Frame interpolation generates in-between frames to increase video frame rate or create smooth slow motion. How it works: Estimate motion (optical flow) between existing frames, warp and blend frames to synthesize intermediate frames. Approaches: Flow-based: Compute optical flow, backward warp frames, blend. Learned synthesis: End-to-end networks directly predict intermediate frames (FILM, RIFE, DAIN). Kernel-based: Predict adaptive convolution kernels for synthesis. Key challenges: Occlusion handling (revealed/hidden regions), large motions, complex scenes, temporal consistency. Models: RIFE (Real-Time Intermediate Flow Estimation) is fast with good quality. FILM (Google) offers high quality and handles motion blur. DAIN provides depth-aware interpolation. Applications: 24fps to 60fps conversion, slow motion from normal video, video restoration, animation smoothing, video stabilization. Frame doubling: 2x, 4x, 8x interpolation stacking for extreme slow-mo. Artifacts: Ghosting, warping artifacts in occlusion regions, temporal flicker. Tools: RIFE, Flowframes, Topaz Video AI, DaVinci Resolve plugins.