ffmpeg-decklink

Pre-built ffmpeg binaries with Blackmagic DeckLink support, for use with osc-record.

Download

Platform	File	Notes
macOS arm64	ffmpeg-decklink-darwin-arm64.tar.gz	Apple Silicon
Windows x64	ffmpeg-decklink-windows-amd64.zip	Includes required DLLs

See Releases.

What's in the binary

Both builds include:

• --enable-decklink — native Blackmagic DeckLink input/output
• --enable-libx264 — H.264 encoding
• --enable-libx265 — HEVC encoding
• --enable-gpl --enable-nonfree

macOS also includes --enable-videotoolbox --enable-audiotoolbox.

The Windows zip bundles required MinGW runtime and codec DLLs alongside ffmpeg-decklink.exe so no separate installation is needed.

Requirements

• Blackmagic Desktop Video drivers 14.3+ installed on the host machine
• For Windows: DeckLink CLSIDs are registered by the Desktop Video installer — the binary uses COM to find the device

---

Building

macOS

macOS builds use Homebrew with the homebrew-ffmpeg/ffmpeg tap:

brew tap homebrew-ffmpeg/ffmpeg
brew install homebrew-ffmpeg/ffmpeg/ffmpeg --with-decklink

Place the DeckLink SDK headers in a path accessible to the build (e.g. /opt/homebrew/include).

Configure flags used:

--prefix=/opt/homebrew
--enable-gpl --enable-nonfree --enable-decklink
--enable-libx264 --enable-libx265
--enable-videotoolbox --enable-audiotoolbox
--extra-cflags=-I/opt/homebrew/include
--extra-cxxflags=-I/opt/homebrew/include
--extra-ldflags=-L/opt/homebrew/lib

---

Windows (MSYS2/MinGW64)

This is the non-obvious one. Full details below.

1. Install prerequisites

Install MSYS2 (e.g. winget install MSYS2.MSYS2), then from an MSYS2 MinGW64 shell:

pacman -S mingw-w64-x86_64-gcc \
          mingw-w64-x86_64-x264 \
          mingw-w64-x86_64-x265 \
          diffutils zip

# make is not in PATH by default in MinGW64:
ln -sf /mingw64/bin/mingw32-make.exe /usr/bin/make

2. Get the DeckLink SDK

Download the DeckLink SDK from Blackmagic Design and extract it to ~/decklink-sdk/. The SDK ships .idl files on Windows (COM Interface Definition Language), not pre-compiled headers.

3. Generate headers from IDL

Use widl (the Wine IDL compiler, included in MinGW) to generate .h and _i.c files from the .idl source:

cd ~/decklink-sdk

# Generate DeckLinkAPI.h (all interface declarations):
widl -I. --win64 -h -o DeckLinkAPI.h DeckLinkAPI.idl

# Generate DeckLinkAPI_i.c (CLSID and IID constant definitions):
widl -I. -I/mingw64/include --win64 -u -o DeckLinkAPI_i.c DeckLinkAPI.idl

The versioned IDL files (DeckLinkAPI_v14_2_1.idl, etc.) cannot be compiled standalone by widl because they reference types only available in the main IDL context. Since the main DeckLinkAPI.h already contains all versioned interfaces, create stub headers that point to it:

for f in DeckLinkAPI_v10_2.h DeckLinkAPI_v10_11.h DeckLinkAPI_v11_4.h \
          DeckLinkAPI_v11_5.h DeckLinkAPI_v11_5_1.h DeckLinkAPI_v11_6.h \
          DeckLinkAPI_v12_0.h DeckLinkAPI_v14_2_1.h DeckLinkAPI_v15_2.h; do
  printf '#pragma once\n#include "DeckLinkAPI.h"\n' > "$f"
done

4. Write the Windows COM dispatch file

The SDK ships DeckLinkAPIDispatch.cpp for Linux/macOS which uses dlopen/dlsym. Windows uses COM instead — CoCreateInstance with CLSIDs registered by the Desktop Video driver.

Create ~/decklink-sdk/DeckLinkAPIDispatch.cpp (see build/windows/DeckLinkAPIDispatch.cpp in this repo).

5. Clone and configure ffmpeg

git clone --depth=1 https://github.com/FFmpeg/FFmpeg.git ~/ffmpeg-src
cd ~/ffmpeg-src

./configure \
  --prefix=/home/$USER/ffmpeg-out \
  --enable-gpl \
  --enable-nonfree \
  --enable-decklink \
  --enable-libx264 \
  --enable-libx265 \
  --enable-static \
  --disable-shared \
  --disable-debug \
  --disable-doc \
  --disable-ffplay \
  --disable-ffprobe \
  --extra-cflags="-I/home/$USER/decklink-sdk" \
  --extra-cxxflags="-I/home/$USER/decklink-sdk" \
  --extra-ldflags='-Wl,--start-group' \
  --extra-libs='-Wl,--end-group'

Verify DeckLink was picked up:

grep 'CONFIG_DECKLINK_INDEV' ffbuild/config.mak
# Should print: CONFIG_DECKLINK_INDEV=yes

The --start-group/--end-group linker flags resolve circular archive dependencies between libavdevice (which contains DeckLink code) and libavcodec (whose internal symbols DeckLink calls).

6. Patch ffbuild/library.mak

MSYS2 sets RESPONSE_FILES=yes in ffbuild/config.mak, which makes the build write object file lists to a .objs response file then pass @file to ar. The original implementation uses echo $^ > $@.objs in a shell recipe. With ~1000 object files in libavcodec, the expanded command exceeds Windows' 32767-character CreateProcess limit — the echo fails silently and ar creates an empty archive.

Fix: replace echo with GNU Make's $(file ...) built-in, which writes to a file entirely within Make without spawning a shell process:

sed -i 's/$(Q)echo $^ > $@.objs/$(file > $@.objs,$^)/' ffbuild/library.mak

Why this works:

• $(file > filename,text) is a GNU Make 4.0+ built-in that writes text to filename directly — no process spawn, no command line length limit
• The call expands to an empty string, so the shell recipe line becomes a no-op
• MinGW's ar @file correctly reads space-separated object paths from the response file

7. Build

make -j$(nproc)
make install

# Name the output binary ffmpeg-decklink.exe:
cp /home/$USER/ffmpeg-out/bin/ffmpeg.exe \
   /home/$USER/ffmpeg-out/bin/ffmpeg-decklink.exe

Verify DeckLink support in the built binary:

./ffmpeg-decklink.exe -f decklink -list_devices true -i "" 2>&1
# Should list connected DeckLink devices

8. Bundle required DLLs and package

The binary dynamically links several MinGW runtime and codec DLLs not present on standard Windows. Identify them and bundle alongside the exe:

# List required DLLs:
objdump -p ffmpeg-decklink.exe | grep 'DLL Name'

# Copy MinGW DLLs (Windows system DLLs like KERNEL32.dll are already present):
DLLS=(
  libgcc_s_seh-1.dll libstdc++-6.dll libwinpthread-1.dll
  libx264-165.dll libx265-215.dll
  libbz2-1.dll libiconv-2.dll liblzma-5.dll
  zlib1.dll libva.dll libva_win32.dll
)
for dll in "${DLLS[@]}"; do cp /mingw64/bin/$dll .; done

zip ffmpeg-decklink-windows-amd64.zip ffmpeg-decklink.exe "${DLLS[@]}"

Note: DLL names are versioned (e.g. libx264-165.dll). When the MinGW toolchain is updated, run objdump -p again to get the current names.

See build/windows/build.sh for a complete automated script.