OpenCV 获取 RTSP 摄像头视频流保存至本地

介绍

Java OpenCV 是一个强大的开源计算机视觉库，它提供了丰富的图像处理和分析功能，越来越多的应用需要使用摄像头来获取实时视频流进行处理和分析。

在 Java 中使用 OpenCV 打开摄像头的基本步骤如下：

确保已经安装了OpenCV库
使用 OpenCV 的 VideoCapture 类来打开摄像头
使用 Mat 类来存储每一帧的图像
使用循环来不断从摄像头中读取帧，并显示这些帧
处理完毕后，释放摄像头资源

安装 OpenCV

下载地址：https://opencv.org/releases

从 OpenCV 官网下载适合自己操作系统版本的，然后双击安装（实质就是解压），解压完打开文件夹是：

txt 复制代码

build/
sources/
LICENSE.txt
LICENSE_FFMPEG.txt
README.md.txt

build 是 OpenCV 使用时要用到的一些库文件，而 sources 中则是 OpenCV 官方为我们提供的一些 demo 示例源码

配置环境变量可以不用配置，直接将用到的 dll（opencv_java411.dll、opencv_world411.dll、opencv_videoio_ffmpeg411_64.dll）文件复制到 C:\Windows\System32 下即可。

编码实现

将 OpenCV 库添加到 Java 项目的构建路径中，使用 VideoCapture 类来打开摄像头。

添加依赖

xml 复制代码

<!--openCV 依赖包-->
<dependency>
    <groupId>org.opencv</groupId>
    <artifactId>opencv</artifactId>
    <version>4.1.1</version>
    <scope>system</scope>
    <systemPath>${project.basedir}/src/main/resources/lib/opencv-411.jar</systemPath>
</dependency>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <configuration>
                <fork>true</fork> <!-- 如果没有该配置，devtools不会生效 -->
                <includeSystemScope>true</includeSystemScope>
            </configuration>
        </plugin>
    </plugins>
</build>

注：fork、includeSystemScope 不配置，打包不生效。

打开摄像头

java 复制代码

package com.demo.utils;

import lombok.extern.slf4j.Slf4j;
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.Size;
import org.opencv.videoio.VideoCapture;
import org.opencv.videoio.VideoWriter;

import static org.opencv.videoio.Videoio.CAP_PROP_FRAME_HEIGHT;
import static org.opencv.videoio.Videoio.CAP_PROP_FRAME_WIDTH;

@Slf4j
public class RtspRecordingUtil {

    public static void main(String[] args) {
        init();
    }

    public static void init() {
        // 加载库
        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
        
        VideoCapture capture = new VideoCapture();
        capture.open("rtsp://admin:123456@192.168.1.11/Streaming/Channels/101");

        log.info("=======isOpen:{}========", capture.isOpened());
        if (capture.isOpened()) {
            Mat mat = new Mat();
            VideoWriter vw = new VideoWriter();
            Size size = new Size();
            size.width = capture.get(CAP_PROP_FRAME_WIDTH);
            size.height = capture.get(CAP_PROP_FRAME_HEIGHT);

            boolean t = vw.open("F:\\test.avi", VideoWriter.fourcc('M', 'P', '4', '2'), 30, size);
        
            // 录制
            while (capture.read(mat)) {
                vw.write(mat);
            }
            capture.release();
            vw.release();
        }
        log.info("=======结束======");
    }

}

上述示例代码首先加载了 OpenCV 库，并创建了一个 VideoCapture 对象，打开默认摄像头。然后使用一个循环读取每一帧图像写到 VideoWriter 中保存。

打开多个摄像头

要打开多个摄像头，我们可以通过创建多个线程来拉取不同的视频流。

java 复制代码

package com.demo.util;

import lombok.extern.slf4j.Slf4j;
import org.opencv.core.Core;
import org.opencv.core.Mat;
import org.opencv.core.Size;
import org.opencv.videoio.VideoCapture;
import org.opencv.videoio.VideoWriter;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

import java.nio.file.Files;
import java.nio.file.Paths;
import java.time.Duration;
import java.time.Instant;
import java.util.Objects;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

import static org.opencv.videoio.Videoio.CAP_PROP_FRAME_HEIGHT;
import static org.opencv.videoio.Videoio.CAP_PROP_FRAME_WIDTH;

