jmfprocessing.html

jmf指导文件参考资料

</p>


<p>
  <a name="96219"> </a><font face="Palatino, Times New Roman, Times, serif">You can also select the output format that you want by using a <code>ProcessorModel</code> to create the <code>Processor</code>. (See <a href="JMFPresenting.html#97813">Using a ProcessorModel to Create a Processor</a> for more information.) </font>
</p>


<p>
  <a name="96223"> </a><font face="Palatino, Times New Roman, Times, serif">Specifying an output data format automatically selects the default processing options for this format, overriding the previous processing options selected through the <code>TrackControls</code>. Setting the output data format to <code>null</code> causes the media data to be rendered instead of output to the <code>Processor</code> object's output <code>DataSource</code>.</font>
</p>


<h3>
  <a name="96155"> </a><font color="#003366" face="Palatino, Times New Roman, Times, serif">Specifying the Media Destination</font>
</h3>


<p>
  <a name="96444"> </a><font face="Palatino, Times New Roman, Times, serif">You can specify a destination for the media stream by selecting a particular <code>Renderer</code> for a track through its <code>TrackControl</code>, or by using the output from a <code>Processor</code> as the input to a particular <code>DataSink</code>. You can also use the <code>Processor</code> output as the input to another <code>Player</code> or <code>Processor</code> that has a different destination.</font>
</p>


<h4>
  <a name="96547"> </a><font color="#003366" face="Palatino, Times New Roman, Times, serif">Selecting a Renderer</font>
</h4>


<p>
  <a name="96548"> </a><font face="Palatino, Times New Roman, Times, serif">To select the <code>Renderer</code> that you want to use, you:</font>
</p>

<ol type="1">
  <li value="1"><a name="96549"> </a><font face="Palatino, Times New Roman, Times, serif">Call <code>getTrackControls</code> on the <code>Processor</code> to get a <code>TrackControl</code> for each track in the media stream. The <code>Processor</code> must in the <em>Configured</em> state before you call <code>getTrackControls</code>.</font>
  <li value="2"><a name="96550"> </a><font face="Palatino, Times New Roman, Times, serif">Call the <code>TrackControl</code> <code>setRenderer</code> method to specify the <code>Renderer</code> plug-in.</font>
</ol>

<h4>
  <a name="96157"> </a><font color="#003366" face="Palatino, Times New Roman, Times, serif">Writing Media Data to a File</font>
</h4>


<p>
  <a name="96269"> </a><font face="Palatino, Times New Roman, Times, serif">You can use a <code>DataSink</code> to read media data from <code>Processor </code>object's output <code>DataSource</code> and render the data to a file. </font>
</p>

<ol type="1">
  <li value="1"><a name="96270"> </a><font face="Palatino, Times New Roman, Times, serif">Get the output <code>DataSource</code> from the <code>Processor</code> by calling <code>getDataOutput.</code></font>
  <li value="2"><a name="97335"> </a><font face="Palatino, Times New Roman, Times, serif">Construct a file writer <code>DataSink</code> by calling <code>Manager.createDataSink. </code>Pass in the output <code>DataSource</code> and a <code>MediaLocator</code> that specifies the location of the file to which you want to write.</font>
  <li value="3"><a name="96271"> </a><font face="Palatino, Times New Roman, Times, serif">Call <code>open</code> on the <code>DataSink</code> to open the file.</font>
  <li value="4"><a name="96272"> </a><font face="Palatino, Times New Roman, Times, serif">Call <code>start</code> on the <code>DataSink</code> to begin writing data.</font>
</ol>

<p>
  <a name="97456"> </a><font face="Palatino, Times New Roman, Times, serif">The format of the data written to the specified file is controlled through the <code>Processor</code>.  By default, a <code>Processor</code> outputs  raw data. To change the content type of a <code>Processor</code> object's output <code>DataSource</code>, you use the <code>setContentDescriptor</code> method.</font>
</p>


<a name="97227"> </a><font  size="1" face="Palatino, Times New Roman, Times, serif">

<table border="1" bordercolorlight="#FFFFFF" bordercolordark="#000000"
       cellpadding="5" cellspacing="0">
  <caption><b><i><font face="Palatino, Times New Roman, Times, serif"><a name="97233"> </a>Example 4-1:  Using a DataSink to write media data to a file.</font></i></b></caption>
  <tr>
    <td><font face="Palatino, Times New Roman, Times, serif"><pre>
<a name="97241"> </a>DataSink sink;
<a name="97242"> </a>MediaLocator dest = new MediaLocator(file://newfile.wav);
<a name="97243"> </a>try{
<a name="97244"> </a>	 sink = Manager.createDataSink(p.getDataOutput(), dest); 
<a name="97245"> </a>	 sink.open();
<a name="97246"> </a>	 sink.start();
<a name="97247"> </a>} catch (Exception) {} 
</pre>
</font></td>
  </tr>
</table>



<br></font>


<p>
  <a name="97479"> </a><font face="Palatino, Times New Roman, Times, serif">A <code>Processor</code> can enable user control over the maximum number of bytes that it can write to its destination by implementing the <code>StreamWriterControl</code>. You find out if a <code>Processor</code> provides a <code>StreamWriterControl</code> by calling <code>getControl("javax.media.datasink.StreamWriterControl")</code> on the <code>Processor</code>. </font>
</p>


<h4>
  <a name="97481"> </a><font color="#003366" face="Palatino, Times New Roman, Times, serif">Connecting a Processor to another Player</font>
</h4>


<p>
  <a name="96309"> </a><font face="Palatino, Times New Roman, Times, serif">The output from a <code>Processor</code> can be used as the input to another <code>Player</code>. To get the output from a <code>Processor</code>, you call <code>getDataOutput</code>, which returns a <code>DataSource</code>. This <code>DataSource</code> can in turn be used to construct a <code>Player</code> or <code>Processor</code> through the <code>Manager</code>.</font>
</p>


<h3>
  <a name="96323"> </a><font color="#003366" face="Palatino, Times New Roman, Times, serif">Using JMF Plug-Ins as Stand-alone Processing Modules</font>
</h3>


<p>
  <a name="96492"> </a><font face="Palatino, Times New Roman, Times, serif">JMF Plug-ins can also be used outside of the JMF framework. You can instantiate the plug-in directly and call its processing method to perform the processing operation.</font>
</p>


<p>
  <a name="96499"> </a><font face="Palatino, Times New Roman, Times, serif">You might want to do this to encode or decode a media stream, or convert a stream from one format to another.</font>
</p>
</blockquote>
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