Audio description is a new text type which offers the prototypical receiver - blind or partially sighted people - a narrated representation of what is occurring at specific moments in the other audiovisual text to which it is subordinated. An AD script is subject to multiple subordination: to what is happening on the screen, to the distribution of silent spaced in the other text, and to the amount of time provided in each space; This fact, however, does not prevent the AD script from offering a representation of the general knowledge encoded by specific fragments of the film. Such a representation of knowledge, understood as the description in word or other signs of a specific reality, may serve as a semantic basis for the creation of a local grammar of AD scripts.