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<title>(r1.1 vs. r1.2) VideoChromaKey &lt; Cinelerra &lt; TWiki</title>
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<div class="twikiMiddleContainer"><div class="twikiMain"><div class="twikiSearchResults"><div class="twikiSearchResultsHeader">&nbsp;<tt><b>&lt;&lt;O&gt;&gt;</b></tt>&nbsp; Difference Topic
		<b><a href="../../view/Cinelerra/VideoChromaKey">VideoChromaKey</a></b>
		(<a href="http://www.ftconsult.com/twiki/bin/view/Cinelerra/VideoChromaKey?rev=r1.2">r1.2</a> - 16&nbsp;Jan&nbsp;2004 - <a class="twikiLink" href="../../view/Main/AlexFerrer">AlexFerrer</a>)</div>
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<tr><th class="twikiFirstCol" bgcolor="#99CCCC"> <strong>META TOPICPARENT</strong> </th><td colspan="2" bgcolor="#FFFFCC"> <a class="twikiLink" href="../../view/Cinelerra/VideoEffect">VideoEffects</a> </td></tr>
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<tr><th class="twikiFirstCol" bgcolor="#99CCCC"> <strong>META TOPICPARENT</strong> </th><td colspan="2" bgcolor="#FFFFCC"> <a class="twikiLink" href="../../view/Cinelerra/VideoEffect">VideoEffect</a> </td></tr>
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<h3><a name="VideoChromaKey"> </a> <a class="twikiLink" href="../../view/Cinelerra/VideoChromaKey">VideoChromaKey</a> </h3>
This effect replaces the selected color or intensity with black if there is no <span class="twikiNewLink" style="background : #FFFFCE;"><font color="#0000FF">AlphaChannel</font><a href="http://www.ftconsult.com/twiki/bin/edit/Cinelerra/AlphaChannel?topicparent=Cinelerra.VideoChromaKey"><sup>?</sup></a></span> and replaces it with <a class="twikiLink" href="../../view/Cinelerra/Transparency">transparency</a> if there is an <span class="twikiNewLink" style="background : #FFFFCE;"><font color="#0000FF">AlphaChannel</font><a href="http://www.ftconsult.com/twiki/bin/edit/Cinelerra/AlphaChannel?topicparent=Cinelerra.VideoChromaKey"><sup>?</sup></a></span>. The selection of <a class="twikiLink" href="../../view/Cinelerra/ColorModel">ColorModel</a> is important.
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</table></div><div class="twikiSearchResults"><div class="twikiSearchResultsHeader">&nbsp;<tt><b>&lt;&lt;O&gt;&gt;</b></tt>&nbsp; Difference Topic
		<b><a href="../../view/Cinelerra/VideoChromaKey">VideoChromaKey</a></b>
		(<a href="http://www.ftconsult.com/twiki/bin/view/Cinelerra/VideoChromaKey?rev=r1.1">r1.1</a> - 19&nbsp;Dec&nbsp;2003 - <a class="twikiLink" href="../../view/Main/AlexFerrer">AlexFerrer</a>)</div>
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<tr><th class="twikiFirstCol" bgcolor="#99CCCC"> <strong>META TOPICPARENT</strong> </th><td colspan="2" bgcolor="#FFFFCC"> <a class="twikiLink" href="../../view/Cinelerra/VideoEffect">VideoEffects</a> </td></tr>
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<h3><a name="VideoChromaKey"> </a> <a class="twikiLink" href="../../view/Cinelerra/VideoChromaKey">VideoChromaKey</a> </h3>
This effect replaces the selected color or intensity with black if there is no <span class="twikiNewLink" style="background : #FFFFCE;"><font color="#0000FF">AlphaChannel</font><a href="http://www.ftconsult.com/twiki/bin/edit/Cinelerra/AlphaChannel?topicparent=Cinelerra.VideoChromaKey"><sup>?</sup></a></span> and replaces it with <a class="twikiLink" href="../../view/Cinelerra/Transparency">transparency</a> if there is an <span class="twikiNewLink" style="background : #FFFFCE;"><font color="#0000FF">AlphaChannel</font><a href="http://www.ftconsult.com/twiki/bin/edit/Cinelerra/AlphaChannel?topicparent=Cinelerra.VideoChromaKey"><sup>?</sup></a></span>. The selection of <a class="twikiLink" href="../../view/Cinelerra/ColorModel">ColorModel</a> is important.
<p />
<a class="twikiLink" href="../../view/Cinelerra/VideoChromaKey">VideoChromaKey</a> uses either the value or the <span class="twikiNewLink" style="background : #FFFFCE;"><font color="#0000FF">hue</font><a href="http://www.ftconsult.com/twiki/bin/edit/Cinelerra/Hue?topicparent=Cinelerra.VideoChromaKey"><sup>?</sup></a></span> to determine what is erased. If this parameter is within a certain threshold it's erased. It's not a simple on/off switch, however. As the selected parameter approaches the edge of the threshold, it gradually gets erased if the slope is low or is completely erased if the slope is high.
<p />
The slope tries to soften the edges of the <a class="twikiLink" href="../../view/Cinelerra/VideoChromaKey">VideoChromaKey</a> but it doesn't work well for compressed sources. A popular softening technique is to use a maximum slope and chain a <span class="twikiNewLink" style="background : #FFFFCE;"><font color="#0000FF">VideoBlur</font><a href="http://www.ftconsult.com/twiki/bin/edit/Cinelerra/VideoBlur?topicparent=Cinelerra.VideoChromaKey"><sup>?</sup></a></span> effect below the <a class="twikiLink" href="../../view/Cinelerra/VideoChromaKey">VideoChromaKey</a> effect to blur just the alpha.
<p />
-- <a class="twikiLink" href="../../view/Main/AlexFerrer">AlexFerrer</a> - 19 Dec 2003
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</table></div><div class="twikiTopicAction"><a href="../../view/Cinelerra/VideoChromaKey">View topic</a>
 <span class="twikiSeparator">|</span> <a href="VideoChromaKey">Diffs</a>  | <a href="http://www.ftconsult.com/twiki/bin/view/Cinelerra/VideoChromaKey?rev=1.2">r1.2</a> | &gt; | <a href="http://www.ftconsult.com/twiki/bin/view/Cinelerra/VideoChromaKey?rev=1.1">r1.1</a>
 <span class="twikiSeparator">|</span> <a href="http://www.ftconsult.com/twiki/bin/oops/Cinelerra/VideoChromaKey?template=oopsmore&param1=1.2&param2=1.2">More</a>
</div><div class="twikiTopicInfo"><span class="twikiRevInfo twikiGrayText">Revision r1.1 - 19 Dec 2003 - 00:07 - <a class="twikiLink" href="../../view/Main/AlexFerrer">AlexFerrer</a><br />
Revision r1.2 - 16 Jan 2004 - 22:19 - <a class="twikiLink" href="../../view/Main/AlexFerrer">AlexFerrer</a></span></div>
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