Creating Video

Creating Video

Claude cannot render video itself, but it can direct a generator. This skill drives a multi-clip pipeline — script → per-scene generation → review → assembly — with Claude as the editing agent overseeing continuity and cut.

Requires ffmpeg/ffprobe and Cloudflare AI Gateway creds (/mnt/project/proxy.env).

Default model: Gemini Omni Flash (gemini-omni-flash-preview, Interactions API) — Google's own guidance as of 2026-07. It beats Veo on character consistency, reference-image control, text rendering, and conversational editing, and generates faster (~30–90 s/clip vs 1–3 min). Fall back to Veo 3.1 (scripts/veo_generate.py, kept intact) only for scene extension, first+last-frame interpolation, or legacy pipelines — Omni supports neither.

The five stages

1. Shot list — break the story into beats, up to 10 s each, one prompt per shot.
2. Generate — scripts/omni_generate.py, run detached.
3. Review — parsing-video on each clip and on the assembled cut.
4. Assemble — scripts/assemble.py, run detached.
5. Iterate — re-review, then edit failing scenes conversationally (cheaper and more stable than regenerating from scratch).

Stage 2 — Generation (Omni via Cloudflare AI Gateway)

Auth is CF AI Gateway BYOK: proxy.env supplies CF_ACCOUNT_ID, CF_GATEWAY_ID, CF_API_TOKEN; the Google key lives inside the gateway. Both the interactions call and the files/{id}:download retrieval route through it (verified 2026-07-20).

Run detached. The Interactions API is synchronous — the HTTP call holds open for the whole generation (~30–90 s/clip). bash_tool caps at ~50 s. Launch and adaptive-wait on the DONE sentinel:

# prompts.json = {"1": "...", "2": {"text": "...", "images": ["ref0.png"]}, ...}
set -a; . /mnt/project/proxy.env; set +a
(setsid python3 scripts/omni_generate.py prompts.json --out omni/ \
    --negative "on-screen watermark" &)
# then, in a separate call:
timeout 45 sh -c 'while [ ! -f omni/DONE ]; do sleep 3; done'; cat omni/generate.log

Gotchas (all verified 2026-07-20 — the script already handles them):

• No dry run exists. Even input:"" returns 200 and bills a full generation (~58k video output tokens). Every request costs money; never "validate" with a throwaway call.
• No negativePrompt parameter (Veo had one; Omni 400s on unsupported params). --negative folds into the prompt as "Do not include: X."
• Videos >4MB need delivery:"uri" → poll files/{id} to ACTIVE → download via the gateway. The script always uses uri delivery, inline base64 as fallback.
• Output is up to 10 s 1280×720 mp4 with synchronized audio + SynthID watermark. No video extension, no first↔last-frame interpolation, no multi-video referencing — those are Veo territory.
• The egress proxy 503s on cold start → retry with backoff.

Omni defaults to multi-shot. Left alone it invents its own cuts inside a clip, which fights a shot-list pipeline. Every per-scene prompt should say "single continuous shot" / "no scene cuts" unless the beat wants internal cuts.

Stage 3 — Review (use the parsing-video skill)

Contact-sheet each clip and the assembled cut. Per-clip sheets miss cross-clip continuity; the full-cut sheet is where character drift, prop jumps, and logic breaks show up in one read (Oskar, 2026-07-18: review the whole assembly, not just scenes). Scan every sheet against the continuity checklist:

• Character — same face/hair/wardrobe across every shot they appear in.
• Prop — same identity, size, color, and attachment point shot to shot.
• Physical logic — is the world coherent (a window must be open before a bird lands on the sill)?
• Action completeness — is the key action actually shown, not cut around?

Stage 4 — Assembly (scripts/assemble.py)

Trims each clip to its beat, crossfades, drops audio by default, optionally burns an overlay word, and holds the final frame so the ending lands.

(setsid python3 scripts/assemble.py omni/scene_1.mp4 ... omni/scene_6.mp4 \
    --out film.mp4 --tail-hold 1.3 &)

Run detached too — six trims plus a 30 s stitch exceed the bash ceiling on the single-core container. Diagnosed: abrupt ending → --tail-hold; jarring cuts between independently generated ambiences → audio dropped by default (--keep-audio to acrossfade instead).