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<TITLE>sane-devel: Re: Writing Fujitsu M3091 backend</TITLE>
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<META NAME="Author" CONTENT="Nick Lamb (njl98r@ecs.soton.ac.uk)">
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<META NAME="Subject" CONTENT="Re: Writing Fujitsu M3091 backend">
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<H1>Re: Writing Fujitsu M3091 backend</H1>
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<!-- received="Tue Feb 27 09:24:25 2001" -->
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<!-- sent="Tue, 27 Feb 2001 17:38:11 +0000" -->
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<!-- name="Nick Lamb" -->
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<!-- email="njl98r@ecs.soton.ac.uk" -->
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<!-- subject="Re: Writing Fujitsu M3091 backend" -->
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<STRONG>From:</STRONG> Nick Lamb (<A HREF="mailto:njl98r@ecs.soton.ac.uk?Subject=Re:%20Writing%20Fujitsu%20M3091%20backend&In-Reply-To=<20010227173811.F14413@ecs.soton.ac.uk>"><EM>njl98r@ecs.soton.ac.uk</EM></A>)<BR>
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<STRONG>Date:</STRONG> Tue Feb 27 2001 - 09:38:11 PST
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<P>
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<LI><STRONG>Next message:</STRONG> <A HREF="0235.html">Frederik Ramm: "Re: Fujitsu fi-4750C Backend Project"</A>
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<UL>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0233.html">Davis, Tom: "Fujitsu fi-4750C Backend Project"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0232.html">Frederik Ramm: "Writing Fujitsu M3091 backend"</A>
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<LI><STRONG>Next in thread:</STRONG> <A HREF="0236.html">Frederik Ramm: "Re: Writing Fujitsu M3091 backend"</A>
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<HR NOSHADE><P>
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<P>
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<EM>> Question 1 - How to do duplex scanning.
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> If SANE doesn't support that, I could introduce a new parameter that
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</EM><BR>
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<EM>> controls whether the front or rear side is to be scanned, and each
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</EM><BR>
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<EM>> page would have to be run through the scanner twice. A waste, but
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</EM><BR>
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<EM>> possible.
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</EM><BR>
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<P><EM>> I've grepped for "duplex" in the existing backends (1.0.4) but found
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</EM><BR>
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<EM>> nothing.
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</EM><BR>
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<P>None of the backends in 1.0.4 can do duplex scanning AFAICT
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<BR>
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<P>Handling duplex in the front-ends is probably a bit much, certainly
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<BR>
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not something that can supported through the SANE 1.0 standard without
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<BR>
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incompatible tweaks.
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<BR>
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<P>You might consider buffering the alternate side in SANE driver, which
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<BR>
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will typically be on a decent-sized PC or server. A whole page is a
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<BR>
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lot of data to buffer, especially in color, but these days that might
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<BR>
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be a lot more practical than re-scanning everything.
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<BR>
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<P>When scanning the first page, half the data goes in this large buffer,
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<BR>
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then when the frontend asks for another page it comes out of the
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<BR>
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buffer very quickly. The buffer can be discarded when the frontend
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<BR>
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calls ..._close() so it won't take up RAM all the time.
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<BR>
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<P>Of course you still need a "duplex?" setting, because users don't want
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<BR>
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to scan both sides of a single-sided document :)
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<BR>
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<P><EM>> Question 2 - How to do the color thing.
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</EM><BR>
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<EM>>
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</EM><BR>
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<EM>> incomplete data at the beginning and the end of the data stream. If I
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</EM><BR>
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<EM>> request an image of, say, 100 pixels in height, will the scanner then
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</EM><BR>
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<EM>> give me 100 of which only 84 are fully usable, or will it give me 116?
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</EM><BR>
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<P>This sounds like something very specific to your scanner. I hope you can
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<BR>
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figure out how to get the right results to the frontend.
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<BR>
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<P>Nick.
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<BR>
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<P><PRE>
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--
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Source code, list archive, and docs: <A HREF="http://www.mostang.com/sane/">http://www.mostang.com/sane/</A>
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To unsubscribe: echo unsubscribe sane-devel | mail <A HREF="mailto:majordomo@mostang.com?Subject=Re:%20Writing%20Fujitsu%20M3091%20backend&In-Reply-To=<20010227173811.F14413@ecs.soton.ac.uk>">majordomo@mostang.com</A>
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</PRE>
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<LI><STRONG>Next message:</STRONG> <A HREF="0235.html">Frederik Ramm: "Re: Fujitsu fi-4750C Backend Project"</A>
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<LI><STRONG>Previous message:</STRONG> <A HREF="0233.html">Davis, Tom: "Fujitsu fi-4750C Backend Project"</A>
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<LI><STRONG>In reply to:</STRONG> <A HREF="0232.html">Frederik Ramm: "Writing Fujitsu M3091 backend"</A>
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This archive was generated by <A HREF="http://www.hypermail.org/">hypermail 2b29</A>
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