If you want really accurate timestamps, the current state of the art is to ask claude to implement forced alignment using a CTC transcription model. It uses the logprobs of a character based transcription model to find the best matching overlap. I've used this technique to generate sync files for epub/audiobooks and it's really good even when the data is dirty.

This method aligns the transcript of a 60 hour book in 20 minutes on my GPU using Parakeet CTC 0.6B which is english only, but there's similarly sized models in other languages, the models don't need to be that good at transcribing to generate good alignments.