Compiling ffmpeg for Raspberry Pi 4 (script only works fine on RPi OS 32bit). x64 does not support mmal (see https://github.com/raspberrypi/userland/issues/688)

compile-ffmpeg.sh

#!/bin/bash

# Note that there's no libdrm because this lib cause errors

sudo apt update -y && sudo apt upgrade -y

sudo apt-get -y install \
    autoconf \
    automake \
    build-essential \
    cmake \
    doxygen \
    git \
    graphviz \
    imagemagick \
    libasound2-dev \
    libass-dev \
    libavcodec-dev \
    libavdevice-dev \
    libavfilter-dev \
    libavformat-dev \
    libavutil-dev \
    libfreetype6-dev \
    libgmp-dev \
    libmp3lame-dev \
    libopencore-amrnb-dev \
    libopencore-amrwb-dev \
    libopus-dev \
    librtmp-dev \
    libsdl2-dev \
    libsdl2-image-dev \
    libsdl2-mixer-dev \
    libsdl2-net-dev \
    libsdl2-ttf-dev \
    libsnappy-dev \
    libsoxr-dev \
    libssh-dev \
    libssl-dev \
    libtool \
    libv4l-dev \
    libva-dev \
    libvdpau-dev \
    libvo-amrwbenc-dev \
    libvorbis-dev \
    libwebp-dev \
    libx264-dev \
    libx265-dev \
    libxcb-shape0-dev \
    libxcb-shm0-dev \
    libxcb-xfixes0-dev \
    libxcb1-dev \
    libxml2-dev \
    lzma-dev \
    meson \
    nasm \
    pkg-config \
    python3-dev \
    python3-pip \
    texinfo \
    wget \
    yasm \
    libsrt-gnutls-dev \
    zlib1g-dev

mkdir ~/ffmpeg-libraries

#AAC
git clone --depth 1 https://github.com/mstorsjo/fdk-aac.git ~/ffmpeg-libraries/fdk-aac \
  && cd ~/ffmpeg-libraries/fdk-aac \
  && autoreconf -fiv \
  && ./configure \
  && make -j$(nproc) \
  && sudo make install

#AV1
git clone --depth 1 https://code.videolan.org/videolan/dav1d.git ~/ffmpeg-libraries/dav1d \
  && mkdir ~/ffmpeg-libraries/dav1d/build \
  && cd ~/ffmpeg-libraries/dav1d/build \
  && meson .. \
  && ninja \
  && sudo ninja install

#HEVC
git clone --depth 1 https://github.com/ultravideo/kvazaar.git ~/ffmpeg-libraries/kvazaar \
  && cd ~/ffmpeg-libraries/kvazaar \
  && ./autogen.sh \
  && ./configure \
  && make -j$(nproc) \
  && sudo make install

#VP8 and VP9
git clone --depth 1 https://chromium.googlesource.com/webm/libvpx ~/ffmpeg-libraries/libvpx \
  && cd ~/ffmpeg-libraries/libvpx \
  && ./configure --disable-examples --disable-tools --disable-unit_tests --disable-docs \
  && make -j$(nproc) \
  && sudo make install

#AP1
git clone --depth 1 https://aomedia.googlesource.com/aom ~/ffmpeg-libraries/aom \
  && mkdir ~/ffmpeg-libraries/aom/aom_build \
  && cd ~/ffmpeg-libraries/aom/aom_build \
  && cmake -G "Unix Makefiles" AOM_SRC -DENABLE_NASM=on -DPYTHON_EXECUTABLE="$(which python3)" -DCMAKE_C_FLAGS="-mfpu=vfp -mfloat-abi=hard" .. \
  && sed -i 's/ENABLE_NEON:BOOL=ON/ENABLE_NEON:BOOL=OFF/' CMakeCache.txt \
  && make -j$(nproc) \
  && sudo make install

#zimg
git clone --recursive https://github.com/sekrit-twc/zimg.git ~/ffmpeg-libraries/zimg \
  && cd ~/ffmpeg-libraries/zimg \
  && sh autogen.sh \
  && ./configure \
  && make \
  && sudo make install

sudo ldconfig

git clone --depth 1 https://github.com/FFmpeg/FFmpeg.git ~/FFmpeg \
  && cd ~/FFmpeg \
  && ./configure \
    --extra-cflags="-I/usr/local/include" \
    --extra-ldflags="-L/usr/local/lib" \
    --extra-libs="-lpthread -lm -latomic" \
    --arch=armhf \
    --enable-gmp \
    --enable-gpl \
    --enable-libass \
    --enable-libdav1d \
    --enable-libfdk-aac \
    --enable-libfreetype \
    --enable-libkvazaar \
    --enable-libmp3lame \
    --enable-libopencore-amrnb \
    --enable-libopencore-amrwb \
    --enable-libopus \
    --enable-librtmp \
    --enable-libsnappy \
    --enable-libsoxr \
    --enable-libssh \
    --enable-libvorbis \
    --enable-libvpx \
    --enable-libzimg \
    --enable-libwebp \
    --enable-libx264 \
    --enable-libx265 \
    --enable-libxml2 \
    --enable-mmal \
    --enable-nonfree \
    --enable-omx \
    --enable-omx-rpi \
    --enable-version3 \
    --target-os=linux \
    --enable-pthreads \
    --enable-openssl \
    --enable-hardcoded-tables \
  && make -j$(nproc) \
  && sudo make install

I've built ffmpeg before and it took such a long time I was really pleased to stumble on this sadly things were going so well untill the tail end where I got....

Cloning into '/home/chris/FFmpeg'...
remote: Enumerating objects: 7765, done.
remote: Counting objects: 100% (7765/7765), done.
remote: Compressing objects: 100% (6029/6029), done.
remote: Total 7765 (delta 2175), reused 3233 (delta 1446), pack-reused 0
Receiving objects: 100% (7765/7765), 16.32 MiB | 3.94 MiB/s, done.
Resolving deltas: 100% (2175/2175), done.
Updating files: 100% (7827/7827), done.

**ERROR: OpenMAX IL headers from raspberrypi/firmware not found**

I'm using a Pi3 and the O/S build is

PRETTY_NAME="Raspbian GNU/Linux 11 (bullseye)"
NAME="Raspbian GNU/Linux"
VERSION_ID="11"
VERSION="11 (bullseye)"
VERSION_CODENAME=bullseye
ID=raspbian
ID_LIKE=debian

My hardware revision is
Hardware : BCM2835
Revision : a02082
Serial : 0000000032c2bc5b
Model : Raspberry Pi 3 Model B Rev 1.2

Could you find 5 mins to point me in the right direction to help resolve it please?

*** UPDATE:****
In case anyone else has this issue turns out I needed to update the firmware to a more recent one using rpi-updat.

Worked perfectly after that so big thanks for publishing this.