From my arrival in academia, 20 years ago, I have been looking for a way to create multimedia educational content without having to record and edit video. In the early days video took a lot of bandwidth. The networks have become faster and the compression technology better, but this can still be a problem for some students (and staff). Also video take considerable time and skill to produce. I don't lack the skill (I learned video production for training at the Canberra Institute of Technology, back when it was ACT TAFE). But I do not want to spend my time lining audio up with video clips. What I have aimed for was something like slides with an audio commentary.
As an early attempt I used a system which would play an audio file and synchronize this with HTML content. That works but was not really stable enough to be usable.
For the last two years I have been using Vidnami, which appears to have been developed more for marketers, than educators. With this I provide a script in the form of plain text and the system finds suitable stock video and images, creates synthetic audio, an option music track and makes a video. Normally I would substitute my own presentation slides for most, or all, the stock footage (which can be a bit silly at times).
I use the synthetic voice videos to supplement text based notes and live events. This works well for the flipped classroom. I can easily produce a video to accompany the notes for students to study before a live class (be it face to face, online or a hybrid of both). A video recording is also made of the live class for later review by students and for those who could not attend.
However, Vidnami has been sold for integration into GoDaddy Studio. So I have been looking for an alternative. Vidnami helpfully provided a list of video product suggestions, but as they say, these don't quite do the same thing.
There are many text to speech systems available, some which integrate into Powerpoint, but most sound like robots. And with standalone systems, you still have to manually add the images, which is very tedious.