#环境：opencv 3.4.0    python 3.5.2

#读取视频

import cv2

cap = cv2.VideoCapture('video.avi')

#读取摄像头,0为摄像头索引，当有多个摄像头时，从0开始编号

cap = cv2.VideoCapture(0)

#从视频或摄像头中读取一帧（即一张图像）,返回是否成功标识ret(True代表成功，False代表失败），img为读取的视频帧

ret,frame = cap.read()

#完整的读取视频流并播放视频流代码

# -*- coding:utf-8 -*-

import cv2

cap = cv2.VideoCapture("video.avi")

while(1):

# 读取视频帧

ret, frame = cap.read()

# 显示视频帧

cv2.imshow("capture", frame)

#等候50ms,播放下一帧，或者按q键退出

if cv2.waitKey(50) &0xFF ==ord('q'):

break

#释放视频流

cap.release()

#关闭所有窗口

cv2.destroyAllWindows()

#创建视频流写入对象，VideoWriter_fourcc为视频编解码器，20为帧播放速率，（640，480）为视频帧大小

videoWriter = cv2.VideoWriter('video.avi', cv2.VideoWriter_fourcc('I', '4', '2', '0'), 20, (640,480))

#向视频文件写入一帧

videoWriter.write(frame)

#详解cv2.VideoWriter_fourcc对象(摘自Learning OpenCV3 Computer Vision with Python,坦白讲不太懂)

#fourcc意为四字符代码（Four-Character Codes），顾名思义，该编码由四个字符组成,下面是VideoWriter_fourcc对象一些常用的参数，注意：字符顺序不能弄混

#cv2.VideoWriter_fourcc('I', '4', '2', '0'),该参数是YUV编码类型，文件名后缀为.avi

#cv2.VideoWriter_fourcc('P', 'I', 'M', 'I'),该参数是MPEG-1编码类型，文件名后缀为.avi

#cv2.VideoWriter_fourcc('X', 'V', 'I', 'D'),该参数是MPEG-4编码类型，文件名后缀为.avi

#cv2.VideoWriter_fourcc('T', 'H', 'E', 'O'),该参数是Ogg Vorbis,文件名后缀为.ogv

#cv2.VideoWriter_fourcc('F', 'L', 'V', '1'),该参数是Flash视频，文件名后缀为.flv

#以下为写视频的完整代码

#-*-coding:utf-8-*-

import cv2

cap = cv2.VideoCapture('./dataset/video/cap_zhihao.avi')

fps =int(cap.get(cv2.CAP_PROP_FPS))

size = (int(cap.get(cv2.CAP_PROP_FRAME_WIDTH)),

int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT)))

videoWriter = cv2.VideoWriter('video.avi', cv2.VideoWriter_fourcc('I','4','2','0'), fps, size)

ret, frame = cap.read()

while(ret):

# 展示一帧

cv2.imshow("capture", frame)

videoWriter.write(frame)

cv2.waitKey(fps)

ret,frame = cap.read()

cap.release()

cv2.destroyAllWindows()