Build IMAGE_REF tags in Python for up to 10 Omni references

Gemini Omni Flash 1.1 on Sume refers to reference images by tag, <IMAGE_REF_0> for the first URL in reference_image_urls, <IMAGE_REF_1> for the second and so on up to <IMAGE_REF_9>. A short Python helper can build the tags from the list so the numbers never drift from the order.

The rule

The Video Router docs allow at most ten reference images and three reference videos, and number the tags from zero in list order. If you reorder the list, the tags must change with it, or the prompt will point at the wrong picture.

The helper

The script prints a request body. It makes no network call, so you can run it before you spend anything. Send the body to POST /v1/video-router/generate.

import json

refs = {
    "mug": "https://example.com/mug.png",
    "desk": "https://example.com/desk.png",
    "logo": "https://example.com/logo.png",
}
assert 1 <= len(refs) <= 10, "Omni takes 1 to 10 images"

tag = {name: f"<IMAGE_REF_{i}>" for i, name in enumerate(refs)}
prompt = (f"Place the {tag['mug']} on the {tag['desk']}, "
          f"with the {tag['logo']} facing the camera.")

body = {"model": "gemini-omni-flash-1.1", "prompt": prompt,
        "reference_image_urls": list(refs.values()),
        "resolution": "720p", "duration": 5,
        "aspect_ratio": "16:9", "mode": "async"}
print(json.dumps(body, indent=2))

Cost of this request

Five seconds at 720p is 5 x 12.5 = 62.5, rounded up to 63 cents. Three references or ten make no difference to the billable amount. Use the dictionary keys as your own labels in logs, so a failed take can be traced to which asset was named.

Keep each image a clear, public HTTPS URL. A private link or an unsupported file type will fail the job.

The same length at every tier

For reference, a 5-second Omni Flash clip at each resolution. Every price is the seconds times the billable rate, rounded up to a whole cent, as of 2026-10-08.

Limits to remember

These apply to every request on this page, from the Video Router and Video generation docs:

• Length is 3 to 10 whole seconds in generation modes; an edit takes no duration.
• Aspect ratio is 16:9 or 9:16; an edit takes no aspect ratio.
• Native synced audio is always on, and generate_audio: false is rejected.
• There is no bitrate_mode, no reference audio and no seed.
• Billing is the provider list times 1.25 per output second, reserved at submit and shown in usage.cost.