This is an old revision of this page, as edited by Binksternet (talk | contribs) at 00:59, 18 May 2009 (→Classical music: wording). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.
Revision as of 00:59, 18 May 2009 by Binksternet (talk | contribs) (→Classical music: wording)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)| File:SACDlogo.png | |
 | |
| Media type | Optical disc |
|---|---|
| Encoding | Digital (DSD) |
| Capacity | up to 7.95 GiB/GB |
| Read mechanism | 650 nm laser |
| Developed by | Sony & Philips |
| Usage | Audio storage |
Super Audio CD (SACD) is a high-resolution read-only optical audio disc format designed to provide high-resolution audio in both stereo and surround sound, in contrast to the old audio CD format which cannot provide high-resolution audio, nor any kind of surround sound. Introduced in 1999, SACD was developed by Sony and Philips Electronics, the same companies that created the Compact Disc. SACD was in a format war with DVD-Audio. As of May 2009, the number of titles released on SACD is approximately 20 times larger than available in any other high-resolution format.
Overview
SACD is a disc of identical physical dimensions to the compact disc but it uses a very different technology from CD and DVD-Audio to encode its audio data, a 1-bit delta-sigma modulation process known as Direct Stream Digital at the very high sampling rate of 2822.4 kHz. This is 64 times the sampling rate used in Compact Disc Digital Audio (CDDA), which specifies 44.1 kHz at a resolution of 16-bit. Because the resolution of SACD is 16 times smaller than CDDA, the bitrate for a given channel is 4 times as large.
| CD | SACD | |
|---|---|---|
| Format | 16 bit PCM | 1 bit DSD |
| Sampling frequency | 44.1 kHz | 2822.4 kHz |
| Dynamic range | 96 dB | 120 dB |
| Frequency range | 20 Hz - 20 kHz | 20 Hz - 100 kHz |
| Disc capacity | 700 MB | 7.95 GB |
| Stereo | Yes | Yes |
| Multi-channel | No | Yes |
There are three types of SACDs:
- Hybrid: The most popular of the three types, hybrid discs include a "Red Book" layer compatible with most legacy Compact Disc players, dubbed the "CD layer," and a 4.7 GB SACD layer, dubbed the "HD layer." It is not uncommon for hybrid discs to carry the "Compact Disc Digital Audio" logo to show that the disc is CDDA-compliant.
- Single-layer: Physically a DVD-5 DVD, a single-layer SACD includes a 4.7 GB HD layer with no CD layer.
- Dual-layer: Physically a DVD-9 DVD, a dual-layer SACD includes two HD layers totaling 8.5 GB, with no CD layer. It enables nearly twice as much data to be stored, but eliminates CD player compatibility. This type is rarely used. A notable example is the "Multi-Ch" release of Toto IV.
SACD authoring guidelines suggest that an SACD should always contain a 2-channel stereo mix though not all SACD have it (for example, in 2005 Sony Music Entertainment (Germany) GmbH released Charles Rosen's performance of the Goldberg Variations as a hybrid SACD with 16-bit PCM and DSD 5.1 surround but no DSD stereo). They may optionally contain a surround mix — either 5.0 or 5.1 layout. Although the disc always stores all channels, the surround mix does not have to use them all, and some may be mute; for example the 2001 SACD release of Mike Oldfield's Tubular Bells remains in the quadraphonic 4.0 mix made in 1975, and the RCA reissue of the 1957 Chicago Symphony Orchestra recording of Mussorgsky's Pictures at an Exhibition marks the first time the original 3.0 (three track) recording is available in a consumer format. The correct designation for the surround part of an SACD is "multi-channel", and usually has either the label "SACD Surround" or its own "Multi-Ch" logo on the back cover.
Market forces
The standard redbook CD continues to be the mainstream optical disk format for audio, mainly competing on price and the large installed base of compatible players. As all SACD players can play older CD issues, and since almost all SACD discs are now issued as hybrids (playable on both on older CD players and newer SACD machines), the new SACD format essentially nests the older CD format (rather than competing with it).
