Image and media alternatives - Clear labelling

[KevinP-NZ]

Where, for example, a video is an alternate presentation of information found elsewhere and contasins no additional information it should be marked as such with a clear indication of the location of the base content.

this would ensure that say, a screenreader user, could just ignore the content in the knowledge that they have all they need in the text (or at least as much as anyone else). It's kind of the inverse of a transcript being the alternative to the video where the video is an audio visual presentation of the page text (or text on another page perhaps)