Transcribing Video Without Captions: How AI Recognizes Speech

An old upload, a niche channel, an unedited stream: plenty of YouTube videos simply have no captions, manual or automatic. For most transcription tools, that's a dead end: they only read ready-made captions and quietly refuse without them. Cruxly has a separate path for this case.

The full guide to video transcription

How the speech recognition works

If a video has no captions, or the automatic ones turn out too inaccurate, the service recognizes speech directly from the audio track through Chirp 2, Google's speech recognition model. What comes out is the same verbatim text split by speaker turns as with ready-made captions. The only difference is one extra processing step before the text reaches the language model.

What changes in timing and in the result

Speech recognition takes more time and resources than reading ready-made captions, so there's a reasonable length cap regardless of plan. But for an ordinary lecture or podcast with no captions, the resulting text comes out just as detailed as it would with captions in place. The difference shows up in processing speed, not in the quality of the result.

When recognition won't help

If a video genuinely has no speech in it, a music video with no lyrics or a purely visual clip, say, neither captions nor recognition will produce a transcript: there's nothing to work with. Recognition is also noticeably more accurate on a clean recording than on a video with heavy background noise or several people talking at once. If there's a choice between several sources of the same material, the cleaner-sounding one is the better pick.

YouTube's captions and speech recognition aren't always the same thing

YouTube's automatic captions are also a product of speech recognition, just an earlier and often less accurate pass, especially on video with specialized terminology or a heavy accent. Chirp 2 on average produces cleaner text from the same source audio, so even when a video technically has automatic captions, recognition through Cruxly can turn out more accurate. The service decides on its own when to switch to direct recognition instead of using YouTube's ready-made captions.

How transcription works technically

Translation works the same regardless of the source

It doesn't matter whether the source text came from captions or from speech recognition: translation across 12 languages works the same way, in both directions. A video in a less common language with no captions can come back transcribed and translated in a single pass, with no manual step in between.

A video having no captions isn't a reason to give up on an exact transcript, the service just needs one extra step to get there. The end result for an ordinary lecture or podcast comes out just as detailed as it would with captions ready to go.

Looking for a summary rather than the full verbatim text? YouTube video analysis works the same way without captions.