QR Multiplex Lab

Three ways to share one screen between receivers: spread one file over colors and tiles, give each user their own channel, or layer a coarse and a fine code for near and far users. Simple version · Quiz mode

1 · Scheme

Same file to all Fountain packets spread over color channels and screen tiles at once. Every receiver gets the whole file, faster. Different files per user Each color channel or screen tile carries its own file. Receivers save the one meant for them. Mixed distances (layered) A coarse base code every phone can read, plus a fine code that near phones recover after cancelling the base (SIC).

2 · File and layout File for everyone

Color channels Screen tiles

Transmission settings

QR size (one full-screen code) Frames per second Block size (bytes) QR error correction File-info frame every

A smaller QR size has bigger squares and reads from farther away, but carries less per frame. With 2 or 4 tiles each code is drawn smaller, so choose a smaller level. The frame rate changes live while playing.

The screen cycles through all 7 QR sizes, about a second each. Receivers open the Receive tab and camera; each phone shows the largest level it reads reliably.

3 · Broadcast

Choose the file or files for this scheme.

Open the camera and point it at the sender's screen. The page works out which scheme is being sent. For the layered scheme, stand far away to get only the base file, or close to get both.

Processing resolution

Scheme: not detected yet.

Experiment log

Record labelled runs for statistics. Each run starts decoding from scratch, logs every frame and every QR code read, and is kept on this phone until you clear it.

Run label Distance to screen (m) Stop the run Duration (s)

Notes Measure raw module error rate (adds some processing per frame)

No run in progress.

Recorded runs

Frame loss is averaged over the streams in a run. Module errors are raw, before QR error correction. The dataset holds every frame and QR read. To turn it into figures and tables, run the analysis script.

GitHub settings

Repository Folder This phone's name Access token

Remember the token on this phone

Datasets go to a separate data repository, so a token shared with a class can't change this website. Use a fine-grained token limited to that repository, with Contents: Read and write permission only. The token stays in this phone's browser and is sent only to GitHub. Each save adds one dataset file, holding only the runs not saved before.