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3.1 KiB
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68 wiersze
3.1 KiB
HTML
<!-- received="Wed May 26 03:50:23 1999 PDT" -->
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<!-- sent="Wed, 26 May 1999 10:58:21 +0200" -->
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<!-- name="abel deuring" -->
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<!-- email="a.deuring@satzbau-gmbh.de" -->
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<!-- subject="Re: version 0.20 of ths Sharp backend available" -->
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<!-- inreplyto="version 0.20 of ths Sharp backend available" -->
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<title>sane-devel: Re: version 0.20 of ths Sharp backend available</title>
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<h1>Re: version 0.20 of ths Sharp backend available</h1>
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<b>abel deuring</b> (<a href="mailto:a.deuring@satzbau-gmbh.de"><i>a.deuring@satzbau-gmbh.de</i></a>)<br>
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<i>Wed, 26 May 1999 10:58:21 +0200</i>
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<p>
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<ul>
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<li> <b>Messages sorted by:</b> <a href="date.html#259">[ date ]</a><a href="index.html#259">[ thread ]</a><a href="subject.html#259">[ subject ]</a><a href="author.html#259">[ author ]</a>
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<li> <b>Next message:</b> <a href="0260.html">Jeff Lopes: "Mustek 600 III EP Plus"</a>
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<li> <b>Previous message:</b> <a href="0258.html">dch: "Re: To UMAX Astra 6X0S users"</a>
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<li> <b>Maybe in reply to:</b> <a href="0255.html">abel deuring: "version 0.20 of ths Sharp backend available"</a>
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</ul>
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Milon Firikis wrote:<br>
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<p>
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<i>> > - a separate process is forked which reads data from the</i><br>
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<i>> > scanner and delivers the data to the parent process.</i><br>
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<i>> > Unlike several other backends, which also fork a reader</i><br>
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<i>> > process and transfer the data to parent process through</i><br>
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<i>> > a pipe, the Sharp backend uses shared memory for this</i><br>
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<i>> > purpose.</i><br>
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<i>> </i><br>
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<i>> May I ask why?</i><br>
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<p>
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Firstly, because I did not get a sufficiently fast reader <br>
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process using a pipe - at least for the Sharp JX-250. <br>
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This scanner is a relatively fast scanner (the data <br>
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transfer for an A4 gray scale scan with 400 dpi needs <br>
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less than 10 seconds), but has obviously only a very small <br>
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internal buffer. In order to avoid carriage stops, the <br>
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reader process must issue a read command to the scanner as <br>
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soon as possible after processing the data from the <br>
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previous read command. Writing the scan data into a pipe <br>
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needs, at least on a P166 under Linux, enough time to <br>
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cause some carriage stops.<br>
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<p>
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Secondly, with shared memory it is easy to use a larger<br>
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buffer. This can avoid some carriage stops if the frontend<br>
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is temporarily too slow to read the scan data as fast as it<br>
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is delivered by the backend.<br>
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<p>
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Abel<br>
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<p>
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<pre>
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--
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</pre>
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<p>
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<ul>
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<!-- next="start" -->
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<li> <b>Next message:</b> <a href="0260.html">Jeff Lopes: "Mustek 600 III EP Plus"</a>
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<li> <b>Previous message:</b> <a href="0258.html">dch: "Re: To UMAX Astra 6X0S users"</a>
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<li> <b>Maybe in reply to:</b> <a href="0255.html">abel deuring: "version 0.20 of ths Sharp backend available"</a>
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<!-- nextthread="start" -->
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</ul>
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