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</style><div role="note" class="hatnote navigation-not-searchable">For conversion of vector images to raster images, see <a href="Rasterisation" title="Rasterisation">Rasterisation</a>.</div>

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<p><b>Scan conversion</b> or <b>scan converting rate</b> is a <a href="Video_processing" title="Video processing">video processing</a> technique for changing the vertical / horizontal scan frequency of video signal for different purposes and applications. The device which performs this conversion is called a <b>scan converter</b>.<sup id="cite_ref-patent_CA1103345A1_1-0" class="reference"><a href="#cite_note-patent_CA1103345A1-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>

</p><p>The application of scan conversion is wide and covers video projectors, cinema equipment, TV and <a href="Video_capture" title="Video capture">video capture</a> cards, standard and HDTV <a href="Television" title="Television">televisions</a>, LCD monitors, radar displays and many different aspects of picture processing.

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<div class="mw-heading mw-heading2"><h2 id="Mechanisms_and_methods">Mechanisms and methods</h2></div>

<p>Scan conversion involves changing the picture information data rate and wrapping the new picture in appropriate <a href="Synchronization" title="Synchronization">synchronization</a> signals.

There are two distinct methods for changing a picture's data rate:

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<dl><dt>Analog Methods (Non retentive, memory-less or real time method)</dt></dl>

<p>This conversion is done using large numbers of delay cells and is appropriate for analog video. It may also be performed using a specialized scan converter vacuum tube.<sup id="cite_ref-patent_CA1103345A1_1-1" class="reference"><a href="#cite_note-patent_CA1103345A1-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> In this case <a href="Polar_coordinates" class="mw-redirect" title="Polar coordinates">polar coordinates</a> (angle and distance) data from a source such as a radar receiver, so that it can be displayed on a <a href="Raster_scan" title="Raster scan">raster scan</a> (TV type) display.

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<dl><dt>Digital methods (Retentive or buffered method)</dt></dl>

<p>In this method, a picture is stored in a line or frame buffer with n1 speed (data rate) and is read with n2 speed, several picture processing techniques are applicable when the picture is stored in buffer memory including kinds of interpolation from simple to smart high order comparisons, motion detection and … to improve the picture quality and prevent the conversion artifacts.<sup id="cite_ref-patent_CA1103345A1_1-2" class="reference"><a href="#cite_note-patent_CA1103345A1-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="How_to_realize">How to realize</h2></div>

<p>The process in practice is applicable only using integrated circuits in <a href="Large_Scale_Integration" class="mw-redirect" title="Large Scale Integration">LSI</a> and <a href="VLSI" class="mw-redirect" title="VLSI">VLSI</a> scales. Timing, interference between digital and analog signals, clocks, noise and exact synchronization have important roles in the circuit.

Digital conversion method needs the analog video signal to be converted to digital data at the first step.

A scan converter can be made in its basic structure using some high speed integrated circuits as a circuit board however there are some integrated circuits which perform this function plus other picture processing functions like scissoring, change of <a href="Aspect_ratio_(image)" title="Aspect ratio (image)">aspect ratio</a> and … an easy to use example was SDA9401.

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<div class="mw-heading mw-heading2"><h2 id="Some_examples">Some examples</h2></div>

<p>Up conversion (<a href="Interpolation" title="Interpolation">interpolation</a>):

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<ul><li>In many <a href="LCD" class="mw-redirect" title="LCD">LCD</a> monitors there is a native picture mode, however the monitor can display different graphical modes using a scan converter.</li>

<li>In a <a href="100_Hz" class="mw-redirect" title="100 Hz">100 Hz</a>/120 Hz analog TV, there is a scan converter circuit which converts the vertical frequency (refresh rate) from standard 50/60 Hz to 100/120 Hz to achieve a low level of flicker which is important in large screen (high inch) TVs.</li>

<li>An external TV card receives the TV signals and converts them to VGA or <a href="SVGA" class="mw-redirect" title="SVGA">SVGA</a> format to display on monitor.</li></ul>

<p>Down conversion (<a href="Decimation_(signal_processing)" class="mw-redirect" title="Decimation (signal processing)">decimation</a>):

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<ul><li>Many <a href="Graphic_cards" class="mw-redirect" title="Graphic cards">graphic cards</a> have output for <a href="Standard-definition_television" title="Standard-definition television">standard-definition television</a>. Here there is a conversion from computer graphical modes to TV standard formats.</li>

<li>Other graphic cards lack an SDTV output, but their VGA outputs can still be connected to an SDTV through an external scan converter (pictured).</li></ul>

<p>Scan conversion serves as a bridge between TV and computer graphics technology.

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<li><a href="Analog-to-digital_converter" title="Analog-to-digital converter">Analog-to-digital converter</a></li>

<li><a href="Digital-to-analog_converter" title="Digital-to-analog converter">Digital-to-analog converter</a></li>

<li><a href="International_Telecommunication_Union" title="International Telecommunication Union">International Telecommunication Union</a></li>

<li><a href="Video_scaler" title="Video scaler">Video scaler</a></li></ul>

<div class="mw-heading mw-heading2"><h2 id="References">References</h2></div>

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<li id="cite_note-patent_CA1103345A1-1"><span class="mw-cite-backlink">^ <a href="#cite_ref-patent_CA1103345A1_1-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-patent_CA1103345A1_1-1"><sup><i><b>b</b></i></sup></a> <a href="#cite_ref-patent_CA1103345A1_1-2"><sup><i><b>c</b></i></sup></a></span> <span class="reference-text"><a rel="nofollow" class="external text" href="https://patents.google.com/patent/US4220969">US patent US4220969 / CA1103345A1</a>, Kazuhiko Nitadori, "Digital scan converter", published September 2, 1980. assigned to OKI Electric Ind. C. Ltd. Retrieved August 19, 2013</span>

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<ul><li>Television Engineering Handbook (K. Blair Benson) <style data-mw-deduplicate="TemplateStyles:r1238218222">

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</style><a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0070047790</bdi></li>

<li>A technical introduction to digital video. (Charles A. Poynton) <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>047112253X</bdi></li>

<li>Television and Video Systems. (Charles G. Buscombe) <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>013903014X</bdi></li>

<li>Printed Circuits Handbook. (Clyde F. Coombs) <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0070126097</bdi></li>

<li>Handbook of Filter Synthesis (Anatol I. Zverev) <a href="ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <bdi>0471986801</bdi></li></ul>

<div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2></div>

<ul><li><a rel="nofollow" class="external text" href="http://www.commsdesign.com/main/multsupp/0005/0005hdtv.htm">A/D, D/A Conversion for HDTV</a></li>

<li><a rel="nofollow" class="external text" href="http://elm-chan.org/works/sc/report.html">NTSC to VGA scan converter circuit</a></li>

<li><a rel="nofollow" class="external text" href="https://accessscanning.com/">Video Duplication with Access Scanning</a></li>

<li><a rel="nofollow" class="external text" href="http://www.asm-pc.com/SC.htm">Scan Converter General Idea</a></li></ul></div><div><div class="zim-footer">

This article is issued from <a class="external text" title="Last edited on 2024-06-08" href="https://en.wikipedia.org/wiki/?title=Scan_conversion&oldid=1227949365">Wikipedia</a>. The text is available under <a class="external text" href="https://creativecommons.org/licenses/by-sa/4.0/deed.en">Creative Commons Attribution-Share Alike 4.0</a> unless otherwise noted. Additional terms may apply for the media files.

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