51 lines
8.2 KiB
HTML
51 lines
8.2 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>The Be Book - System Overview - The Media Kit</title><link rel="stylesheet" href="be_book.css" type="text/css" media="all" /><link rel="shortcut icon" type="image/vnd.microsoft.icon" href="./images/favicon.ico" /><!--[if IE]>
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<link rel="stylesheet" type="text/css" href="be_book_ie.css" />
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<![endif]--><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /><meta name="keywords" content="Access, BeOS, BeBook, API" /><link rel="start" href="index.html" title="The Be Book" /><link rel="up" href="TheMediaKit_Overview.html" title="The Media Kit" /><link rel="prev" href="TheMediaKit_ExampleNode.html" title="A BMediaEventLooper Example" /><link rel="next" href="BBufferConsumer_Overview.html" title="BBufferConsumer" /></head><body><div id="header"><div id="headerT"><div id="headerTL"><a accesskey="p" href="TheMediaKit_ExampleNode.html" title="A BMediaEventLooper Example"><img src="./images/navigation/prev.png" alt="Prev" /></a> <a accesskey="u" href="TheMediaKit_Overview.html" title="The Media Kit"><img src="./images/navigation/up.png" alt="Up" /></a> <a accesskey="n" href="BBufferConsumer_Overview.html" title="BBufferConsumer"><img src="./images/navigation/next.png" alt="Next" /></a></div><div id="headerTR"><div id="navigpeople"><a href="http://www.haiku-os.org"><img src="./images/People_24.png" alt="haiku-os.org" title="Visit The Haiku Website" /></a></div><div class="navighome" title="Home"><a accesskey="h" href="index.html"><img src="./images/navigation/home.png" alt="Home" /></a></div><div class="navigboxed" id="navigindex"><a accesskey="i" href="ClassIndex.html" title="Index">I</a></div><div class="navigboxed" id="naviglang" title="English">en</div></div><div id="headerTC">The Be Book - System Overview - The Media Kit</div></div><div id="headerB">Prev: <a href="TheMediaKit_ExampleNode.html">A BMediaEventLooper Example</a> Up: <a href="TheMediaKit_Overview.html">The Media Kit</a> Next: <a href="BBufferConsumer_Overview.html">BBufferConsumer</a></div><hr /></div><div class="section"><div xmlns="" xmlns:d="http://docbook.org/ns/docbook" class="titlepage"><div><div xmlns:d="http://docbook.org/ns/docbook"><h2 xmlns="http://www.w3.org/1999/xhtml" class="title"><a id="BBuffer_Overview"></a>BBuffer</h2></div></div></div><a id="id583429" class="indexterm"></a><p>A <a class="link" href="BBuffer.html" title="BBuffer"><code class="classname">BBuffer</code></a>
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references a chunk of shared memory where media data can be
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passed between applications and nodes. The control header for these
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buffers is passed through the use of a safer IPC mechanism, but the
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actual data these headers represent typically require a high data rate,
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and for the sake of maximizing performance, shared memory is the method
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by which the buffers are managed.</p><p><a class="link" href="BBuffer.html" title="BBuffer"><code class="classname">BBuffer</code></a>s
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originate at some
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<a class="link" href="BBufferProducer.html" title="BBufferProducer"><code class="classname">BBufferProducer</code></a>,
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which has a
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<a class="link" href="BBufferGroup.html" title="BBufferGroup"><code class="classname">BBufferGroup</code></a>
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that acts as a source of
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<a class="link" href="BBuffer.html" title="BBuffer"><code class="classname">BBuffer</code></a>s (see
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<a class="link" href="BBufferConsumer.html#BBufferConsumer_SetOutputBuffersFor" title="SetOutputBuffersFor()"><code class="methodname">BBufferConsumer::SetOutputBuffersFor()</code></a>).
