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Smooth Regularization for Efficient Video Recognition
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Proposes a Gaussian Random Walk (GRW) smoothness regularizer over frame embeddings, combining a permutation-based contrastive frame-ordering loss with an acceleration prior, to improve lightweight video recognition models (MoViNets, MobileNetV3) on Kinetics.
Problem
Lightweight video recognition models under-exploit temporal structure; the paper seeks a temporal inductive bias that improves accuracy within tight FLOP and memory budgets.
Approach
Model frame-to-frame embedding velocities as a Gaussian random walk, so the loss penalizes large accelerations; a contrastive loss over permutations of frame order prevents collapse to a single point. Applied as an extra loss term on intermediate or final-layer embeddings with a small Transformer head.
Key results
- MoViNet-A0-S-GRW reaches 78.4% Top-1 on K600 at 2.7 GFLOPs vs 72.3% for MoViNet-A0, and MoViNet-A3-GRW reaches 85.6% at 56.4 GFLOPs, the claimed SOTA in its FLOP group.
- MobileNetV3-S-GRW reaches 67.3% Top-1 on K600 at 30 MB vs 61.3% baseline.
- Ablation on K600 (MoViNet-A2-S): final-layer GRW gives 83.3% vs 78.4% baseline and 79.3% for attention-only head.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| Add GRW smoothing | MoViNet-A0-S on Kinetics-600 · Kinetics-600 | Top-1 accuracy: 72.3 -> 78.4 | Helped |
| Add GRW smoothing | MoViNet-A1-S on Kinetics-600 · Kinetics-600 | Top-1 accuracy: +5.2% | Helped |
| Add GRW smoothing | MoViNet-A2-S on Kinetics-600 · Kinetics-600 | Top-1 accuracy: 78.4 -> 83.3 | Helped |
| Add GRW smoothing | MoViNet-A3 on Kinetics-600 · Kinetics-600 | Top-1 accuracy: 81.8 -> 85.6 | Helped |
| Add GRW smoothing | MobileNetV3-S on Kinetics-600 · Kinetics-600 | Top-1 accuracy: 61.3 -> 67.3 | Helped |
| Add GRW smoothing | MoViNet-A0 on Kinetics-400 · Kinetics-400 | Top-1 accuracy: 65.8 -> 70.4 | Helped |
| Add GRW smoothing | MoViNet-A2 on Kinetics-400 · Kinetics-400 | Top-1 accuracy: 75.0 -> 77.6 | Helped |
| Add GRW smoothing | MoViNet-A3 on Kinetics-400 · Kinetics-400 | Top-1 accuracy: 78.2 -> 81.7 | Helped |
| Add a 2-layer Transformer head without GRW smoothing (ablation) | MoViNet-A2-S on Kinetics-600 · Kinetics-600 | Top-1 accuracy: +0.9 Top-1 | Helped |
| Add GRW smoothing to the final layer (ablation) | MoViNet-A2-S + attention on Kinetics-600 · Kinetics-600 | Top-1 accuracy: +4.0 absolute | Helped |
| Add GRW smoothing to an intermediate layer (ablation) | MoViNet-A2-S on Kinetics-600 · Kinetics-600 | Top-1 accuracy: +2.4 | Helped |
| Set GRW window T to 3 instead of no smoothing (ablation) | MoViNet-A0-S-GRW on Kinetics-600 · Kinetics-600 | Top-1 accuracy: 72.0 -> 77.3 | Helped |
Surprising findings
- Adding only the 2-layer Transformer head without GRW gives just +0.9 Top-1, so most gain is attributed to the smoothing loss.
- Empirically centering is not required when a learnable linear transformation precedes GRW.
Limitations
- Assumes Gaussian random walk dynamics, which may not hold for abrupt or discontinuous motion.
- Not evaluated on very large-capacity models due to compute constraints.
- Frame-ordering permutation loss adds complexity; denominator requires enumeration or sampling of permutations.
Experimental setup
Datasets: Kinetics-600 Kinetics-400 Airplanes (warm-up toy dataset, 1,000 train videos)
Benchmarks: Kinetics-600 Kinetics-400
Metrics: Top-1 accuracy GFLOPs memory (MB)
Baselines: MoViNet-A0 MoViNet-A1 MoViNet-A2 MoViNet-A3 MobileNetV3-S MobileNetV3-S+TSM X3D MViTv2-B-32x3 UniFormer VideoMamba
Builds on: MoViNets MobileNetV3 slow feature analysis TSM
Closest papers by meaning
- Slow and Steady Feature Analysis: Higher Order Temporal Coherence in Video (CVPR 2016 · similarity 0.87)
- DejaVid: Encoder-Agnostic Learned Temporal Matching for Video Classification (CVPR 2025 · similarity 0.85)
- GenRec: Unifying Video Generation and Recognition with Diffusion Models (NeurIPS 2024 · similarity 0.84)
- TTVidT: Decoupling the Temporal Axis for Efficient Motion-Centric Video Pretraining (NeurIPS 2026 · similarity 0.84)
- LookWhen? Fast Video Recognition by Learning When, Where, and What to Compute (NeurIPS 2026 · similarity 0.84)
- Instant Video Models: Universal Adapters for Stabilizing Image-Based Networks (NeurIPS 2025 · similarity 0.84)
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