ISO/IEC TS 20071-21:2015 provides recommendations for describing audiovisual content in an auditory modality for use in recorded video presentations, broadcast television, cinema, live or recorded drama, museum and art gallery exhibits, heritage tours, news, and comedies, regardless of the language and technology being used to transmit and present the recorded or live audiovisual content.
NOTE 1 There are many secondary users of audio description, but the primary and intended users of audio description are blind persons or persons with low vision and their friends and family.
ISO/IEC TS 20071-21:2015 provides guidance on the subjective nature of creating audio description.
It also provides guidance for audio description developers (script writers, voice narrators, and organizations or groups responsible for delivering audio description) in faithfully and accurately representing audiovisual content.
NOTE 2 It might not always be possible to provide an equivalent experience due to limitations in the amount of time available for audio description depending on the content being described.
ISO/IEC TS 20071-21:2015 applies to describing audiovisual content and does not consider the devices or transmission mechanisms used to deliver the content or the audio description. These devices include, but are not limited to, televisions, computers, wireless devices, projection equipment, DVD and home cinema equipment and other forms of user interface technology. Therefore, this part of ISO/IEC 20071 does not consider transcoding files for the various video outputs.
NOTE 3 Technical matters of transmission and distribution are covered by other International Standards (e.g. MPEG standards and other technical international standards such as IEC 62731).
ISO/IEC TS 20071-21:2015 provides guidance on how to approach user preferences, available styles and flexibility in approaches to audio description.
It does not apply to static images contained in electronic documents (see ISO/IEC 20071−11 for guidance on text alternatives for images).
It applies to auditory presentations intended to be transmitted or delivered simultaneously to the original audiovisual content.
NOTE 4 Limitations experienced by broadcasters or people in synchronous environments might be reduced online or in asynchronous environments.