Combine Videos MXD

Video extension workflows run on the same trick: generate a segment, use its tail to seed the next segment, repeat. Combine Videos MXD is the node that finally puts those segments back together - it concatenates two videos end-to-end and hands you one longer clip. front_video plays first, back_video plays after, output video is the merged result.

What it does under the hood

It works on ComfyUI's newer VIDEO type (the comfy_api-era representation that carries frames, audio, and metadata as one object), and it does three things:

1. Concatenates the frames along the time axis - pure ordering, no blending, no crossfade. This is a hard cut.
2. Concatenates audio sequentially, if either video has any. Audio-less videos just stay silent.
3. Checks before it stitches. This is the part that saves your render: the two videos must share the same frame rate and the same resolution, or it raises an error. If they match, you get a clean join; if not, you get a clear message instead of a corrupted file.

The resolution check's error text is worth quoting because it's the pack author doing your debugging for you: it tells you both videos' sizes and suggests using the "WAN 2.2 Video Prep I2V MXD" node to scale the base video before generation - so the scaled base and the generated clip actually match when you combine them. That's the real-world trap this node exists to catch: people generate a clip at one resolution, try to append it to a base at another, and wonder why nothing lines up.

When to use it

The classic arc: generate a base clip, extend it with the next segment (seeded by the tail), combine, extend again. Each extension pass adds one combine. It also works for simpler jobs - slapping an intro clip in front of a main clip, or joining two takes you like from one render. If you just want the videos side-by-side to compare them, that's the Video Comparer MXD's job; this node is for the actual join.

Gotchas

• Hard cuts only. No crossfade, no easing - if you want a transition, you'll build it with frame-level tools.
• Both videos must already be at the same FPS and resolution. If the node complains, fix it before generation (the pack's WAN prep nodes do this for you), not after.
• It requires a ComfyUI that ships comfy_api (the Nodes 2.0-era API). Not in your menu? Update ComfyUI first.

Install

ComfyUI Manager → search Maxed Out → install → restart, or:

cd ComfyUI/custom_nodes
git clone https://github.com/Maxed-Out-99/ComfyUI-MaxedOut

No requirements.txt, no models to download. Under MXD/video. For anyone extending WAN clips segment by segment, this is the node that makes "longer video" a wiring problem instead of an ffmpeg side quest.