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.
Compared to the compact disc, the much higher capacity DVD format enables the inclusion of either:
Audio on a DVD-Audio disc can be stored in many different bit-rate/sampling rate/channel combinations:
|16-, 20- or 24-bit|
|44.1 kHz||48 kHz||88.2 kHz||96 kHz||176.4 kHz||192 kHz|
|Stereo + mono surround (3.0 or 3.1)|
|Quad (4.0 or 4.1)|
|3-stereo (3.0 or 3.1)|
|3-stereo + mono surround (4.0 or 4.1)|
|Full surround (5.0 or 5.1)|
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..
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.
However encrypted digital formats have now been approved by the DVD Forum, the first of which was Meridian Audio's MHR (Meridian High Resolution). The High Definition Multimedia Interface (HDMI 1.1) also allows encrypted digital audio to be carried up to DVD-Audio specification (6 × 24-bit/96 kHz channels or 2 × 24-bit/192 kHz channels). The six channels of audio information can thus be sent to the amplifier by several different methods:
It is uncertain whether average listeners can hear the difference between DVD-Audio and CD-Audio, and many consumers do not regard any supposed quality improvements offered as sufficient reason to justify purchasing new playback equipment and repurchasing albums in higher-resolution formats. Many DVD-Audio releases are older, standard definition audio recordings that have been remixed in 5.1 and upsampled to DVD-Audio's higher resolution. However, the fidelity of the upsampled audio will be limited by the source material quality and may not exceed the quality of existing CD releases of the same albums. When new recordings are made using high-resolution PCM encoding, a substantial difference in fidelity can be achieved.
Three of the major music labels, Universal Music, EMI and Warner Bros. Records and several smaller audiophile labels (such as AIX Records and DTS Entertainment) have released or are continuing to release albums on DVD-Audio, but the number is minimal compared to standard CDs. New high-definition titles have been released in standard DVD-Video format (which can contain 2-channel Linear PCM audio data ranging from 48 kHz/16-bit to 96 kHz/24-bit), "HDAD", which includes a DVD-Video format recording on one side and DVD-Audio on the other, CD/DVD packages, which can include the album on both CD and DVD-Audio, or DualDisc, which can contain DVD-Audio content on the DVD side. In addition, some titles that were initially released as a standalone DVD-Audio disc, such as The Grateful Dead's American Beauty and R.E.M.'s Automatic for the People, were re-released as a CD/DVD package or as a DualDisc.
Because DVD-Video's content-scrambling system (CSS) was quickly broken, DVD-Audio's developers sought a better method of blocking unauthorized duplications. They developed CPPM, which uses a media key block (MKB) to authenticate DVD-Audio players. In order to decrypt the audio, players must obtain a media key from the MKB, which also is encrypted. The player must use its own unique key to decrypt the MKB. If a DVD-Audio player's decryption key is compromised, that key can be rendered useless for decrypting future DVD-Audio discs. DVD-Audio discs can also utilize digital watermarking technology developed by the Verance Corporation, typically embedded into the audio once every thirty seconds. If a DVD-Audio player encounters a watermark on a disc without a valid MKB, it will halt playback. The 4C Entity also developed a similar specification, Content Protection for Recordable Media (CPRM), which is used on Secure Digital cards.
DVD-Audio's copy protection was overcome in 2005 by tools which allow data to be decrypted or converted to 6 channel .WAV files without going through lossy digital-to-analog conversion. Previously that conversion had required expensive equipment to retain all 6 channels of audio rather than having it downmixed to stereo. In the digital method, the decryption is done by a commercial software player which has been patched to allow access to the unprotected audio.
In 2007 the encryption scheme was overcome with a tool called dvdcpxm. In 12 February 2008 a program called DVD-Audio Explorer 2008 was released, containing aforementioned libdvdcpxm coupled with an open source MLP decoder.
Like DVD-Video decryption, such tools may be illegal to use in the United States under the controversial Digital Millennium Copyright Act. While the Recording Industry Association of America has been successful in keeping these tools off websites, they are still distributed on P2P file sharing networks and newsgroups, Additionally, in 2007 the widely-used commercial software DVDFab Platinum added DVD-Audio decryption, allowing users to backup a full DVD-A image to ISO.
Normal DVD(Video) authoring software usually does not support DVD-Audio creation, so there is some special software: