[sane-devel] Need sane docs

[Gene Heskett]

On Thursday 05 May 2016 10:31:53 Richard Ryniker wrote:

> I doubt a gigabit Ethernet connection will make any significant
> difference.

After investigating the lcd panels network settings for a wired lan, and 
finding the best it can do is 100mbit-fd, that switch isn't going to do 
a lot of good.  But the old one had a port that comes and goes very 
intermittently, so I expect its been tapped by a local lightnings EMP 
somewhere along the 6+ years its been in use here.

I as I said before, can ping it in an average time of .3 milliseconds.
But when xsane inits on the lan address, on launch from a shell, the 
little "looking for scanners" box is drawn for about 1 screen refresh 
and its wiped.  Then the is a 5 or 6 second pause before xsane draws its 
windows.  Hooked up with a usb cable, the opening screen draws are a 
small fraction of a second being drawn.  And this is perceptually the 
exact same lag as the command delay is. So while its working, I'm of the 
opinion that the command lag is in xsane someplace.

Since 99.9% of the scanners sane runs are hooked up to a USB cable, this 
lag may be a bug someplace that because its so rare, has not been well 
investigated.  The wheel only squeaks on the 29th day of February sort 
of thing. ;-)

According to an xsane -v:
gene at coyote:/etc$ xsane -v
xsane-0.998 (c) 1998-2010 Oliver Rauch
  E-mail: Oliver.Rauch at xsane.org
  package xsane-0.996
  compiled with GTK-2.24.10
  with color management function
  with GIMP support, compiled with GIMP-2.6.12
  XSane output formats: jpeg, pdf(compr.), png, pnm, ps(compr.), tiff, 
txt

From that it looks like its been a while since xsane has had any great 
amount of TLC.  Its also odd that the "about screen" says 0.998, not 
0.996. ???

Perhaps its time to troll thru the networking code & see if anything 
bites? So I'll renew my offer to serve as a test mule again.

But please don't cut too deep, I am on 7.5 mg of warfarin a day for blood 
thinner. :)  One of those defective takata air bags could kill me long 
before the sirens could be heard in the distance. :(


> Data rate from your scanner is dependent on the 
> mechanical speed of the sensor and scan resolution.  If you scan a
> page 8.5 by 11 inches at 600 pixels per inch resolution with 24 bits
> per pixel, there is about 100 megabytes of data.  With a 100-megabit
> Ethernet connection, that is about 10 seconds transmission time.  If
> your scanner requires 10 seconds for mechanical movement at that
> resolution, the Ethernet connection should not limit scan speed.
>
> At 1200 pixel per inch resolution, there would be four times as much
> data (400 Mbytes.) This would need roughly 40 seconds to transfer
> using a 100-megabit Ethernet connection, but your scanner likely moves
> more slowly at that resolution.  If you can scan faster than 40
> seconds with a USB connection at that resolution, then gigabit
> Ethernet might help.  Do you have any reason to believe your machine
> even supports gigabit Ethernet?  Most do not.
>
> Eight seconds instead of two seconds to start a scan sounds like some
> sort of time-out situation.  The tcpdump command could provide some
> details about timing of the Ethernet traffic, though interpretation of
> the data might be a challenge.


Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>