[sane-devel] "stop and go" and colour lines with epson 1250

[Gerhard Jaeger]

Hi,

the 1250 is a "stupid" LM983x based scanner which knows nothing about
jpeg compression. The stop and go is a "feature" of the LM983x to avoid
data loss (of course you encounter this problem...)

I think that the libusb and or the usb-stack itself is the problem. I've
currently not testet here with 2.6 kernels.
Another thing is the image size you scan. Tests showed, that scanning
only small portions of a picture in 600dpi will work fine (of course - less
data), while scanning larger portions will not work very well, but full-size
scanning @300dpi should be no problem, at least with the plustek backend.

Can you switch back to 2.4 kernel?

Ciao,
  Gerhard


On Friday 07 May 2004 16:11, m. allan noah wrote:
> if this scanner is usb 1.1 and capable of jpeg compression in hardware,
> that might explain the difference, since color scans at anything above 200
> dpi can usually fill the usb. windows might use the jpeg compression, and
> sane might not.
>
> another possible cause might be usb packet timeouts. are there any error
> messages in /var/log/messages?
>
> but i dont know much about epsons...
>
> allan
>
> On Fri, 7 May 2004, Prakash K. Cheemplavam wrote:
> > Hi,
> >
> > I am using sane-backends 1.0.14 with epson 1250 scanner and have
> > following problem:
> >
> > When I try to scan with higher dpi (eg 600, but starts at 240dpi
> > already) the scanning process isn't done in one go. It is more like
> > scan-pause-scan-pause-scan-pause...etc. Not only the speed suffers by
> > this, but also the quality: Sometimes at the pause points i get
> > horizontal coloured lines which don't belong there. (using xsane)
> >
> > I am using libusb 0.18 with 2.6.6-rc3-mm2 based kernel, but I tested an
> > old 2.6.0-test11 kernel on other hardware, as well, here with libusb and
> > scanner module and both at least show the "stop and go" symptom. (I
> > haven't checked image quality. (Tested with scanimage)
> >
> > It seems xsane does more of that stop and goes than scanimage, but I
> > haven't thoroughly tested it.
> >
> >
> > As a check I tried to scan in windows and here there is no problem. The
> > scan is done in one shot, so it is fast and the quality is great here -
> > so it is not a hardware problem.
> >
> >
> > SO I wonder what the problemin Linux is. I don't remember correctly
> > whether I didn't have that problem with older sane-backends. Should I
> > try older plustek drivers? How can I easily do it?
> >
> > Thanks,
> >
> > Prakash
>
> --
> "so don't tell us it can't be done, putting down what you don't know.
> money isn't our god, integrity will free our souls" - Max Cavalera