Editing digital audio

This paper explores some of the general problems of editing digital audio whether it is stored on longitudinally recorded magnetic tape or rotating media such as a Winchester disc. The objective is to provide the facilities to which audio editors have grown accustomed, while maintaining high operational speed and precisely controlled edits even when a tape is cut. Three levels of performance are discussed. The first and simplest involves cutting a tape and relying on the error correction and concealment systems of a recorder to ´smooth´ the splice. In the second, the concept of separate cutting-point and edit-point is introduced. Additional formatted information recorded on the tape controls a buffer store permitting a jump over the corrupted data in the region of the splice. In the third, this approach is extended so that a separate editor, based on a disc store, is loaded with data in the vicinity of the edit. This provides not only the conventional editing features but also a number of new facilities. An editing system has been built using a Winchester disc. A microprogrammed I/O device allows real-time stereo transfers and provides real-time processing for cross-fading, gain adjustment and interleaving of control data.