A major selling point of DVD video is that its storage capacity allows for a wide variety of extra features in addition to the feature film itself. This can include audio commentary that is timed to the film sequence, documentary features, unused footage, trivia text commentary, simple games and film shorts.

In DVD video, an audio commentary is a bonus track added to the video consisting of a lecture or comments by one or more speakers, who talk about the movie as it progresses. Depending on the nature of the movie, and upon the person providing the spoken dialogue, an audio commentary can add a wealth of informative, entertaining information about a movie that most audience members would not be at all aware of.

Audio commentaries are located on separate audio tracks on the DVD. A single DVD disc can have several separate audio tracks that can be selected by the viewer from the main menu of the DVD or by pressing a designated button on the remote. Each separate track contains different content: one track has the actual dialogue and sound of the movie, while other tracks can contain different language dialogue (for translation into different languages), a different type of audio encoding (Dolby Digital or DTS), music-only soundtracks, and audio commentaries. Some DVD productions include multiple audio tracks with many commentaries from different persons.

There are several different varieties of commentary tracks:

*Partial commentary only covers selected scenes of the film.

*Feature-length commentary goes from the beginning of the film to the end.

*Live commentary is recorded in one session; the speakers watch the movie from beginning to end and give their thoughts on the matter.

*Edited commentary was recorded at various sessions, often with various speakers. Multiple-person commentary tracks recorded for Criterion are noted for this technique. The various speakers and their audio are edited into a cohesive whole, one person speaking here, and one person speaking there.

*Single-person commentary is just that; one person taking you through the film.

*Multiple-person commentary can either take live or edited form. A live multiple-person commentary track is sometimes called a party track, especially when there are several persons.

*Cast, crew, or director commentary is from those people involved in the making of the film. They can often describe how the work was done, why a certain choice was made, or discuss generally the themes and limitations of their film.

*Scholarly commentary is performed by a film critic, historian, or scholar, taking us through the significance of the film, the technique, and at times telling the story behind its making.

*Carrottop commentary features someone not associated or knowledgeable about the film in any way, shape, or form. They are very rare and so-called because of the commentary track by comedian Carrot Top on Roger Avary s The Rules of Attraction .

== History of audio commentaries ==

The value of audio commentaries as a marketing tool was revealed during the heyday of laserdisc, the laser-based video format produced before the introduction of DVDs. The Criterion Collection company, for example, produced high-quality deluxe editions of classic movies on laserdisc, using the best available prints and re-edited versions. These deluxe laserdiscs (which were often very expensive compared to today s DVDs) included bonus features such as production stills and movie trailers, deleted scenes, behind-the-scenes information, and audio commentaries from the directors, producers, cast, editors and cinemaphotographers and designers. These deluxe laserdiscs were marketed to movie professionals, fans and scholars who were seen as an elite niche of consumers who could afford to pay more for definitive, quality editions. The audio commentaries on laserdiscs was typically encoded on to secondary analogue tracks which had become redundant as modern laserdisc movies had their stereo audio encoded digitally alongside. This is why certain older videodisc players which predate the digital audio standard, are only able to play back analogue tracks with audio commentary.

The decline of the laserdisc format and the increasing popularity of DVD was highlighted in the fall of 1997, when simultaneous laserdisc and DVD editions of the movie Contact (movie) were released. The laserdisc edition contained one bonus audio commentary track by director Robert Zemeckis; however, the DVD contained two additional, separate audio commentaries in addition (by Jodie Foster and the special effects producers), as well as other bonus features.

== Notable DVD audio commentaries ==