[sane-devel] ADF Duplex performance problems

Ilmārs Poikāns ilmars at delibero.lv
Sun Apr 25 20:45:25 UTC 2010


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. Any ideas where could be the
bottleneck? Scanner can't send data so fast over USB? Buffer too small for
USB transfers, so too many data exchange transactions creates delay and
slowdown of throughput? I guess scanner is sending data from duplex scan
interleaved - data block for front side, data block for back side.
Inefficient processing of such data in fujitsu-backend? Maybe problem caused
by scanadf (or any other frontend), that can read images only one by one?
Any ideas?

What is the status of SANE 2.0? Is there any functionality for retrieving
many images simultaneously from one physical scan, like front and back of
page during duplex scan, several image regions on pages?

Best regards,
Ilmars Poikans
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