1、簡介
The JavaTM Media Framework (JMF) is an application programming interface (API) for incorporating media data such as audio and video into
Java applications and applets. It is specifically designed to take advantage of Java platform features.
這個框架是SUN公司出的，最新更新至2003年，用JMF來處理圖像和音頻設備並直接應用到JAVA應用程序中，雖然年代有點久遠，但卻還是可以用的。
The JMF 2.1.1 Reference Implementation supports SunVideo / SunVideoPlus capture devices on Solaris. On Windows, most capture devices
that have VFW drivers are supported. On Linux, devices that have a Video4Linux driver are expected to work, but not extensively tested.
今天小試了下，自己的laptop也有個攝像頭，錄製了一段視頻到本地，第一次玩這個東西：）
2、模型
JMF的模型如下：
基本上是攝像頭數據、文件數據、網絡媒體流通過process輸出到設備、文件或網絡中。
Design Goals for JMF：
1、Be easy to program
2、Support capturing media data
3、Enable the development of media streaming and conferencing applications in Java
4、Enable advanced developers and technology providers to implement custom solutions based on the existing API and easily integrate new features with the existing framework
5、Provide access to raw media data
6、Enable the development of custom, downloadable demultiplexers, codecs, effects processors, multiplexers, and renderers (JMF plug-ins)
Design Goals for RTP：（RTP是JMF數據流在網絡上的傳輸協議）
1、Enable the development of media streaming and conferencing applications in Java
2、Support media data reception and transmission using RTP and RTCP
3、Support custom packetizer and depacketizer plug-ins through the JMF 2.0 plug-in architecture.
4、Be easy to program
3、媒體數據展現
Streaming Media
媒體流，可以存儲爲多種文件格式或通過HTTP,RTP等協議傳輸在網絡上。
Media Presentation
Most time-based media is audio or video data that can be presented through output devices such as speakers and monitors. Such devices are the
most common destination for media data output. Media streams can also be sent to other destinations--for example, saved to a file or transmitted
across the network. An output destination for media data is sometimes referred to as a data sink.
Media Data Storage and Transmission
A DataSink is used to read media data from a DataSource and render the media to some destination--generally a destination other
than a presentation device. A particular DataSink might write data to a file, write data across the network, or function as an RTP broadcaster.
DataSink用來做數據存儲和傳輸。
開始presenting time-based media
Presenting Time-Based Media
To present time-based media such as audio or video with JMF, you use a Player. Playback can be controlled programmatically, or you can display a control-panel component that enables the user to control playback interactively. If you have several media streams that you want to play,
you need to use a separate Player for each one. to play them in sync, you can use one of the Player objects to control the operation of the others.
基本上是說播放實時多媒體需要用到Player，且每個單獨的媒體需要單獨的Player。
代碼如下：
// create processor
ProcessorModel processorModel = new ProcessorModel(mixedDataSource, outputFormat, outputType);
// 創建model，類似JTable控件的 JModel，The ProcessorModel defines the input and output requirements for the Processor
Processor processor = null;
try
{
processor = Manager.createRealizedProcessor(processorModel);// 創建model，類似JTable控件的 JModel
}
catch (IOException e) { Stdout.logAndAbortException(e); }
catch (NoProcessorException e) { Stdout.logAndAbortException(e); }
catch (CannotRealizeException e) { Stdout.logAndAbortException(e); }
創建processor後，可以裝進不同的compont裏來present。
For example, you can call getControls to determine if a Player supports the CachingControl interface.
Control[] controls = player.getControls();
for (int i = 0; i < controls.length; i++)
{
if (controls[i] instanceof CachingControl)
{ cachingControl = (CachingControl) controls[i];
}
}
JMF提供了很多“播放器”，當然也提供了基本的控制，比如播放、停止以及播放信息等等。
控制產生事件。
Responding to Media Events
ControllerListener is an asynchronous interface for handling events generated by Controller objects.
for example:
if (event instanceof EventType){
...
} else if (event instanceof OtherEventType){
...
