README.md

---
license: cc-by-nc-4.0
task_categories:
  - depth-estimation
tags:
  - stereo-matching
  - disparity
  - stereo4d
  - foundationstereo
pretty_name: FFS Stereo4D
size_categories:
  - 100K<n<1M
---

# FFS Stereo4D

Disparity maps for stereo matching, generated from the [Stereo4D](https://github.com/niconielsen32/Stereo4D) dataset using [FoundationStereo](https://github.com/NVlabs/FoundationStereo).

## Dataset Structure

```
data/train/
  metadata.csv
  0000000.zip   (first 50,000 images)
  0000001.zip   (next 50,000 images)
  ...
  0000025.zip
```

Each zip contains disparity PNG files named `{vid_id}_frame_{frame_idx:06d}.png`.

- **Disparity images**: 3-channel uint8 784×784 PNG files encoding per-pixel disparity. Decode with: `disp = (R * 255*255 + G * 255 + B) / 1000.0`. See also: https://github.com/NVlabs/FoundationStereo/blob/master/scripts/vis_dataset.py
- **metadata.csv**: Links each disparity image back to its source YouTube video, with a `zip_file` column indicating which zip contains the image.

### Metadata Columns

| Column | Description |
|---|---|
| `file_name` | Disparity image filename (inside the zip) |
| `zip_file` | Which zip file contains this image |
| `vid_id` | Clip identifier (matches the `.npz` calibration file) |
| `frame_idx` | Frame index in the rectified stereo output |
| `youtube_video_id` | YouTube video ID of the source 360 video |
| `timestamp_us` | Timestamp in microseconds in the original video |
| `timestamp_sec` | Timestamp in seconds |
| `video_frame_index` | Estimated frame number in the original video |
| `fps` | FPS of the source video |

## Retrieving Source RGB Frames

This dataset contains **disparity maps only**. Due to the copyrights of these videos, users need to download on your own behalf. The corresponding left/right RGB stereo pairs can be recovered by:

1. Following [stereo4d toolkit](https://github.com/Stereo4d/stereo4d-code) to download the YouTube video using `youtube_video_id`.
2. Seek to `timestamp_sec` (or `video_frame_index`) to locate the source frame.
3. Apply equirectangular rectification using the Stereo4D calibration `.npz` files to obtain the left and right perspective images.

## Generation Pipeline

1. **Source**: YouTube 360 videos from the Stereo4D dataset.
2. **Rectification**: Equirectangular frames are rectified and cropped to 1024×1024 perspective stereo pairs.
3. **Disparity estimation**: FoundationStereo computes dense disparity at 784×784 resolution (resized by `scale=0.765625` of the 1024×1024 input).

### Camera Parameters

The rectified stereo pairs are generated at 1024×1024 with the following pinhole camera model:

| Parameter | Value (1024×1024 rectified) | Value (784×784 disparity) | Formula |
|---|---|---|---|
| HFOV | 60° | 60° | `output_hfov` in `batch_rectify.py` |
| Baseline | 0.063 m | 0.063 m | Assumed interpupillary distance for VR180 cameras |
| fx, fy | 886.8 px | 678.8 px | `size * 0.5 / tan(0.5 * HFOV * pi/180)` |
| cx, cy | 512 px | 392 px | Image center |

Depth is derived as: `depth = fx * baseline / disparity`.

Since disparity is computed at 784×784 resolution (scale factor 784/1024 = 0.765625 of the 1024×1024 input), use the 784×784 camera parameters when converting disparity to depth:

```python
import numpy as np
hfov = 60  # degrees
baseline = 0.063  # meters
imw = 784
fx = imw * 0.5 / np.tan(0.5 * np.radians(hfov))  # 678.8 px
depth = fx * baseline / disparity
```


## Citation

If you use this dataset, please consider cite:

```bibtex
@article{wen2026fastfoundationstereo,
  title={Fast-FoundationStereo: Real-Time Zero-Shot Stereo Matching},
  author={Bowen Wen and Shaurya Dewan and Stan Birchfield},
  journal={CVPR},
  year={2026}
}
@article{wen2025foundationstereo,
  title={FoundationStereo: Zero-Shot Stereo Matching},
  author={Wen, Bowen and Trepte, Matthew and Aribido, Joseph and Kautz, Jan and Birchfield, Stan and Wan, Yao},
  journal={CVPR},
  year={2025}
}
@inproceedings{jin2025stereo4d,
  title={{Stereo4D: Learning How Things Move in 3D from Internet Stereo Videos}},
  author={Jin, Linyi and Tucker, Richard and Li, Zhengqi and Fouhey, David and Snavely, Noah and Holynski, Aleksander},
  booktitle={Proceedings of the IEEE/CVF Conference on Computer Vision and Pattern Recognition},
  year={2025},
}
```