Lesson 4 of 7
The hard part: staying consistent
7 min read
AI video has one stubborn weakness. Ask for more than a few seconds and the subject starts to slip — a face rearranges, a colour shifts, a logo turns into gibberish. Why is length the hard part?
Every frame has to agree
Remember that a clip is a run of frames, each one generated. For it to look real, every frame has to agree with the one before it — the same character, the same clothes, the same colours. That agreement across time is the whole game, and it's genuinely hard: tiny differences between frames pile up, and after a few seconds they add up to a subject that has quietly drifted into something else.
How well each frame agrees with the ones around it is called temporal consistency. Small frame-to-frame errors accumulate, so the longer a clip runs, the more the subject drifts.
That's why clips are short
This is the real reason clips stay short — not just cost, but drift. A tool can hold a subject together for a few seconds; stretch it longer and the wheels come off. So today's clips top out at a handful of seconds, and if you push past that, expect faces to morph and details to wander.
Length and consistency pull against each other: the longer the clip, the more it drifts. That trade-off is why clips are short by default.
Making something longer, anyway
So how do people make a minute-long video? They don't ask for one long clip. They make several short ones and join them end to end — stitching — often using the last good frame of one clip as the starting keyframe of the next, so it picks up where the last left off. More work, but each piece stays consistent.
Plan long videos as a series of short shots, not one long take. Keep each clip short enough to stay consistent, then stitch — and reuse the final frame as the next clip's start so the join is seamless.
The gist
- —Temporal consistency = every frame agreeing with the next; small errors pile up over time
- —The longer a clip runs, the more the subject drifts — which is why clips stay short
- —To go longer, make several short clips and stitch them, reusing the last frame as the next start
Your five-second clip looks perfect, but pushing the same generation to fifteen seconds makes the character's face keep morphing. What's going on, and what's the fix?
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