Software calculates missing in-between frames to smooth motion or raise framerate — motion interpolation in post. Popular for slow-motion, risky without precise motion analysis.
The software calculates missing intermediate frames between two existing images—the core principle of temporal filling. You're working with 24fps footage and suddenly need 48fps for an elegant slow-motion sequence? Instead of reshooting, you let the computer fill in the gaps. Sounds practical, but it's a tightrope walk between a professional technique and a visual disaster. The algorithms analyze motion vectors between two frames, extrapolate direction and speed, and construct intermediate images. This works elegantly with uniform, predictable movements—a car driving straight, a camera move, a pan. Chaos arises as soon as objects overlap, occlude each other, or suddenly change direction.
In practical work on set, you quickly observe where temporal filling is detrimental: cuts between actors occluding each other lead to ghosting artifacts. The software doesn't know that one character is disappearing behind another—it just paints wildly in between. The same applies to flying hair, particles, water. Temporal filling is safest with controlled, technical shots: camera moves through 3D spaces, motion graphics sequences, visual effects with clear geometric paths. You also need to evaluate the input frames yourself—the cleaner and more stable the original footage, the more reliably the algorithm works.
Standard tools like Twixtor or the native interpolation features in Premiere, After Effects, or DaVinci Resolve offer different degrees of motion analysis. High-quality GPU-accelerated options (such as Optical Flow in modern systems) deliver better results than simple frame blending but cost render time. The most common mistake: uncritically increasing the frame rate without a preview. Render your test renders at a lower resolution before letting 4K footage process for an hour. It's often cheaper to do 2–3 additional takes on set than to experiment in post-production later. For final deliverables (especially broadcast), you should compare the interpolated frames with the original footage—some clients don't accept the smoothness, while others actively expect it.