Re: Scan ahead

From: Stephen Williams (
Date: Fri Mar 30 2001 - 12:54:19 PST

  • Next message: Oliver Rauch: "Re: big endian vs little endian" said:
    > I dont know a scanner that can store a single frame completely. For an
    > A4 scan at 600 dpi with 24bit you would need about 100MB of memory.

    I know several, and they are grayscale and color. And we keep building
    more because this pipelining really does help when you are talking about
    large batches. Of course, we are not talking about desk-top flat-bed
    scanners here:-)

    And even on scanners that don't, it is possible that you want to start
    the engine moving the next page before you have all of the current page,
    because the mechanical latencies are such that you can get away with it.
    In the case of many scanners, this is the *only* way to get the rated
    speed. In these cases, it is up to the host driver to pull images out
    fast enough that you don't get overrun.

    So Marius asked a valid question and I'm curious myself how this issue
    was dealt with by others. I suspect the answer is going to be something
    like "a child process does the pipelining."

    Steve Williams                "The woods are lovely, dark and deep.              But I have promises to keep,            and lines to code before I sleep,       And lines to code before I sleep."

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