Although SACD and the traditional LP record both may have minuscule shares of the total market, SACD has gained significant momentum within certain genres. SACD is strong within classical, jazz and acoustic music, genres that appeal to the audiophile or high fidelity community. In the more general music market, the dominant market force now appears to be convenience: the rise of digital downloads, in particular lower-quality mp3 files (partly fed by widely-available pirated content), and the decline in older CD format sales. Accordingly, what appears to be emerging is a dichotomous market structure of extremes: the mass market is moving toward a lower-quality convenience model, while the high-end audiophile market has seen a recent resurgence through the SACD format. As of May 2009, there are in excess of 5500 SACD titles on the market. By contrast, the total number of titles available in all other competing high-resolution formats combined (DVD-Audio, Blu-ray Audio and downloads), total in the low hundreds.
DVD-Audio
DVD-Audio is a format with somewhat similar features as SACD, and was brought to the market two years earlier. Sales for DVD-Audio peaked in 2005 at 0.5 million units, and subsequently dropped to approximately 0.2 million units per year, with a market share (in dollars, not units) of 1.2 and 1.3% in 2006 and 2007, respectively.
Blu-ray
BD-Audio is a newer format that uses the Blu-ray Disc physical format for high-resolution, multichannel audio-only playback, but there has yet to be any music industry support for Blu-ray as an audio format.
Downloads
There is no inherent reason why downloads must be of lower quality, other than the longer time to download larger files. For example, sixty minutes of typical CD quality audio contains an average of about 660 MB of uncompressed data or about 350 MB of data processed with lossless compression, an mp3 version of it might be 60 to 240 MB depending on compression quality, whereas an SACD disc contains about 5 gigabytes of data (though this may also be compressed losslessly if downloaded). Given the popularity of non-physical media distribution such as iTunes, some think that physical media will lose market share to downloadable media, even in the high fidelity market. FLAC media files with data rates equaling that of physical media are available from niche record companies.. However, there are a number of significant obstacles to be overcome before high-quality downloads can practically be perceived to threaten the market position of SACD. First, almost all computers ship with 44.1/48 kHz D/A converters, and unless special sound cards are purchased, standard computers cannot reproduce 96 kHz or 192 kHz high-resolution recordings. Second, the downloaded tracks cannot currently be played or supported within mainstream media players such as iTunes; the Windows Media Player can support up to 96 kHz provided the computer has a sound card capable of 96 kHz D/A conversion. Third, there are only a tiny number of titles available for download: for example, as of March 2009, there are less than 50 high-resolution classical titles that have been licensed. Fourth, because these downloads exist outside of iTunes and Windows Media Player, there is no widespread DRM management system available to protect the property rights of content owners. This acts as something of a 'catch 22': almost all high-resolution downloads that are available in March 2009 are free of DRM restrictions, and equally, the same freedom may explain the unwillingness of content owners to license their content. Fifth, the SACD format has not been cracked, and SACD recordings are not available as downloads. DSD files are not offered as they are not playable on personal computers.
Content
As of May 2009, there have been over 5,500 titles released on SACD, slightly more than half of which are classical. Jazz and popular music albums, mainly remastered previous releases, are the next two most numerous genres represented.
Today, most SACDs are issued as SACD hybrid discs. A hybrid disc can be played in high-resolution audio on a SACD player and on all existing Red Book CD or DVD video players, with standard CD quality. The SACD format is thus backward compatible. Equally, all SACD machines can play all SACD discs and all old CDs.
Popular artists
Notable popular artists who have released some or all of their back catalog include Pink Floyd, whose seminal album The Dark Side of the Moon was released on the 30th anniversary of the original vinyl LP, and Roxy Music whose album Avalon was released on SACD to take advantage of the format's multi-channel capability.
