In 1993 ITS proposed an audio/video quality of service testing framework in a standards contribution. To support that contribution, ITS produced a McGurk Effect demonstration video.
The video demonstrates how the eyes and ears work together to understand speech. This is called audiovisual perception or cross-modal perception. Audio of a woman saying "ba ba ba" has been dubbed over the picture of that woman saying "da da da". Your perception of what she is saying changes as you open and close your eyes.
Subtitles are not provided, because the McGurk effect is an audiovisual effect.