Corridor Digital's CorridorKey 2.0 Keys Green Screen on 4 GB of VRAM With a Free Engine

TL;DR

Corridor Digital, the Los Angeles production studio behind the Corridor Crew channel, has released CorridorKey 2.0, a neural green and blue screen keyer. The inference engine and its roughly 5 GB of weights are free to download and use on paid work for anyone whose company made under $20M last year, and they key 1440p footage on an NVIDIA card with 4 GB of VRAM (6 GB for 4K). The paid part is the plugin pack for DaVinci Resolve, Nuke, After Effects, Premiere Pro and Blender, at $49.50 in beta and $99 from November 21. Corridor ran more than 400 shots of its own series through it, the launch video passed 3.46 million views in six days, and the Hacker News thread reached 191 points on October 26.

What shipped, and when

The 2.0 engine landed on GitHub on October 13 as an "initial public release", with the weights going up on Hugging Face the same day. The launch video, "I Solved Green Screen, and I'm Giving it to YOU!", followed on October 21, and the repo sits at 1,661 stars this morning.

CorridorKey 1.0, released in March, was a research-grade Python tool that Corridor co-founder Niko Pueringer built on an RTX Pro 6000 with 96 GB of VRAM. It collected 14,970 stars, a community GUI called EZ-CorridorKey and an Apple Silicon MLX path, and its README only came down to "6-8 gig of VRAM" after community optimisation. Version 2.0 is a new model (designed and trained by Zachary Harris), a rewritten engine, and Corridor's first official plugin, built by Alê Alvaro. The README opens with "You may rest easy, weary artist. The green beast has been slain," which is more confidence than most changelogs bring.

The unmixing problem

A classic chroma keyer picks a screen colour and makes pixels close to it transparent. That falls apart at edges: hair, motion blur, out-of-focus rims and glass are all pixels where the subject and the green are mixed together, and a threshold either eats them or leaves a green fringe. The "AI roto" tools of the last few years output a hard mask and throw the semi-transparent pixels away.

CorridorKey predicts two things per pixel: how much of the pixel is foreground (a linear alpha) and what colour the foreground was before the green got in (the straight, un-premultiplied colour). Think of a splash of milk stirred into tea. A normal keyer discards every pixel that looks too beige, while CorridorKey estimates how much milk was in each one and what shade it was before the tea reached it. That is the "un-mixing" Corridor's product page keeps repeating, and it is why the output keeps motion blur and bokeh where other tools leave hard edges.

How the 2.0 engine works

CorridorKey 2.0 doesn't train a vision backbone from scratch. It sits on three frozen foundation models that the download script pulls from their original publishers: C-RADIOv4-SO400M from NVIDIA as the visual feature extractor, MoGe-2 ViT-B from Microsoft for geometry features, and the small RVM recurrent video model from Google DeepMind for temporal features. Corridor's own trained weights, a single corridorkey_v2.safetensors file, sit on top and are the part under its licence.

Inference runs in two stages. Stage 1 processes overlapping windows of frames (up to 80 frames with a stride of 40 on a big card) and blends their hidden states with a Hann taper, so each frame's prediction is informed by its neighbours and the window seams don't show. Stage 2 streams the full-resolution alpha and foreground from those blended states, one frame at a time by default. The network runs in bfloat16 in an asinh HDR domain, which the README says bounds accuracy to roughly 1-2% relative error across the HDR range. Pass --output_format exr and you get unclipped scene-linear OpenEXR sequences in half or full float. Otherwise you get 10-bit 4:4:4 x264 previews and a ProRes 4444 cutout with alpha.

The product version of all this is a single node. The manual lists two controls that matter: "Time Awareness", the plugin's name for the stage-1 window size, and "Alpha Hints", a black-and-white mask you supply for either every frame or a single reference frame that the model propagates forwards and backwards through the shot. Corridor suggests starting a hint at 0.75 strength and turning it up for a near-perfect mask. The hint is how you remove tracking markers, C-stands and dirty screen edges without a garbage matte.

What it costs in VRAM

This is the part that moves CorridorKey from "studio with a 96 GB card" to "anyone with a gaming laptop". The engine measures free GPU memory at launch and picks the largest Hann window that fits. The README's table for 1080p footage, read as frames of temporal context per card:

At 4 GB you get two frames of context at 1080p and one frame at 1440p, with 4K off the table. At 6 GB every resolution runs, including 4K, in low-VRAM mode, which trades disk for memory (the plugin's "Low GPU Memory" toggle saves about 1.5 GB of VRAM and needs up to 10 GB of free disk for a 4K clip). From 12 GB up you get the full 80-frame window at 720p, and 32 GB gives you 80 frames at 1080p. Corridor's own tests found a 96/48 window unstable at native 4K even on the 96 GB card, and 80/40 "used most of the available VRAM" there.

Time awareness is optional. The manual says many shots key fine from a single frame, and that you turn the window up for compressed, noisy or flickering footage, or when you want a single-frame hint to spread through the clip.

