Re: bar code bit encoding.

From: Jan Karrman <jan_at_it_dot_uu_dot_se>
Date: Wed Sep 17 2003 - 05:45:09 CDT

On Tue, 16 Sep 2003, Chris Schaefer wrote:

> At this point our primary goal is to get a working demo running. For
> this demo it's not super important which encoding we use since we all
> agree that alot of this code will need to be completely rewritten
> before we have a real system. So from the perspective of readability
> during debugging in the demo the encoding technique is not that
> important. Whatever makes the developer's job easier ( you, I think,
> right ? )
> However, I believe there may be one reason to consider an bit
> encoding technique will different from the 116 bit vector. And this
> has to do with reliability of scanning in the final demo. We will
> be using inexpensive scanners. It makes sense to me ( and I have
> little experience with barcodes other than supermarket shopping) that
> the shorter the code is, the more likely it will be to read reliably.
> If this is true, then if we can have with fewer bits than 116 then
> wouldn't our reliability go up even in the face of using cheap
> scanners? You have far more experience than me in this area. I'd be
> curious of your opinions here!!!

Yes, that is exactly what I'm after: to get as small bar code as
possible, i.e as few digits as possible in the huge decimal number.
There was some mentioning in another mail of a 60-digit number, and
I am afraid that may be too long do reliable scanning at the demo.
Just converting a 116-bit binary to decimal aught to work, as I
suggested. Otherwise it doesn't matter at all to me how data is
represented internally. So, either this or some compression would
be enough as I see it.

When having long messages, there is a tradeoff between using a
small font size and getting a long bar code. In the first case,
(cheap) scanner may fail reading the code (can also happen if the
printer has too low resolution), and in the second case it may be
hard to follow the entire bar code with a scanner that reads by
moving it over the bar code. In the demo it would look bad if we
repeatedly fail to scan a bar code, even if we say that other
equipment will be used in a real system.

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Received on Tue Sep 30 23:17:06 2003

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