Why does Seedance limit AI video output to 15 seconds per generation?

Seedance 2.0 caps each generation at 15 seconds because longer single-pass diffusion runs scale compute and VRAM non-linearly with frame count, and temporal coherence — character identity, lighting, motion logic — degrades the further the model has to extrapolate. The 15-second ceiling is the point where quality, cost, and render time stay predictable.

Plan around the cap rather than fight it: the invideo agent automatically decomposes any longer shot list into discrete generations capped at 15 seconds, so you don't sequence manually. Three things drive the 15-second ceiling in current diffusion video models:

Compute scales non-linearly with duration. Frame count, attention window, and VRAM pressure all grow with clip length — doubling duration more than doubles cost and render time. At 1080p, a single 15-second Seedance 2.0 render already takes ~20 minutes during peak load; dropping to 720p cuts that dramatically, which is why 720p is the practical default for vertical formats. The cap keeps per-generation cost and queue time predictable.

Temporal coherence degrades past ~15 seconds. Diffusion-based video models hold character identity, lighting, and motion logic through a finite attention context. Beyond roughly 15 seconds the model starts drifting — faces shift, fabric stops behaving consistently, lighting wanders. Capping output is the cleanest way to keep what you generate usable; pushing the model further trades render budget for clips you'd reject anyway.

Discrete duration steps (4, 5, 6, 8, 10, 12, 15s) match how directors actually cut. Most ad and film beats live in the 4–10 second range. A 15-second ceiling lets one generation hold a multi-shot sequence in a single pass when continuity matters (audio and visual carry across cuts cleanly), while shorter discrete steps let you spend credits only on the beat length you need.

For anything longer, batch and stitch. Ask the invideo agent for the shot breakdown — it splits the script into 15-second-or-less generations, holds character sheets and location keyframes across them, and you assemble in invideo's Slate timeline or Premiere. The Batch-5 cadence (generate five clips at a time, review, lock the winners, regenerate the rest) is the standard credit-efficient loop — smaller batches let you catch drift early instead of burning credits on 15 clips that all inherit the same mistake. As one production noted, "smaller batches just give me more freedom to iterate quickly and early, and more importantly, they save a ton of credits compared to if I was generating all 15 clips at once."

Where other models sit. Kling 3.0 generates multi-shot sequences natively and Veo offers longer windows, but both pay for it in compute cost and their own coherence trade-offs at the long end. invideo has all of these models — the invideo agent routes each shot to whichever fits the beat (Seedance 2.0 for reference-to-video continuity, Kling for native multi-shot, Veo where its strengths apply), so the 15-second cap on any single model is rarely the binding constraint on your finished film.

The practical move: stop thinking of 15 seconds as a limit and start thinking of it as the natural unit of generation. Batches of 5 clips, locked frames before video credits, agent-managed stitching — that's how multi-minute ads get built without quality drift.

Watch some of these to see what works for you:

smaller batches just give me more freedom to iterate quickly and early, and more importantly, they save a ton of credits compared to if I was generating all 15 clips at once and then finding something that's gone off

— invideo's creative team, on the Batch-5 generation cadence