Wow! One of those moments when you realize that someone is doing exactly what you have been doing. My hobby project was seriously called QRTX. And each data frame started with ###-- where # are padded frame numbers. Pretty much identical to this guys project. Thanks for that find, I'm chuckling.

Points of difference: I was using a leading metadata frame with filename and total number of frames etc, and the receiving device were ACK'ing frame decodes with its own QR codes. Still, wow.

You are welcome, great project :)