Digitising CDs (aka using your phone as an image scanner)

I recently found, under the rain, next to a book swap box, a pile of 90's “software magazines” which I spent my evening cleaning, drying, and sorting in the days afterwards.

Magazine cover CDs with nary a magazine 

Those magazines are a peculiar thing in France, using the mechanism of “Commission paritaire des publications et des agences de presse” or “Commission paritaire” for short. This structure exists to assess whether a magazine can benefit from state subsidies for the written press (whether on paper at the time, and also the internet nowadays), which include a reduced VAT charge (2.1% instead of 20%), reduced postal rates, and tax exemptions.

In the 90s, this was used by Diamond Editions[1] (a publisher related to tech shop Pearl, which French and German computer enthusiasts probably know) to publish magazines with just enough original text to qualify for those subsidies, bundled with the really interesting part, a piece of software on CD.

If you were to visit a French newsagent nowadays, you would be able to find other examples of this: magazines bundled with music CDs, DVDs or Blu-rays, or even toys or collectibles. Some publishers (including the infamous and now shuttered Éditions Atlas) will even get you a cheap kickstart to a new collection, with the first few issues (and collectibles) available at very interesting prices of a couple of euros, before making that “magazine” subscription-only, with each issue being increasingly more expensive (article from a consumer protection association).

Other publishers have followed suite.

I guess you can only imagine how much your scale model would end up costing with that business model (50 eurocent for the first part, 4.99€ for the second), although I would expect them to have given up the idea of being categorised as “written press”.

To go back to Diamond Editions, this meant the eventual birth of 3 magazines: Presqu'Offert, BestSellerGames and StratéJ. I remember me or my dad buying a few of those, an older but legit and complete version of ClarisWorks, CorelDraw or a talkie version of a LucasArt point'n'click was certainly a more interesting proposition than a cut-down warez version full of viruses when budget was tight.

3 of the magazines I managed to rescue from the rain

You might also be interested in the UK “covertape wars”.

Don't stress the technique 

This brings us back to today and while the magazines are still waiting for scanning, I tried to get a wee bit organised and digitising the CDs.

Some of them will have printing that covers the whole of the CD, a fair few use the foil/aluminium backing of the CD as a blank surface, which will give you pretty bad results when scanning them with a flatbed scanner: the light source keeps moving with the sensor, and what you'll be scanning is the sensor's reflection on the CD.

My workaround for this is to use a digital camera (my phone's 24MP camera), with a white foam board behind it, so the blank parts appear more light grey. Of course, this means that you need to take the picture from an angle, and that the CD will appear as an oval instead of perfectly circular.

I tried for a while to use GIMP perspective tools, and “Multimedia” Mike Melanson's MobyCAIRO rotation and cropping tool. In the end, I settled on Darktable, which allowed me to do 4-point perspective deskewing, I just had to have those reference points.

So I came up with a simple "deskew" template, which you can print yourself, although you could probably achieve similar results with grid paper.

My janky setup

 

The resulting picture 

After opening your photo with Darktable, and selecting the “darkroom” tab, go to the “rotate and perspective tool”, select the “manually defined rectangle” structure, and adjust the rectangle to match the centers of the 4 deskewing targets. Then click on “horizontal/vertical fit”. This will give you a squished CD, don't worry, and select the “specific” lens model and voilà.

Tools at the ready

Targets acquired

 Straightened but squished

You can now export the processed image (I usually use PNG to avoid data loss at each step), open things up in GIMP and use the ellipse selection tool to remove the background (don't forget the center hole), the rotate tool to make the writing straight, and the crop tool to crop it to size.

And we're done!

 The result of this example is available on Archive.org, with the rest of my uploads being made available on Archive.org and Abandonware-Magazines for those 90s magazines and their accompanying CDs.

[1]: Full disclosure, I wrote a couple of articles for Linux Pratique and Linux Magazine France in the early 2000s, that were edited by that same company.

wireless_status kernel sysfs API

(I worked on this feature last year, before being moved off desktop related projects, but I never saw it documented anywhere other than in the original commit messages, so here's the opportunity to shine a little light on a feature that could probably see more use)

    The new usb_set_wireless_status() driver API function can be used by drivers of USB devices to export whether the wireless device associated with that USB dongle is turned on or not.

    To quote the commit message:

This will be used by user-space OS components to determine whether the
battery-powered part of the device is wirelessly connected or not,
allowing, for example:
- upower to hide the battery for devices where the device is turned off
  but the receiver plugged in, rather than showing 0%, or other values
  that could be confusing to users
- Pipewire to hide a headset from the list of possible inputs or outputs
  or route audio appropriately if the headset is suddenly turned off, or
  turned on
- libinput to determine whether a keyboard or mouse is present when its
  receiver is plugged in.

This is not an attribute that is meant to replace protocol specific
APIs [...] but solely for wireless devices with
an ad-hoc “lose it and your device is e-waste” receiver dongle.
 

    Currently, the only 2 drivers to use this are the ones for the Logitech G935 headset, and the Steelseries Arctis 1 headset. Adding support for other Logitech headsets would be possible if they export battery information (the protocols are usually well documented), support for more Steelseries headsets should be feasible if the protocol has already been reverse-engineered.

    As far as consumers for this sysfs attribute, I filed a bug against Pipewire (link) to use it to not consider the receiver dongle as good as unplugged if the headset is turned off, which would avoid audio being sent to headsets that won't hear it.

    UPower supports this feature since version 1.90.1 (although it had a bug that makes 1.90.2 the first viable release to include it), and batteries will appear and disappear when the device is turned on/off.

A turned-on headset