Daniel Reetz, the founder of the DIY Book Scanner community, has recently started making videos of prototyping and shop tips. If you are tinkering with a book scanner (or any other project) in your home shop, these tips will come in handy. https://www.youtube.com/channel/UCn0gq8 ... g_8K1nfInQ

Making it faster: Raspberry Pi 3, better SD-card, other possibilities?

Johannes Baiter's Spreads and SpreadPi are the latest control systems and postprocessors for DIY scanning. http://spreads.readthedocs.org
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Joined: 13 Oct 2015, 07:16
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Country: Germany

Making it faster: Raspberry Pi 3, better SD-card, other possibilities?

Post by TeAge1 » 30 Mar 2016, 13:25

Hello there,

i am curious if SpreadPi works with that new Raspberry Pi 3... Is there anyone who has tried it yet? It has a wireless-module, a faster processor, more Ram etc.
Do you think the wireless-module will work with spreadpi?

And another little question besides:
I have a Sandisk-Ultra (the one that came with the archivist...)
At Amazon it says it has 25 MB/s writing speed.
There are, of course, better cards available now, some that say 80 MB/s writing speed.
Do you think that will work? Sometimes i am faster than my cameras/my raspberry, or only one camera has saved its image, and then when i click on take the next 2 pictures, there is one page missing... It would be great to have that fixed.

I did one thing i want to tell you:
It is possible to change the Compression Rate of the jpegs in the camera, and even without an energysource, that setting is saved in the camera.
My images hat 3,7MB per img, and now they only have 980KB, which already made a huuuge nice difference in terms of speed and stability.
(And by the way, turning off the camera-sounds is also a huge improvement, but you do that in normal camera settings...)

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Posts: 384
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Re: Making it faster: Raspberry Pi 3, better SD-card, other possibilities?

Post by duerig » 30 Mar 2016, 15:50

When using Spreads, getting a faster SD card will likely make a noticeable difference in speed. Saving the images to the SD card is one of the important time sinks that Spreads has.

I don't think anyone has tried it on a Raspberry Pi 3 yet, but if it works then that will increase speed as well. One of the big things that Spreads spends a lot of time on is generating the preview photos for each scan. A Raspberry Pi 3 would speed up this process, though I am not sure by how much.

An alternative might be Pi Scan. When I wrote the capture process for Pi Scan, I couldn't figure out how to make generating previews as fast as Spreads does it. And so I tweaked the process so that it no longer generates previews for every scan. Instead, it only does the (slow) preview process when you explicitly ask for it. This makes the overall scanning speed faster in Pi Scan, but you have to remember to stop and do a preview every hundred pages or so to make sure things look good as you scan.

See: https://github.com/Tenrec-Builders/pi-scan

One other thing is that it is probably not worthwhile to lower the image quality to improve speed. You will end up with smaller JPEGs, but you will be sad when you come to read your pages or OCR them later.

Using a Raspberry Pi 2 and a fast SD card, I have been able to get a scan every four seconds or so on Spreads. Which is about as fast as I can physically turn the pages and press the page against the platen.


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