Re: Hangs with B&W QuickCam

Andrew Kuchling (amk@magnet.com)
Mon, 14 Jul 1997 11:24:53 -0400 (EDT)

On Sun, 13 Jul 1997, Guido Muesch wrote:
> No, you are right. I experience the same problem with xcam and BW
> QuickCam. After the first scan it hangs. But using scanimage works so
> far. I have not looked into this problem because I thought it is a
> minor 'feature' which will get fixed soon, now that the BW support
> actually does return at least one scan.

scanimage should always work, because it only reads one image,
and therefore opens the device, reads from it, closes it and exits.
It's only things which try to read from the camera more than once
which hang.

Thomas Mirlacher wrote:
>Well, IMHO the problem is caused by different End Of Frame sequences,
>used by the color and BW quickcam. so the usual workaround (for not so
>clean coded drivers ;) should be to reset the cam after each scan.

Adding qc_reset(q) after the qc_lock() in sane_start
(resetting things *before* the scan) seems to fix things, but I have
no idea what else that might break on colour qcams, so I wouldn't
consider that a fix just yet. Perhaps if qc_reset() was only called
if q->version!=QC_COLOR?

Another minor problem: run xscanimage using the qcam, and set
it to high resolution. The dialog box isn't redrawn properly, with
some doubled text; an xwd dump of the result is at
http://starship.skyport.net/crew/amk/ocr/bug.xwd . The resulting scan
doesn't work; does high resolution mode exist on the B&W qcam?

Andrew Kuchling
amk@magnet.com
http://people.magnet.com/%7Eamk/

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