Reference limits: Veo 3.1, Gemini Omni Flash and Sume Video 1.0

Veo 3.1 takes up to 3 reference images, Gemini Omni Flash takes up to 3 reference clips of 3 seconds each, and Sume Video 1.0 takes 1 to 9 reference images. Pick by what you need to keep fixed: faces and products fit image references, motion and framing fit clip references.

What each source says

The Veo guide lists up to 3 reference images and notes that reference images require an 8 second clip. The Omni guide lists a maximum of 3 reference clips of up to 3 seconds each, says audio references are unsupported, and says negative prompts are not available. We read both on 2026-10-03; where a cell says not listed, the page we read did not state it.

Sume's side

Sume documents these by model, and the lists are machine readable. supported_input_references at GET /v1/videos/models tells you which of image_url, video_url and audio_url a model accepts. The docs list Video 1.0, now a retiring compatibility alias for Video Router Auto, with 1 to 9 reference_image_urls, and gemini-omni-flash-1.1 with image and video references but no audio reference, and video edits through video_url on the Video Router. See the Sume video docs.

A quick rule

• Need a product or a face to stay the same across shots: use image references and check the cap first.
• Need a camera move or a motion to carry over: use a video reference and keep it under the clip limit.
• Need to match a voice: none of the listed models above takes an audio reference, so plan a separate audio step.