视频正在保存但仅显示 0 KB。这些 OpenCv 代码中可能出现的错误是什么

Question

我正在尝试使用 python 在 openCv 中使用 videocapture 对象保存视频。但在按下 'q' 后，视频保存为 'output.avi' 但其大小显示为 0 KB。需要您的帮助，无法找出错误。

import numpy as np
import cv2
cap = cv2.VideoCapture(0)
#1.2. Gui Features in OpenCV 25
#OpenCV-Python Tutorials Documentation, Release 1
# Define the codec and create VideoWriter object
fourcc = cv2.VideoWriter_fourcc(*'XVID')
out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))
while(cap.isOpened()):
    ret, frame = cap.read()
    if ret==True:
        frame = cv2.flip(frame,0)
# write the flipped frame
        out.write(frame)
        cv2.imshow('frame',frame)
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break
    else:
        break
# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()

Answer 1

这里需要玩一下fourCC码

FourCC 代码作为 cv2.VideoWriter_fourcc('M','J','P','G') 或 cv2.VideoWriter_fourcc(*'MJPG ) 对于 MJPG。

import numpy as np
import cv2

cap = cv2.VideoCapture(0)

# Define the codec and create VideoWriter object
#fourcc = cv2.cv.CV_FOURCC(*'DIVX')
#out = cv2.VideoWriter('output.avi',fourcc, 20.0, (640,480))
out = cv2.VideoWriter('output.avi', -1, 20.0, (640,480))

while(cap.isOpened()):
    ret, frame = cap.read()
    if ret==True:
        frame = cv2.flip(frame,0)

        # write the flipped frame
        out.write(frame)

        cv2.imshow('frame',frame)
        if cv2.waitKey(1) & 0xFF == ord('q'):
            break
    else:
        break

# Release everything if job is finished
cap.release()
out.release()
cv2.destroyAllWindows()

更多阅读，OpenCV saving doc and FourCC doc

Answer 2

可能 XVID 的 codecs 没有正确安装。

（如果您使用的是 Jupyter Notebook，则会有以 OpenCV: FFMPEG: ... 开头的 jupyter 日志）

如果您使用 linux，您可以尝试使用 cv2.VideoWriter_fourcc(*'mp4v')，如下所示：

fourcc = cv2.VideoWriter_fourcc(*'mp4v')
out = cv2.VideoWriter('output.mp4', -1, 20.0, (640,480))

注意，扩展名mp4很重要！应选择与 codec.

匹配的正确扩展名

视频正在保存但仅显示 0 KB。这些 OpenCv 代码中可能出现的错误是什么

video is saving but showing 0 KB only. What is the probable error in these code of OpenCv

video-processing

python-2.7

opencv3.0