--- a
+++ b/tools/data/build_videos.py
@@ -0,0 +1,127 @@
+# Copyright (c) OpenMMLab. All rights reserved.
+import argparse
+import glob
+import os
+import os.path as osp
+import sys
+from multiprocessing import Pool
+
+
+def encode_video(frame_dir_item):
+    """Encode frames to video using ffmpeg.
+
+    Args:
+        frame_dir_item (list): Rawframe item containing raw frame directory
+            full path, rawframe directory (short) path, rawframe directory id.
+
+    Returns:
+        bool: Whether synthesize video successfully.
+    """
+    full_path, frame_dir_path, frame_dir_id = frame_dir_item
+    out_full_path = args.out_dir
+
+    img_name_tmpl = args.filename_tmpl + '.' + args.in_format
+    img_path = osp.join(full_path, img_name_tmpl)
+
+    out_vid_name = frame_dir_path + '.' + args.ext
+    out_vid_path = osp.join(out_full_path, out_vid_name)
+
+    cmd = osp.join(
+        f"ffmpeg -start_number {args.start_idx} -r {args.fps} -i '{img_path}' "
+        f"-vcodec {args.vcodec} '{out_vid_path}'")
+    os.system(cmd)
+
+    print(f'{frame_dir_id} {frame_dir_path} done')
+    sys.stdout.flush()
+    return True
+
+
+def parse_args():
+    parser = argparse.ArgumentParser(description='synthesize videos')
+    parser.add_argument('src_dir', type=str, help='source rawframe directory')
+    parser.add_argument('out_dir', type=str, help='output video directory')
+    parser.add_argument(
+        '--fps', type=int, default=30, help='fps of videos to be synthesized')
+    parser.add_argument(
+        '--level',
+        type=int,
+        choices=[1, 2],
+        default=2,
+        help='directory level of data')
+    parser.add_argument(
+        '--num-worker',
+        type=int,
+        default=8,
+        help='number of workers to build videos')
+    parser.add_argument(
+        '--in-format',
+        type=str,
+        default='jpg',
+        choices=['jpg', 'png'],
+        help='input format')
+    parser.add_argument(
+        '--start-idx', type=int, default=0, help='starting index of rawframes')
+    parser.add_argument(
+        '--filename-tmpl',
+        type=str,
+        default='img_%05d',
+        help='filename template of rawframes')
+    parser.add_argument(
+        '--vcodec', type=str, default='mpeg4', help='coding method of videos')
+    parser.add_argument(
+        '--ext',
+        type=str,
+        default='mp4',
+        choices=['mp4', 'avi'],
+        help='video file extensions')
+    parser.add_argument('--num-gpu', type=int, default=8, help='number of GPU')
+    parser.add_argument(
+        '--resume',
+        action='store_true',
+        default=False,
+        help='resume optical flow extraction instead of overwriting')
+    args = parser.parse_args()
+
+    return args
+
+
+if __name__ == '__main__':
+    args = parse_args()
+
+    if not osp.isdir(args.out_dir):
+        print(f'Creating folder: {args.out_dir}')
+        os.makedirs(args.out_dir)
+
+    if args.level == 2:
+        classes = os.listdir(args.src_dir)
+        for classname in classes:
+            new_dir = osp.join(args.out_dir, classname)
+            if not osp.isdir(new_dir):
+                print(f'Creating folder: {new_dir}')
+                os.makedirs(new_dir)
+
+    print('Reading rgb frames from folder: ', args.src_dir)
+    print('Input format of rgb frames: ', args.in_format)
+    fullpath_list = glob.glob(args.src_dir + '/*' * args.level)
+    done_fullpath_list = glob.glob(args.src_dir + '/*' * args.level + '.' +
+                                   args.ext)
+    print('Total number of rgb frame folders found: ', len(fullpath_list))
+
+    if args.resume:
+        fullpath_list = set(fullpath_list).difference(set(done_fullpath_list))
+        fullpath_list = list(fullpath_list)
+        print('Resuming. number of videos to be synthesized: ',
+              len(fullpath_list))
+
+    if args.level == 2:
+        frame_dir_list = list(
+            map(
+                lambda p: osp.join(
+                    osp.basename(osp.dirname(p)), osp.basename(p)),
+                fullpath_list))
+    elif args.level == 1:
+        frame_dir_list = list(map(osp.basename, fullpath_list))
+
+    pool = Pool(args.num_worker)
+    pool.map(encode_video,
+             zip(fullpath_list, frame_dir_list, range(len(frame_dir_list))))