# CSJ2K.j2k.codestream.writer.HeaderEncoder.writeMainQCD

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<h1 id="CSJ2K_j2k_codestream_writer_HeaderEncoder_writeMainQCD_" data-uid="CSJ2K.j2k.codestream.writer.HeaderEncoder.writeMainQCD*">writeMainQCD Method
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<h4 id="CSJ2K_j2k_codestream_writer_HeaderEncoder_writeMainQCD" data-uid="CSJ2K.j2k.codestream.writer.HeaderEncoder.writeMainQCD">writeMainQCD()</h4>
<div class="markdown level1 summary"><p>Writes QCD marker segment in main header. QCD is a functional marker
segment countaining the quantization default used for compressing all
the components in an image. The values can be overriden for an
individual component by a QCC marker in either the main or the tile
header.</p>
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<h5 class="declaration">Declaration</h5>
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  <pre><code class="lang-csharp hljs">protected virtual void writeMainQCD()</code></pre>
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  <pre><code class="lang-vbnet hljs">Protected Overridable Sub writeMainQCD()</code></pre>
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