Alpha clips, two routes
Cut the background out of footage with or without a green screen
Kamply explodes the clip to frames, mattes every frame with BiRefNet on your own Mac, and reassembles a ProRes 4444 alpha .mov. Every frame is its own model pass, so a 20-second clip takes roughly 20 to 60 minutes.
Shot on a green screen
chromakey.sh key
0x00ff00, similarity 0.10, blend 0.10, then a green despill.
Shot in a room
nobg.sh
One BiRefNet pass per frame, about 20 to 60 minutes for a 20-second clip.
.mov
ProRes 4444
Default, alpha survives
.webm
VP9
Chromium and Remotion only, and this ffmpeg build drops the alpha
.mp4
h264
Refused, h264 drops alpha silently
The keying defaults are the built-in arguments of chromakey.sh, and the matte timing is the measured range recorded in the engine's tool docs.
What it actually does
Kamply is a Mac desktop app with two background-removal routes for video. If the shot was filmed on a green screen, chromakey.sh keys it in one ffmpeg pass, with a despill that pulls the green cast off hair and edges. If it was filmed in a room, nobg.sh explodes the clip to PNG frames, mattes each one with BiRefNet in a single model load, and rebuilds an alpha-carrying clip. The frame-by-frame route writes a ProRes 4444 .mov in yuva444p10le unless you ask for a .webm. The green-screen route takes the file name you give it and picks the encoder from the extension, .mov or .webm. The frame-by-frame route writes its alpha clip next to your source file, and the green-screen route writes it wherever you name it. Either one gets layered into the reel when the video is built.
What this is not
There is no upload box on this site and no cloud queue. The matte runs on your own Mac, one model pass per frame, so a 20-second clip takes roughly 20 to 60 minutes. Kamply also does not shoot the footage, light a green screen, rotoscope by hand, or track a new scene in behind your subject.
How it runs, start to finish
Three steps, in the order the app actually does them.
Key it if the footage allows
Footage shot on green goes through chromakey.sh key: an ffmpeg chromakey filter at 0x00ff00 with similarity 0.10 and blend 0.10, then a green despill to pull the colour cast off the subject. The colour, similarity and blend are arguments, so a key that eats too much or too little is a number change rather than a different tool. The despill is written for green, which is the screen the engine assumes.
Matte every frame when it does not
For footage that cannot be keyed, nobg.sh explodes the clip into PNG frames with ffmpeg, mattes each frame with BiRefNet in one model load, then rebuilds the frames into an alpha clip at the source's own frame rate. The model runs on your Mac's GPU through MPS and falls back to the CPU for the few operations MPS lacks. Nothing is sent to a keying service.
Composite it, do not conform it
The cutout is a working file rather than a finished shot. Something else goes behind it when the reel is built at 1080x1920, 30 fps. One trap the engine is explicit about is conform, the step that scales and centre-crops a stock clip to that canvas. Conform re-encodes to h264, which drops alpha, so it is the right step for opaque stock footage and the wrong one for a cutout.
The numbers, and where they come from
Every figure on this page traces to a published source or to Kamply's own measurements. Nothing is modelled.
- Frame-by-frame output
- ProRes 4444 .mov, yuva444p10le
- Written with prores_ks -profile:v 4444, the alpha output the engine's tool docs treat as the default
- Measured matte speed
- 60 frames at 540x960 in about 2 min 20 s
- Measured on an Apple M4 with MPS, recorded in the engine's tool docs
- A full clip
- About 20 to 60 minutes for 20 seconds
- Every frame is a separate model inference, and all of them run on your own Mac
- Green-screen defaults
- 0x00ff00, similarity 0.10, blend 0.10
- chromakey.sh key arguments you can change. The despill itself is written for green
- .mp4 output
- Refused
- h264 drops alpha silently, so both tools error out on a .mp4 target rather than hand back a file that lost it
- Reel canvas
- 1080x1920 at 30 fps
- Where the cutout gets composited. The conform step that scales stock clips to this canvas writes h264, so a cutout skips it
Questions people actually ask
If yours is not here, ask it in the walkthrough. The form below reaches a human.
Can I upload a video here and get it back cut out?
No. This site has one backend route, the walkthrough form, and every free tool on it runs entirely in your browser. Video background removal happens inside the Mac app, on your own machine, against files already in your project folder.
Why can I not get an .mp4 with a transparent background?
h264 in an .mp4 drops alpha silently, so Kamply refuses to write one instead of handing you a file that quietly lost its transparency. That leaves ProRes 4444 .mov, which is the default and the one that works. A VP9 .webm is offered, but the ffmpeg build measured here encodes it without alpha, so the frame-by-frame route probes the file it just wrote and warns you when the alpha is gone. The .mov is large, and no measured file size exists for it, so treat it as a working file rather than something to email.
How slow is it, really?
Every frame is its own model pass. 60 frames at 540x960 measured about 2 minutes 20 seconds on an M4 with MPS, and a full 20-second clip runs roughly 20 to 60 minutes. That is why the engine tells you to shoot on green and key it when the shoot allows.
Do I still need a green screen?
No. Green screen is faster, so Kamply recommends it, but footage of a person filmed against a room still becomes an alpha clip. What Kamply will not do is film it for you, light the screen, rotoscope by hand, or track a replacement scene in behind the subject. It removes what is behind them and hands back a clip to composite.
Does the audio come back with the cutout?
No. Both the matte reassembly and the green-screen key encode with audio off, because a cutout is going to be composited over something else. If you need the voice track, that is a separate mix step in the reel build.
Is there anything to install, and what does it cost?
Kamply's onboarding runs the setup itself and installs ffmpeg as step 8, so the green-screen route is ready before you build anything. It asks for your password once, for the package manager underneath it. The frame-by-frame matte carries a one-time BiRefNet install of roughly 2 to 3 GB of torch plus about 880 MB of weights, which onboarding deliberately skips; the tool prints the install line the first time you use it. Pricing is one plan: $69 a week, $199 a month, or $1,990 a year, with founding rates ending 2026-09-15.
Bring one brief. Watch your first campaign take shape.
We build the first direction with your brand during the walkthrough. You leave knowing exactly what Kamply would make next.