A Fast Data Structure for Disk-Based Audio Editing

For some time, ordinary personal computers have been powerful enough to allow people to edit, filter, and mix digital audio without any special added hardware. The earliest editors, such as those described by Freed (1987), Kirby and Shute (1988), and Moorer (1990), were modeled after tape-based editors, with similar control panels and basic operations; the main advantage of this is that edits could be performed non-destructively and then changed or "undone" later. However, these types of editors still force users to keep track of all of the original audio clips that are used to create the final mix, and once the editing is complete, an additional step is required to actually produce the output audio file from the originals. As personal computers have grown faster and more powerful, new audio editors have etnerged that more closely resemble a computer word processor or computer painting program than a reel-to-reel tape editor. These editors allow users to perform many operations on their audio files in place, with all changes affecting the original waveform data on disk. Furthermore, the visual display reflects the results of all edits, which is not always the case for nondestructive editors. This makes editing much simpler and faster, especially for small files, and eliminates the extra step at the end, because the current copy of the entire project is always stored on disk. However, these "in-place" audio editors are not usually able to provide more than a single level of undo, and they are often very slow in dealing with large files. Today, one can find a variety of both types of audio editors for personal computers. Some popular in-place editors are SoundEdit 16 from Macromedia, CoolEdit from Syntrillium, and Sound Forge from Sonic Foundry. Non-destructive editors include Cubase from Steinberg Media Technologies AG, Digital Performer from Mark of the Unicorn, Inc., and ProTools from Digidesign, a division of Avid Technology, Inc.