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Tutorial 2: Adding New Dataset

Customize Datasets by Reorganizing Data

Reorganize datasets to existing format

The simplest way is to convert your dataset to existing dataset formats (RawframeDataset or VideoDataset).

There are three kinds of annotation files.

  • rawframe annotation

    The annotation of a rawframe dataset is a text file with multiple lines, and each line indicates frame_directory (relative path) of a video, total_frames of a video and the label of a video, which are split by a whitespace.

    Here is an example.

    some/directory-1 163 1
some/directory-2 122 1
some/directory-3 258 2
some/directory-4 234 2
some/directory-5 295 3
some/directory-6 121 3

  • video annotation

    The annotation of a video dataset is a text file with multiple lines, and each line indicates a sample video with the filepath (relative path) and label, which are split by a whitespace.

    Here is an example.

    some/path/000.mp4 1
some/path/001.mp4 1
some/path/002.mp4 2
some/path/003.mp4 2
some/path/004.mp4 3
some/path/005.mp4 3

  • ActivityNet annotation The annotation of ActivityNet dataset is a json file. Each key is a video name and the corresponding value is the meta data and annotation for the video.

    Here is an example.

    {
  "video1": {
      "duration_second": 211.53,
      "duration_frame": 6337,
      "annotations": [
          {
              "segment": [
                  30.025882995319815,
                  205.2318595943838
              ],
              "label": "Rock climbing"
          }
      ],
      "feature_frame": 6336,
      "fps": 30.0,
      "rfps": 29.9579255898
  },
  "video2": {
      "duration_second": 26.75,
      "duration_frame": 647,
      "annotations": [
          {
              "segment": [
                  2.578755070202808,
                  24.914101404056165
              ],
              "label": "Drinking beer"
          }
      ],
      "feature_frame": 624,
      "fps": 24.0,
      "rfps": 24.1869158879
  }
}

There are two ways to work with custom datasets.

  • online conversion

    You can write a new Dataset class inherited from BaseDataset, and overwrite three methods load_annotations(self), evaluate(self, results, metrics, logger) and dump_results(self, results, out), like RawframeDataset, VideoDataset or ActivityNetDataset.

  • offline conversion

    You can convert the annotation format to the expected format above and save it to a pickle or json file, then you can simply use RawframeDataset, VideoDataset or ActivityNetDataset.

After the data pre-processing, the users need to further modify the config files to use the dataset. Here is an example of using a custom dataset in rawframe format.

In configs/task/method/my_custom_config.py:

...
# dataset settings
dataset_type = 'RawframeDataset'
data_root = 'path/to/your/root'
data_root_val = 'path/to/your/root_val'
ann_file_train = 'data/custom/custom_train_list.txt'
ann_file_val = 'data/custom/custom_val_list.txt'
ann_file_test = 'data/custom/custom_val_list.txt'
...
data = dict(
    videos_per_gpu=32,
    workers_per_gpu=4,
    train=dict(
        type=dataset_type,
        ann_file=ann_file_train,
        ...),
    val=dict(
        type=dataset_type,
        ann_file=ann_file_val,
        ...),
    test=dict(
        type=dataset_type,
        ann_file=ann_file_test,
        ...))
...

We use this way to support Rawframe dataset.

An example of a custom dataset

Assume the annotation is in a new format in text files, and the image file name is of template like img_00005.jpg The video annotations are stored in text file annotation.txt as following

directory,total frames,class
D32_1gwq35E,299,66
-G-5CJ0JkKY,249,254
T4h1bvOd9DA,299,33
4uZ27ivBl00,299,341
0LfESFkfBSw,249,186
-YIsNpBEx6c,299,169

We can create a new dataset in mmaction/datasets/my_dataset.py to load the data.

import copy
import os.path as osp

import mmcv

from .base import BaseDataset
from .registry import DATASETS


@DATASETS.register_module()
class MyDataset(BaseDataset):

    def __init__(self,
                 ann_file,
                 pipeline,
                 data_prefix=None,
                 test_mode=False,
                 filename_tmpl='img_{:05}.jpg'):
        super(MyDataset, self).__init__(ann_file, pipeline, test_mode)

        self.filename_tmpl = filename_tmpl

    def load_annotations(self):
        video_infos = []
        with open(self.ann_file, 'r') as fin:
            for line in fin:
                if line.startswith("directory"):
                    continue
                frame_dir, total_frames, label = line.split(',')
                if self.data_prefix is not None:
                    frame_dir = osp.join(self.data_prefix, frame_dir)
                video_infos.append(
                    dict(
                        frame_dir=frame_dir,
                        total_frames=int(total_frames),
                        label=int(label)))
        return video_infos

    def prepare_train_frames(self, idx):
        results = copy.deepcopy(self.video_infos[idx])
        results['filename_tmpl'] = self.filename_tmpl
        return self.pipeline(results)

    def prepare_test_frames(self, idx):
        results = copy.deepcopy(self.video_infos[idx])
        results['filename_tmpl'] = self.filename_tmpl
        return self.pipeline(results)

    def evaluate(self,
                 results,
                 metrics='top_k_accuracy',
                 topk=(1, 5),
                 logger=None):
        pass

Then in the config, to use MyDataset you can modify the config as the following

dataset_A_train = dict(
    type='MyDataset',
    ann_file = ann_file_train,
    pipeline=train_pipeline
)

Customize Dataset by Mixing Dataset

MMAction2 also supports to mix dataset for training. Currently it supports to repeat dataset.

Repeat dataset

We use RepeatDataset as wrapper to repeat the dataset. For example, suppose the original dataset as Dataset_A, to repeat it, the config looks like the following

dataset_A_train = dict(
        type='RepeatDataset',
        times=N,
        dataset=dict(  # This is the original config of Dataset_A
            type='Dataset_A',
            ...
            pipeline=train_pipeline
        )
    )