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<a class="link" href="BBuffer.html" title="BBuffer"><code class="classname">BBuffer</code></a>s are sent through all
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participating nodes, possibly being sent down a long chain—much
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like a bucket brigade—until finally the node arrives at a node that
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chooses not to pass along the
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<a class="link" href="BBuffer.html" title="BBuffer"><code class="classname">BBuffer</code></a>
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any further, at which the buffer's
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<a class="link" href="BBuffer.html#BBuffer_Recycle" title="Recycle()"><code class="methodname">Recycle()</code></a>
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function is called to return the buffer to the
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<a class="link" href="BBufferGroup.html" title="BBufferGroup"><code class="classname">BBufferGroup</code></a>'s
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store, where it gets reused by another batch of data.</p><p>An application or custom node can set up
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<a class="link" href="BBuffer.html" title="BBuffer"><code class="classname">BBuffer</code></a>s that reference a
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specific area of memory, such as a low-level driver buffer, a
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<a class="link" href="BBitmap.html" title="BBitmap"><code class="classname">BBitmap</code></a>, or
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a <a class="link" href="BDirectWindow.html" title="BDirectWindow"><code class="classname">BDirectWindow</code></a>'s
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area of a frame buffer. This ability can provide for
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great optimization by avoiding unnecessary copy operations.</p><p>The <a class="link" href="BSmallBuffer.html" title="BSmallBuffer"><code class="classname">BSmallBuffer</code></a>
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class, derived from
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<a class="link" href="BBuffer.html" title="BBuffer"><code class="classname">BBuffer</code></a>, is used for very small
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buffers; they don't go in
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<a class="link" href="BBufferGroup.html" title="BBufferGroup"><code class="classname">BBufferGroup</code></a>s,
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and get handled specially to optimize performance.</p><div class="admonition warning"><div class="title">Warning</div><div class="graphic"><img class="icon" alt="Warning" width="32" src="./images/admonitions/Stop_32.png" /><div class="text"><p><a class="link" href="BBuffer.html" title="BBuffer"><code class="classname">BBuffer</code></a>
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should never be subclassed, since they're mostly owned and
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managed by the Media Server. Even if you create your own
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<a class="link" href="BBuffer.html" title="BBuffer"><code class="classname">BBuffer</code></a>, once
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you've called
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<a class="link" href="BBufferConsumer.html#BBufferConsumer_SetOutputBuffersFor" title="SetOutputBuffersFor()"><code class="methodname">BBufferConsumer::SetOutputBuffersFor()</code></a>,
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the "same" buffer received back by your
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<a class="link" href="BBufferConsumer.html" title="BBufferConsumer"><code class="classname">BBufferConsumer</code></a>
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may actually be another instance of the
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<a class="link" href="BBuffer.html" title="BBuffer"><code class="classname">BBuffer</code></a> class.</p></div></div></div></div><div id="footer"><hr /><div id="footerT">Prev: <a href="TheMediaKit_ExampleNode.html">A BMediaEventLooper Example</a> Up: <a href="TheMediaKit_Overview.html">The Media Kit</a> Next: <a href="BBufferConsumer_Overview.html">BBufferConsumer</a> </div><div id="footerB"><div id="footerBL"><a href="TheMediaKit_ExampleNode.html" title="A BMediaEventLooper Example"><img src="./images/navigation/prev.png" alt="Prev" /></a> <a href="TheMediaKit_Overview.html" title="The Media Kit"><img src="./images/navigation/up.png" alt="Up" /></a> <a href="BBufferConsumer_Overview.html" title="BBufferConsumer"><img src="./images/navigation/next.png" alt="Next" /></a></div><div id="footerBR"><div><a href="http://www.haiku-os.org"><img src="./images/People_24.png" alt="haiku-os.org" title="Visit The Haiku Website" /></a></div><div class="navighome" title="Home"><a accesskey="h" href="index.html"><img src="./images/navigation/home.png" alt="Home" /></a></div></div><div id="footerBC"><a href="http://www.access-company.com/home.html" title="ACCESS Co."><img alt="Access Company" src="./images/access_logo.png" /></a></div></div></div><div id="licenseFooter"><div id="licenseFooterBL"><a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/" title="Creative Commons License"><img alt="Creative Commons License" style="border-width:0" src="https://licensebuttons.net/l/by-nc-nd/3.0/88x31.png" /></a></div><div id="licenseFooterBR"><a href="./LegalNotice.html">Legal Notice</a></div><div id="licenseFooterBC"><span id="licenseText">This work is licensed under a
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<a rel="license" href="http://creativecommons.org/licenses/by-nc-nd/3.0/">Creative
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Commons Attribution-Non commercial-No Derivative Works 3.0 License</a>.</span></div></div></body></html>
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