视频转图片序列、图像序列转视频等处理（mmcv vs. opencv）

mmcv简介

mmcv是商汤科技用于计算机视觉研究的基础python库，API比opencv更简洁，很适合深度学习项目的图像、视频预处理。

安装mmcv依赖库：

pip install mmcv

与opencv相比，mmcv.VideoReader提供通过序列访问视频帧的API，VideoReader会在内部缓存已访问的帧。

The VideoReader class provides sequence like apis to access video frames. It will internally cache the frames which have been visited.

视频常用代码片段

加载视频

# 加载视频
video = mmcv.VideoReader('test.mp4')

# 打印视频长度、分辨率、fps
print(len(video))
print(video.width, video.height, video.resolution, video.fps)

读取视频帧

# 迭代访问所有帧
for frame in video:
    print(frame.shape)

# read the next frame
img = video.read()

# read a frame by index
img = video[100]

# read some frames
imgs = video[5:10]

视频转图像序列