[sane-devel] fi-5900 caching options

[Viktor Ivanov]

I am working with a fi-5900C scanner and have noticed that the windows
driver has an option for caching. Some of the possible values are None, Use
Scanner Memory, Use RAM, Use Both. Using the scanner's memory for caching
makes scanning very fast and I'd like to be able to do that from Linux.
However, no options pertaining to the caching mode are available from
scanimage.

I also noticed the following: If the scanner is used from windows with the
use scanner mem caching option and the PC is then rebooted into linux the
setting seems to persist and the scanner is blazingly although the scanimage
parameters are exactly the same. However, the images produced are wrong. I
diagnosed this to be a color planes interlacing issue - planar data was
being interpreted as interlaced. I changed s->color_interlace for this model
to COLOR_INTERLACE_RRGGBB and tested it out. Sure enough the images produces
were of the same quality as with the "slow" scanimage.

The above observations led me to believe that the fi-5900 has a number of
options that the user cant set from scanimage. The caching would be very
useful since it gives about a 50% speedup.

I welcome any pointers as to how I might set the caching option in the
backend and ultimately with a scanimage parameter.

-- 
Viktor R. Ivanov <v.shrike at gmail.com>
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