Audio description supplies the visual facts dialogue never says
Aliases: described video · AD · video description
What it is
Audio description (AD, described video) fills in facts the dialogue never says and the picture does: who came through the door, a face that changed, the text on a close-up message, which bar the presenter pointed at. It serves people who cannot see, or cannot see the picture well. It is not another kind of caption for people who cannot hear. Captions move sound into type. Description moves picture into speech.
Why it happens
Plot often never enters the ear. A look exchanged, a file appearing on the table, an on-screen “transferred” — dialogue can skip all of it. Listeners are left with a hole in causation: where the next burst of anger came from, why someone ran. Description has to pick visuals that change understanding, not catalogue a costume — unless the costume is a clue.
The choice is the same kind as equivalent text for images: information and function, not decoration. The carrier differs. Equivalent text can be read once; description has to track action as it happens and tell the listener what in the frame is now load-bearing. Empty establishing shots and furniture that never acts are usually not; the few seconds that first build the room are.
Studying it
Listen only (dialogue plus description versus dialogue alone). Items must ask facts the picture carried: what was on the table, who reached first — not whether the scene moved you. Blind advisors reviewing the script are worth more than sighted people with eyes closed, who still patch holes from visual memory.
Independent variables: description present or not, event versus appearance, whether on-screen type is read out. Dependent variables: accuracy on visual plot points, decorative details mistaken for plot.
Mark, in advance, the turns that happen only in the picture. Those are the required items.
Where it stops holding
A talking-head lecture whose picture carries no extra facts needs little description; a full transcript is usually the better channel. Decorative B-roll need not be narrated beat by beat. Live meetings almost never get full AD. Action the dialogue already states (“I’m closing the door”) is duplication if described again. Description also cannot restore composition and light. It supplies facts. It does not remake the film for the ear.
Applying it
- List visual events the dialogue never mentions that change understanding or the next step. Read on-screen type aloud.
- Present tense, short, concrete: “she slides the contract across the table,” not “the shot is beautiful.”
- Clothes, weather, décor only when they are clues.
- How to check: play the soundtrack only. Ask someone new to the piece the pre-marked visual questions. Each blank is description still reporting appearance, or still missing.