[sane-devel] Webcam-like book scanners

[Low Salt Popcorn]

On 24/12/24 14:40, Ralph Little wrote:
> Hi,
> 
> 
> On Mon, Dec 23, 2024 at 9:14 PM Low Salt Popcorn 
> <thelowsaltpopcorn at hotmail.com <mailto: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/ <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 <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 <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.

Just curious, did the old sane backend do something more than, say, 
"ffmpeg -i /dev/video0 scan.xxx"?

Anyway, I guess I have to take my chances and hope the el-cheapo book 
scanners are standards compliant and don't use some proprietary protocol.