FROSTER: Frozen CLIP is a Strong Teacher for Open-vocabulary Action Recognition

This repository is the official implementation of the ICLR2024 paper: "FROSTER: Frozen CLIP is a Strong Teacher for Open-vocabulary Action Recognition"

Xiaohu Huang, Hao Zhou, Kun Yao, Kai Han

[Webpage] | [Paper]

Introduction

teaser.mp4

This paper introduces FROSTER, an effective framework for open-vocabulary action recognition. The overall pipeline of FROSTER consists of two key components, namely, model finetuning to bridge the gap between image and video tasks, and knowledge distillation to maintain the generalizability of the pretrained CLIP.

License

Froster is released under the CC BY-NC-SA 4.0 license.

Performance

We conduct experiments on two open-vocabulary settings, i.e., base-to-novel and cross-dataset. FROSTER achieves state-of-the-art performance on both the two benchmarks.

Table 1: Performance comparison (Top1-Acc (%)) with the CLIP-based methods using ViT-B/16 under the base-to-novel evaluation setting. "HM" denotes the harmonic mean of the accuracy from the base and novel sets. The results of most other papers are taken from Open-VCLIP and ViFiCLIP. † denotes the results with our implementation. The best results are bolded, and the second-best results are underlined.

Method	K-400			HMDB-51			UCF-101			SSv2
-	Base	Novel	HM	Base	Novel	HM	Base	Novel	HM	Base	Novel	IMM
FrozenCLIP	$62.3$	$53.4$	$57.5$	$53.3$	$46.8$	$49.8$	$78.5$	$63.6$	$70.3$	$4.9$	$5.3$	$5.1$
ActionCLIP	$61.0$	$46.2$	$52.6$	$69.1$	$37.3$	$48.5$	$90.1$	$58.1$	$70.7$	$13.3$	$10.1$	$11.5$
XCLIP	$74.1$	$56.4$	$64.0$	$69.4$	$45.5$	$55.0$	$89.9$	$58.9$	$71.2$	$8.5$	$6.6$	$7.4$
VPT	$69.7$	$37.6$	$48.8$	$46.2$	$16.0$	$23.8$	$90.5$	$40.4$	$55.8$	$8.3$	$5.3$	$6.4$
AIM †	$74.6$	$62.5$	$68.0$	$64.0$	$51.6$	$57.1$	$89.8$	$76.4$	$82.6$	$8.5$	$7.9$	$8.2$
ST-Adapter †	$73.6$	$62.0$	$67.3$	$65.3$	$48.9$	$55.9$	$85.5$	$76.8$	$80.9$	$9.3$	$8.4$	$8.8$
ViFi-CLIP	$76.4$	$61.1$	$67.9$	$\underline{73.8}$	$\underline{53.3}$	$\underline{61.9}$	$92.9$	$67.7$	$78.3$	$\underline{16.2}$	$\underline{12.1}$	$\underline{13.9}$
OpenVCLIP	$\underline{76.5}$	$\underline{62.6}$	$\underline{68.9}$	$70.3$	$50.4$	$58.7$	$\underline{94.8}$	$\underline{77.5}$	$\underline{85.3}$	$16.0$	$11.0$	${13.0}$
FROSTER (Ours)	$\mathbf{77.8}$	$\mathbf{64.3}$	$\mathbf{70.4}$	$\mathbf{74.1}$	$\mathbf{58.0}$	$\mathbf{65.1}$	$\mathbf{95.3}$	$\mathbf{80.0}$	$\mathbf{\mathbf{87.0}}$	$\mathbf{18.3}$	$\mathbf{12.2}$	$\mathbf{14.6}$

Table 2: Performance comparison (Top1-Acc (%)) with the previous approaches under the cross-dataset evaluation protocol. All methods are based on CLIP ViT-B/16, except for ER-ZASR (TSM pre-trained on ImageNet-1k) and Text4Vis (ViT-L/14). UCF* and HMDB* indicate evaluating the full validation set, while UCF and HMDB denote evaluating across the three validation splits. The results of most other papers are taken from Open-VCLIP and ViFi-CLIP. † denotes the results produced with our implementation.