Classical music
Classical music has enjoyed much more attention than popular music in the SACD format. Many new high-resolution recordings have been released since the introduction of SACD, with recordings encompassing the majority of the classical canon as well as the fringes of the repertoire. In addition to new high-resolution recordings generally recorded post-2000, there are hundreds of older analog recordings re-mastered to DSD and issued on SACD, providing the closest thing to the original studio analog master tapes that has ever been released.
High definition audio formats continue to attract few major record labels. This is, in part, because, in the mid-2000s, the major labels such as Universal adopted a downmarket marketing strategy of seeking high sales from a small number of releases (typically crossover discs such as a classical star performing tangos), and increased their marketing of low-cost compressed audio formats. With the major labels vacating the high-end long tails of the market and failing to address market niches, dozens of smaller companies have entered the market in the last few years to cater to audiophile and classical enthusiasts. As of May 2009, over 440 labels have released one or more SACDs. Some major orchestras and artists have released SACD recordings on their own in-house labels.
Disc reading
Objective lenses in conventional CD players have a longer working distance, or focal length, than lenses designed for SACD players. This means that when a hybrid SACD is placed into a conventional CD player, the laser beam passes the high-resolution layer and is reflected by the conventional layer at the standard 1.2 mm distance, and the high-density layer is out of focus. When the disc is placed into an SACD player, the laser is reflected by the high-resolution layer (at 600 µm distance) before it can reach the conventional layer. Conversely, if a conventional CD is placed into an SACD player, the laser will read the disc without difficulty since there is no high-resolution layer.
Playback hardware
Hybrid Super Audio CDs (which include both a Stereo CD and a Super Audio CD layer) can be played back on CD players. To hear the Super Audio CD Stereo, and on many discs the Super Audio CD Multichannel layer, requires a Super Audio CD player.
As would be expected, Sony and Philips – designers of the CD and SACD formats – have the most players on the market in many guises such as standalone players, combined DVD/SACD players, in-car players,.
The Sony SCD-1 was a player which was introduced concurrently with the SACD format in 1999 for a price of approximately US$5,000. It weighs over 26 kg (57 lb). The SCD-1, no longer produced, was introduced before multi-channel SACDs existed and plays two channel SACDs and Red Book CDs only.
Many other electronics manufacturers, including Denon/Marantz, Pioneer and Yamaha offer SACD playback capabilities throughout their product lines. None, however, has offered a portable SACD player capable of playing the high-definition layer of an SACD. Most portable CD players will play the conventional CD layer of a Hybrid SACD.
SACD players are not permitted to digitally output an unencrypted stream of DSD. Players initially supported only analog output; later some proprietary digital interfaces such as Denon Link permitted encrypted transmission of DSD. There are now two standard digital connection methods capable of carrying DSD in encrypted form: i.Link and HDMI (version 1.2 or later, standardised in August 2005).
The older i.Link interface is generally found on older mid- to high-end equipment and some current top of the line units from the Japanese manufacturers. HDMI is more common, being the standard digital connection method for high-definition video with audio. Most new mid-level and higher 2007 model year and later A/V processors support the HDMI 1.2 specification's DSD over HDMI feature. Most boutique manufacturers still do not support DSD. Some HDMI 1.1 spec DVD players convert DSD to LPCM and then pass it to an HDMI 1.1 spec or later processor. Lower end processors usually convert the DSD to LPCM, higher end ones usually convert it to LPCM for bass management or DSP but can also process it natively at the expense of DSP and bass management. Some new DVD players from Oppo Digital, Pioneer, Onkyo, etc. now support HDMI 1.2 or 1.3 and will pass DSD over HDMI as well as LPCM. Be aware that some players, for instance, Onkyo DV-SP504, will not support DSD or LPCM over HDMI without resampling it to 48 kHz. SACD or DVD-A will be played through analog outputs instead. The older i.Link interface has been dropped from all but high-end A/V processors and DVD players.
Some players, such as the PlayStation 3 (not the 40GB version), do not output DSD over HDMI, but instead convert it to PCM.
PlayStation 3 and SACD playback
The first two generations of Sony's PlayStation 3 game console are capable of reading SACD discs. Starting with the third generation (introduced October/November 2007), SACD playback was removed altogether.
