[sane-devel] Scanning speed slower, or is it just me?

[Bertrik Sikken]

Jeremy L Rosenberger wrote:
> This may not be a particularly useful e-mail since it will be a little
> short on specifics, but hopefully it may provide enough information to
> give someone (with more knowledge of SANE internals than I have) an idea
> of what might be going on.
> 
> Once upon a time, I used my Microtek X6 USB with Windows 2000 and with
> SANE on Linux. The performance under both was about equal. This was on a
> 750MHz Athlon system with a VIA chipset using some variant of the 2.4
> kernel.
> 
> Then, somewhere along the line of 2.4 kernel versions (using the uhci,
> or "alternate" UHCI driver) and SANE versions, things stopped working:
> The scanner lamp would turn on and move about an inch before "hanging."
> I can't recall whether this locked up the machine or not. Unfortunately
> I don't know whether this problem was ever resolved, because I stopped
> using said Athlon system and now pretty much exclusively use my laptop,
> which is a 700MHz Pentium III.
> 
> Now on my laptop (still using the "alternate" uhci kernel driver),
> scanning works but is much slower than it was before. (Of course this
> could be due to the new hardware, but there is near parity in the two
> machines' capabilities.) I tried a couple of color scans at 200dpi and
> 300dpi, and the scanner head will move about an inch, pause for a few
> seconds, move another inch, pause, and so on. (Before, the motion was
> pretty much continuous.) It's as if the scanner is producing data too
> quickly and has to wait for the computer to catch up (although this
> doesn't seem very likely).
> 
> I'd be happy to do additional testing and provide more data, if someone
> would tell me what sort of data (perhaps turn on debugging somewhere and
> send log output?) would be interesting.
> 
> Of course, I am glad that even though it's slow, it works! :-)

I've seen the same with the uhci USB driver, getting a throughput
of something like only 60 kB/s. I think it happened somewhere between
kernel version 2.4.8 and 2.4.16.
I'm now running 2.4.18 but I have not checked whether it has been
fixed.

Bertrik