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<title>Receiving and Presenting RTP Media Streams </title>
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<td align="right"><em>JMF 2.0 API Guide</em>
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<a name="104326"> </a><font size="3" face="Palatino, Times New Roman, Times, serif">9 <br></font>
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<h2>
<a name="110034"> </a><font color="#003366" face="Palatino, Times New Roman, Times, serif">Receiving and Presenting RTP Media Streams</font>
</h2>
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<p>
<a name="107455"> </a><font face="Palatino, Times New Roman, Times, serif">JMF <code>Players</code> and <code>Processors</code> provide the presentation, capture, and data conversion mechanisms for RTP streams. </font>
</p>
<a name="108222"> </a><font size="1" face="Palatino, Times New Roman, Times, serif"><img src="images/RTPPresentinga.gif" height="117" width="480">
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<a name="107448"> </a><font size="2" face="Palatino, Times New Roman, Times, serif">Figure 9-1: RTP reception data flow.<br></font>
<p>
<a name="110048"> </a><font face="Palatino, Times New Roman, Times, serif">A separate player is used for each stream received by the session manager. You construct a <code>Player</code> for an RTP stream through the standard <code>Manager</code> <code>createPlayer</code> mechanism. You can either:</font>
</p>
<ul>
<li><a name="104998"> </a><font face="Palatino, Times New Roman, Times, serif">Use a <code>MediaLocator</code> that has the parameters of the RTP session and construct a <code>Player</code> by calling <code>Manager.createPlayer(MediaLocator)</code></font>
<li><a name="104999"> </a><font face="Palatino, Times New Roman, Times, serif">Construct a <code>Player</code> for a particular <code>ReceiveStream</code> by retrieving the <code>DataSource</code> from the stream and passing it to <code>Manager.createPlayer(DataSource</code>). </font>
</ul>
<p>
<a name="107631"> </a><font face="Palatino, Times New Roman, Times, serif">If you use a <code>MediaLocator</code> to construct a <code>Player</code>, you can only present the first RTP stream that's detected in the session. If you want to play back multiple RTP streams in a session, you need to use the <code>SessionManager</code> directly and construct a <code>Player</code> for each <code>ReceiveStream</code>. </font>
</p>
<h3>
<a name="107637"> </a><font color="#003366" face="Palatino, Times New Roman, Times, serif">Creating a Player for an RTP Session</font>
</h3>
<p>
<a name="105158"> </a><font face="Palatino, Times New Roman, Times, serif">When you use a<code> MediaLocator</code> to construct a <code>Player</code> for an RTP session, the <code>Manager</code> creates a <code>Player</code> for the first stream detected in the session. This <code>Player</code> posts a <code>RealizeCompleteEvent</code> once data has been detected in the session. </font>
</p>
<p>
<a name="108117"> </a><font face="Palatino, Times New Roman, Times, serif">By listening for the <code>RealizeCompleteEvent</code>, you can determine whether or not any data has arrived and if the <code>Player</code> is capable of presenting any data. Once the <code>Player</code> posts this event, you can retrieve its visual and control components. </font>
</p>
<p>
<a name="108096"> </a><font face="Palatino, Times New Roman, Times, serif">Note: Because a <code>Player</code> for an RTP media stream doesn't finish realizing until data is detected in the session, you shouldn't try to use <code>Manager.createRealizedPlayer</code> to construct a <code>Player</code> for an RTP media stream. No <code>Player</code> would be returned until data arrives and if no data is detected, attempting to create a <em>Realized</em> <code>Player</code> would block indefinitely. </font>
</p>
<p>
<a name="105181"> </a><font face="Palatino, Times New Roman, Times, serif">A <code>Player</code> can export one RTP-specific control, <code>RTPControl</code>, which provides overall session statistics and can be used for registering dynamic payloads with the <code>SessionManager</code>. </font>
</p>
<a name="107724"> </a><font size="1" face="Palatino, Times New Roman, Times, serif">
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<caption><b><i><font face="Palatino, Times New Roman, Times, serif"><a name="110417"> </a>Example 9-1: Creating a Player for an RTP session (1 of 2)</font></i></b></caption>
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<td><font face="Palatino, Times New Roman, Times, serif"><pre>
<a name="113392"> </a><code> String url= "rtp://224.144.251.104:49150/audio/1";
</code><a name="113393"> </a>
<a name="113394"> </a><code> MediaLocator mrl= new MediaLocator(url);
</code><a name="113395"> </a><code>
</code><a name="113396"> </a><code> if (mrl == null) {
</code><a name="113397"> </a><code> System.err.println("Can't build MRL for RTP");
</code><a name="113398"> </a><code> return false;
</code><a name="113399"> </a><code> }
</code><a name="113400"> </a><code>
</code><a name="113401"> </a><code> // Create a player for this rtp session
</code><a name="113402"> </a><code> try {
</code><a name="113403"> </a><code> player = Manager.createPlayer(mrl);
</code><a name="113404"> </a><code> } catch (NoPlayerException e) {
</code><a name="113405"> </a><code> System.err.println("Error:" + e);
</code><a name="113406"> </a><code> return false;
</code><a name="113407"> </a><code> } catch (MalformedURLException e) {
</code><a name="113408"> </a><code> System.err.println("Error:" + e);
</code><a name="113409"> </a><code> return false;
</code><a name="113410"> </a><code> } catch (IOException e) {
</code><a name="113411"> </a><code> System.err.println("Error:" + e);
</code><a name="113412"> </a><code> return false;
</code><a name="113413"> </a><code> }
</code><a name="113414"> </a><code>
