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Java视频流详解

一、视频流概述

视频流(Video Streaming),即以实时传输的方式在计算机网络上传送音频和视频。优点在于不需要当整个文件下载完成之后才能播放,一旦有一部分缓冲完成就可以播放,同时可以实现直播、点播、实时视频监控等应用场景。

二、Java中的视频流技术

Java中的视频流技术主要涉及到Java Media Framework(JMF)和Java Advanced Imaging(JAI)。

1. JMF(Java Media Framework)

JMF是Java平台的音频和视频处理框架,它包括了:媒体播放、捕捉、转码、编辑、流媒体和视频会议等功能。在使用JMF之前,需要在计算机上安装JMF软件包。以下是使用JMF进行视频播放的示例代码:

import java.awt.*;
import java.net.*;
import javax.media.*;
import javax.swing.*;

public class VideoPlayer extends JFrame {

    private Player mediaPlayer;

    public static void main(String[] args) throws Exception {
        URL mediaUrl = new URL("rtsp://192.168.0.100:8554/");
        new VideoPlayer(mediaUrl);
    }

    public VideoPlayer(URL mediaUrl) {
        setTitle("Video Player");
        setBounds(100, 100, 800, 600);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        setLayout(new BorderLayout());

        Manager.setHint(Manager.LIGHTWEIGHT_RENDERER, true);

        try {
            mediaPlayer = Manager.createRealizedPlayer(mediaUrl);
            Component video = mediaPlayer.getVisualComponent();
            Component controls = mediaPlayer.getControlPanelComponent();
            add(video, BorderLayout.CENTER);
            add(controls, BorderLayout.SOUTH);
        } catch (Exception e) {
            e.printStackTrace();
        }

        setVisible(true);
        mediaPlayer.start();
    }
}

2. JAI(Java Advanced Imaging)

JAI是Java平台的高级图像处理框架,它提供了各种高级的图像处理算法和技术。以下是使用JAI进行视频流转码的示例代码:

import java.awt.image.BufferedImage;
import java.io.File;
import javax.imageio.ImageIO;
import javax.media.Buffer;
import javax.media.Format;
import javax.media.Manager;
import javax.media.MediaLocator;
import javax.media.Player;
import javax.media.control.FrameGrabbingControl;
import javax.media.format.VideoFormat;

public class Transcoder {

    public static void main(String[] args) throws Exception {

        // 加载视频文件
        File file = new File("video.avi");
        MediaLocator mediaLocator = new MediaLocator(file.toURI().toURL());
        Player player = Manager.createRealizedPlayer(mediaLocator);
        player.start();

        // 获取视频源格式
        Format sourceFormat = player.getFormat();
        System.out.println("Source Format : " + sourceFormat);

        // 获取满足指定编码器和视频大小的目标格式
        VideoFormat targetFormat = new VideoFormat(VideoFormat.H263);
        Format[] supportedFormats = Manager.getSupportedFormats(null, targetFormat);
        Format targetFormatBest = null;
        float targetFormatScore = 0.0f;
        for (Format format : supportedFormats) {
            if (format.getEncoding().equalsIgnoreCase(targetFormat.getEncoding())) {
                float score = format.match(sourceFormat);
                if (score > targetFormatScore) {
                    targetFormatBest = format;
                    targetFormatScore = score;
                }
            }
        }

        // 创建转码器
        Player transcodingPlayer = Manager.createProcessor(mediaLocator);
        transcodingPlayer.realize();
        while (transcodingPlayer.getState() < Processor.Realized) Thread.sleep(100);
        FrameGrabbingControl frameGrabbingControl = (FrameGrabbingControl) transcodingPlayer.getControl("javax.media.control.FrameGrabbingControl");

        // 转码并保存视频
        int frameCount = 0;
        BufferedImage buffer;
        while ((buffer = (BufferedImage) frameGrabbingControl.grabFrame()) != null) {
            ++frameCount;
            Buffer bufferInput = new Buffer();
            bufferInput.setFormat(sourceFormat);
            bufferInput.setData(buffer);
            Buffer bufferOutput = transcodingPlayer.getProcessor().convertData(bufferInput, targetFormatBest);
            buffer = (BufferedImage) bufferOutput.getData();
            ImageIO.write(buffer, "jpeg", new File(String.format("%08d.jpg", frameCount)));
        }

        // 释放资源
        while (player.getState() < Player.Realized) Thread.sleep(100);
        player.close();
        while (transcodingPlayer.getState() < Player.Realized) Thread.sleep(100);
        transcodingPlayer.close();

    }

}

三、总结

通过本文,我们对Java中的视频流技术进行了介绍。JMF和JAI作为Java平台中成熟的音视频处理框架,拥有强大的功能和广泛的应用场景。掌握这些技术,可以为我们的开发工作带来很大的帮助。