Hi, Thanks everybody for the reactions. Even though I haven't solved the backtracking problem yet, I now know a bit more. The exact name of the scanner I'm using is indeed Trust Direct WebScan 19200 (see http://www.trust.nl/products/product.aspx?artnr=12389). Apart from the backtracking (which might be NSLU2-related) it works correctly, so I suppose it can be added to the list of supported devices. If you need more info, feel free to ask. When I have time I will test it on a regular PC running Linux (don't have Linux installed currently, so will try a live CD). I didn't get scantime.c working yet, I will look into that later on as well (probably need to upgrade sane to a later version).
Kind regards, Ruud Senden. Henning Meier-Geinitz wrote: >Hi, > >On Fri, Dec 09, 2005 at 02:29:31PM +0100, s...@rsenden.speedlinq.nl wrote: > > >>I've got sane installed on a LinkSys NSLU2 embedded linux device >>running the OpenSlug Linux distribution (see >>http://www.nslu2-linux.org) for use with my Trust Direct WebScan >>19200 scanner. >> >> > >Is "Trust Direct WebScan 19200" the exact name of the scanner? I'm >asking because a scanner with this exact name is not yet on our the list >of supported devices. > >Are these the ids of the scanner? > > >>Bus 001 Device 005: ID 055f:021c Mustek Systems, Inc. BearPaw 1200 CU Plus >> >> > > > >>The scanner basically works, but scanning is slow due to the scanner >>hopping backwards quite often. E.g. basically it scans one >>centimeter, and then hops back half a centimeter. This happens when >>scanning A4-width at 300dpi. The higher the resolution, the smaller >>the steps get. >> >> > >That's called "backtracking" and happens when the internal buffer of >the scanner is filled completely. As the buffer has a size of only 16 >kB (kilo not mega), this can happen quite quickly. In high >resolutions, this is only one scan line. > > > >>I guess every now and then some data gets lost so the scanner has to >>rescan a line. When doing an 'export SANE_DEBUG_GT68XX=5', I see the >>following for about every 13th line (at 300dpi A4 width): >> >> > > > >>[gt68xx] sane_read: getting line 190 of 3531 >>[gt68xx] sane_read: getting line 191 of 3531 >>[gt68xx] sane_read: exit (line 192 of 3531, byte_count 1987 of 2563, 32768 >>bytes, 491520 total) >>[gt68xx] sane_read: start (line 192 of 3531, byte_count 1987 of 2563) >>[gt68xx] sane_read: getting line 192 of 3531 >> >>Does anybody know a solutions for this? Using the scanner on a >>regular PC running Windows, scans are smooth. >> >> > >I don't have this exact scanner, but with similar gt68xx devices >backtracking also occurs on Windows, but it happens less often. > > > >>Scanning is also smooth >>on the nslu2 when scanning at low resolutions (preview) or scanning >>only a small width. Could it be that the NSLU2 is too slow for >>handling the amount of data? I've also read something about different >>ohci-drivers, but I'm not sure whether that is applicable to my >>situation, and how to find/build/use another version. >> >> > >Hardware performance in general and the speed of USB drivers can make >a difference. On the same computer I have no backtracking with the one >USB host adapter and some backtracking with another one. With kernel >2.4 there were two uhci kernel drivers IIRC and one was a bit faster. >As far as I know, there is only one in 2.6. > >Other tips that may reduce backtracking: Use a lower width. Sometimes >even a few mm less help. Use 8 bit/color instead of higher depths. > >The gt68xx backend does its best to get the USB data as fast as >possible. It uses a reader process which is forked and constantly >tries to get data from the scanner. The only thing I'll try once it's >implemented in libusb is using non-blocking I/O. But I'm not sure yet >if that's better. > >For comparison here are the scan speeds I get with Mustek Bearpaw 1200 CU Plus >which >has the same USB ids as your scanner. They are measured with the >scanimate.c tool which is in experimental SANE CVS. In the modes which >result in below 20 lines/s I also get backtracking. > >Checking