Things we measured while building this API, written down because we could not find them written down anywhere else. Numbers here come from real runs, and the method is named so you can repeat them.
The official Data API has a captions.download endpoint, and it will not help you: it requires OAuth as the video's owner and returns 403 for anyone else's. Here is what actually works, why your server gets IP-blocked the moment you self-host it, and the curl test that will lie to you while you debug.
read →One chat-completions call for a whole transcript took 35 seconds — past the timeout of most HTTP clients. Splitting it into concurrent chunks brought it to 6.6, but smaller chunks started dropping lines. The measurements, the trade-off, and why the billing constant must not share a value with the chunk size.
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