Hat tip to @mathew - I just learned that France had a graeter than 720i broadcast standard in the 1940s!
I gotta find some old french gear, I guess.
HD broadcasting in 1948!
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:
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.