For models that are capable of reading SACD, three output options exists.
- Using the AV output will give an analog stereo sound for SACDs that include a stereo track.
- Using HDMI will give access to multichannel high-resolution PCM audio (converted from DSD).
- Using S/PDIF will give digital stereo sound (of either the stereo track, or a down-mix of the surround track)
- PS3 was capable of converting surround DSD to lossy 1.5 Mbit/s DTS for playback over S/PDIF using the 2.00 software. The immediate revision after that removed the feature.
DSD
SACD audio is stored in a format called Direct Stream Digital (DSD), which differs from the conventional PCM used by the compact disc or conventional computer audio systems.
DSD is 1-bit, has a sampling rate of 2.8224 MHz, and makes use of noise shaping quantization techniques in order to push 1-bit quantization noise up to inaudible ultrasonic frequencies. This gives the format a greater dynamic range and wider frequency response than the CD. The SACD format is capable of delivering a dynamic range of 120 dB from 20 Hz to 20 kHz and an extended frequency response up to 100 kHz, although most currently available players list an upper limit of 80–90 kHz.
Because of the nature of sigma-delta converters, one cannot make a direct comparison between DSD and PCM. An approximation is possible, though, and would place DSD in some aspects comparable to a PCM format that has a bit depth of 20 bits and a sampling frequency of 192 kHz.
DST
To reduce the space and bandwidth requirements of DSD (2.8 Mbit/s per channel), a lossless data compression method called Direct Stream Transfer (DST) is used — DST compression is compulsory for multi-channel regions and optional for stereo regions. This typically compresses by a factor of between two and three, allowing a disc to contain 80 minutes of both 2-channel and 5.1-channel sound.
Pit Signal Processing
SACD includes various copy protection measures of which the most prominent is Pit Signal Processing (PSP), a physical watermarking feature that contains a digital watermark modulated in the width of pits on the disc (data is stored in the pit length). The optical pickup must contain special circuitry to read the PSP watermark, which is then compared to information on the disc to make sure it's legitimate. Because the majority of DVD players and all DVD-ROM drives use an optical pickup that lacks this specialized watermark detection circuitry they cannot read the data on the SACD layer of a protected SACD disc.
On hybrid SACD discs, PSP is only applied to the SACD layer — not to the CD layer.
Sound quality of SACD vs CD
In the audiophile community, SACD is generally considered to provide substantially higher quality compared to older format redbook CD recordings.
Getting "High resolution" sound reproduction
SACD has a superior bandwidth compared to CD, SACD has a superior signal to noise ratio compared to CD, and the increased media bitrate in itself is an argument for increased sound quality. The DSD technology behind SACD enables reproduction of sound in a way that is essentially identical to the studio master. Proponents argue that the medium offers greater clarity, depth and warmth than CD, with less harshness.
Surround sound vs stereo
SACD allows for 5.1 channels of lossless, high-quality surround sound. This is impossible to achieve on a regular CD, and there is general agreement that surround sound has the potential for a different, and often better, subjective experience .
Copy protection
SACD has several copy protection features at the physical level which, for the moment, appear to make SACD discs impossible to copy without resorting to the analog hole, or ripping of the conventional 700MB layer on hybrid discs. These include physical pit modulation and 80-bit encryption of the audio data, with a key encoded on a special area of the disk that is only readable by a licensed SACD device. The HD layer of an SACD disc cannot be played back on computer CD/DVD drives, nor can SACDs be created except by the licensed disc replication facilities in Shizuoka and Salzburg.
It is possible to capture the DSD digital audio signal after the decryption stage right before the digital to analog converters of an SACD player, but since there is no practical way for the public to make their own SACDs, this does not pose a major threat.
The hacking of protection methods used on HD DVD and Blu-ray Disc, when they accounted for only 4% of digital movie sales in 2007, shows either that the latter formats are relatively insecure, or that market share creates not only the demand for technologies that enable consumers to bypass the protection but also the supply of same, or that the content on SACDs (predominantly audiophile Classical and Jazz) is simply inconsistent with the interests of hackers.
