Re: Snapscan.... Help! (a few extra data)

From: John Coppens (jcoppens@linux2.uccor.edu.ar)
Date: Wed Dec 20 2000 - 19:00:20 PST

  • Next message: Ian Cartwright: "RE: Snapscan.... Help! (a few extra data)"

    Hello Steve.

    Thanks for the info. If only I could find a source for this data, I wouldn't
    bother the list with such basic questions.

    Anyway, I experimented a bit more, but I cannot find a way to get the
    color organized. As I wrote a mail before, the image appears, in different
    colors, displaced horizontally. Something like
    should be Is

    aaabbbcccddd aaabbbcccddd
    aaabbbcccddd abbbcccdddaa
    aaabbbcccddd cccdddaaabbb
    aaabbbcccddd daaabbbcccdd

    note: these stripes are 5 to 50 scan lines wide...

    And colors are changing too. It seems to have something to do with the
    machine's activity at the moment: the horizontal stripes are wider with
    less activity. It's a bit difficult to describe in words.

    I have the impression there's some data loss at the beginning of the
    transferred block... Any way to test this?

    John

    On Thu, 21 Dec 2000 02:25:06 +0800 Steve Underwood <steveu@coppice.org> wrote/El dddd> John Coppens wrote:
    >
    > > Hi Chris.
    > >
    > > A few (possibly) hints...
    > >
    > > I've been checking the debug log and found a few strange things.
    > >
    > > - Says buffer is size = 31725 bytes, 55 lines. At 1269 bytes/lines this
    > > can't be (should be 25). I checked the source code and found:
    >
    > Have you allowed for the chroma offset ring-buffer?

    Mmmm... how much space does this occupy? And why is the effective
    space calculated without subtracting this space first?

    >
    > > DBG (DL_DATA_TRACE,
    > > "%s: effective buffer size = %lu bytes, %lu lines\n",
    > > me,
    > > (u_long) pss->buf_sz,
    > > (u_long) (pss->buf_sz ? pss->buf_sz / pss->lines : 0));
    > >
    > > I suppose this should be / pss->bytes_per_line
    >
    > Yes, this looks like a silly slip.
    >
    > > - A bit before that, it says : set_window: bits-per-pixel set to 30
    > >
    > > How can this result in 3 bytes/pixel afterwards? I couldn't find
    > > how the extra 2 bits (*3) are sent... Are they packed in another block?
    >
    > The scanner is using 30 bits, but after gamma correction it only outputs 24 bits to the host. This is normal behaviour for a 30 bit
    > scanner.
    >
    > Regards,
    > Steve
    >
    >
    >
    > --
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