build1.sh

# !/bin/bash -x

set -e -o pipefail

# I follow [this](https://emscripten.org/docs/getting_started/downloads.html) to install emscripten manually
# then source the env file
source ../emsdk/emsdk_env.sh

# I manually run these steps to compile x264
# cd ~/ffmpeg/
# mkdir build sources
# cd sources
# git clone https://code.videolan.org/videolan/x264.git
# emconfigure ./configure --host=i686-gnu --disable-cli --disable-asm --enable-static --prefix=~/ffmpeg/build
# emmake make -C ~/ffmpeg/sources/x264 install-lib-static -j
# emmake make -C ~/ffmpeg/sources/x264 clean


# verify Emscripten version
emcc -v

BUILD_DIR=~/ffmpeg/build
CFLAGS="-I$BUILD_DIR/include -O3"
LDFLAGS="$CFLAGS -L$BUILD_DIR/lib"

# configure FFMpeg with Emscripten
CONFIG_ARGS=(
  --target-os=none        # use none to prevent any os specific configurations
  --arch=x86_32           # use x86_32 to achieve minimal architectural optimization
  --enable-cross-compile  # enable cross compile
  --disable-x86asm        # disable x86 asm
  --disable-inline-asm    # disable inline asm
  --disable-stripping     # disable stripping
  --disable-programs      # disable programs build (incl. ffplay, ffprobe & ffmpeg)
  --disable-doc           # disable doc
  --nm="llvm-nm"
  --ar=emar
  --ranlib=emranlib
  --cc=emcc
  --cxx=em++
  --objcc=emcc
  --dep-cc=emcc
  --extra-cflags="$CFLAGS"
  --extra-cxxflags="$CFLAGS"
  --extra-ldflags="$LDFLAGS"

  --disable-avdevice
  --disable-swresample
  --disable-postproc
  --disable-network
  --disable-pthreads
  --disable-w32threads
  --disable-os2threads
  --disable-everything
  
  --enable-asm
  --enable-bsf=h264_mp4toannexb
  --enable-ffmpeg
  --enable-avcodec
  --enable-avformat
  --enable-avutil
  --enable-swresample
  --enable-swscale
  --enable-avfilter
  --enable-libx264
  --enable-gpl

  --enable-encoder=libx264,mpeg4,mov,gif,h264
  --enable-decoder=rawvideo,hevc,h264,mpeg4,gif
  --enable-parser=mpeg4video,mpegaudio,gif
  --enable-demuxer=h264,mov,gif,concat,image2,image2pipe,mpegps
  --enable-muxer=mp4,gif,mov
  --enable-protocol=file
  --enable-filter=scale,overlay,fps,movie
)
emconfigure ./configure "${CONFIG_ARGS[@]}"

# build dependencies
emmake make -j4

# build ffmpeg.wasm
mkdir -p wasm/dist
ARGS=(
  -I. -I./fftools # Add directory to include search path
  -Llibavcodec -Llibavfilter -Llibavformat -Llibavresample -Llibavutil -Llibpostproc -Llibswscale -Llibswresample # Add directory to library search path
  -Qunused-arguments # Don't emit warning for unused driver arguments.
  -o wasm/dist/ffmpeg-core.js fftools/ffmpeg_opt.c fftools/ffmpeg_filter.c fftools/ffmpeg_hw.c fftools/cmdutils.c fftools/ffmpeg.c # output
  -lavfilter -lavformat -lavcodec -lswresample -lswscale -lavutil -lm # library
  -s USE_SDL=2 # use SDL2
  -s MODULARIZE=1 # use modularized version to be more flexible
  -s EXPORT_NAME="createFFmpegCore" # assign export name for browser
  -s EXPORTED_FUNCTIONS="[_main]" # export main and proxy_main funcs
  -s EXTRA_EXPORTED_RUNTIME_METHODS="[FS, cwrap, ccall, setValue, writeAsciiToMemory]" # export extra runtime methods
  -s INITIAL_MEMORY=33554432 # 33554432 bytes = 32MB
  -s ALLOW_MEMORY_GROWTH=1 # allows the total amount of memory used to change depending on the demands of the application
  --post-js wasm/post-js.js # emits a file after the emitted code. use to expose exit function
  -O3 # optimize code and reduce code size
)
emcc "${ARGS[@]}"