A number of new SACD players have encrypted IEEE 1394 (also called FireWire or i.Link) or HDMI digital outputs carrying DSD data, and it may be possible to get the raw DSD data from these links. The protection mechanism used is Digital Transmission Content Protection (DTCP), which can be used in "Copy Once" or "Copy Never" modes. It is unlikely, however, that the SACD license agreement rules permit anything but the "Copy Never" mode to be used.
There seems to be one solution for obtaining digital non-DRM output on SACD as well as DVD-A players. A Switzerland-based company is offering a modified output-board that taps into the digital datastream prior to D/A conversion as well as converting DSD to PCM that the S/PDIF port can transfer.
See also
- Audio format
- Audio storage
- DualDisc
- Earlier attempts at higher fidelity that stayed within the CDDA standard: XRCD and HDCD.
- Later attempts at higher fidelity that stayed within the CDDA standard: DSD-CD and Blu-spec CD.
References
- ^ RIAA. 2007 Year-End Shipment Statistics. Retrieved on May 4, 2009.
- RIAA. 2007 Consumer Profile. Retrieved on May 7, 2009.
- Spector CD Extinction
- http://www.highfidelityreview.com/news/index.asp
- http://www.amazon.com/s?url=search-alias%3Dpopular&field-keywords=SACD
- "Sony Announces Three Super Audio CD Car Stereo Players". HighFidelityReview.com. Retrieved 2007-01-18.
- "The Sony SCD-1 SACD Player". @udiophilia. Retrieved 2006-05-18.
- "Why did Sony take SA-CD out of PS3 again?". Retrieved 2009-01-04.
- "PS3SACD.com News, November 22, 2007".
- "Details of DVD-Audio and SACD". DVDdemystified.com. Retrieved 2007-07-12.
- Toole, E. Floyd (2008), Sound reproduction - Loudspeakers and rooms, Focal press, ISBN 9780240520094
- "Sony Starts Hybrid Super Audio CD Production Facilities in Europe". SA-CD.net. 2003-01-22. Retrieved 2007-07-12.
- dvdupgrades.ch
Bibliography
- Janssen, E.; Reefman, D. "Super-audio CD: an introduction". Signal Processing Magazine, IEEE Volume 20, Issue 4, July 2003 Page(s): 83 - 90
External links
- SA-CD.net (full listing of available albums and comprehensive FAQ)
- SA-CD site at Sony Music
- Youtube SACD spec ad (Super Audio CD spec ad on youtube)
- puresuperaudio.blogspot.com (All about SACD and DSD)
- Multichannel SACD Rating: album guide for surround-sound lovers.
- PS3SACD.com FAQ: a dedicated FAQ about SACD functionality on PlayStation3
- Super Audio Compact Disc: A Technical Proposal (PDF), Sony.
- The SA-CD explained
- "Breaking the Sound Barrier: Mastering at 96 kHz and Beyond" (PDF) Audio Engineering Society Convention Paper 4357 on "HD" audio.
- "A Native Stereo Editing System for Direct-Stream Digital" (PDF) Audio Engineering Society Convention Paper 4719 on the 1st DSD commercial editor.
- "Why Direct Stream Digital is the best choice as a digital audio format" (PDF) Audio Engineering Society Convention Paper 5396.
- "Why 1-Bit Sigma-Delta Conversion is Unsuitable for High-Quality Applications" (PDF) Audio Engineering Society Convention Paper 5395.
- "DVD-Audio versus SACD: Perceptual Discrimination of Digital Audio Coding Formats" (PDF) Audio Engineering Society Convention Paper 6086.
| High-definition (HD) | |
|---|---|
| Concepts | |
| Resolutions | |
| Analog broadcast (All defunct) | |
| Digital broadcast | |
| Audio | |
| Filming and storage | |
| HD media and compression | |
| Connectors | |
| Deployments | |