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+# Preparing HMDB51
+
+## Introduction
+
+<!-- [DATASET] -->
+
+```BibTeX
+@article{Kuehne2011HMDBAL,
+  title={HMDB: A large video database for human motion recognition},
+  author={Hilde Kuehne and Hueihan Jhuang and E. Garrote and T. Poggio and Thomas Serre},
+  journal={2011 International Conference on Computer Vision},
+  year={2011},
+  pages={2556-2563}
+}
+```
+
+For basic dataset information, you can refer to the dataset [website](https://serre-lab.clps.brown.edu/resource/hmdb-a-large-human-motion-database/).
+Before we start, please make sure that the directory is located at `$MMACTION2/tools/data/hmdb51/`.
+
+To run the bash scripts below, you need to install `unrar`. you can install it by `sudo apt-get install unrar`,
+or refer to [this repo](https://github.com/innerlee/setup) by following the usage and taking [`zzunrar.sh`](https://github.com/innerlee/setup/blob/master/zzunrar.sh)
+script for easy installation without sudo.
+
+## Step 1. Prepare Annotations
+
+First of all, you can run the following script to prepare annotations.
+
+```shell
+bash download_annotations.sh
+```
+
+## Step 2. Prepare Videos
+
+Then, you can run the following script to prepare videos.
+
+```shell
+bash download_videos.sh
+```
+
+## Step 3. Extract RGB and Flow
+
+This part is **optional** if you only want to use the video loader.
+
+Before extracting, please refer to [install.md](/docs/install.md) for installing [denseflow](https://github.com/open-mmlab/denseflow).
+
+If you have plenty of SSD space, then we recommend extracting frames there for better I/O performance.
+
+You can run the following script to soft link SSD.
+
+```shell
+# execute these two line (Assume the SSD is mounted at "/mnt/SSD/")
+mkdir /mnt/SSD/hmdb51_extracted/
+ln -s /mnt/SSD/hmdb51_extracted/ ../../../data/hmdb51/rawframes
+```
+
+If you only want to play with RGB frames (since extracting optical flow can be time-consuming), consider running the following script to extract **RGB-only** frames using denseflow.
+
+```shell
+bash extract_rgb_frames.sh
+```
+
+If you didn't install denseflow, you can still extract RGB frames using OpenCV by the following script, but it will keep the original size of the images.
+
+```shell
+bash extract_rgb_frames_opencv.sh
+```
+
+If both are required, run the following script to extract frames using "tvl1" algorithm.
+
+```shell
+bash extract_frames.sh
+```
+
+## Step 4. Generate File List
+
+you can run the follow script to generate file list in the format of rawframes and videos.
+
+```shell
+bash generate_rawframes_filelist.sh
+bash generate_videos_filelist.sh
+```
+
+## Step 5. Check Directory Structure
+
+After the whole data process for HMDB51 preparation,
+you will get the rawframes (RGB + Flow), videos and annotation files for HMDB51.
+
+In the context of the whole project (for HMDB51 only), the folder structure will look like:
+
+```
+mmaction2
+├── mmaction
+├── tools
+├── configs
+├── data
+│   ├── hmdb51
+│   │   ├── hmdb51_{train,val}_split_{1,2,3}_rawframes.txt
+│   │   ├── hmdb51_{train,val}_split_{1,2,3}_videos.txt
+│   │   ├── annotations
+│   │   ├── videos
+│   │   │   ├── brush_hair
+│   │   │   │   ├── April_09_brush_hair_u_nm_np1_ba_goo_0.avi
+
+│   │   │   ├── wave
+│   │   │   │   ├── 20060723sfjffbartsinger_wave_f_cm_np1_ba_med_0.avi
+│   │   ├── rawframes
+│   │   │   ├── brush_hair
+│   │   │   │   ├── April_09_brush_hair_u_nm_np1_ba_goo_0
+│   │   │   │   │   ├── img_00001.jpg
+│   │   │   │   │   ├── img_00002.jpg
+│   │   │   │   │   ├── ...
+│   │   │   │   │   ├── flow_x_00001.jpg
+│   │   │   │   │   ├── flow_x_00002.jpg
+│   │   │   │   │   ├── ...
+│   │   │   │   │   ├── flow_y_00001.jpg
+│   │   │   │   │   ├── flow_y_00002.jpg
+│   │   │   ├── ...
+│   │   │   ├── wave
+│   │   │   │   ├── 20060723sfjffbartsinger_wave_f_cm_np1_ba_med_0
+│   │   │   │   ├── ...
+│   │   │   │   ├── winKen_wave_u_cm_np1_ri_bad_1
+
+```
+
+For training and evaluating on HMDB51, please refer to [getting_started.md](/docs/getting_started.md).