They listed AVI at the time on their main page, but on another page they did not. When I asked them about it (Twitter I think) they removed the AVI entry on their supported formats and apologized for the mistake.
Even for the formats that are supported, some of the resolutions that should be are not. Either the Nook HD+ isn't powerful enough to handle true 1920x1080 resolution mp4 videos and B&N need to update their page or the software needs additional work.
I've been playing true 1080p video and for the most part it looks amazing.
I didn't encode the videos myself, the source is edx.org classes, specifically CS50x.
The videos are in mp4 format, unsure of the codec.
> when the HD+ came out last month, I thought it listed a lot more formats as compatible. Does anyone remember that? <
Not really much help to you, because I'm not sure if I'm remembering or imagining , but I did check out their Video Formats Supported when they were first announced (a long time ago, and not yet shipping), and the list was not only longer, but included either TS or MPEG. I remember thinking, "It's about time".
And also that would enable me to stream MPEG2 content from my video server without having to format-convert it first. (However, I didn't give it a lot of thought because I don't see much reason when I'm home to watch videos on a 7 or 9" display when I have several 55-61" displays and an 8-foot projection screen. With excellent sound systems to go with them.)
.FLV was definitely there as well, along with codecs for xVID, and H264, H263. I don't have to rely on my memory there, since those are still listed on their Developer site. Which says nothing about WEBM, BTW. Nor AVI.