How to record or stream your DMA overlay without a capture card

No capture card? You can still record or stream with your overlay showing. Your main PC sends the game to OBS on your second PC over your home network, and OBS puts your overlay window on top. The second PC records or streams the result. If you'd rather use a capture card, How to record or stream with your DMA overlay showing wires one in after your fuser.

How it works

The game comes over your network.
Your main PC sends its picture and sound to the second PC with NDI, or as a stream that OBS picks up. Nothing extra plugs into your fuser or your monitor.
The overlay is already on the second PC.
Your software draws it there, in a window on a black background. OBS captures that window.
OBS keys out the black.
A key filter makes the black see-through, the same way a fuser treats black, so only what your software draws sits over the game.
The second PC does the recording.
Your main PC only has to send the picture.

What you see while you play doesn't change. Keep your fuser or spare monitor set up the way it is now.

What you need

Both PCs on the same router with Ethernet cables, or one cable straight between them. Wi-Fi drops frames
OBS Studio on your second PC. It's free
For NDI, the free DistroAV plugin for OBS on your second PC. It sets up the NDI Runtime it needs
A way to send from your main PC: OBS with DistroAV there too, or the free NDI Tools Screen Capture app. For a stream instead of NDI, OBS on its own is enough

Send the game from your main PC

With NDI

Install OBS and DistroAV on your main PC, and add your game as a Game Capture source
Open Tools, then DistroAV NDI Settings, turn on Main Output and give it a name you'll recognise
Or skip OBS on the main PC and run Screen Capture from NDI Tools. It shows up on your network as an NDI source by itself

As a stream

If NDI won't show up on your network, send an SRT stream instead.

On your second PC, find its local IP address: open Settings, Network & internet, then your connection's Properties, and look for IPv4 address
On your main PC in OBS, open Settings, Stream, pick Custom, and set the server to srt://SECOND-PC-IP:9000, with your second PC's address in place of SECOND-PC-IP
Under Output, pick your graphics card's encoder (NVIDIA NVENC, AMD or Intel Quick Sync) so the work stays off your CPU, and a bitrate around 20,000 Kbps for 1080p at 60fps. It's your own network, so it can be high
Press Start Streaming once the second PC is listening (next part)

Build the scene on your second PC

Add the game first. NDI: +, NDI Source, and pick your main PC's output. Stream: +, Media Source, untick Local File, and enter srt://0.0.0.0:9000?mode=listener
Add the overlay on top of it: +, Window Capture, and pick your software's overlay window. If it won't capture, use Display Capture of the screen it's on
Right-click the overlay source, open Filters, and add a Color Key with the key color set to black. A Luma Key works too, and hides anything darker than the level you set. A Chroma Key is made for green screens and doesn't key black well
Right-click each source, Transform, Fit to screen, so the two line up
Check the boxes sit on the players. If they don't, see Resolution below

Settings that matter

Resolution.
Set the OBS canvas, Settings, Video, Base Resolution, to the resolution you play at, and run your software's overlay at that same resolution. If the overlay and the game are different sizes, the boxes drift off the players towards the edges. Output Resolution can be lower to save the second PC some work, like 1080p or 720p for a stream.
Frame rate.
60fps is plenty for a recording or a stream, even if you play at 240Hz. Set it under Settings, Video, Common FPS Values. Sending 60 also keeps the network and both PCs lighter.
Latency.
The game reaches OBS a little after the overlay does, so the boxes can run slightly ahead of the players in the recording. Add a Render Delay filter to the overlay source and raise it a few milliseconds at a time until they line up. NDI over a cable is usually only a frame or two behind, and a stream is further. This only changes the recording, never what you see while you play.
Keep the main PC light.
Send 60fps rather than your full refresh rate, and 1080p rather than 1440p if it struggles. Screen Capture HX in NDI Tools, or the graphics card's encoder for a stream, hands the work to your graphics card. Don't record on the main PC as well.
Keep the second PC breathing.
It's running your DMA software too. Watch its CPU in Task Manager while you record. If it sits near 100%, your software can't keep up with the card's reads. Use its graphics card's encoder if it has one, record at 720p, or drop to 30fps. Power settings on your second PC helps as well.
The network.
Full NDI at 1080p and 60fps uses around 125 to 150 Mbps, so it wants a wired gigabit connection. NDI HX and an SRT stream use far less.

Sound

NDI and SRT both carry your main PC's sound along with the picture, so the game is in your recording without a fuser having to pass it through. Check the meter in OBS's Audio Mixer before you go live. A microphone on the second PC goes in as an audio input there.

If it doesn't work

No NDI source shows up.
Both PCs have to be on the same network. Set that network to Private in Windows on both, and allow OBS and NDI through Windows Firewall when it asks.
The picture stutters.
Use a cable instead of Wi-Fi, lower the resolution or frame rate, or switch to NDI HX.
Black shows around the overlay.
The key filter isn't on the overlay source, or the window's background isn't pure black. Raise the Color Key's Similarity a little.
The boxes don't line up.
Match the overlay's resolution to the game's, then Fit to screen on both sources.

Still stuck? Open a ticket in our Discord with how you're sending the game, how the two PCs are connected, and a screenshot of your OBS scene.