DVD-Video

DVD-Video (DVD 视频) is an audio and video application specification within the DVD family of standards, used to organize movies, television programs, concerts, and bonus content on media such as DVD-ROM. It specifies the encoding ranges and playback structure for video, audio, subtitles, and navigation data, but is not synonymous with the physical DVD medium; DVD-ROM can also be used for general data, and DVD-Audio employs a different application specification. The first commercial DVD-Video discs and players were released in Japan in 1996.

Video primarily uses MPEG-2 Video, though certain MPEG-1 modes are also permitted. The full frame for 525/60 systems is typically 720×480, while for 625/50 systems it is 720×576; lower-resolution modes also exist. Programs can be interlaced video or, with appropriate encoding and repeat-field flags, preserve the progressive-scan images from the film source. Both 4:3 and 16:9 content use non-square pixels, and players determine the display aspect ratio based on the aspect ratio flag; directly converting the stored resolution to a square-pixel ratio would result in an incorrect aspect ratio.

A single disc can contain multiple audio tracks. DVD-Video supports linear PCM, Dolby Digital, and MPEG Audio, with optional formats such as DTS; there have been variations in the required audio combinations that players must support depending on the television standard and region of sale. Audio, video, subtitles, and navigation data are constrained by the system’s total bitrate; adding audio tracks, subtitles, or longer programs will alter the capacity and bitrate allocated to the main video. The multi-view feature allows different camera angles to be stored on the same timeline, but it is rarely used for full-length programs due to the significant space it occupies.

The content of a typical disc is located in the `VIDEO_TS` directory. VOB files multiplex video, audio, subpicture, and navigation packets; IFO files record titles, program chains, chapters, stream attributes, and menu commands; and BUP files store backups of key IFO information. A continuous program displayed on a single screen may span multiple VOB files, and the playback order does not necessarily correspond exactly to the literal order of the filenames; chapters serve as navigation entry points and are not inherently equivalent to separate video files. Subtitles and menus typically use subtitle data, which consists of bitmap graphics with transparency and a limited color palette. This data can specify fixed fonts, positions, and graphic styles, and can also be used to highlight menu buttons. Menu navigation is controlled by virtual machine commands, allowing jumps to different program chains based on language, region, playback status, or user selection. Some discs use menu-less autoplay while still complying with the DVD-Video specification.

Commercial releases may also employ region codes, CSS encryption, and analog output protection. Region codes divide discs and players into several sales regions, while CSS controls access to encrypted content; these are access control mechanisms that do not alter video encoding or physical capacity. Dual-layer DVD-9 discs contain layer-switching points within the program; the player must refocus to the other recording layer. Whether a visible pause occurs during the switch depends on the mastering position and the device’s buffer.

DVD-Video is based on the standard-definition system. Labels on the packaging such as “HD restoration,” “high bitrate,” or widescreen indicators do not transform the disc into an HD disc; programs produced from high-resolution master recordings still need to be converted to the aspect ratios and encoding ranges permitted by the specification.