Re: SANE frames

David Mosberger-Tang (David.Mosberger@acm.org)
Tue, 17 Aug 1999 09:18:46 -0700

>>>>> On Mon, 16 Aug 1999 17:42:47 +0200, Oliver Rauch <oliver.rauch@Wolfsburg.DE> said:

Oliver> the sane standard defines of how much frames an image
Oliver> consists. After the last frame - that means if the image is
Oliver> transferred completly - the frontend has to call
Oliver> sane_cancel.

Actually, IIRC, our intent was indeed to allow the call sequence that
Tom describes. Note that in 4.4 it says:

"If the frontend expects additional frames (e.g., the individual channels
in of a red/green/blue image or multiple images), it can call sane_start()
^^^^^^^^^^^^^^^^^^
again."

Also, note that xcam does acquire multiple images without calling
sane_cancel(). (It's an amusing exercise to test a scanner with xcam,
actually ;-)

In other words, the idea is to have sane_start() be called, and
collect as many images as the frontend wants (which could in turn
consist of multiple frames each as indicated by frame-type) and when
the frontend is done, it should call sane_cancel(). Sometimes it's
better to think of sane_cancel() as "sane_stop()" but that name would
have had some misleading connotations as well, that's why we stuck
with "cancel".

--david

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