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<!-- sent="Sat, 14 Aug 1999 23:04:25 -0500 (CDT)" -->
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<!-- name="Henry Miller" -->
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<!-- subject="Re: Starting a discussion about SANE and TWAIN..." -->
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<!-- inreplyto="Pine.LNX.4.10.9908150331510.20001-100000@chef.ecs.soton.ac.uk" -->
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<title>sane-devel: Re: Starting a discussion about SANE and TWAIN...</title>
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<h1>Re: Starting a discussion about SANE and TWAIN...</h1>
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<b>Henry Miller</b> (<a href="mailto:hank@black-hole.com"><i>hank@black-hole.com</i></a>)<br>
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<i>Sat, 14 Aug 1999 23:04:25 -0500 (CDT)</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#158">[ date ]</a><a href="index.html#158">[ thread ]</a><a href="subject.html#158">[ subject ]</a><a href="author.html#158">[ author ]</a>
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<li> <b>Next message:</b> <a href="0159.html">Milon Firikis: "Re: Starting a discussion about SANE and TWAIN..."</a>
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<li> <b>Previous message:</b> <a href="0157.html">Stephen Williams: "Re: Starting a discussion about SANE and TWAIN..."</a>
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</ul>
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On Sun, 15 Aug 1999, Nick Lamb wrote:<br>
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<p>
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<i>> </i><br>
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<i>> On Sat, 14 Aug 1999, Stephen Williams wrote:</i><br>
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<i>> </i><br>
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<i>> > So all I'm looking for at the moment is some sort of means to negotiate</i><br>
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<i>> > frame formats.</i><br>
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<i>> </i><br>
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<i>> Ok. IIRC Your scanners can do RGB, but prefer not to for speed reasons?</i><br>
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<i>> So in writing the backend, first start by supporting this (slow) option</i><br>
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<i>> as the default and then add an option (eventually to be a well-known</i><br>
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<i>> option in SANE 2.0) which controls the compression.</i><br>
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<p>
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We really need more extensiablility, preferabliy so that the future can be<br>
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added without a Sane version 3.0. (this is an ideal, not nessicarly<br>
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achivable in practice.<br>
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<p>
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Looking to telnet, you have a default mode that everything needs to<br>
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support. there is also a "Will/ Won't, Do/Don't" protocol that can be<br>
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extended as needed, this is entirly behind the users back. <br>
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<p>
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I'm proposing adding a similear layer of non-viewbale controls. A backend<br>
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supports everything in Sane 1.0, plus the non-user protocol. If the<br>
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backend prefers jpeg, it can send "I will do jpeg" (which is probably a<br>
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numerical value) and the frontend responds "Do jpeg", or "Don't jpeg"<br>
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<p>
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Anouther backend might offer to send a dust channel, (by a protocl defined<br>
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in whatever standard defins the dust collection) and if the frontend<br>
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refuses, it just sends RGB, otherwise it sends the dust channel by some<br>
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means.<br>
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<p>
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There also needs to be middle laywer commands, for instance the net<br>
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connection might want to negociate compression. Normally this is<br>
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reasonable, but if the backends are sending jpeg it should not. Thus, is<br>
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all options are refused between ultimate front end and backend, then mid<br>
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layers can do something, if there is an option allowed, the mid layers<br>
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should not do anything unless told to. The dust colletion option<br>
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could result in a backend sending a command "I don't do do compression,<br>
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but you can". If the mid layer happens to understand the dust collection<br>
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it could still do something else that it the other ends don't know about<br>
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if compatable. Basicly, if you understand an option you can take whatever<br>
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action you want, if you don't understand one in effect you should take no<br>
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action.<br>
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<p>
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I'm not sure if I ultimatly like the idea of conversion layers, but in the<br>
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above example, a frontend could refuse dustcollection, at which point the<br>
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conversion layer steps in and affers to do that correction. (at which<br>
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point it might negate the compression option already agreed to, because it<br>
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doesn't understand compression even though the other layers do) <br>
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<p>
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I'm Not sure if that makes sense, but I hope you can get the idea: This<br>
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is a more flexable alternative, and every layer can take part. It is not<br>
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of course perfect, so I won't be mad if you pick it apart.<br>
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<p>
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<p>
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<pre>
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--
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<a href="http://www.black-hole.com/users/henrymiller/">http://www.black-hole.com/users/henrymiller/</a>
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<a href="mailto:hank@black-hole.com">hank@black-hole.com</a>
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<p>
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<p>
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<p>
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<p>
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<p>
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<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">majordomo@mostang.com</a>
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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="0159.html">Milon Firikis: "Re: Starting a discussion about SANE and TWAIN..."</a>
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<li> <b>Previous message:</b> <a href="0157.html">Stephen Williams: "Re: Starting a discussion about SANE and TWAIN..."</a>
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<!-- nextthread="start" -->
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</ul>
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