veo-clip-planner

Small, dependency-free Rust library that answers one planning question for Google's Veo 3.1 video model: how do I reach a target length, and what does it cost in requests?

It compares the two routes that the developer documentation allows:

1. Separate clips. One Veo 3.1 clip is 4, 6 or 8 seconds long (Gemini API and Vertex AI). The planner uses 8-second clips: clips = ceil(target / 8), one request per clip (the Gemini API returns one video per request). min_surplus_mix also finds a 4/6/8 mix with the least surplus, e.g. 30 s = 8 + 8 + 8 + 6.
2. Extension (Gemini API). One 8-second 720p clip, then 7-second extensions, at most 20 of them, so the longest result is 8 + 7 x 20 = 148 seconds. extensions = ceil((target - 8) / 7), requests = extensions + 1. Vertex AI states different extension limits (37 s maximum) and is exposed only as a constant.

Frame counts are plain arithmetic at 24 fps (8 s = 192 frames), not a number published by Google. Status-polling calls are not counted as requests.

use veo_clip_planner::{separate_clips, extension_plan};

let clips = separate_clips(30).unwrap();
assert_eq!((clips.clips, clips.generated_seconds, clips.requests), (4, 32, 4));

let ext = extension_plan(30).unwrap();
assert_eq!((ext.extensions, ext.final_seconds, ext.requests), (4, 36, 5));

assert!(extension_plan(149).is_err()); // over the 148 s Gemini API ceiling

Target	Separate 8 s clips	Gemini API extension
30 s	4 clips, 32 s, 4 requests	4 extensions, 36 s, 5 requests
60 s	8 clips, 64 s, 8 requests	8 extensions, 64 s, 9 requests
148 s	19 clips, 152 s, 19 requests	20 extensions, 148 s, 21 requests
149 s	19 clips, 152 s, 19 requests	not possible

The limits with their primary sources (the ai.google.dev page "Generate videos with Veo 3.1 in Gemini API" and Google's Vertex AI documentation, read on 11 Oct 2026) and an in-browser version of this planner are on MakeRoll's Veo 3.1 video length limit page. Limits change; check the official pages before relying on these constants.

License: MIT