I wish to create custom ffmpeg.wasm build

Now the official GUIDE show four commands "make dev" "make prd" etc

So I cloned THE REPO and ran "make prd". It did build, but obviously, this build was with default settings, whatever exactly they made be.

So pardon my stupidity, as I cannot figure out how / where / what do I edit to set the custom flags about what I want to be included / excluded in the build?

I wish to create custom ffmpeg.wasm build

Now the official GUIDE show four commands "make dev" "make prd" etc

So I cloned THE REPO and ran "make prd". It did build, but obviously, this build was with default settings, whatever exactly they made be.

So pardon my stupidity, as I cannot figure out how / where / what do I edit to set the custom flags about what I want to be included / excluded in the build?

• ffmpeg
• makefile
• ffmpeg-wasm

• It is not clear what custom flags you are talking about, with reference to the Makefile. You need to explain exactly what you want to do any why you cannot do it with the existing Makefile. – Mike Kinghan Commented 2 days ago
• @MikeKinghan I posted what i did as an answer – Ettur Commented yesterday

1 Answer 1

For anyone else wondering about this, I got my custom build. Here is what I did

1. This is more of a prerequisite but just in case : Im on windows so I have Docker Desktop running and WSL 2 enabled and running. I boot up my Ubuntu installation and run commands there. (Tried directly from windows but was a headache and I did not get it to work)

2. I only needed webm muxers. 0 encoders / 0 decoders

3. I removed most of the stuff from Dockerfile

this is my Dockerfile

# syntax=docker/dockerfile-upstream:master-labs

# Stage 1: Base Emscripten environment
FROM emscripten/emsdk:3.1.40 AS emsdk-base
ARG EXTRA_CFLAGS
ARG EXTRA_LDFLAGS
ENV INSTALL_DIR=/opt
ENV FFMPEG_VERSION=n5.1.4
ENV CFLAGS="-I$INSTALL_DIR/include $CFLAGS $EXTRA_CFLAGS"
ENV CXXFLAGS="$CFLAGS"
ENV LDFLAGS="-L$INSTALL_DIR/lib $LDFLAGS $CFLAGS $EXTRA_LDFLAGS"
ENV EM_PKG_CONFIG_PATH=$EM_PKG_CONFIG_PATH:$INSTALL_DIR/lib/pkgconfig:/emsdk/upstream/emscripten/system/lib/pkgconfig
ENV EM_TOOLCHAIN_FILE=$EMSDK/upstream/emscripten/cmake/Modules/Platform/Emscripten.cmake
ENV PKG_CONFIG_PATH=$PKG_CONFIG_PATH:$EM_PKG_CONFIG_PATH
RUN apt-get update && \
    apt-get install -y pkg-config autoconf automake libtool ragel

# Stage 2: Build zlib
FROM emsdk-base AS zlib-builder
ENV ZLIB_BRANCH=v1.2.11
ADD https://github/ffmpegwasm/zlib.git#$ZLIB_BRANCH /src
COPY build/zlib.sh /src/build.sh
RUN bash -x /src/build.sh

# Stage 3: Base FFmpeg image with source code and zlib
FROM emsdk-base AS ffmpeg-base
RUN embuilder build sdl2 sdl2-mt
ADD https://github/FFmpeg/FFmpeg.git#$FFMPEG_VERSION /src
COPY --from=zlib-builder $INSTALL_DIR $INSTALL_DIR

# Stage 4: Build FFmpeg with specified configuration
FROM ffmpeg-base AS ffmpeg-builder
COPY build/ffmpeg.sh /src/build.sh
RUN bash -x /src/build.sh \
    --disable-all \
    --enable-protocol=file \
    --enable-avcodec \
    --enable-avformat \
    --enable-avfilter \
    --enable-demuxer=concat,matroska \
    --enable-muxer=matroska \
    --enable-parser=vp8,vp9,opus,vorbis

