DVD-Audio
DVD-Audio (commonly abbreviated as DVD-A) is a digital format for delivering very high-fidelity audio content on a DVD. DVD-Audio is not intended to be a video delivery format and should not be confused with video DVDs containing concerts and music videos. The first discs entered the marketplace in 2000. Future occasional DVD-Audio releases are expected and/or have been announced. DVD-Audio is in a format war with Super Audio CD (SACD), another format for delivering high-fidelity audio content. Neither has gained a strong position in the marketplace. As media players that can play both DVD-Audio and SACD (and many other formats) are available, both are likely to co-exist.
DVD-Audio offers many possible configurations of audio channels, ranging from single-channel mono to 5.1-channel surround sound, at various sampling frequencies and sample rates. (The ".1" denotes a Low-frequency effects channel (LFE) for bass and/or special audio effects.)
Compared to the compact disc, the much higher capacity DVD format enables the inclusion of either:
- Considerably more music (with respect to total running time and quantity of songs) or
- Far higher audio quality, reflected by higher linear sampling rates and higher bit-per-sample resolution, and/or
- Additional channels for spatial sound reproduction.
Different bit-rate/sampling rate/channel combinations can be used on a single disc. For instance, a DVD-Audio disc may contain a 96 kHz/24-bit 5.1-channel audio track as well as a 192 kHz/24-bit stereo audio track. Also, the channels of a track can be split into two groups stored at different resolutions. For example, the front speakers could be 96/24, while the surrounds are 48/20.
Audio is stored on the disc in Linear PCM format, which is either uncompressed or losslessly compressed with Meridian Lossless Packing. The maximum permissible total bitrate is 9.6 Megabits per second. Channel/resolution combinations that would exceed this need to be compressed. In uncompressed modes, it is possible to get up to 96/16 or 48/24 in 5.1, and 192/24 in stereo. To store 5.1 tracks in 88.2/20, 88.2/24, 96/20 or 96/24 MLP encoding is mandatory.
The LFE channel is actually full range, and can be recorded at the same resolution as the other channels. This permits it to be used instead as an extra main channel, for example as a "height" speaker above the listening position; this has been done on some releases. Such usage is non-standard, and will often require special set-up by the end user.
If no native stereo audio exists on the disc, the DVD-Audio player may be able to downmix the 5.1-channel audio to two-channel stereo audio if the listener does not have a surround sound setup (provided that the coefficients were set in the stream at authoring). Downmixing can only be done to two-channel stereo, not to other configurations, such as 4.0 quad. DVD-Audio may also feature menus, text subtitles, still images and video, plus in high end authoring systems it is also possible to link directly into a Video_TS folder that might contain video tracks, as well as PCM stereo and other "bonus" features..
With the introduction of the DVD-Audio format, some kind of backward compatibility with existing DVD-Video players was desired, although not required. To address this, most DVD-Audio discs contain a Dolby Digital 5.1-channel audio track on the disc (which can be downmixed to two channels for listeners with no surround sound setup). Some discs also include a native Dolby Digital 2.0 stereo, and even a DTS 96/24 5.1-channel, audio track.
Because the DVD-Audio format is a member of the DVD family, a single disc can have multiple layers and even two sides that contain media. A common configuration includes a "DVD-Video" zone on a DVD-Audio formatted single sided disc. The high-resolution, multichannel audio losslessly encoded using MLP is only playable on DVD-Audio hardware but the DVD-Video zone, which can contain Dolby or DTS 5.1 mixes and even video makes the disc compatible with all DVD players. Other configurations include double layer DVDs (DVD-9) and two-sided discs (DVD-10, DVD-14 or DVD-18). Some labels are releasing DVD titles that are formatted as DVD-Audio on one side and DVD-Video on the other, the DualDisc being one such example.
There are some software players that support the playback of DVD-Audio discs, including WinDVD and PowerDVD.ELS Surround is one of the few vehicle audio systems which can play DVD-A.