scan speed of device gt68xx:libusb:004:003 (Mustek Bearpaw 1200 CU >Plus flatbed scanner) >mode: Color, depth: 8, dpi: 50, KB: 246 (100%), secs: 4, KB/s: > 61, lines/s: 49, mm/s: 25.0 >mode: Color, depth: 8, dpi: 75, KB: 553 (100%), secs: 11, KB/s: > 50, lines/s: 26, mm/s: 9.1 >mode: Color, depth: 8, dpi: 150, KB: 2217 (100%), secs: 10, KB/s: >221, lines/s: 59, mm/s: 10.0 >mode: Color, depth: 8, dpi: 300, KB: 8867 (100%), secs: 21, KB/s: >422, lines/s: 56, mm/s: 4.8 >mode: Color, depth: 8, dpi: 600, KB: 35471 (100%), secs: 42, KB/s: >844, lines/s: 56, mm/s: 2.4 >mode: Color, depth: 8, dpi: 1200, KB: 100352 ( 70%), secs: 60, KB/s: >1672, lines/s: 55, mm/s: 1.2 >mode: Color, depth: 12, dpi: 50, KB: 492 (100%), secs: 4, KB/s: >123, lines/s: 49, mm/s: 25.0 >mode: Color, depth: 12, dpi: 75, KB: 1107 (100%), secs: 11, KB/s: >100, lines/s: 26, mm/s: 9.1 >mode: Color, depth: 12, dpi: 150, KB: 4435 (100%), secs: 10, KB/s: >443, lines/s: 59, mm/s: 10.0 >mode: Color, depth: 12, dpi: 300, KB: 17735 (100%), secs: 21, KB/s: >844, lines/s: 56, mm/s: 4.8 >mode: Color, depth: 12, dpi: 600, KB: 3072 ( 4%), secs: 65, KB/s: > 47, lines/s: 1, mm/s: 0.1 >mode: Color, depth: 12, dpi: 1200, KB: 136704 ( 48%), secs: 60, KB/s: >2278, lines/s: 37, mm/s: 0.8 >mode: Color, depth: 16, dpi: 50, KB: 492 (100%), secs: 5, KB/s: > 98, lines/s: 39, mm/s: 20.0 >mode: Color, depth: 16, dpi: 75, KB: 1107 (100%), secs: 11, KB/s: >100, lines/s: 26, mm/s: 9.1 >mode: Color, depth: 16, dpi: 150, KB: 4435 (100%), secs: 13, KB/s: >341, lines/s: 45, mm/s: 7.7 >mode: Color, depth: 16, dpi: 300, KB: 17735 (100%), secs: 26, KB/s: >682, lines/s: 45, mm/s: 3.8 >mode: Color, depth: 16, dpi: 600, KB: 1024 ( 1%), secs: 65, KB/s: > 15, lines/s: 0, mm/s: 0.0 >mode: Color, depth: 16, dpi: 1200, KB: 78848 ( 27%), secs: 60, KB/s: >1314, lines/s: 21, mm/s: 0.5 >mode: Gray, depth: 8, dpi: 50, KB: 82 (100%), secs: 5, KB/s: > 16, lines/s: 39, mm/s: 20.0 >mode: Gray, depth: 8, dpi: 75, KB: 184 (100%), secs: 4, KB/s: > 46, lines/s: 73, mm/s: 25.0 >mode: Gray, depth: 8, dpi: 150, KB: 739 (100%), secs: 5, KB/s: >147, lines/s: 118, mm/s: 20.0 >mode: Gray, depth: 8, dpi: 300, KB: 2955 (100%), secs: 21, KB/s: >140, lines/s: 56, mm/s: 4.8 >mode: Gray, depth: 8, dpi: 600, KB: 11823 (100%), secs: 48, KB/s: >246, lines/s: 49, mm/s: 2.1 >mode: Gray, depth: 8, dpi: 1200, KB: 47295 (100%), secs: 34, KB/s: >1391, lines/s: 138, mm/s: 2.9 >mode: Gray, depth: 12, dpi: 50, KB: 164 (100%), secs: 5, KB/s: > 32, lines/s: 39, mm/s: 20.0 >mode: Gray, depth: 12, dpi: 75, KB: 369 (100%), secs: 4, KB/s: > 92, lines/s: 73, mm/s: 25.0 >mode: Gray, depth: 12, dpi: 150, KB: 1478 (100%), secs: 5, KB/s: >295, lines/s: 118, mm/s: 20.0 >mode: Gray, depth: 12, dpi: 300, KB: 5911 (100%), secs: 22, KB/s: >268, lines/s: 53, mm/s: 4.5 >mode: Gray, depth: 12, dpi: 600, KB: 8192 ( 34%), secs: 60, KB/s: >136, lines/s: 13, mm/s: 0.6 >mode: Gray, depth: 12, dpi: 1200, KB: 94590 (100%), secs: 43, KB/s: >2199, lines/s: 109, mm/s: 2.3 >mode: Gray, depth: 16, dpi: 50, KB: 164 (100%), secs: 5, KB/s: > 32, lines/s: 39, mm/s: 20.0 >mode: Gray, depth: 16, dpi: 75, KB: 369 (100%), secs: 4, KB/s: > 92, lines/s: 73, mm/s: 25.0 >mode: Gray, depth: 16, dpi: 150, KB: 1478 (100%), secs: 5, KB/s: >295, lines/s: 118, mm/s: 20.0 >mode: Gray, depth: 16, dpi: 300, KB: 5911 (100%), secs: 21, KB/s: >281, lines/s: 56, mm/s: 4.8 >mode: Gray, depth: 16, dpi: 600, KB: 1024 ( 4%), secs: 97, KB/s: > 10, lines/s: 1, mm/s: 0.0 >mode: Gray, depth: 16, dpi: 1200, KB: 22528 ( 23%), secs: 60, KB/s: >375, lines/s: 18, mm/s: 0.4 >mode: Lineart, dpi: 50, KB: 10 (100%), secs: 5, KB/s: 2, lines/s: >39, mm/s: 20.0 >mode: Lineart, dpi: 75, KB: 23 (100%), secs: 5, KB/s: 4, lines/s: >59, mm/s: 20.0 >mode: Lineart, dpi: 150, KB: 92 (100%), secs: 5, KB/s: 18, lines/s: >118, mm/s: 20.0 >mode: Lineart, dpi: 300, KB: 369 (100%), secs: 21, KB/s: 17, lines/s: > 56, mm/s: 4.8 >mode: Lineart, dpi: 600, KB: 1476 (100%), secs: 48, KB/s: 30, lines/s: > 49, mm/s: 2.1 >mode: Lineart, dpi: 1200, KB: 5905 (100%), secs: 33, KB/s: 178, lines/s: > 143, mm/s: 3.0 > >Bye, > Henning > > >
