Is there a free real time transcription API?

I am looking for something that is either on device or online with free / unlimited minutes. I’m building a video player app which adds subtitles in real time. However, Google (which has the best subtitles) gets expensive quickly.

I have stumbled across DeepSpeech from Mozilla but apparently this isn’t what I am looking for. I’ve heard from other people that Android has a Live Transcription API but I cannot find it anywhere.

From what I have seen, everyone seems to be gatekeeping this accessibility feature. Google provides free transcription on Youtube, Meet and other services. They also have their own app called ‘live transcribe’ which does what I want too. I just cannot find the API so I can implement it into the video player.

Any help would be appreciated. This project will be open sourced and free to use. Hence why I cannot afford to use paid services and would prefer to have the audio stream transcribe on device.