Hat tip to @mathew - I just learned that France had a graeter than 720i broadcast standard in the 1940s!

That's Astounding.

I gotta find some old french gear, I guess.

HD broadcasting in 1948!

https://www.earlytelevision.org/grammont.html

The sets were 4:3 of course, but basically they were 4:3 720i black and white.

(in practice it was actually more like 816×736 px vs 720's 960×720, but also it was analog so the minor differences were probably lost anyway.)

The standard was used in to the 80s, but I'm having a really hard time finding any information about it.

If you're french, and you know what this was called in france, please let me know!

Here's a thread where some folks are driving 819 line sets from a VGA cable: https://www.vintage-radio.net/forum/showthread.php?t=167674

and from a converter box that doesn't appear to be sold anymore.

I wrote a blog post summarizing the things I learned about HD broadcasting in the 40s:

http://ajroach42.com/high-definition-television-in-1949/

The big takeaway from the blog post is that I need a Teleavia P111, and that I need to rig up a board that converts 720P HDMI to the ~730i RF signal that this thing would be expecting.

And a power supply.

Followup on yesterdays ramblings about a 70+ year old french High Definition TV standard:

I found a Teleavia P111 for sale, submitted an offer for 1/4 of the listing price, and the offer was accepted.

In a few weeks, I'll have a mid-century french HD TV to start experimenting with.

I guess it's time to join an old TV forum and actually read my "Handbook of Television Repair" from 1952.