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基于OpenCV的视频流处理

获取VideoCapture实例

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# 读取视频流
strem_capture = cv2.VideoCapture("rtst://192.168.0.0/live/demo")

# 读取视频文件
file_capture = cv2.VideoCapture('demo.mp4')

# 读取摄像头
capture = cv2.VideoCapture(0)

获取摄像头编号可使用ls -al /dev/ |grep video,输出信息以video开头其后缀为数字即为可能的摄像头编号。

检查获取VideoCapture实例是否成功

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# 校验获取VideoCapture类实例
if not capture.isOpened():
return

获取视频流信息

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# 获取视频帧的宽
width = capture.get(cv2.CAP_PROP_FRAME_WIDTH)

# 获取视频帧的高
height = cpature.get(cv2.CAP_PROP_FRAME_HEIGHT)

# 获取视频帧率
fps = capture.get(cv2.CAP_PROP_FPS)

获取帧画面

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success, frame = capture.read()

当需要同时处理多路摄像头时一般使用grab()retrieve()代替

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success_1 = capture.grab()
success_2 = stream_capture.grab()

if success_1 and success_2:
frame_1 = capture.retrieve()
frame_2 = stream_capture.retrieve()

设置分辨率

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# 设置摄像头分辨率的宽
capture.set(cv2.CAP_PROP_FRAME_WIDTH, 1920)

# 设置摄像头分辨率的高
capture.set(cv2.CAP_PROP_FRAME_HEIGHT, 1080)

保存视频文件

无论是视频文件存储还是摄像头画面保存都是用VideoWriter类,初始化时需要传入文件名(包含文件格式)、视频编解码器、视频保存帧率 、分辨率,保存视频的帧率最好和读入的帧率一致,分辨率可以更改,只是要求写入的帧大小要与分辨率保持一致。
若指定的文件名已存在则会覆盖文件。

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writer = cv2.VideoWriter('output.mp4', 
cv2.VideoWriter_fourcc(*'MP4V'), 30, (1080,1920))
writer.write(frame)

释放资源

不管是VideoCapture还是VideoWriter类,使用完都应该释放资源

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# 释放VideoCapture资源
capture.release()

# 释放VideoWriter资源
writer.release()

完整示例

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# -*- coding: utf-8 -*-
# /usr/bin/env/python3

import cv2
import time

capture = cv2.VideoCapture('rtsp://192.168.0.0/live/demo)
fourcc = cv2.VideoWriter_fourcc(*'MP$v') # 或H264,H265
fps = capture.get(cv2.CAP_PROP_FPS)
width = capture.get(cv2.CAP_PROP_FRAME_WIDTH)
height = capture.get(cv2.CAP_PROP_FRAME_HEIGHT)

writer = cv2.VideoWriter('demo.mp4', fourcd, fps, (height, width))


while True:
if not capture.isOpened():
time.sleep(0.5)
continue
success, frame = capture.read()
if success:
cv2.imshow('DEMO', frame) # 显示画面
writer.write(frame) # 保存视频文件
if (cv2.waitKey(20) & 0xff) == ord('q'): # 等待20ms并判断是否按下'q'退出,waitkey只能传入整数,
break

capture.release() # 释放VideoCapture
writer.release() # 释放VideoWriter
cv2.destroyAllWindows() # 销毁所有opencv显示窗口