99% accuracy depends on a number of things including quality of the audio, the number of speakers, cross talk by those speakers, background noise, music, use of localized or foreign words etc. Given those variables neither machine nor human can maintain 99% accuracy for a full, live broadcast.
The FCC rules for US broadcasters do not provide an accuracy benchmark but instead say:
FCC rules for TV closed captioning ensure that viewers who are deaf and hard of hearing have full access to programming, address captioning quality and provide guidance to video programming distributors and programmers. The rules apply to all television programming with captions, requiring that captions be:
- Accurate: Captions must match the spoken words in the dialogue and convey background noises and other sounds to the fullest extent possible.
- Synchronous: Captions must coincide with their corresponding spoken words and sounds to the greatest extent possible and must be displayed on the screen at a speed that can be read by viewers.
- Complete: Captions must run from the beginning to the end of the program to the fullest extent possible.
- Properly placed: Captions should not block other important visual content on the screen, overlap one another or run off the edge of the video screen.
Obviously, our goal is to provide the most accurate speech-to-text conversions possible, given the quality of the audio. To that end, we provide two additional ways to improve accuracy:
- Custom Dictionary: A custom dictionary is available to include local, regional and hard to pronounce words, names and geographical places and references, including foreign names and words so you can pre-load these items into the system.
- Alternate Words Dictionary: In addition, we provide an alternate words dictionary that you can populate to swap out words you don’t want going to air, ensure certain words are capitalized or referenced properly to match the needs of your audience.
- Additionally, the entire vocabulary of the speech engine is updated quarterly to ensure continued improvement.