Method	UCF*	UCF	HMDB*	HMDB	K-600
ER-ZASR	-	$51.8 \pm 2.9$	-	$35.3 \pm 4.6$	$42.1 \pm 1.4$
Frozen CLIP †	$74.2$	$73.8 \pm 0.6$	$46.3$	$47.9 \pm 0.5$	$68.1 \pm 1.1$
ActionCLIP †	$77.4$	$77.5 \pm 0.8$	$48.0$	$48.2 \pm 1.5$	$62.5 \pm 1.2$
X-CLIP	-	$72.0 \pm 2.3$	-	$44.6 \pm 5.2$	$65.2 \pm 0.4$
VPT	-	$69.3 \pm 4.2$	-	$44.3 \pm 2.2$	$55.8 \pm 0.7$
Text4Vis	$79.6$	-	$49.8$	-	$68.9 \pm 1.0$
AIM †	$79.0$	$79.4 \pm 1.0$	$49.5$	$50.3 \pm 0.8$	$66.7 \pm 0.5$
ST-Adapter †	$77.9$	$77.6 \pm 0.7$	$50.3$	$51.1 \pm 0.6$	$60.2 \pm 1.8$
Vita-CLIP	-	$75.0 \pm 0.6$	-	$48.6 \pm 0.6$	$67.4 \pm 0.5$
ViFi-CLIP	-	$76.8 \pm 0.7$	-	$51.3 \pm 0.6$	$71.2 \pm 1.0$
Open-VCLIP	$\underline{83.5}$	$\underline{83.4} \pm 1.2$	$\underline{53.2}$	$\underline{53.9} \pm 1.2$	$\underline{73.0} \pm 0.8$
FROSTER (Ours)	$\mathbf{85.0}$	$\mathbf{84.8} \pm 1.1$	$\mathbf{54.5}$	$\mathbf{54.8} \pm 1.3$	$\mathbf{74.8} \pm 0.9$

Dependency

The main dependent packages include: PyTorch 1.11.0 and torchvision 0.12.0 and PySlowFast

Detailed Installation instructions can be viewed in INSTALL.md.

Data Preparation

• Kinetics-400.

  We obtained the compressed version Kinetics-400 dataset, where videos have been resized to 256, from the VoV3d Repo. The repository provides the download link for the dataset: Kinetics-400 dataset link. After downloading and extracting the data, you should rename the folders "train_256" and "val_256" to "train" and "val" respectively. Additionally, please note that the video "val/crossing_river/ZVdAl- yh9m0.mp4" is invalid and needs to be replaced. You should download a new version of the video from here and perform the replacement.

• UCF-101.

  We download UCF-101 dataset by the script provided by MMAction2.

• HMDB-51.

  We download the HMDB-51 dataset by the script provided by MMAction2.

• Kinetics-600 testing.

  The validation data of Kinetics-600 we used can be downloaded from link.

Checkpoint

The pre-trained model on K400 is provided at Google Drive.

Training

• Base-to-Novel Setting The training scripts are in the script/training/temporal_b16 folder. Please use train_clip_B2N_hmdb.sh, train_clip_B2N_k400.sh, train_clip_B2N_ssv2.sh and train_clip_B2N_ucf.sh for the training on HMDB51, K400, SSV2, and UCF101, respectively.

Below is the training script on k400, where you need to modify the ROOT, CKPT, DATA.PATH_TO_DATA_DIR, DATA.PATH_PREFIX, DATA.INDEX_LABEL_MAPPING_FILE variables to fit the paths on your server.

ROOT=PATH_TO_FROSTER_WORKSPACE
CKPT=PATH_TO_FROSTER_WORKSPACE
# TRAIN_FILE can be set as train_1.csv or train_2.csv or train_3.csv;
B2N_k400_file=B2N_k400
TRAIN_FILE=train_1.csv
VAL_FILE=val.csv
TEST_FILE=test.csv
cd$ROOT
TORCH_DISTRIBUTED_DEBUG=INFO python -W ignore -u tools/run_net.py \
--cfg configs/Kinetics/TemporalCLIP_vitb16_8x16_STAdapter_K400.yaml \
--opts DATA.PATH_TO_DATA_DIR $ROOT/zs_label_db/$B2N_k400_file \
TRAIN_FILE $TRAIN_FILE \
VAL_FILE $VAL_FILE \
TEST_FILE $TEST_FILE \
DATA.PATH_PREFIX $ROOT/data/k400 \
DATA.PATH_LABEL_SEPARATOR , \
DATA.INDEX_LABEL_MAPPING_FILE $ROOT/zs_label_db/$B2N_k400_file/train_rephrased.json \
TRAIN.ENABLE True \
OUTPUT_DIR $CKPT/basetraining/B2N_k400_froster \
TRAIN.BATCH_SIZE 64 \
TEST.BATCH_SIZE 240 \
TEST.NUM_ENSEMBLE_VIEWS 3 \
TEST.NUM_SPATIAL_CROPS 1 \
NUM_GPUS 8 \
SOLVER.MAX_EPOCH 12 \
SOLVER.WARMUP_EPOCHS 2.0 \
SOLVER.BASE_LR 3.33e-6 \
SOLVER.WARMUP_START_LR 3.33e-8 \
SOLVER.COSINE_END_LR 3.33e-8 \
TRAIN.MIXED_PRECISION True \
DATA.DECODING_BACKEND "pyav" \
MODEL.NUM_CLASSES 200 \
MIXUP.ENABLE False \
AUG.ENABLE False \
AUG.NUM_SAMPLE 1 \
TRAIN.EVAL_PERIOD 1 \
TRAIN.CHECKPOINT_PERIOD 1 \
MODEL.LOSS_FUNC soft_cross_entropy \
TRAIN.LINEAR_CONNECT_CLIMB False \
TRAIN.CLIP_ORI_PATH /root/.cache/clip/ViT-B-16.pt \
TRAIN.LINEAR_CONNECT_LOSS_RATIO 0.0 \
MODEL.RAW_MODEL_DISTILLATION True \
MODEL.KEEP_RAW_MODEL True \
MODEL.DISTILLATION_RATIO 2.0

