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。