Inference with existing models¶

MMAction2 provides pre-trained models for video understanding in Model Zoo. This note will show how to use existing models to inference on given video.

As for how to test existing models on standard datasets, please see this guide

Inference on a given video¶

MMAction2 provides high-level Python APIs for inference on a given video:

init_recognizer: Initialize a recognizer with a config and checkpoint
inference_recognizer: Inference on a given video

Here is an example of building the model and inference on a given video by using Kinitics-400 pre-trained checkpoint.

Note

If you use mmaction2 as a 3rd-party package, you need to download the conifg and the demo video in the example.

Run ‘mim download mmaction2 –config tsn_imagenet-pretrained-r50_8xb32-1x1x8-100e_kinetics400-rgb –dest .’ to download the required config.

Run ‘wget https://github.com/open-mmlab/mmaction2/blob/main/demo/demo.mp4’ to download the desired demo video.

from mmaction.apis import inference_recognizer, init_recognizer

config_path = 'configs/recognition/tsn/tsn_imagenet-pretrained-r50_8xb32-1x1x8-100e_kinetics400-rgb.py'
checkpoint_path = 'https://download.openmmlab.com/mmaction/v1.0/recognition/tsn/tsn_imagenet-pretrained-r50_8xb32-1x1x8-100e_kinetics400-rgb/tsn_imagenet-pretrained-r50_8xb32-1x1x8-100e_kinetics400-rgb_20220906-2692d16c.pth' # can be a local path
img_path = 'demo/demo.mp4'   # you can specify your own picture path

# build the model from a config file and a checkpoint file
model = init_recognizer(config_path, checkpoint_path, device="cpu")  # device can be 'cuda:0'
# test a single image
result = inference_recognizer(model, img_path)

result is a dictionary containing pred_scores.

An action recognition demo can be found in demo/demo.py.