</code><a name="113415"> </a><code> if (player != null) {
</code><a name="112310"> </a><code> if (this.player == null) {
</code></pre>
</font></td>
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<td><font face="Palatino, Times New Roman, Times, serif"><pre>
<a name="113424"> </a> this.player = player;
<a name="113425"> </a> player.addControllerListener(this);
<a name="113426"> </a> player.realize();
<a name="113427"> </a> }
<a name="113428"> </a> }
</pre>
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<br></font>
<h4>
<a name="110414"> </a><font color="#003366" face="Palatino, Times New Roman, Times, serif">Listening for Format Changes</font>
</h4>
<p>
<a name="107725"> </a><font face="Palatino, Times New Roman, Times, serif">When a <code>Player</code> posts a <code>FormatChangeEvent</code>, it might indicate that a payload change has occurred. <code>Players</code> constructed with a <code>MediaLocator</code> automatically process payload changes. In most cases, this processing involves constructing a new <code>Player</code> to handle the new format. Applications that present RTP media streams need to listen for <code>FormatChangeEvents</code> so that they can respond if a new <code>Player</code> is created.</font>
</p>
<p>
<a name="107929"> </a><font face="Palatino, Times New Roman, Times, serif">When a <code>FormatChangeEvent</code> is posted, check whether or not the <code>Player</code> object's control and visual components have changed. If they have, a new <code>Player</code> has been constructed and you need to remove references to the old <code>Player </code>object's components and get the new <code>Player </code>object's<code> </code>components.</font>
</p>
<a name="110620"> </a><font size="1" face="Palatino, Times New Roman, Times, serif">
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<caption><b><i><font face="Palatino, Times New Roman, Times, serif"><a name="110850"> </a>Example 9-2: Listening for RTP format changes (1 of 2)</font></i></b></caption>
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<td><font face="Palatino, Times New Roman, Times, serif"><pre>
<a name="110743"> </a><code> public synchronized void controllerUpdate(ControllerEvent ce) {
</code><a name="110744"> </a><code> if (ce instanceof FormatChangeEvent) {
</code><a name="110745"> </a><code> Dimension vSize = new Dimension(320,0);
</code><a name="110746"> </a><code> Component oldVisualComp = visualComp;
</code><a name="110747"> </a><code>
</code><a name="110748"> </a><code> if ((visualComp = player.getVisualComponent()) != null) {
</code><a name="110749"> </a><code> if (oldVisualComp != visualComp) {
</code><a name="110750"> </a><code> if (oldVisualComp != null) {
</code><a name="110751"> </a><code> oldVisualComp.remove(zoomMenu);
</code><a name="110752"> </a><code> }
</code><a name="110753"> </a><code>
</code><a name="110754"> </a><code> framePanel.remove(oldVisualComp);
</code><a name="110755"> </a><code>
</code><a name="110756"> </a><code> vSize = visualComp.getPreferredSize();
</code><a name="110757"> </a><code> vSize.width = (int)(vSize.width * defaultScale);
</code><a name="110758"> </a><code> vSize.height = (int)(vSize.height * defaultScale);
</code><a name="110759"> </a><code>
</code><a name="110760"> </a><code> framePanel.add(visualComp);
</code><a name="110761"> </a><code>
</code><a name="110762"> </a><code> visualComp.setBounds(0,
</code><a name="110763"> </a><code> 0,
</code><a name="110764"> </a><code> vSize.width,
</code><a name="110765"> </a><code> vSize.height);
</code><a name="112796"> </a><code> addPopupMenu(visualComp);
</code><a name="112791"> </a><code> }
</code></pre>
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<td><font face="Palatino, Times New Roman, Times, serif"><pre>
<a name="112801"> </a><code> }
</code><a name="110846"> </a>
<a name="110802"> </a><code> Component oldComp = controlComp;
</code><a name="110803"> </a><code>
</code><a name="110804"> </a><code> controlComp = player.getControlPanelComponent();
</code><a name="110805"> </a>
<a name="110806"> </a><code> if (controlComp != null)
</code><a name="110807"> </a><code> {
</code><a name="110808"> </a><code> if (oldComp != controlComp)
</code><a name="110809"> </a><code> {
</code><a name="110810"> </a><code> framePanel.remove(oldComp);
</code><a name="110811"> </a><code> framePanel.add(controlComp);
</code><a name="110812"> </a><code>
</code><a name="110813"> </a><code> if (controlComp != null) {
</code><a name="110814"> </a><code> int prefHeight = controlComp
</code><a name="110815"> </a><code> .getPreferredSize()
</code><a name="110816"> </a><code> .height;
</code><a name="110817"> </a><code>
</code><a name="110818"> </a><code> controlComp.setBounds(0,
</code><a name="110819"> </a><code> vSize.height,
</code><a name="110820"> </a><code> vSize.width,
</code><a name="110821"> </a><code> prefHeight);
</code><a name="110822"> </a><code> }
</code><a name="110823"> </a><code> }
</code><a name="110824"> </a><code> }
</code><a name="110825"> </a><code> }
</code><a name="110826"> </a><code> }
</code></pre>
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<h3>
<a name="107661"> </a><font color="#003366" face="Palatino, Times New Roman, Times, serif">Creating an RTP Player for Each New Receive Stream</font>
</h3>
<p>
<a name="110501"> </a><font face="Palatino, Times New Roman, Times, serif">To play all of the <code>ReceiveStreams</code> in a session, you need to create a separate <code>Player</code> for each stream. When a new stream is created, the session manager posts a <code>NewReceiveStreamEvent</code>. Generally, you register as a <code>ReceiveStreamListener</code> and construct a <code>Player</code> for each new <code>ReceiveStream</code>. To construct the <code>Player</code>, you retrieve the <code>DataSource</code> from the <code>ReceiveStream</code> and pass it to <code>Manager.createPlayer</code>. </font>
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