[sane-devel] Questions and suggestions

[Mattias Kregert]

Simon Matter wrote:
>> - The network should be fast enough to keep up with the scanning speed,
>> but still the scanner pauses a little between each page - as if it is
>>[snip]
>
> My experience with FI-6x30 is that it seems to have enough memory to do a
> duplex scan (at least with 300DPI which is what we are using here) and
> keep the whole 2 pages in it's memory. However, the connection to the host
> computer is limited by it's USB speed. Connecting the scanner to an old
> computer with no high speed USB2 things get very slow. Even with fast USB,
> I saw delays between pages with rising scan resolution. I guess that doing
> via network adds a little period to it as well.
> So, do you see the same delay between pages when scanning for example at
> 100DPI with lineart?

Nope,  no delays. I can run two scanners simultaneously, scanning 200dpi 
grayscale in duplex (80 ipm) without any problems at all.
The two fi-6130:s are connected to an EeeBox 202  (USB2, gigabit lan). PGM 
images are about 4MB each.
I get what i think is disk flush spikes now and then (very slow disk + 
filesystem installed on top of NTFS). Because of that, scanning is 
effectively limited to 140 images per minute when i scan directly on the eee 
box.


When I use saned and the net backend I scan 200dpi grayscale, but it is 
simplex only, just one scanner, and nothing hits the local slow disk. It 
*should* be able to scan as fast as the scanner can go... and sending data 
over the net should only use about 20mbit or so.

And if i use both scanners via saned/net at the same time, then the scanning 
takes exactly the same time as with one scanner only. So obviously it is not 
a network congestion problem. Something in saned or net backend introduces 
this small pause between pages...


> Also, I don't know how saned works but if it would close the device after
> every page you would see a delay for opening it again. You could try
> commenting out all unneeded backends in your sane config to make it a bit
> faster.
> If all doesn't help you may want to strace things to see where it delays.

I commented out all backends except fujitsu, but it didn't make any 
difference...


I'll try to look into the saned/net source if i can find some time...

Thanks!

/Mattias