ATEM Mini — Webcam Streaming & Fleet Integration

Lab-bench setup: Raspberry Pis have HDMI out to ATEM Mini HDMI inputs. USB-C output acts as a USB webcam. ATEM Ethernet port allows programmatic input switching.

Hardware overview

[Pi 1] HDMI ---+
[Pi 2] HDMI ---+  ATEM Mini  --(USB-C)-->  Mac/Linux: /dev/video0 or AVFoundation
[Pi 3] HDMI ---+  (Ethernet: 192.168.x.x)
[Pi 4] HDMI ---+

• ATEM Mini: 4 HDMI inputs, source IDs 1-4
• USB-C output: UVC-class webcam, no driver needed on macOS 11+ or Linux 5.x+
• Ethernet: ATEM protocol over UDP port 9910

1. USB-C Webcam Capture

macOS — AVFoundation (ffmpeg)

# List devices
ffmpeg -f avfoundation -list_devices true -i "" 2>&1 | grep -i atem

# Capture to file (replace "0" with device index)
ffmpeg -f avfoundation -framerate 30 -video_size 1920x1080 -i "0" -c:v libx264 -preset fast out.mp4

# Low-latency preview
ffplay -f avfoundation -framerate 30 -video_size 1920x1080 -i "0"

# Single-frame snapshot
ffmpeg -f avfoundation -framerate 30 -video_size 1920x1080 -i "0" -vframes 1 /tmp/atem-snap.jpg

Linux — v4l2

# List devices
v4l2-ctl --list-devices

# Capture
ffmpeg -f v4l2 -framerate 30 -video_size 1920x1080 -i /dev/video0 -c:v libx264 -preset fast out.mp4

# Snapshot
ffmpeg -f v4l2 -framerate 30 -video_size 1920x1080 -i /dev/video0 -vframes 1 /tmp/atem-snap.jpg

udev rule for stable symlink:

# /etc/udev/rules.d/99-atem-mini.rules
SUBSYSTEM=="video4linux", ATTRS{idVendor}=="1edb", ATTRS{idProduct}=="bd6e", SYMLINK+="atem-mini"

USB IDs: Vendor 1edb (Blackmagic Design), Product bd6e (ATEM Mini), bd6f (ATEM Mini Pro).

2. ATEM Network Protocol (UDP 9910)

Source IDs

Minimal raw-socket switcher (Python, stdlib only)

License note: PyATEMMax=GPL-3.0, pyatem=LGPL-3.0 — both disallowed. This uses only stdlib.

#!/usr/bin/env python3
"""atem_switch.py — Minimal ATEM Mini input switcher (stdlib only)
Usage: python3 atem_switch.py 192.168.1.240 2
"""
import socket, struct, sys

ATEM_PORT = 9910
INIT_PKT = b'\x10\x14\x53\xab\x00\x00\x00\x00\x00\x3a\x00\x00'

def atem_switch(ip: str, source_id: int, timeout: float = 3.0):
    s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    s.settimeout(timeout)
    addr = (ip, ATEM_PORT)

    # Initiate connection
    s.sendto(INIT_PKT, addr)
    data, _ = s.recvfrom(4096)
    session_id = struct.unpack_from('>H', data, 2)[0]
    atem_pkt_id = struct.unpack_from('>H', data, 10)[0]

    # ACK the init
    ack = struct.pack('>BBHHHH', 0x80, 0x0c, session_id, atem_pkt_id, 0, 0)
    s.sendto(ack, addr)

    # Drain state dump
    s.settimeout(0.2)
    try:
        while True:
            data, _ = s.recvfrom(65535)
            atem_pkt_id = struct.unpack_from('>H', data, 10)[0]
    except socket.timeout:
        pass
    s.settimeout(timeout)

    # CPgI command: switch program input
    cmd = struct.pack('>HH4sHH', 10, 0, b'CPgI', 0, source_id)
    header = struct.pack('>BBHHHH', 0x01, 12 + len(cmd), session_id, atem_pkt_id, 0, 1)
    s.sendto(header + cmd, addr)

    s.settimeout(1.0)
    try:
        s.recvfrom(4096)
    except socket.timeout:
        pass
    s.close()

if __name__ == '__main__':
    if len(sys.argv) != 3:
        print(f'Usage: {sys.argv[0]} <atem-ip> <source 1-4>')
        sys.exit(1)
    atem_switch(sys.argv[1], int(sys.argv[2]))
    print(f'Switched program to input {sys.argv[2]}')

Command tags

3. Fleet Integration — Ansible

Convention: Pi N = ATEM input N.

# Switch to Pi 3
ansible-playbook playbooks/atem_switch.yml -e "input=3"

# Cycle all inputs with snapshots
ansible-playbook playbooks/atem_cycle.yml

4. Pi HDMI Gotchas

Force HDMI output (Pis won't output without detected display):

# /boot/config.txt
hdmi_force_hotplug=1
hdmi_group=1
hdmi_mode=16

5. ATEM Network Setup

# Find ATEM on subnet
nmap -sU -p 9910 192.168.1.0/24 2>/dev/null | grep -B2 "open"

Set static IP via ATEM Software Control > Preferences > Network.

Common Mistakes

Related Skills

• raspberry-pi — Pi fleet management, boot config
• ansible-fleet — safety-first rollout, inventory
• fleet-irc — IRC dispatch, #agents channel