[sane-devel] ADF Duplex performance problems

[Ilmārs Poikāns]

Just for information for those who will google about Fujitsu ScanSnap
S500 on Linux (and most probably applies to other small like S510 and
maybe not so small scanners too).

On Mon, Apr 26, 2010 at 1:13 AM, m. allan noah <kitno455 at gmail.com> wrote:
> On Sun, Apr 25, 2010 at 4:45 PM, Ilmārs Poikāns <ilmars at delibero.lv> wrote:
>>
>> I'm running latest SANE from git source on Ubuntu 9.10. I was testing
>> scaning A4 on Fujitsu ScanSnap 500 in 300 dpi Color uncompressed using
>> scanadf. Everything is fine when scanning only one side of sheet (image size
>> 24MB). But when scanning with "ADF Duplex" as source, scanner pauses 3 times
>> during scanning. Two 24MB files are saved successfully. Clearly pausing is
>> caused by data transfer issues somewhere.
>
> Does this happen on windows?

Original windows scanning program (few years ago) that came together
with Fujitsu S500 scanner scans A4 color page without stopping. But
there were two problems - no TWAIN driver and it scanned color only
with compression. That's why I was looking for some Linux solution
where I could do everything from command line and without compression.

>> Any ideas where could be the bottleneck? Scanner can't send data so fast over USB?
>
> Almost certainly.

It isn't case with Fujitsu S500.

>> Buffer too small for USB transfers, so too many data exchange transactions creates delay and
>> slowdown of throughput?

This was exactly the cause of too slow data transfer, so scanner
stopped and waited few times during A4 color scan.

> You can try increasing the buffer-size option in /etc/sane.d/fujitsu.conf.

I don't know if I didn't specify something when building from sources
with ./configure & make & sudo make install, but building SANE from
sources like this ment that SANE didn't look for config file in
/etc/sane.d. Only after I put fujitsu.conf with increased buffer-size
in current working directory, A4 color scan went through without any
stop. I used buffer-size 1MB (expressed in bytes), instead of default
64KB.

So, SANE rocks :)

Thanks for your efforts,
Ilmars