Some snapscan feedback

From: Steffen Kluge (kluge@fujitsu.com.au)
Date: Fri May 26 2000 - 08:08:45 PDT

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    Hi,
    I've been playing a bit with my Acer Prisa 620ST and the new
    snapscan backend. This is what I found:

    - The problems I reported earlier on this list with warped
      system timers (making screensavers and DPMS kick in and wreak
      havoc among some GUI clocks) have disappeared when I stopped
      using the AHA1542B host adapter. I believe they were to blame on
      either the adapter or the driver but not on sane, the snapscan
      backend or the sg driver. I'm using a Tekram DC315U now.

    - Steve's new snapscan backend (snapscan-20000514) does a
      remarkable job, the transparency unit works well and the three
      channels are aligned perfectly without post-processing.

    - I'm having problems with the preview scan when using xsane.
      The scanner stops after about 30% and proceeds very slowly
      (like one line at a time every now and then). After a minute
      or two it goes on as normal until it reaches about 90%, then
      stops again and eventually finishes. Sometimes it pauses
      longer sometimes shorter. Sometimes switching desktops (in
      enlightenment) or randomly clicking mouse buttons helps. This
      behaviour can't be changed through any of the settings in the
      xsane dialog boxes, as long as the preview mode is colour
      (doesn't happen in bi-level, line-art or gray scale). A gdb
      run of xsane shows that it sits on a select, like in this bt:

       #0 0x4039854e in __select () from /lib/libc.so.6
       #1 0x404584f8 in __DTOR_END__ ()
          from /usr/local/lib/sane/libsane-snapscan.so.1
       #2 0x4045316a in sanei_scsi_cmd (fd=32, src=0x80eaef8, src_size=10,
           dst=0x80eaff8, dst_size=0x80f2c00) at sanei_scsi.c:2065
       #3 0x40446d6e in scsi_read (pss=0x80eaec0, read_type=0 '\000')
           at snapscan-scsi.c:785
       #4 0x404475b2 in SCSISource_get (pself=0x837e248,
           pbuf=0x839f10d "\021", '\f' <repeats 54 times>, plen=0xbfffcc5c)
           at snapscan-sources.c:158
       #5 0x40447fbc in TxSource_get (pself=0x839eac8,
           pbuf=0x839f10d "\021", '\f' <repeats 54 times>, plen=0xbfffcc5c)
           at snapscan-sources.c:439
       #6 0x40448943 in RGBRouter_get (pself=0x839eac8,
           pbuf=0xbfffe224 "\f\021\f\f\021\f\f\021\f\f\021\f\f\021", plen=0xbfffcd24)
           at snapscan-sources.c:688
       #7 0x4044fac8 in sane_snapscan_read (h=0x80eaec0, buf=0xbfffcd30 "",
           maxlen=8192, plen=0xbfffcd24) at snapscan.c:2508
       #8 0x402bad7f in sane_dll_read (handle=0x80f3078, data=0xbfffcd30 "",
           max_length=8192, length=0xbfffcd24) at dll.c:837
       #9 0x402bb09d in sane_read (h=0x80f3078, buf=0xbfffcd30 "", maxlen=8192,
           lenp=0xbfffcd24) at dll-s.c:52
       #10 0x805bb93 in preview_read_image_data (data=0x817b528, source=-1,
           cond=GDK_INPUT_READ) at xsane-preview.c:840

      The funny thing is that xscanimage's preview doesn't ever show
      this behaviour. I really like xsane's preview better, though
      (zoom etc). I've been testing with xsane version 0.57 and
      0.59, both versions behave this way. I also recompiled sane
      and xsane with no optimisations (I thought that might be a
      good idea since I'm using an Athlon), but it made no
      difference.

    - I can't for the heck of it scan at resolutions higher than
      600dpi, although the scanner supports up to 19200dpi. The
      program (scanimage, xscanimage or xsane) just freezes (enters
      an endless loop) in function measure_transfer_rate. I can
      follow the loop in the debugger but I don't understand the
      program logic so I can't say what's going wrong. I believe
      (but am not sure) that I could use higher resolutions with
      previous versions of the backend.

    - I'm doing all this with sane-1.0.2, kernel-2.2.14, sg-3.0.15,
      and the host adapter/scanner look like this:

       scsi0 : Tekram DC395U/UW/F DC315/U V1.10, 1999/07/19
       scsi : 1 host.
         Vendor: Color Model: FlatbedScanner_9 Rev: 0117
         Type: Scanner ANSI SCSI revision: 02
       Detected scsi generic sg0 at scsi0, channel 0, id 2, lun 0, type 6

    All in all I'm quite happy with the pace of progress so far. If
    it goes on like this the scanner will be ready for prime time
    soon :-) Time to acquire some GIMP photo editing skills...

    Cheers
    Steffen.

    -- 
    Steffen Kluge <kluge@fujitsu.com.au>
    Fujitsu Australia Ltd
    Keywords: photography, Mozart, UNIX, Islay Malt, dark skies
    --
    

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