[sane-devel] Scanning from fujitsu ScanSnap S1500 Error during device I/O

[m. allan noah]

Thanks for the testing guys. Looks like this one is squashed.

For the record, the problem was caused by code I added to reduce the
memory usage of the backend.

Sane backends 1.0.20 and before used a full-size buffer for both front
and backside data. Total of 200Mb for 600dpi color duplex A4. 1.0.21
uses a full-size buffer for the back, and a small buffer for the
front, usually 64k. This effectively cuts memory usage in half.

Unfortunately, 1.0.21 continues to read the backside image into the
big buffer, even when it did not read from the front. Eventually, we
get too far ahead of the scanner, and it's buffers fill up. What
happens at that point seems model or firmware version specific, good
scan, slow scan, bad image, error, etc. Using the -B option fixes
1.0.21 because the front-end keeps the small frontside buffer drained,
and we never get behind.

1.0.22 does not read from the backside if there was no read from the
front, so the problem goes away. -B might improve speed a little on
1.0.22 as well, along with increasing the buffer size in fujitsu.conf.
Would be interesting to compare the speed with the windows driver...

allan

On Tue, Feb 8, 2011 at 5:56 AM, Simon Matter <simon.matter at invoca.ch> wrote:
>> I just did a quick git testing.
>> The buffer problem seems to be solved now.
>
> I can confirm this for the S510 as well - which didn't show any I/O error
> but is really slow. I can also confirm that using "-B" solves the issue
> with 1.0.21. Here is my list of tests using the ScanSnap S510:
>
>
> Scan time for A4 duplex at 300dpi in Color from ADF
>
> 1.0.20:
> 0:16
>
> 1.0.21:
> 2:23
>
> 1.0.21 with -B/--buffer-size:
> 0:16
>
> git20110207:
> 0:16
>
>
> Nice to see it will work fine again with 1.0.22!
>
> Regards,
> Simon
>
>
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