [[ "${GOOS:-}" == "windows" ]]; then
+elif [[ "$GOOS" == "windows" ]]; then
   EXTRA_FFMPEG_FLAGS="$EXTRA_FFMPEG_FLAGS --enable-cuda --enable-cuda-llvm --enable-cuvid --enable-nvenc --enable-decoder=h264_cuvid,hevc_cuvid,vp8_cuvid,vp9_cuvid --enable-filter=scale_cuda,signature_cuda,hwupload_cuda --enable-encoder=h264_nvenc,hevc_nvenc"
 elif [[ -e "/usr/local/cuda/lib64" ]]; then
   echo "CUDA SDK detected, building with GPU support"
@@ -181,7 +219,7 @@ if [[ ! -e "$ROOT/ffmpeg/libavcodec/libavcodec.a" ]]; then
     --enable-parser=aac,aac_latm,h264,hevc,vp8,vp9 \
     --enable-filter=abuffer,buffer,abuffersink,buffersink,afifo,fifo,aformat,format \
     --enable-filter=aresample,asetnsamples,fps,scale,hwdownload,select,livepeer_dnn,signature \
-    --enable-encoder=aac,opus,libx264 \
+    --enable-encoder=aac,opus \
     --enable-decoder=aac,opus,h264 \
     --extra-cflags="${EXTRA_CFLAGS} -I${ROOT}/compiled/include -I/usr/local/cuda/include" \
     --extra-ldflags="${EXTRA_FFMPEG_LDFLAGS} -L${ROOT}/compiled/lib -L/usr/local/cuda/lib64" \