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Exocentric-to-Egocentric Video Generation
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Exo2Ego-V generates egocentric videos from four 360°-configured exocentric videos using a diffusion pipeline with a multi-view exocentric encoder, a PixelNeRF-based view translation prior, and temporal layers.
Problem
Generating egocentric videos of daily-life skilled human activities from sparse, widely spread 4-view exocentric videos, which is hard due to large viewpoint differences, complex dynamic motion, and real-world environments.
Approach
A trainable copy of the ego UNet encodes multi-view exo videos as appearance conditions via concatenated self-attention, and a generalizable PixelNeRF renders spatially aligned ego features concatenated to the noisy ego latents as a geometric prior, with temporal layers added for frame consistency.
Key results
- On Ego-Exo4D unseen actions, Exo2Ego-V reaches LPIPS 0.249 on basketball and 0.235 on covid test versus 0.397 and 0.477 for SVD, with the abstract claiming an average 35% LPIPS improvement.
- On H2O, Exo2Ego-V achieves PSNR 18.600, SSIM 0.581, LPIPS 0.189 versus SVD's 16.530, 0.468, 0.271.
- Ablation on cooking (unseen action): full model PSNR 17.367 and LPIPS 0.408; removing the exo2ego prior lowers LPIPS to 0.364 but reduces PSNR to 17.268 and misses limbs in qualitative results.
Measured effects reported in the paper
| What was changed | Where | Measured | Effect |
|---|---|---|---|
| use Exo2Ego-V instead of SVD | Exo2Ego-V · Ego-Exo4D categories, unseen actions | LPIPS: average of 35% | Helped |
| remove multi-view exocentric encoder (ablation) | Exo2Ego-V · Cooking, unseen action | PSNR: 17.367 -> 16.777 | Hurt |
| remove Exo2Ego view translation prior (ablation) | Exo2Ego-V · Cooking, unseen action | PSNR: 17.367 -> 17.268 | Hurt |
| remove Exo2Ego view translation prior (ablation) | Exo2Ego-V · Cooking, unseen action | LPIPS: 0.408 -> 0.364 | Helped |
| add temporal layers to the exocentric encoder (ablation) | Exo2Ego-V · Cooking, unseen action | LPIPS: 0.408 -> 0.507 | Hurt |
| use 3 exocentric views instead of 4 (ablation) | Exo2Ego-V · Cooking, unseen action | LPIPS: 0.408 -> 0.383 | Hurt |
| use 2 exocentric views instead of 4 (ablation) | Exo2Ego-V · Cooking, unseen action | LPIPS: 0.408 -> 0.399 | Hurt |
| use 1 exocentric view instead of 4 (ablation) | Exo2Ego-V · Cooking, unseen action | LPIPS: 0.408 -> 0.395 | Hurt |
| replace the exocentric encoder with CLIP features (ablation) | Exo2Ego-V · Cooking, unseen action | LPIPS: 0.408 -> 0.425 | Hurt |
| use temporal-spatial rather than spatial-temporal attention (ablation) | Exo2Ego-V · Cooking, unseen action | LPIPS: 0.408 -> 0.402 | Mixed |
Surprising findings
- Removing the Exo2Ego view translation prior gives the best LPIPS on cooking but yields inaccurate egocentric content, so LPIPS alone is misleading.
- PixelNeRF gets competitive PSNR despite blurry outputs, since PSNR favors blur.
Limitations
- Focuses on several categories of skilled activities; not yet general activities.
- Inference is not real-time (9.06 s per 8-frame clip).
- Unseen-scene performance is limited; the authors note the difficulty of generalizing to new environments with few scenes.
Experimental setup
Datasets: Ego-Exo4D H2O
Benchmarks: Ego-Exo4D H2O
Metrics: PSNR SSIM LPIPS
Baselines: PixelNeRF Stable Diffusion Stable Video Diffusion Exo2Ego (image-level)
Builds on: Stable Diffusion AnimateDiff PixelNeRF ReconFusion MVDream
Closest papers by meaning
- Grounded-Exo2Ego: Structured Semantic Grounding for Robust Exocentric-to-Egocentric Video Generation (NeurIPS 2026 · similarity 0.91)
- EgoVid-5M: A Large-Scale Video-Action Dataset for Egocentric Videos Generation (NeurIPS 2025 · similarity 0.90)
- EgoExo-Gen: Ego-centric Video Prediction by Watching Exo-centric Videos (ICLR 2025 · similarity 0.87)
- EgoGen: An Egocentric Synthetic Data Generator (CVPR 2024 · similarity 0.87)
- Bootstrap Your Own Views: Masked Ego-Exo Modeling for Fine-grained View-invariant Video Representations (CVPR 2025 · similarity 0.87)
- Viewpoint Rosetta Stone: Unlocking Unpaired Ego-Exo Videos for View-invariant Representation Learning (CVPR 2025 · similarity 0.87)
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