Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!rpi!uupsi!sunic!news.funet.fi!funic!santra!fuug!sti!ttl
From: ttl@sti.fi (Timo Lehtinen)
Newsgroups: comp.std.internat
Subject: Re: CCITT Group 3 question: "early" EOL
Message-ID: <1990Aug29.212103.6943@sti.fi>
Date: 29 Aug 90 21:21:03 GMT
References: <1990Aug29.194009.6820@sdd.hp.com>
Reply-To: ttl@sti.fi (Timo Lehtinen)
Distribution: comp
Organization: Stream Technologies Inc.
Lines: 35

In article <1990Aug29.194009.6820@sdd.hp.com> andrea@sdd.hp.com (Andrea K. Frankel) writes:
>
>	-  Or should a robust implementation be able to decode
>	Group 3 files where some rows are ended "early" with an EOL 
>	(in which case presumably the rest of the row is white)?

In my opinion Rec. T.4 does not give an explicit answer to this question.
In addition to section 2.1 (which you quoted) the only other lines in the
part of the document that define the one-dimensional coding scheme that
might be relevant to the question at hand are in section 4.1.1. :

	...White runs and black runs alternate. A total of 1728 picture
	elements represent one horizontal scan line of 215 mm length.

The sentence above, the fact that the FAX machines I've tested this feature 
against have all choked on early EOL's and mostly the same reasoning that
you give at the end of your message has lead me to think that an 
implementation that outputs lines with early EOL's s non-conformant.  I've 
only seen early EOL's generated by software tools that are not nessessarily
meant to be used with FAX modems as that. The G3 filters in the PBMPLUS
package behave like this and (if my memory serves) the encode/decode
routines in the ISODE/QUIPU/PHOTO system also produce scan lines shorter
than 1728. (I'm not absolutely sure about the latter one.)

BTW, The newsgroup alt.fax might be a more appropriate place for this 
discussion.

Timo Lehtinen


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