system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: how do closed captions on TV work?
gpt
If the program is live, then it is likely that a real human is involved in giving you your captions. Some programs have a stenographer who types things out, while others use text to voice programs. For some broadcasts the BBC has a single person read back the commentary to a computer to improve the accuracy of the voice to text conversion. Others just have a person typing on a stenotype that feeds the captions. ESPN has one stenographer per person speaking on their sports reporting shows.

Other programs simply feed the transcript to the TV captions.