• Cross-Dataset Setting

The training script is also in the script/training/temporal_b16 folder. Please use train_clip.sh for the training on K400, where you also need to modify the ROOT, CKPT, DATA.PATH_TO_DATA_DIR, DATA.PATH_PREFIX, DATA.INDEX_LABEL_MAPPING_FILE variables to fit the paths on your server.

Average the models

To improve the generalizability of your model, after training, you can use weight_average_tool.py to average the models from different epochs. The source folder source_dir should be changed according to your saved path.

python weight_average_tool.py

Evaluation

• Base-to-Novel Setting

Please use hmdb_clip_B2N.sh, k400_clip_B2N.sh, ssv2_clip_B2N.sh and ucf_clip_B2N.sh for the evaluation on HMDB51, K400, SSV2, and UCF101, respectively, where you need to modify the ROOT, CKPT, DATA.PATH_TO_DATA_DIR, DATA.PATH_PREFIX, DATA.INDEX_LABEL_MAPPING_FILE and LOAD_CKPT_FILE variables to fit the paths on your server.

Below is the evaluation script for k400 dataset.

ROOT=PATH_TO_FROSTER_WORKSPACE
CKPT=PATH_TO_FROSTER_WORKSPACE
OUT_DIR=$CKPT/testing
OAD_CKPT_FILE=$ROOT/basetraining/B2N_k400_froster/wa_checkpoints/swa_2_22.pth
# TRAIN_FILE can be set as train_1.csv or train_2.csv or train_3.csv;# TEST_FILE can be set as val.csv (base set) or test.csv (novel set).# rephrased_file can be set as train_rephrased.json (base set) or test_rephrased.json (novel set)
B2N_k400_file=B2N_k400
TRAIN_FILE=train_1.csv
VAL_FILE=val.csv
TEST_FILE=val.csv
rephrased_file=train_rephrased.json
cd$ROOT
python -W ignore -u tools/run_net.py \
--cfg configs/Kinetics/TemporalCLIP_vitb16_8x16_STAdapter_K400.yaml \
--opts DATA.PATH_TO_DATA_DIR $ROOT/zs_label_db/$B2N_k400_file \
TRAIN_FILE $TRAIN_FILE \
VAL_FILE $VAL_FILE \
TEST_FILE $TEST_FILE \
DATA.PATH_PREFIX $ROOT/data/k400 \
DATA.PATH_LABEL_SEPARATOR , \
DATA.INDEX_LABEL_MAPPING_FILE $ROOT/zs_label_db/B2N_k400/$rephrased_file \
TRAIN.ENABLE False \
OUTPUT_DIR $OUT_DIR \
TEST.BATCH_SIZE 480 \
NUM_GPUS 8 \
DATA.DECODING_BACKEND "pyav" \
MODEL.NUM_CLASSES 200 \
TEST.CUSTOM_LOAD True \
TEST.CUSTOM_LOAD_FILE $LOAD_CKPT_FILE \
TEST.SAVE_RESULTS_PATH temp.pyth \
TEST.NUM_ENSEMBLE_VIEWS 3 \
TEST.NUM_SPATIAL_CROPS 1 \
TEST.PATCHING_MODEL False \
TEST.PATCHING_RATIO $PATCHING_RATIO \
TEST.CLIP_ORI_PATH ~/.cache/clip/ViT-B-16.pt \
DATA_LOADER.NUM_WORKERS 4 \

• Cross-Dataset Setting

Please use hmdb_clip.sh, ucf_clip.sh, and k600_clip.sh for the evaluation on HMDB51, UCF101, and K600, respectively, where you need to modify the ROOT, CKPT, DATA.PATH_TO_DATA_DIR, DATA.PATH_PREFIX, DATA.INDEX_LABEL_MAPPING_FILE and LOAD_CKPT_FILE variables to fit the paths on your server.

Acknowledgement

This repository is built upon OpenVCLIP, PySlowFast and CLIP. Thanks for those well-organized codebases.

Citation

@inproceedings{
huang2024froster,
title={FROSTER: Frozen CLIP is a Strong Teacher for Open-Vocabulary Action Recognition},
author={Xiaohu Huang and Hao Zhou and Kun Yao and Kai Han},
booktitle={International Conference on Learning Representations},
year={2024}
}