[sane-devel] USB scanner slow, hopping back and forward
Ruud Senden
sane at rsenden.speedlinq.nl
Tue Dec 13 12:36:54 UTC 2005
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, sane at 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
>
>
>
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