@Slf4j
@Component
public class RtspRecordingUtil {

    // 视频保存地址
    @Value("${video.video-path}")
    private String videoPath;

    // 录制视频的默认时长
    @Value("${video.video-recording-duration}")
    private Long videoRecordingDuration;

    // 默认开启十个线程
    private String DEFAULT_THREAD_POOL = 10;

    ExecutorService executorService = Executors.newFixedThreadPool(DEFAULT_THREAD_POOL);

    {
        /**
         * 将以下三个文件：
         * opencv_java411.dll、
         * opencv_world411.dll、
         * opencv_videoio_ffmpeg411_64.dll
         * 文件拷贝到 C:\Windows\System32 目录下
         */

        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);

        // 本地运行可以，打包后找不到文件
        /**
        String path = this.getClass().getClassLoader().getResource("").getPath();
        System.load(path + "lib/dll/opencv_java411.dll");
        System.load(path + "lib/dll/opencv_world411.dll");
        System.load(path + "lib/dll/opencv_videoio_ffmpeg411_64.dll");
        */
    }

    public String recording(String username, String password, String ip, Integer chanelId, String videoName, Integer duration) {
        executorService.submit(new VideoCaptureTask(username, password, ip, chanelId, videoName, duration));
        return "ok";
    }

    class VideoCaptureTask implements Runnable {

        // 设备用户名
        private String username;
        // 设备密码
        private String password;
        // 设备IP
        private String ip;
        // 设备通道号
        private Integer chanelId;
        // 视频名称
        private String videoName;
        // 录制时长
        private Integer duration;

        public VideoCaptureTask(String username, String password, String ip, Integer chanelId, String videoName, Integer duration) {
            this.username = username;
            this.password = password;
            this.ip = ip;
            this.chanelId = chanelId;
            this.videoName = videoName;
            this.duration = duration;
        }

        @Override
        public void run() {
            VideoCapture capture = null;
            VideoWriter vw = null;
            try {

                capture = new VideoCapture(videoName);

                String url = "rtsp://" + username + ":" + password + "@" + ip + "/Streaming/Channels/" + (Objects.nonNull(chanelId) ? chanelId : "1");
                capture.open(url);
                
                log.info("==== VideoCapture 开始....URL: {} ======= isOpened：{}=====", url, capture.isOpened());

                if (capture.isOpened()) {
                    Mat mat = new Mat();
                    Size size = new Size(capture.get(CAP_PROP_FRAME_WIDTH), capture.get(CAP_PROP_FRAME_HEIGHT));

                    // 视频存储地址
                    vw = new VideoWriter();

                    // 判断存储目录是否存在
                    if (Files.notExists(Paths.get(videoPath))) {
                        Files.createDirectories(Paths.get(videoPath));
                    }
                    vw.open(videoPath + videoName + ".avi", VideoWriter.fourcc('M', 'P', '4', '2'), 30, size);

                    Instant start = Instant.now();
                    long seconds = 0;
                    long _duration = Objects.nonNull(duration) ? duration : videoRecordingDuration;
                    while (capture.read(mat) && seconds <= _duration) {
                        vw.write(mat);
                        seconds = Duration.between(start, Instant.now()).getSeconds();
                    }
                } 

                log.info("==== VideoCapture 结束....URL: {} =====", url);
            } catch (Exception e) {
                log.error("==== VideoCapture 异常：{}", e);
            } finally {
                if (Objects.nonNull(capture)) capture.release();
                if (Objects.nonNull(vw)) vw.release();
            }
        }
    }

}

需要处理不同摄像头之间分辨率和帧率的不匹配问题，以及考虑如何有效地管理多个 VideoCapture 实例问题，这里使用视频名称作为摄像头的索引（new VideoCapture(videoName)）防止重复实例化。