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QR Channel

LIVE

This is an experiment in establishing WebRTC peer connection with a data channel between two devices equipped with web cams by exchanging QR codes with offer/answer SDP data and ICE candidate data.

I also have a Web Bluetooth based solution in the works, BT Channel.

Running

start index.html

Debugging

  • Use the video and canvas views in portrait to be able to verify that video to canvas drawing works correctly
  • Use the facing mode selector in portrait to switch between environment and use facing modes
    • The user mode is production screen-to-screen workflow where the user faces the phone to the laptop and the devices connect
    • The environment mode is debugging sequential workflow where the developer alternates the screens to guide the flow and debug
  • Clear iOS Safari website cache: Settings > Safari > Advanced > Website Data > tomashubelbauer.github.io > swipe
  • Make sure your iPhone is not in the power saver mode, otherwise camera access won't be granted to the page
  • Make sure you are not using the camera in another browser/tab if Chrome gives you a blank stream (2×2 pixels)

Contributing

GitHub issues are closed, use a pull request to start discussion about a patch or email me at tomas@hubelbauer.net.

The PR will be type checked before it can be merged. This is a JavaScript project which uses JSDoc through TypeScript.

To-Do

Finalize reply.js using the test rig

Verify with real devices

Test that the candidate melt function works in the coding test laying ground for the ICE compression/decompression

Compress and decompress ICE in encode & melt, fit multiple into a QR code (limit to type number 5)

Figure out this problem and fix jsQR not being seen by TypeScript

See if jsQR maintainers find a way

See if it could be possible to pull the dependencies as ES native modules

Crediting

Prior Art

This has been done before and I've attempted it several times before as well.

Unfortunately, this idea has also been patented in 2018.

I hope that the patent is invalid as there was prior art before the time of application, but has been granted and overturning it would require a court challenge I think. Until that happens, it's probably unsafe to use this in a commercial product.

I am doing it again because I like the idea and I want to finally put forth a prototype of my own that I'll actually finish. In the future I'd like to explore ways of bringing down the time required to establish the peer connection.

Packages Used

jsQR by @cozmo: reading QR codes from ImageData

qrcode-generator by @kazuhikoarase: calculating QR code modules for drawing on canvas

I started working on https://github.com/TomasHubelbauer/js-qr-scanner-library-comparison to see if there is a QR library that is faster or better at scanning than Cozmo's but that doesn't appear to be the case.

I could also use the JavaScript QR reader on desktop only because phones have a built-in one these days. But it would probably be better to make the roles explicit in tha case and simplify the flow:

  • User opens the camera app on their phone and set it to the selfie camera
  • User opens the web app and an offer code is automatically displayed and answer scanning started
  • User scans the offer code by pointing the phone's display to the latop screen (which makes the latop see the phone screen)
  • The QR scanner on the phone finds the offer code and opens the browser with the offer in the URL which shows the answer
  • The web app scan its field of view until it sees the answer code at which point the flow end
  • A WebRTC connection using the offer and the answer is established

On Android the QR scanner is in Camera app settings under Google Lens Suggestions.

On iOS the QR scanner is a widget that can be added to the Control Centre and starts camera with scanning enabled.