Short answers, pulled from the story.
Subtitles are on-screen texts representing the audio content of a film, television show, opera, or other audiovisual media. They can transcribe or translate spoken dialogue, describe non-dialogue sounds, or add cultural context for viewers unfamiliar with a reference, such as explaining that sake is a type of Japanese wine.
Closed captions are a form of subtitles specifically designed for people who are deaf or hard-of-hearing. Unlike standard translation subtitles, closed captions transcribe the original language and include written descriptions of non-dialogue audio such as sound effects and music, typically placed in parentheses.
SDH stands for Subtitles for the Deaf or Hard-of-Hearing, a term introduced by the DVD industry. The main difference is visual: closed captions appear as white text on a solid black band, while SDH subtitles use the same proportional font as translation subtitles, with an outline or shadow for readability.
A 2021 UK survey found that 80% of viewers between 18 and 25 regularly use subtitles. Contributing factors include advances in microphone technology that allow actors to speak more softly, studios growing less willing to re-record unclear dialogue, and theatrical surround sound losing clarity when compressed to stereo or mono for home devices.
Run Run Shaw of Shaw Brothers Studio pioneered Standard Chinese subtitling in Hong Kong during the 1960s, according to HK Magazine. He recorded his films in Mandarin to reach the widest Chinese-speaking audience and added both Standard Chinese and English subtitles to every Shaw Brothers release.
In October 2015, major studios and Netflix were sued for omitting song lyrics from subtitle tracks, with plaintiffs citing false advertising and California's Unruh Civil Rights Act. Judge Stephen Victor Wilson dismissed the suit in September 2016. He ruled there was no evidence of intentional discrimination and that the advertising claims fell far short of showing that consumers would be deceived.