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From: "Andy Cave" <andy.cave@hamillroad.com>
To: "Joris" <joris.at.lebbeke@skynet.be>,
        "ComSquare Martin Osieka" <martin.osieka@comsquare.ch>,
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Subject: Re: [Tiff] G3 fax: EOL needed at the beginning of each strip?
Date: Mon, 24 Sep 2007 09:45:34 +0100
Organization: Hamillroad Software
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Status:   

Hi Joris,

Absolutely (and I know both specs pretty well, having written a G3/G4 
encoder that is 4x faster than that in TIFFLib).

ITU states that:
4.1.2 End-of-line (EOL)
This code word follows each line of data. It is a unique code word that can 
never be found within a valid line of data; therefore, resynchronization 
after an error burst is possible. In addition, this signal will occur prior 
to the first data line of a page.

Who says that a strip is equiavlent to a page? The TIFF spec doesn't. If it 
is, then sure each strip is defined as beginning with an EOL. However, if 
you do not define a strip as equiavlent to a page, then there is no 
requirement for a strip to being with an EOL.

I personally lean towards the view that you should treat each strip/tile as 
a separate (part of the) image and therefore each strip should being with an 
EOL (that's what our Lightning TIFF plugin for the Hqn RIP does), however, 
since in TIFF you know where each strip starts, there really is no 
requirement to have an EOL at the start of each strip from a s/w point of 
view.

I think it's therefore not true that strips have to begin with EOL.

Regards,

Andy.

----- Original Message ----- 
From: "Joris" <joris.at.lebbeke@skynet.be>
To: "Andy Cave" <andy.cave@hamillroad.com>; "ComSquare Martin Osieka" 
<martin.osieka@comsquare.ch>; <tiff@lists.maptools.org>
Sent: Monday, September 24, 2007 9:32 AM
Subject: Re: [Tiff] G3 fax: EOL needed at the beginning of each strip?


> Andy,
>
> Andy Cave wrote:
>> I'm curious - where in the spec does it indicate strips have to start
>> with EOL? I don't remember it saying so, and checking quickly, I
>> can't find a reference to that.
>
> The TIFF 6.0 document does not describe the G3 algorithm at all, really. 
> G3 and G4 are instead described in the ITU T.4 and ITU T.6 standards. G3 
> is also described in RFC 804.
>
>
> Best regards,
>
> Joris Van Damme
> info@awaresystems.be
> http://www.awaresystems.be/
> Download your free TIFF tag viewer for windows here:
> http://www.awaresystems.be/imaging/tiff/astifftagviewer.html
> 


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