Audio data
The audio data on a DVD movie can be PCM, DTS, MPEG-1 Audio Layer II (MP2), or Dolby Digital (AC-3) format. In countries using the PAL system standard DVD-Video releases must contain at least one audio track using the PCM, MP2, or AC-3 format, and all standard PAL players must support all three of these formats. A similar standard exists in countries using the NTSC system, though with no requirement mandating the use of or support for the MP2 format. DTS audio is optional for all players, as DTS was not part of the initial draft standard and was added later; thus, many early players are unable to play DTS audio tracks. The vast majority of commercial DVD-Video releases today employ AC-3 audio. The official allowed formats for the audio tracks on a DVD Video are:
- PCM: 48 kHz or 96 kHz sampling rate, 16 bit or 24 bit L-PCM, 2 to 6 channels, up to 6144 kbit/s. N.B. 16-bit 48kHz 8 channel PCM is allowed by the DVD-Video specification but is not well-supported by authoring applications or players.
- AC-3: 48 kHz sampling rate, 1 to 5.1 (6) channels, up to 448 kbit/s
- DTS: 48 kHz or 96 kHz sampling rate, 2 to 6.1 channels, Half Rate (768 kbit/s) or Full Rate (1536 kbit/s)
- MP2: 48 kHz sampling rate, 1 to 7.1 channels, up to 912 kbit/s
DVDs can contain more than one channel of audio to go together with the video content, supporting a maximum of 8 simultaneous audio tracks per video. This is most commonly used for different audio formats—DTS 5.1, AC-3 2.0 etc.—as well as for commentary and audio tracks in different languages.
Connection issues
Due to multiple audio (and video) output sources, a consumer has many outputs on a DVD player, and may become confused with connecting their player to their TV and/or amplifier. Most systems include an optional digital audio connector for this task, which is then paired with a similar input on the amplifier. The physical connection is typically RCA connectors or TOSLINK, which transmits a S/PDIF stream carrying either uncompressed digital audio (PCM) or the original compressed audio data (Dolby Digital, DTS, MPEG audio) to be decoded by the audio equipment.
Video is another issue which continues to present most problems. Current players typically output analog video only, both composite video on an RCA jack, as well as S-Video in the standard connector. However neither of these connectors were intended to be used for progressive video, so yet another set of connectors has started to appear, to carry a form of component video, which keeps the three components of the video, one luminance signal and two color difference signal, as stored on the DVD itself, on fully separate wires (whereas S-Video uses two wires, uniting and degrading the two color signals, and composite only one, uniting and degrading all three signals). The connectors are further confused by using a number of different physical connectors on different player models, RCA or BNC, as well as using VGA cables in a non-standard way (VGA is normally analog RGB—a different, incompatible form of component video). Even worse, there are often two sets of component outputs, one carrying interlaced video, and the other progressive, or a interlaced/progressive switch (either a physical switch or a menu setting).
In Europe (but not most other PAL areas), SCART connectors are typically used, which can carry composite and analog RGB interlaced video signals (RGB can be progressive, but not all DVD players and displays support this mode) or Y/C (S-Video), as well as analog two-channel sound and automatic 4:3 or 16:9 (widescreen) switching on a single convenient multiwire cable. The analog RGB component signal offers video quality which is superior to S-Video and identical to YPbPr component video. However, analog RGB and S-Video signals can not be carried simultaneously, due to each using the same pins for different uses, and displays often must be manually configured as to the input signal, since no switching mode exists for S-Video. (A switching mode does exist to indicate whether composite or RGB is being used.) Some DVD players and set-top boxes offer YPbPr component video signals over the wires in the SCART connector intended for RGB, though this violates the official specification and manual configuration is again necessary. (Hypothetically, unlike RGB component, YPbPr component signals and S-Video Y/C signals could both be sent over the wire simultaneously, since they share the luminance (Y) component.)
HDMI is a new digital connection similar to DVI; it carries High Definition, Enhanced Definition and Standard Definition video. Along with video HDMI also supports up to eight-channel digital audio. Some HDMI-equipped DVD players can upconvert the video to higher definition formats such as 720p and 1080i, and sometimes to 1080p.