Re: Barcode Email
From: Walter Roberson (roberson_at_ibd.nrc-cnrc.gc.ca)
Date: Sat, 30 Jul 2005 04:54:25 +0000 (UTC)
In article <firstname.lastname@example.org>,
Ari Silversteinn <email@example.com> wrote:
:On Fri, 29 Jul 2005 14:19:48 +0000 (UTC), Walter Roberson wrote:
:> You have indicated that you can reliably get about 8000 characters
:> encoded into a single PDF417 symbol. A PDF417 symbol is restricted to
:> 30 rows by 90 columns, *including* the Reed- Solomon error-correction
:> code words. 30 * 90 is 2700, so your statements imply that you are
:> consistantly getting 3:1 compression.
:Compression is not used, technically.
Okay, let's back off a step for a cross-check that we are talking
about the same thing:
- Is it correct that you find that you are able to reliably store and
retreive (using an optical scanner), approximately 8000 input octets as
a single PDF417 symbol? If not, then it would be good if you would
clarify the number of source characters that you are able to store and
retreive from a single PDF417 symbol.
- Is the PDF417 symbol you are using larger than 30 rows or 90 columns?
If so, then it would be good if you would clarify the PDF417 symbol
size and provide a reference to a PDF417 definition that allows
those sizes to be exceeded (earlier I provided a link to a
PDF417 manufacturer which indicated the 30x90 maximum theoretical size.)
- When you indicate that you are able to reliably retreive more than
800 characters from a PDF417, are you using commercial
off-the-shelf PDF417 scanners, or custom [or uncommon] scanners?
- When you refer to the storage capacity of about 8000 characters,
is that an optimum (maximum), typical, constant, or worst-case
- When you refer to the PDF417 symbol storage capacity, are you
referring just to information stored in the plain barcode, or are
you including additional information hidden in the barcode image?
For example, if I were to take one of the output PDF417 symbols,
fax it (bi-level encoding) to someone, and they were to gun the
printout, would the full information be available [barring
transmission errors] ?
-- Entropy is the logarithm of probability -- Boltzmann