首先说一下报错的地方，是在使用VideoWriter保存视频时：

'''
opencv读取摄像头视频流,并且显示
'''
 
import cv2
import numpy as np
 
#调用摄像头
cap = cv2.VideoCapture(0)
 
#DIVX,X264
fourcc = cv2.VideoWriter_fourcc(*'X264')
fps = 20
#获取图像的高宽
width  = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
height = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))
 
writer = cv2.VideoWriter('video.mp4',fourcc,fps,(width,height))
 
while True:
    #读取视频帧
    rec, frame = cap.read()
 
    #镜像
    frame = cv2.flip(frame,1)
    #灰度图片
    gray = cv2.cvtColor(frame,cv2.COLOR_BGR2GRAY)
 
    #保存视频
    writer.write(frame)
 
    #显示图片
    cv2.imshow('demo',frame)
 
    #退出条件
    if cv2.waitKey(10) & 0xFF == ord('q'):
        break
 
cap.release()
writer.release()
cv2.destroyAllWindows()

出现如下错误：

OpenCV: FFMPEG: tag 0x34363258/'X264' is not supported with codec id 27 and format 'mp4 / MP4 (MPEG-4 Part 14)'
OpenCV: FFMPEG: fallback to use tag 0x31637661/'avc1'
[ERROR:0@0.234] global cap_ffmpeg_impl.hpp:2991 open Could not find encoder for codec_id=27, error: Encoder not found
[ERROR:0@0.234] global cap_ffmpeg_impl.hpp:3066 open VIDEOIO/FFMPEG: Failed to initialize VideoWriter

经过查找网上资料，发现是cv2.VideoWriter_fourcc()参数存在问题，

解决方法：

将

fourcc = cv2.VideoWriter_fourcc(*'X264')

修改为：

fourcc = cv2.VideoWriter_fourcc(*'mp4v')

即可完美解决问题。