Video Understanding — Temporal Modeling

A video is a sequence of images plus the physics that connects them. Every video model either treats time as an extra axis (3D conv), a sequence to attend over (transformer), or a feature to extract once and pool (2D+pool).

Learn + Build 45 min Python

Prerequisites: Phase 4 Lesson 03 (CNNs), Phase 4 Lesson 04 (Image Classification)

#Learning Objectives

  • Distinguish the three main video-modelling approaches (2D+pool, 3D conv, spatio-temporal transformer) and predict their cost and accuracy trade-offs
  • Implement frame sampling, temporal pooling, and a 2D+pool baseline classifier in PyTorch
  • Explain why I3D's "inflated" 3D kernels transfer well from ImageNet weights and what a factorised (2+1)D conv does differently
  • Read the standard action-recognition datasets and metrics: Kinetics-400/600, UCF101, Something-Something V2; top-1 accuracy at the clip and video level
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The text and code of this lesson are based on AI Engineering from Scratch by Rohit Ghumare, MIT licensed.