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Q: CD-Audio


A: CD-Audio or Compact Discs have been around since the beginning of the 1980s. Developed as a replacement for LPs/vinyl by Sony and Phillips, this was the first consumer digital audio format. CDs carry 2-channel of PCM [Pulse Code Modulation] audio with a sampling rate of 44.1 kHz and word lengths of 16-bits. The Redbook standard defines the electrical, logical and physical specifications of compact discs. The fidelity of the audio reproduced by a CD is limited by the sample rate and word size. The frequency range is generously between 30 Hz and 20 kHz. Dynamic range is a theoretical 96 dB but in practice hovers around 85 dB. CDs are still the primary delivery platform for pre-recorded music with billions sold every year.

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Q: ECD


A: ECDs or Enhanced CDs combine computer readable multimedia and CD-Audio quality music. The first ECDs were developed in the mid 1990s and continue to be released by many labels. The configuration of an ECD can take several different forms depending on the vintage of the disc. The very first ones used a CD format know as Mixed Mode. The data portion was placed in Track 1 of the disc and the music began at Track 2. Discs arranged in this way failed to succeed with the public and the labels because the first track played as noise in a standard CD player. This was commonly referred to as the 'Track 1 Problem'. A second format involved putting the data in the 'PreGap' area of the Track 1. CD players would play audio from Track 1 but could fast rewind into the data. 'Rhythm of the Pridelands' was the first ECD created in this fashion in the early part of 1995. A final format and the one used today places the multimedia in the second session of a multi-session CD. The CD plays correctly in a CD player but a computer CD-ROM drive can locate the multimedia content.


Q: DualDisc


A: DualDiscs are another attempt at combining two distinct optical disc formats into a hybrid. One side of a DualDisc is a CD-Audio surface and the other side is a DVD. DualDiscs were introduced in the early 2000s and have found limited consumer acceptance. The DVD side can be formatted as DVD-Video, DVD-Audio or DVD-ROM although current technology limits the DVD side to a single layer [a DVD-5]. This limitation and the fact that the discs are slightly thicker than normal optical discs [1.48 mm vs. 1.2 mm] has contributed to DualDiscs' commercial failure.


Q: DVD-Plus


A: DVD-Plus was another version of DualDisc developed by a European disc replicator that had very limited distribution. 

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Q: DVD Album

A: In the fall of 2006, Warner Brothers Records announced that they [and their affiliated labels] would be releasing DVD Albums. According to the press articles, the discs would include better fidelity sound [although not HD Audio] surround mixes, photos, MP3s, ring tones, video and web connections. They would not be compatible with existing CD players. AIX Records and Monster Music have been releasing music products that deliver many of these features. In the case of AIX Records, they have been doing it for 7 years...so the concept is nothing new.

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Q: DVD-Video


A: DVD-Video discs were introduced to the United States in the spring of 1997...ten years ago. The format replaced the older analog consumer tape format VHS by offering better picture, surround sound, interactivity, multiple camera angles, subtitles and much more. The discs use MPEG-2 video for the images. The mandated audio formats include 96 kHz/24-bit for 2-channel stereo and/or Dolby Digital for 2-5.1 channels. DTS is an optional format. Both Dolby Digital and DTS are lossy audio encoding techniques and although very reasonable sound can be achieved, they cannot provide true HD Audio quality.

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Q: DVD-Audio


A: At the same time as the DVD-Video specification was being standardized, the DVD-Audio version was also issued. Because CD-Audio had already delivered the promise of digital audio to the recording industry and because Sony/Phillips issued a competing format at the same time, the format never really caught hold. Designed primarily as an audio platform, DVD-Audio provides for true HD Audio in 5.1 channels by encoding multi-channel audio in MLP [see Meridian Lossless Packing]. For the first time, consumers that opted to purchase a DVD-Audio capable player were able hear surround sound in six channels at full 96 kHz/24-bits. Other sample rates and word sizes are available on DVD-Audio discs including 44.1, 48, 88.2, 96, 176.4 and 192 kHz [although the highest 2 rates are limited to stereo PCM]. DVD-Audio discs can also contain a 'DVD-Video' zone that allows Dolby Digital and/or DTS surround version of the audio to be playable on DVD-Video hardware. There are over 2000 titles available from a variety of labels.

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Q: SA-CD


A: SA-CD is a format developed by Sony and Phillips to archive their analog masters. When the DVD Forum decided to use PCM for the DVD-Audio format, Sony and Phillips decided to make SACD available as a competing format. It employs DSD [Direct Stream Digital] technology to deliver HD Audio. SA-CD claims to be a 1-bit encoding scheme using a sampling rate of 44.1 kHz x 64 [2.8224 MHz]. The format can be manufactured with a hybrid CD-Audio layer but does not support multimedia. SA-CDs require a new player and are incompatible with DVD players. The format has attracted a large following of audiophiles but is no longer support by Sony and Phillips. There are over 4000 titles available on SA-CD, although many are repurposed tracks from older SD recordings.

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Q: SuperDisc


A: Monster Music [of Monster Cable fame] has released a number of DVD-Video titles, which bear the name 'SuperDisc'. Like DAD and HDAD, SuperDisc is not a new optical disc format but rather a standard DVD-Video disc. The discs contain several different mixes [a concept first promoted by AIX Records] including a Dolby Headphone version, Dolby Digital, DTS and PCM 96 kHz/24-bit PCM stereo. There are also WMA files at 192 kbps and Apple Lossless files for use on your portable player. The folks at Monster have branded these discs as "High Definition Surround" because they were captured at HD. However, the actual audio on the DVDs is lossy Dolby Digital and DTS.

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Q: HD-DVD


A: HD-DVD is one of the new high definition optical disc formats that employ a blue laser to increase the storage capacity. HD-DVD, a development of Toshiba and other technology partners, offers playback of HD Video and HD Audio on new hardware players. The format is compatible with Dolby Digital, Dolby Digital Plus, Dolby TrueHD, MLP, DTS, DTS HD, DTS HD Master and even uncompressed PCM. The number of channels has increased up to 8. HD DVD has the possibility of being a true HD format but a format war with Blu-Ray and a lack of consumer interest may doom this format. HD-DVD players are compatible with DVD-Audio discs but not SA-CD.

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Q: Blu-Ray


A: Blu-Ray is the competing HD optical format from Sony and Phillips. It can store up to 25 gigs on a single layer and multiple layered discs are beginning to emerge. The audio formats supported are the same as those listed above: Dolby Digital, Dolby Digital Plus, Dolby TrueHD, MLP, DTS, DTS HD, DTS HD Master and even uncompressed PCM. Blu-Ray has the possibility of being a true HD format but a format war with HD-DVD and a lack of consumer interest may doom this format. Blu-Ray players are compatible with SA-CD discs but not DVD-Audio .

 
Q: HDS


A: High Definition Surround is a trademark of Monster Music and can be found on their line of SuperDiscs [see above]. However, like SuperDisc and DAD, this is a marketing term and not officially a format. They are using standard DVD-Video discs to deliver Dolby Digital and DTS files in 5.1 surround. Dolby Digital [AC-3] and DTS are both lossy formats capable of encoding audio at about 48 kHz/20-bits...very much short of REAL HD Audio, which requires at least 88.2 kHz and 24-bits. The original sources may have been recorded at HD Audio standards but the consumer experience is diminished by the encoding method and delivery platform.

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