Slow video reading of imageio.v3 compared to opencv

[zzhuolun]

Test the video reading speed

I benchmarked the reading speed of .MP4 video between Imageio.v3 and opencv::VideoCapture. This is the python code to compare the speed:

import cv2
import time
import imageio.v3 as iio
import argparse
from tqdm import tqdm


def cv2_time(video_path: str, frame_ids: list) -> float:
    # opencv
    video = cv2.VideoCapture(video_path)
    start_time = time.time()
    for frame_id in tqdm(frame_ids, desc='OpenCV seq'):
        video.read()
    return time.time() - start_time


def imiter_time(video_path: str, frame_ids: list) -> float:
    # imiter
    imiter = iio.imiter(video_path, plugin='pyav')
    start_time = time.time()
    for frame_id in tqdm(frame_ids, desc='imiter'):
        next(imiter)
    return time.time() - start_time


def imopen_read_time(video_path: str, frame_ids: list) -> float:
    # imopen read
    imopen = iio.imopen(video_path, 'r', plugin="pyav")
    start_time = time.time()
    for frame_id in tqdm(frame_ids, desc='imopen read'):
        imopen.read(index=frame_id)
    return time.time() - start_time


def imopen_iter_time(video_path: str, frame_ids: list) -> float:
    # imopen iter
    imopen = iio.imopen(video_path, 'r', plugin="pyav")
    iter = imopen.iter()
    start_time = time.time()
    for frame_id in tqdm(frame_ids, desc='imopen iter'):
        next(iter)
    return time.time() - start_time


def compare_time(video_path: str):
    frame_ids = range(500)
    secs_cv2 = cv2_time(video_path, frame_ids)
    secs_imiter = imiter_time(video_path, frame_ids)
    secs_imopen_read = imopen_read_time(video_path, frame_ids)
    secs_imopen_iter = imopen_iter_time(video_path, frame_ids)

    print(f'opencv time {secs_cv2:.3f}s')
    print(f'iio.iter time {secs_imiter:.3f}s')
    print(f'iio.open read time {secs_imopen_read:.3f}s')
    print(f'iio.open ter time {secs_imopen_iter:.3f}s')


if __name__ == '__main__':
    parser = argparse.ArgumentParser()
    parser.add_argument('video', help='Path to video', type=str)
    opt = parser.parse_args()
    compare_time(opt.video)

Result

Testing the above script on a DJI MP4 video gives the following result:

OpenCV seq: 100%|█████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 500/500 [00:04<00:00, 115.35it/s]
imiter: 100%|██████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 500/500 [00:26<00:00, 18.53it/s]
imopen read: 100%|█████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 500/500 [00:26<00:00, 18.66it/s]
imopen iter: 100%|█████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 500/500 [00:26<00:00, 18.76it/s]
opencv time 4.339s
iio.iter time 26.980s
iio.open read time 26.798s
iio.open ter time 26.648s

Imageio.v3 is significantly slower than opencv in video reading.

My environment:

opencv-python                  4.9.0.80
imageio                        2.34.1
imageio-ffmpeg                 0.4.9
av                             12.0.0
Python 3.10.14
OS Ubuntu 22.04.4 LTS

Related issue

I found a similar issue reported: #1050
However, the previous issue is on imageio.v2. The current one is about imageio.v3. Also, seems that the slow reads problem in v2 is also still not solved.