读取本地视频，输出视频到本地

# 加载libraries

import cv2
cv2.__version__

'3.4.2'

# 为了获取视频，要创建一个videoCapture对象，传递的参数是一段车辆视频

videoCapture = cv2.VideoCapture('slow_traffic_small.mp4')
type(videoCapture)

cv2.VideoCapture

# 获取视频的帧率（FPS,frames per second）

fps = videoCapture.get(cv2.CAP_PROP_FPS)
fps

29.97002997002997

# 获取视频的帧宽（frame width）和帧高（frame height）

size = (int(videoCapture.get(cv2.CAP_PROP_FRAME_WIDTH)), int(videoCapture.get(cv2.CAP_PROP_FRAME_HEIGHT)))
size

(640, 360)

# 为了保存视频，要先指定FourCC编码，该编码可从fourcc.org查到

fourcc = cv2.VideoWriter_fourcc('X','V','I','D')

# 然后创建一个videoWriter对象

videoWriter = cv2.VideoWriter('out.avi', fourcc, fps, size)

# 通过read读取视频中的帧，每一帧是一副基于BGR格式的图像，然后通过write将图像一帧帧写入要保存的视频

success, frame = videoCapture.read()

while success:
    videoWriter.write(frame)
    success, frame = videoCapture.read()