I3D Feature Extraction

Usage

• Format the videos to 25 FPS.
• Convert the videos into frame images and optical flows.
• python3 extract_features.py ...

Parameters

--mode:              rgb or flow
--load_model:        path of the I3D model
--input_dir:         folder of converted videos
--output_dir:        folder of extracted features
--batch_size:        batch size for snippets
--sample_mode:       oversample, center_crop or resize
--frequency:         how many frames between adjacent snippet
--usezip/no-usezip:  whether the frame images are zipped

Important: Use PyTorch 0.3

Input Folder Structure

InputFolder
├── video1
│   ├── flow_x.zip
│   ├── flow_y.zip
│   └── img.zip
└── video2
    ├── flow_x.zip
    ├── flow_y.zip
    └── img.zip

Frame images and flows can also be unzipped.

I3D models trained on Kinetics (Old Readme)

Overview

This repository contains trained models reported in the paper "Quo Vadis, Action Recognition? A New Model and the Kinetics Dataset" by Joao Carreira and Andrew Zisserman.

This code is based on Deepmind's Kinetics-I3D. Including PyTorch versions of their models.

Note

This code was written for PyTorch 0.3. Version 0.4 and newer may cause issues.

Fine-tuning and Feature Extraction

We provide code to extract I3D features and fine-tune I3D for charades. Our fine-tuned models on charades are also available in the models director (in addition to Deepmind's trained models). The deepmind pre-trained models were converted to PyTorch and give identical results (flow_imagenet.pt and rgb_imagenet.pt). These models were pretrained on imagenet and kinetics (see Kinetics-I3D for details).

Fine-tuning I3D

train_i3d.py contains the code to fine-tune I3D based on the details in the paper and obtained from the authors. Specifically, this version follows the settings to fine-tune on the Charades dataset based on the author's implementation that won the Charades 2017 challenge. Our fine-tuned RGB and Flow I3D models are available in the model directory (rgb_charades.pt and flow_charades.pt).

This relied on having the optical flow and RGB frames extracted and saved as images on dist. charades_dataset.py contains our code to load video segments for training.

Feature Extraction

extract_features.py contains the code to load a pre-trained I3D model and extract the features and save the features as numpy arrays. The charades_dataset_full.py script loads an entire video to extract per-segment features.