安裝Python庫sudo pip install opencv-python 或者sudo pip install opencv-python -i https://pypi.douban.com/simple/

 1 #get first frame
 2 import os
 3 import cv2
 4 import base64
 5 mp4_loc='./a.mp4'
 6 first_frame_loc='./first_frame.jpg'
 7 videoCapture = cv2.VideoCapture(mp4_loc)
 8 success, frame = videoCapture.read()
 
 9 if(success):
10     cv2.imwrite(first_frame_loc,frame)
11 os.remove(mp4_loc)  #delete mp4 file
12 with open(first_frame_loc, 'rb') as f:
13     first_frame_pic_64=base64.b64encode(f.read())

1、videoCapture = cv2.VideoCapture(mp4_loc)

VideoCapture()中引數是mp4_loc，表示開啟視訊，引數是0則表示開啟筆記本的內建攝像頭，如cap = cv2.VideoCapture(0)

2、success, frame = videoCapture .read()

videoCapture .read()按幀讀取視訊，success, frame是獲cap.read()方法的兩個返回值。其中success是布林值，如果讀取幀是正確的則返回True，如果檔案讀取到結尾，它的返回值就為False。frame就是每一幀的影象，是個三維矩陣。

參考：https://blog.csdn.net/Zhou_yongzhe/java/article/details/80310537