KY Save Video (Alpha Support)

Most of this pack's nodes ship with a bare info_schema and no README coverage at all. This one's an exception - the README describes it directly: save an IMAGE tensor sequence as a video file that actually supports an alpha channel, via a separate MASK input, with a choice of alpha-capable codecs. That alpha support is the entire reason this node exists rather than reaching for a generic video-save node - most video encoders and containers don't carry transparency at all, and the ones that do are a specific, narrower set.

Why the codec and container choices are tied together

codec defaults to prores_ks (ProRes 4444, Apple's professional intermediate codec with real alpha support), and the other two options are png (frame-by-frame PNG encoding inside a video container, also alpha-capable) and qtrle (QuickTime RLE, an older but still alpha-capable codec). format defaults to mov - and that pairing matters: ProRes and QuickTime RLE are historically QuickTime-native codecs. Pairing either of them with format=mp4 instead of mov is likely to fail outright or silently drop the alpha channel, since the MP4 container doesn't reliably support those codecs the way .mov does. If you actually need the transparency from your mask input to survive, stick with format=mov.

Inputs that matter

• images (required IMAGE) and mask (optional MASK) - the mask is what actually gives you alpha; skip it and you get an opaque video regardless of which alpha-capable codec you picked.
• fps (FLOAT, 1–60, step 0.1, default 24) and quality (INT, 0–51, default 18) - quality here follows the familiar CRF-style convention where lower is better, the opposite of a 0–100 "higher is better" slider a beginner might expect. 18 is a solid default; don't push it toward 51 thinking you're improving quality.
• codec/format as covered above.
• Optional audio (AUDIO) to mux a track in, start_frame/end_frame (default 0/-1, where -1 means "through the last frame," the same convention this pack's KY_SaveImageSequence uses) to save a slice of the batch instead of all of it, and loop_count (default 0) if the format/codec combination you've picked supports looping.

Two outputs: video_path (the saved file's location) and preview_url (a URL for previewing it, per the README's own description of this feature) - it's marked an output node, since writing the file is its whole purpose.

Installing it

ComfyUI Manager: search ComfyUI-KYNode, install, restart. Or:

cd ComfyUI/custom_nodes
git clone https://github.com/yorkane/ComfyUI-KYNode

Restart ComfyUI. Encoding to ProRes, PNG-in-video, or QuickTime RLE typically relies on ffmpeg under the hood, consistent with the rest of this pack's video tooling - if it fails outright rather than producing a bad file, check ffmpeg -version from wherever ComfyUI's process runs.

Common issues

The CRF-style quality scale (lower is better, 0–51 range) is the single most common trap - if you set quality to something like 40 expecting a bump in quality, you've done the opposite; keep it near the 18 default and lower it further only if you specifically need higher quality at a larger file size.

Mixing codec=prores_ks or codec=qtrle with format=mp4 instead of the default mov is the second trap - expect it to fail or lose your alpha channel, since those codecs' real alpha support is tied to the QuickTime container conventions, not MP4's.

If your video comes out opaque despite picking an alpha-capable codec, check that you actually wired something into mask - it's optional, and skipping it gets you a normal opaque video even with prores_ks selected.

For comparing this node against its siblings: reach for KY_SaveImageSequence instead when you want individual frame files rather than an encoded video, and reach for KY_FFmpegImagesToVideo instead when your frames are already saved to disk and you want finer-grained ffmpeg encoder control (CRF/QP/bitrate modes, colorspace, pixel format) than this node's simpler quality/codec/format set exposes.