The licence and the money

The licence is the bit Hacker News spent a healthy chunk of the thread litigating, which is HN's love language. The Corridor Key Licence 2.0 is CC BY-NC-SA 4.0 with additional terms that override it where they conflict:

• You may use the tool on commercial projects and the images you produce are yours. The non-commercial clause in the base licence does not reach your output.
• You may not repackage or resell it, charge for access to the code or weights, or offer inference as a paid API, subscription or usage-billed service.
• Any fork or derivative you release must be free to the public. Donations and pay-what-you-want are fine as long as zero is an option.
• Commercial software that wants to embed it needs a written agreement with Corridor.
• A legal entity (counted with its affiliates) with more than $20,000,000 in gross revenue in its last fiscal year loses the free permissions unless it buys a plugin seat for every person using the tool.
• Every fork must keep the "CorridorKey" name in a reasonably prominent position.

So it is source-available and free for almost everyone, and not open source by the OSI definition, a distinction several commenters made. For a one-person shop or a YouTube channel: download it, key your paid work, don't resell it.

The plugin pack is where Corridor makes money. Pricing is a one-time purchase with no subscription:

Personal is $49.50 during the beta (which ends November 20) and $99 from November 21, for one person on up to two machines, with lifetime updates on the 2.x line and a 14-day refund. Studio is $42.50 per seat in beta and $85 after, sold in blocks of 5 to 24 seats with 25 and up negotiated. One purchase covers every host: Resolve, Nuke, After Effects, Premiere Pro, Blender and a standalone app. Windows needs an RTX 30-series or newer, with 20-series support in beta. Mac needs an M-series chip on macOS 14 or later, where the OpenFX plugin, Blender add-on and standalone app ship, with After Effects and Premiere support added in build 2.0.0.146. AMD and Linux are "planned" for the plugin, though the free engine already ships a Linux launcher script for CUDA cards.

Production proof

Corridor built 2.0 for its own series Son of a Dungeon and says over 400 VFX shots went through the app. The product page adds: "We have not used another keying tool in over six months". The series premieres November 7, so the claims get a public test two weeks before the full-price switch.

The launch video is sponsored by NVIDIA and Puget Systems, and the product page's line is "CorridorKey is supported on Windows and NVIDIA GPUs". Every RTX 30-series card clears the 4 GB floor. AMD owners wait.

Caveats

• It is a beta. The manual opens with "Over the next few weeks you WILL encounter bugs and issues," and the plugin's first launch takes 30 to 60 seconds to load models.
• The free engine is CUDA only. The repo asks for an NVIDIA RTX 30-series or newer; Mac support comes only through the paid plugin.
• Low-VRAM mode gives up temporal context. At 4 GB you are keying almost frame by frame at 1080p, which is exactly the flicker case time awareness was built for.
• bfloat16 inference bounds HDR precision to about 1-2% relative error, by the README's own number: invisible in most comps, a known limit for extreme HDR grading.
• The licence's $20M threshold counts the whole corporate group, so a freelancer keying shots on behalf of a large studio falls under the studio's revenue, not their own.
• Corridor publishes no side-by-side against Keylight, Primatte or Resolve's Magic Mask. The quality evidence is Corridor's own shots and the reactions in the HN thread.

Why a builder should care

The architecture transfers to other projects: freeze three public foundation models, train a small head on top, and ship only the head under your own terms. That is how a production studio with one person credited for model design and training produced a model that fits in 4 GB. So does the licence shape: a free engine for everyone small, mandatory seats above a revenue line, paid plugins for convenience. It works like a game engine's revenue-threshold royalty, and it suits a tool whose users are mostly broke and whose would-be abusers are mostly rich.

The plumbing matters as much. The engine takes a hint mask as input and emits EXR, so it drops into an existing Nuke or Resolve pipeline as one node, which is how 400 shots went through it without anyone rewriting a pipeline.

Key Takeaways

• The engine and weights went public on October 13, the launch video (3.46M views) on October 21, and the HN front page on October 26.
• It keys 1440p footage on 4 GB of NVIDIA VRAM and 4K on 6 GB, down from the 96 GB workstation 1.0 was built on.
• The model is a trained head over three frozen public foundation models: NVIDIA C-RADIOv4, Microsoft MoGe-2 and DeepMind RVM.
• The licence is CC BY-NC-SA 4.0 plus terms: commercial output is yours, no resale or paid API, forks must be free, and companies over $20M revenue must buy a seat per user.
• Plugins for Resolve, Nuke, After Effects, Premiere and Blender cost $49.50 in beta and $99 from November 21; studio seats are $42.50 rising to $85.
• Corridor ran 400+ shots of Son of a Dungeon through it; the series premieres November 7.

Sources: CorridorKey 2.0 repository and README, Corridor Key Licence 2.0, CorridorKey 2.0 weights on Hugging Face, corridorkey.com pricing and hardware page, CorridorKey 2.0 user manual, CorridorKey 1.0 repository, Corridor Crew launch video, Hacker News discussion