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CD and DVD release of '' Yoshimi Battles The Pink Robots '', one of the first major albums to employ the DVD-Audio format.]] DVD-Audio is a Format for delivering high-fidelity audio content on a DVD . The first discs entered the marketplace in 2000 and, as of 2006 , titles are still being released. It is currently in a Format War with Super Audio CD , another format for delivering high-fidelity audio content. AUDIO SPECIFICATIONS DVD-AUDIO WHITEPAPER 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. 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: Different bit-rate/sampling rate/channel combinations can be used on a single disc as well. For instance, a DVD-Audio disc may contain a 24-bit/96 kHz 5.1-channel audio track as well as a 24-bit/192 kHz stereo audio track. Audio is stored on the disc in LPCM format, which is either uncompressed or Losslessly Compressed with Meridian Lossless Packing . In uncompressed modes, it is possible to get up to 24/48 in 5.1, and 24/192 in stereo. For 5.1 tracks in either 24/88.2 or 24/96 then MLP encoding is mandatory. 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 co-efficients 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. The maximum permissible total bitrate for all streams is 9.6 Megabits per second. PLAYER COMPATIBILITY The introduction of the DVD-Audio format required some kind of 5.1-channel, audio track5dot1.com: What is DVD-Audio? . In addition to a standard single-sided disc, a "hybrid" DVD-Audio disc (HDAD) also exists. One side of the disc contains content that can be played in a standard DVD-Video player (such as the album in Dolby Digital 5.1 audio) and the other side contains content for DVD-Audio players (such as the album in 24-bit 96kHz PCM 5.1-channel audio). An example of a popular album released on an HDAD is The Beach Boys' 1966 album Pet Sounds . AMPLIFIER INTERFACE In order to play DVD-Audio, an amplifier with six analogue inputs is normally requiredTimeForDVD.com: DVD-Audio Tutorial . Whereas DVD-Video audio formats such as Dolby Digital and DTS can be sent via the player's digital output to a receiver for conversion to analogue form and distribution to speakers, DVD-Audio was not designed be delivered this way due to concerns about digital copying. The six channels of audio information can be sent to the amplifier by three different methods: # The 6 audio channels can be decrypted and extracted in the player and sent to the amplifier along 6 standard analogue cables. # The 6 audio channels can be decrypted and then re-encrypted into an IEEE-1394 (Firewire) signal and sent to the amplifier, which will then decrypt the digital signal and then extract the 6 channels of Audio. The IEEE-1394 encryption is different to the DVD-A encryption and was designed as a general standard for a high quality digital interface. The amplifier has to be equipped with a valid decryption key or it won't play the disk. # The third option is via the S/PDIF (or TOSLINK) digital interface, but this can only output a downmixed 2 channel PCM signal. However, because of concerns over unauthorised copying, DVD-A players are required to handle this digital interface in one of three ways:
SOUND QUALITY From a purely technical standpoint, the sound resolution of a DVD-Audio recording (sampled at 24-bit/96 kHz) is substantially better than a standard CD recording (which is sampled at 16-bit/44.1 kHz). However, some people report that they cannot hear a difference between DVD-Audio and CD-Audio. Furthermore, some doubt that the quality difference is large enough to justify purchasing new playback equipment and repurchasing records in DVD-Audio format. Three of the major Music Labels , Universal Music , EMI and especially Warner Bros. Records , are continuing to release albums on DVD-Audio, however newer titles tend to be released as CD/DVD packages (which usually include the album on both CD and DVD-Audio) or DualDisc (which can contain DVD-Audio on the DVD side of the disc) as opposed to a standalone DVD-Audio disc. 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 ", have since been rereleased as a CD/DVD package or as a DualDisc. COPY PROTECTION DVD-Audio discs employ a , prevents users from extracting audio to computers and portable media players. 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 also can utilize Digital Watermarking technology developed by the Verance Corporation . The 4C Entity also developed a similar specification, Content Protection For Recordable Media (CPRM), which is used on Secure Digital Card s. DVD-Audio's copy protection was overcome in files without going through lossy Digital-to-analogue 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. The method is still in early stages, for example having problems with watermarked disks. As the DVD-A format has not gained wide commercial interest or acceptance, decryption tools are still very primitive. Such tools are most likely illegal in the United States under the Digital Millennium Copyright Act , and the Recording Industry Association Of America has been successful in keeping them off websites. Like much software of dubious legality, they are still distributed from person to person and on the Peer To Peer networksSlashdot: DVD-Audio's CPPM Circumvented . REFERENCES EXTERNAL LINKS
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