Here's the code on GitHub: https://github.com/openva/video-indexer It's terrible (I wrote it for a very narrow use case, and only run it ~200 times each year), but it's enough to get the idea.
I ran across this while researching a way to OCR data from a video of a frequency counter and digital multimeter. I didn't use his exact workflow, but it got me pointed in the right direction. Much better than manually typing in data every second of a 20 minute video.