在不保存 opencv 的情况下编写和读取视频

Question

我想在用 cv2.VideoWriter 编写视频后不保存视频来阅读。

例如：

video =  cv2.VideoWriter('using.mp4', cv2.VideoWriter_fourcc(*'MJPG'), 10, size)

现在，写完这个 cv2.VideoWriter 对象后，是否可以像 video.read() 那样读取它，但是由于 read() 是 cv2.VideoCapture 的函数，它会抛出一个错误

Exception has occurred: AttributeError
'cv2.VideoWriter' object has no attribute 'read'

那么，有没有可能阅读 cv2.VideoWriter 的方法？

Answer 1

从视频编写器读取帧的另一种方法是将帧保存在列表中，而不是将每个帧保存在循环中。完成后，您可以将它们写在循环外并保存为 video.read()

video =  cv2.VideoWriter('using.mp4', cv2.VideoWriter_fourcc(*'MJPG'), 10, size)
for frame in frames:
    writer.write(frame)
for frame in frames:
    # do other stuff here

详细示例（注意我更改了 fourcc - 你的示例对我不起作用）

import cv2


def cam_test(port: int = 0) -> None:
    frames = []
    cap = cv2.VideoCapture(port)
    if not cap.isOpened():  # Check if the web cam is opened correctly
        print("failed to open cam")
    else:
        print('cam opened on port {}'.format(port))

        for i in range(10 ** 10):
            success, cv_frame = cap.read()
            if not success:
                print('failed to capture frame on iter {}'.format(i))
                break
            frames.append(cv_frame)
            cv2.imshow('Input', cv_frame)
            k = cv2.waitKey(1)
            if k == ord('q'):
                break

        cap.release()
        cv2.destroyAllWindows()

    # Now you have the frames at hand

    if len(frames) > 0:
        # if you want to write them
        size = (frames[0].shape[1], frames[0].shape[0])
        video = cv2.VideoWriter(
            filename='using.mp4',
            fourcc=cv2.VideoWriter_fourcc(c1='m', c2='p', c3='4', c4='v'),
            fps=10,
            frameSize=size
        )
        for frame in frames:
            video.write(frame)

        # and to answer your question, you wanted to do video.read() which would have gave you frame by frame
        for frame in frames:
            pass  # each iteration is like video.read() if video.read() was possible

    return


if __name__ == '__main__':
    cam_test()

在不保存 opencv 的情况下编写和读取视频

Writing and Reading video without saving in opencv

python

opencv