Omnimatte in PyTorch

This repository contains a re-implementation of the code for the CVPR 2021 paper "Omnimatte: Associating Objects and Their Effects in Video."

Prerequisites

Linux
Python 3.6+
NVIDIA GPU + CUDA CuDNN

Installation

This code has been tested with PyTorch 1.8 and Python 3.8.

Install PyTorch 1.8 and other dependencies.
- For pip users, please type the command pip install -r requirements.txt.
- For Conda users, you can create a new Conda environment using conda env create -f environment.yml.

Demo

To train a model on a video (e.g. "tennis"), run:

python train.py --name tennis --dataroot ./datasets/tennis --gpu_ids 0,1

To view training results and loss plots, visit the URL http://localhost:8097. Intermediate results are also at ./checkpoints/tennis/web/index.html.

To save the omnimatte layer outputs of the trained model, run:

python test.py --name tennis --dataroot ./datasets/tennis --gpu_ids 0

The results (RGBA layers, videos) will be saved to ./results/tennis/test_latest/.

Custom video

To train on your own video, you will have to preprocess the data:

Extract the frames, e.g.

mkdir ./datasets/my_video && cd ./datasets/my_video 
mkdir rgb && ffmpeg -i video.mp4 rgb/%04d.png

Resize the video to 256x448 and save the frames in my_video/rgb.
Get input object masks (e.g. using Mask-RCNN and STM), save each object's masks in its own subdirectory, e.g. my_video/mask/01/, my_video/mask/02/, etc.
Compute flow (e.g. using RAFT), and save the forward .flo files to my_video/flow and backward flow to my_video/flow_backward
Compute the confidence maps from the forward/backward flows:
```
python datasets/confidence.py --dataroot ./datasets/tennis
```
Register the video and save the computed homographies in my_video/homographies.txt. See here for details.

Note: Videos that are suitable for our method have the following attributes:

Static camera or limited camera motion that can be represented with a homography.
Limited number of omnimatte layers, due to GPU memory limitations. We tested up to 6 layers.
Objects that move relative to the background (static objects will be absorbed into the background layer).
We tested a video length of up to 200 frames (~7 seconds).

Citation

If you use this code for your research, please cite the following paper:

@inproceedings{lu2021,
  title={Omnimatte: Associating Objects and Their Effects in Video},
  author={Lu, Erika and Cole, Forrester and Dekel, Tali and Zisserman, Andrew and Freeman, William T and Rubinstein, Michael},
  booktitle={CVPR},
  year={2021}
}

Acknowledgments

This code is based on retiming and pytorch-CycleGAN-and-pix2pix.