}
if (event instanceof EventType){ ... } else if (event instanceof OtherEventType){ ... } JMF提供ControllerAdapter：
player.addControllerListener(new ControllerAdapter() {
public void endOfMedia(EndOfMediaEvent e) {
Controller controller = e.getSource();
controller.stop();
controller.setMediaTime(new Time(0));
controller.deallocate();
}
})
ControllerAdapter automatically dispatches the event to the appropriate event method, filtering out the events that you're not
interested in.自動爲您分發事件並過濾不需要的事件。
There is a movie in Applet...展現到applet
import java.applet.*;
import java.awt.*;
import java.net.*;
import javax.media.*;
public class PlayerApplet extends Applet implements ControllerListener {
Player player = null;
public void init() {
setLayout(new BorderLayout());
String mediaFile = getParameter("FILE");
try {
URL mediaURL = new URL(getDocumentBase(), mediaFile);
player = Manager.createPlayer(mediaURL);
player.addControllerListener(this);
}
catch (Exception e) {
System.err.println("Got exception "+e);
}
}
public void start() {
player.start();
}
public void stop() {
player.stop();
player.deallocate();
}
public void destroy() {
player.close();
}
public synchronized void controllerUpdate(ControllerEvent event) {
if (event instanceof RealizeCompleteEvent) {
Component comp;
if ((comp = player.getVisualComponent()) != null)
add ("Center", comp);
if ((comp = player.getControlPanelComponent()) != null)
add ("South", comp);
validate();
}
}
}
Presenting RTP Media Streams
Creating a Player for RTP session.
String url= "rtp://224.144.251.104:49150/audio/1";
MediaLocator mrl= new MediaLocator(url);
if (mrl == null) {
System.err.println("Can't build MRL for RTP");
return false;
}
// Create a player for this rtp session
try {
player = Manager.createPlayer(mrl);
} catch (NoPlayerException e) {
System.err.println("Error:" + e);
return false;
} catch (MalformedURLException e) {
System.err.println("Error:" + e);
return false;
} catch (IOException e) {
System.err.println("Error:" + e);
return false;
}
4、媒體數據處理
Converting Media Data from One Format to Another
你可以調整媒體的格式。
Specifying the Media Destination
你可以指定錄像保存的方式，比如輸出到文件， 輸出到另一個player。
Saving captured media data to a file
DataSink sink;
MediaLocator dest = new MediaLocator("file://newfile.wav");
try {
sink = Manager.createDataSink(p.getDataOutput(), dest);
sink.open();
sink.start();
} catch (Exception) {}
5、擴展JMF
Custom JMF plug-ins can be used seamlessly with Processors that support the plug-in API. After you implement your plug-in, you need to install it and register it with the PlugInManager to make it available to plug-in compatible Processors.
Implementing a Codec or Effect Plug-In
Codec plug-ins are used to decode compressed media data, convert media data from one format to another, or encode raw media data into a compressed format.
用戶可以自行擴展壓縮格式，以及格式轉換。
Implementing a Renderer Plug-In
It is a single-input processing component with no output. Renderer plug-ins read data from a DataSource and typically present the media data to the user, but can also be used to provide access to the processed media data for use by another application or device.
To make a custom plug-in available to a Processor through the TrackControl interface, you need to register it with the PlugInManager
// Name of the new plugin
string GainPlugin = new String("COM.mybiz.media.GainEffect");
// Supported input Formats
Format[] supportedInputFormats = new Format[] {
new AudioFormat(
AudioFormat.LINEAR,
Format.NOT_SPECIFIED,
16,
Format.NOT_SPECIFIED,
AudioFormat.LITTLE_ENDIAN,
AudioFormat.SIGNED,
16,
Format.NOT_SPECIFIED,
Format.byteArray
)
};
// Supported output Formats
Format[] supportedOutputFormats = new Format[] {
new AudioFormat(
AudioFormat.LINEAR,
Format.NOT_SPECIFIED,
16,
Format.NOT_SPECIFIED,
AudioFormat.LITTLE_ENDIAN,
AudioFormat.SIGNED,
16,
Format.NOT_SPECIFIED,
Format.byteArray
)
};
// Add the new plug-in to the plug-in registry
PlugInManager.addPlugIn(GainPlugin, supportedInputFormats,
supportedOutputFormats, EFFECT);
// Save the changes to the plug-in registry
PlugInManager.commit();
Implementing a Protocol Data Source
A DataSource is an abstraction of a media protocol-handler. You can implement new types of DataSources to support additional protocols by extending PullDataSource,
Implementing a DataSink
JMF provides a default DataSink that can be used to write data to a file. Other types of DataSink classes can be implemented to facilitate writing data to the network or to other destinations.
6、事例代碼
this test program will capture the video and audio stream from your USB camera for 10 seconds and stores it on a file, named "testcam.avi".