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

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 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

• The DVD release of Men in Black contained a commentary track by director Barry Sonnenfeld and star Tommy Lee Jones. This commentary included a video adaptation of the movie: silhouettes of the two persons were added to the picture, in a manner that made it seem as if the two were sitting in a theater commenting on the movie as it was screened for them. This was seen as a homage to (or rip-off of) Mystery Science Theater 3000. The DVD release of Ghostbusters has a similar feature, accomplished by using one of the subtitle tracks to provide the silhouettes.

• The DVD release of Fantasia features two separate commentaries: one by Roy E. Disney, James Levine, and John Canemaker; and a second by Walt Disney, created using audio clips of interviews and a voice actor reading his production meeting notes, hosted by Canemaker. When its sequel Fantasia 2000 was released on DVD, it also included two separate audio commentaries: One featuring Roy E. Disney, Levine, and Canemaker, and the other featuring commentary on each of the separate segments of the film by the directors and art directors of each segment. For the sections starring Mickey Mouse ("The Sorceror's Apprentice") and Donald Duck ("Pomp and Circumstance"), voice actors Wayne Allwine and Tony Anselmo were used to make it seem as though Mickey and Donald were providing their own commentary on their appearances in the film.

• The DVD releases for Atlantis: The Lost Empire (Special Edition) and Finding Nemo contained specially-edited 'video commentaries'; the feature-length audio commentaries by the directors and producers were punctuated by cues to video segments illustrating various behind-the-scenes aspects.

• Seth MacFarlane, creator of the animated series Family Guy, recorded a commentary track entirely in the voices of Brian and Stewie, two characters he voiced on the show. The commentary was featured on the Family Guy "Freakin' Sweet Collection" DVD release.

• The second DVD of This is Spinal Tap, released in 2000, features a commentary by the three members of the band, in character. They relate how they felt slighted by the film, and how the director (Marty di Bergi in the film) did a "hack job" with the documentary. The commentary is another added element to the fiction of the band. Actors Michael McKean, Christopher Guest and Harry Shearer had previously recorded a commentary for a Criterion Collection DVD which had gone out of print.

• The Ultimate Matrix Collection , a box set of the entire Matrix series, has two audio commentaries on each film—one by philosophers who loved it, and one by critics who hated it.

• The commentary on Trey Parker's (aka Alferd Packer: The Musical) is notable in that the commentators—cast and crew—start out sober at the beginning. As the movie progresses, the group drinks and gets more and more inebriated.

• The laserdisc version of Chasing Amy featured a commentary track by the director, Kevin Smith, who says in the commentary track "Fuck DVD," echoing the thoughts of many Laserdisc fans about the then-new DVD format. On the DVD edition of the same film, the same commentary track was featured but the film begins with a video introduction by Kevin Smith putting his comments into perspective and giving a more favourable opinion of the now more mature DVD format.

• The fourth and fifth season box sets of The Simpsons contains special "illustrated commentaries" on selected episodes, where two animation directors draw on screen while commenting on the episode. This is achieved by using subtitle data to produce the drawings overlayed on top of the video in sync with the audio commentary track.

• The Simpsons and Futurama, both Matt Groening creations, are among the few TV series to have audio commentary tracks on every episode in their season box set DVD releases. The first season set of The Shield is another of these rare instances.