python利用opencv实现保存、播放视频

import numpy as np
import cv2 as cv
cap = cv.VideoCapture(0)
if not cap.isOpened():
  print("Cannot open camera")
  exit()
while True:
  # Capture frame-by-frame
  ret, frame = cap.read()
  # if frame is read correctly ret is True
  if not ret:
    print("Can't receive frame (stream end?). Exiting ...")
    break
  # Our operations on the frame come here
  gray = cv.cvtColor(frame, cv.COLOR_BGR2GRAY)
  # Display the resulting frame
  cv.imshow('frame', gray)
  if cv.waitKey(1) == ord('q'):
    break
# When everything done, release the capture
cap.release()
cv.destroyAllWindows()

import numpy as np
import cv2

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

while(cap.isOpened()):
  ret, frame = cap.read()

  gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

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

cap.release()
cv2.destroyAllWindows()

import numpy as np
import cv2

cap = cv2.VideoCapture(0)

# 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()