[sane-devel] Questions and suggestions

[Simon Matter]

> - 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
> waiting for data to be transferred over the network before it decides to
> start scanning the next page. When watching network activity, i see that
> data is sent in bursts with a not-so-small delay between each burst.
> My completely novice assumption is that saned scans one page, sends it to
> the net backend, scans next page, sends next page, and so on. If this is
> the case; can saned instead be configured to immediately start scanning
> next page and queue it for transmission to the client, not waiting for the
> first page to complete its journey over the network?
> Or is is some other problem, like saned compressing data before
> transmission or something? And if that is the case, can i turn it off?
>

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?
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.

> - Feature request: When looking for scanners (with scanadf -L) saned only
> reports scanners not currently in use. It would be nice to be able to see
> all attached scanners, perhaps with some indication if they are being used
> right now.

I may be wrong because I'm not a SANE expert but I think a device which is
in use by any program can not be used or seen by another program. I think
most of the devices do locking on the USB level but I saw that for some
SANE backends, separate file based locking is used.
But my question to the SANE developers is: what about writing the device
name of every opened scanner to a cache file and include the resulting
list to the list of devices when scanning for it? That way we would still
see all devices even if some of them were currently used.

> - And last (and actually least): I use the fujitsu backend, but with a
> FI-6130 scanner i get weird colors (RGB-BGR problem). I use version
> 1.0.19, but perhaps this has been fixed in cvs?

The FI-6x30 works fine with SANE from CVS. Because I wanted to use SANE
with FI-6230 I was helping Allan to diagnose what needs to be changed to
make it fully supported. However, I don't remember there was any problem
with colors.

Simon