0. Excellent general space, much needed. I have scripted something related out for my own needs (still need to automate even more), but a web services that accepts web URLs is much appreciated and could help others.
0b. Compare/contrast with https://freesubtitles.ai from https://news.ycombinator.com/item?id=33663486 and https://github.com/mayeaux/generate-subtitles
The OP site looks down right now, but it seems that semantic search in this context might mean something like object detection, whereas I am very interested in semantic search as in concept, idea, topic, linguistic search. (The simplest form of this would be direct transcript search, but if that can be transformed into additional useful semantic models to be searched, that would be gravy.)
That said, a constructive critique out of love follows, which may or may not fit with your goals:
1. The 10 minute length limitation makes this useless for most buried spoken content, because, you know, the longer videos have the more buried spoken content. Most detailed presentations are 15-60+ minutes where content would want to be searched IMO. A 3 hour limit would make more sense, but ideally none.
2. The heading says "any video", but the form specifies YouTube link. This needs to support Bitchute, Odysee, and Rumble, at least, because much interesting spoken content (which is totally reasonable content highly suitable for semantic search, if not to say, critically important, BTW) has been repeatedly banned from YouTube. (At least YouTube gives auto-transcripts if enabled for the video, that can be downloaded with tools. This web service actually most needs to exist for video platforms OTHER THAN YouTube, which have not implemented built-in machine-transcription options yet.)
3. The site needs SSL, or else the traffic (video links, titles, search terms) is communicated in plain text and plainly visible to all looking.
Other platforms, I'm sure you can figure out. However, I don't know how you will make this support larger videos affordably, which would be a requirement for it to be really useful IMO.
MOST IMPORTANT IDEA: I think you could support searching GROUPS of videos. So I want to provide URLs of 500 videos, and get their transcript indexed and searchable (with reasonable search capability--verbatim and fuzzy and regex, for example). And I want to share the link to upload more to that group, or to search just that group, with friends. But I do NOT want to simultaneously search the 50,000 videos that other people have listed on your service.
(Extension 1: Another reasonable way to approach searching COLLECTIONS of videos that might satisfy 90% of the use case would be to say: let me input a list of CHANNELS TO SEARCH--YouTube, Bitchute, Odysee, Rumble channel URLs--and show me the text search results for all videos indexed that were retrieved from those CHANNELs.) I might build custom "LISTS OF CHANNELS" to search, and share those collections with friends interested in searching the same content, instead of necessarily curating granular "lists of videos" to search. Though, both might be useful.
(Extension 2: Similarly, accepting input of CHANNELS TO INDEX (YouTube, Bitchute, Odysee, Rumble channel URLs) would be helpful. That way, I don't have to wait each n=? days and add a link to your site manually.)