# Stage 5: Build FFmpeg WebAssembly module
FROM ffmpeg-builder AS ffmpeg-wasm-builder
COPY src/bind /src/src/bind
COPY src/fftools /src/src/fftools
COPY build/ffmpeg-wasm.sh /src/build.sh
RUN mkdir -p /src/dist/umd && bash -x /src/build.sh \
    -o dist/umd/ffmpeg-core.js
RUN mkdir -p /src/dist/esm && bash -x /src/build.sh \
    -sEXPORT_ES6 \
    -o dist/esm/ffmpeg-core.js

# Stage 6: Export the built files
FROM scratch AS exportor
COPY --from=ffmpeg-wasm-builder /src/dist /dist

4. Needed to also edit ffmpeg.sh and ffmpeg-wasm.sh in the "build" folder

this is -wasm.sh

#!/bin/bash
# `-o <OUTPUT_FILE_NAME>` must be provided when using this build script.
# ex:
#     bash ffmpeg-wasm.sh -o ffmpeg.js

set -euo pipefail

EXPORT_NAME="createFFmpegCore"

CONF_FLAGS=(
  -I. 
  -I./src/fftools 
  -I$INSTALL_DIR/include 
  -L$INSTALL_DIR/lib 
  libavfilter/libavfilter.a
  libavformat/libavformat.a
  libavcodec/libavcodec.a
  libavutil/libavutil.a
  -Wno-deprecated-declarations 
  $LDFLAGS 
  -sENVIRONMENT=worker
  -sWASM_BIGINT
  -sUSE_SDL=2
  -sMODULARIZE
  ${FFMPEG_MT:+ -sINITIAL_MEMORY=1024MB}
  ${FFMPEG_MT:+ -sPTHREAD_POOL_SIZE=32}
  ${FFMPEG_ST:+ -sINITIAL_MEMORY=32MB -sALLOW_MEMORY_GROWTH}
  -sEXPORT_NAME="$EXPORT_NAME"
  -sEXPORTED_FUNCTIONS=$(node src/bind/ffmpeg/export.js)
  -sEXPORTED_RUNTIME_METHODS=$(node src/bind/ffmpeg/export-runtime.js)
  -lworkerfs.js
  --pre-js src/bind/ffmpeg/bind.js
  src/fftools/cmdutils.c 
  src/fftools/ffmpeg.c 
  src/fftools/ffmpeg_filter.c  # For filter function definitions
  src/fftools/ffmpeg_hw.c      # For hardware functions
  src/fftools/ffmpeg_mux.c 
  src/fftools/ffmpeg_opt.c 
  src/fftools/opt_common.c 
  src/fftools/ffprobe.c        # Added for ffprobe functionality
)

emcc "${CONF_FLAGS[@]}" $@

and this is ffmpeg.sh

#!/bin/bash

set -euo pipefail

CONF_FLAGS=(
  --target-os=none              # Disable target specific configs
  --arch=x86_32                 # Use x86_32 arch
  --enable-cross-compile        # Use cross compile configs
  --disable-asm                 # Disable asm
  --disable-stripping           # Disable stripping as it won't work
  # --disable-programs          # Removed to allow building programs like ffprobe
  --disable-doc                 # Disable doc build
  --disable-debug               # Disable debug mode
  --disable-runtime-cpudetect   # Disable cpu detection
  --disable-autodetect          # Disable env auto detect
  --enable-avcodec              # Enable avcodec
  --enable-avformat             # Enable avformat
  --enable-avfilter             # Enable avfilter

  # Assign toolchains and extra flags
  --nm=emnm
  --ar=emar
  --ranlib=emranlib
  --cc=emcc
  --cxx=em++
  --objcc=emcc
  --dep-cc=emcc
  --extra-cflags="$CFLAGS"
  --extra-cxxflags="$CXXFLAGS"

  # Disable thread when FFMPEG_ST is NOT defined
  ${FFMPEG_ST:+ --disable-pthreads --disable-w32threads --disable-os2threads}
)

emconfigure ./configure "${CONF_FLAGS[@]}" $@
emmake make -j

Now to say that I completely understand whats going on would be a lie :D
I did some notorious "vibe-coding" with Grok to reach this.

By the end, after running "make prd" I got my .wasm and .js
Original 30mb now 1.06mb

Everything works on the frontend.