White Paper WHP 198 Download
This paper describes the audio description studio signal which comprises a mono audio signal and a data stream containing fade and pan information. The paper is the definitive specification of the audio description studio signal and is primarily intended for those implementing systems that use this signal. The paper brings together all the information necessary to deploy the audio description studio signal in the broadcasting environment.
The audio description studio signal wads first explained in the IBC 2000 paper entitled "Access Services for Digital Television: Matching the Means to the Requirement for Audio Description and Signing".
For additional information on audio description in general see BBC Research & Development White Paper WHP051.