[sane-devel] Webcam-like book scanners

[Ralph Little]

Hi,


On Mon, Dec 23, 2024 at 9:14 PM Low Salt Popcorn <
thelowsaltpopcorn at hotmail.com> wrote:

> These "scanners" basically look like a webcam mounted on an arm atop an
> upside-down letter "L" (or Greek capital letter gamma).
>
> They look like the best option for scanning old books that don't require
> laser-printer quality resolution.
>
> One such scanner is reviewed by CNX software:
>
>
> https://www.cnx-software.com/2023/07/23/czur-et24-pro-book-scanner-review-with-ubuntu-22-04-linux/
>
> The author notes that the scanner practically identifies itself as a
> webcam ("UVC"). So in theory it should "work" on any GNu/Linux computer,
> with only the Windows/Mac user software as the major difference.
>
> I've also seen in various online platforms (e.g. AliExpress) similar,
> but much cheaper no-brand models. So my question is, does anybody here
> have such a device? Is it reasonable to assume that all scanners of this
> type are UVC-compatible devices?
>
> https://en.wikipedia.org/wiki/USB_video_device_class
>
> If these devices are indeed all UVC, my idea is to have ffmpeg take JPEG
> or PNG snapshots of the material I'm scanning. Or otherwise simply take
> one continuous video and later simply pause and screenshot individual
> frames.
>
> Note: I've searched the sane backends page:
>
> http://www.sane-project.org/sane-backends.html#VIDEO
>
> I can't find any reference to UVC-device support
>

So, there is a video camera backend called sane-v4l but it is quite old and
doesn't support the newer v4l2 API standard.
We were just discussing this during the GTK porting effort recently of the
frontend utility xcam. For testing, it appears that none of the current
webcams actually work with it because the backend doesn't support the
colour formats that more recent colour webcams require. Although xcam
supports all backends so testing is possibly, it's not really possible to
test xcam with an actual camera.

If anyone wishes to write a new v4l2 backend or update the existing
sane-v4l one then that would be very welcome. Failing that, one of us might
get to it at some point.

Cheers,
Ralph
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