Super Audio CD
Encyclopedia
Super Audio CD is a high-resolution, read-only
optical disc
for audio storage. Sony
and Philips Electronics
jointly developed the technology, and publicized it in 1999. It is designated as the Scarlet Book
standard. Sony and Philips previously collaborated to define the Compact Disc
standard (as well as the S/PDIF
digital audio cable specification). SACDs allow greater dynamic range
and may hold more playing time than CDs.
or surround sound
. Although SACD audio streams are encoded in a pulse-density modulation
(PDM) scheme called Direct Stream Digital
(DSD), a manufacturer may also write a Pulse-code modulation
(PCM) "layer" compatible with conventional Compact Disc player
s.
SACD is a disc of identical physical dimensions to a standard compact disc; the density of the disc is the same as a DVD
and it encodes audio using a process known as Direct Stream Digital
. The SACD sampling rate is 2.8224 MHz and the resolution is one bit. A stereo SACD recording can stream data at an uncompressed rate of 5.6 Mbit/s, four times the rate for Red Book
CD stereo audio. SACD recordings can have a wider frequency and dynamic range than conventional CDs.
There are three types of SACDs:
Almost all commercially released SACDs have included both stereo (dual-channel) and surround sound (multi-channel) mixes. A multi-channel mix need not be surround, however; some of the Living Stereo reissues (such as the RCA
reissue of the 1957 Chicago Symphony Orchestra
recording of Mussorgsky
's Pictures at an Exhibition
) use only the three front channels to reproduce the original three-track (3.0) stereo recordings. Nor is a surround mix obliged to use all six SACD channels (five full-range plus LFE). For example, the 2001 SACD release of Mike Oldfield
's Tubular Bells
remains in the quadraphonic
4.0 mix.
The CD layer exists primarily for backward compatibility, but is not required. If the CD layer is omitted, the SACD need not be limited to an 80-minute playing time. For stereo material, the space that would have been taken by the multi-channel program can be used to extend playing time to four hours or more. BIS
has taken advantage of this to put all of Bach's organ music on five SACD-only disks.
partnered in May 2002 to develop and install the first SACD hybrid disc production line in the USA, with a production capacity of 3 million discs per year. But SACD did not achieve the same explosive growth that Compact Discs enjoyed in the 1980s, and was not accepted by the mainstream market. By 2008, some considered the Super Audio CD a complete failure. However, the format continues to thrive in the audiophile community, and new SACD recordings and players continue to be made.
Despite the global decline in Compact Disc sales, sales of Super Audio CDs and players increased in 2010.
and popular music albums, mainly remastered previous releases, were the next two most numerous genres represented.
Record companies issue most SACDs as backward-compatible hybrid discs. Such a disc can be played in high-resolution audio on a SACD player and conventional Red Book CD or DVD video players (albeit just with standard CD quality). The SACD format is thus backward compatible. SACD machines can play CDs and SACD discs; CD players can play SACD hybrid discs as audio CDs.
's album The Dark Side of the Moon
sold over 800,000 copies by June 2004 in its SACD Surround Sound edition. The Who
's rock opera Tommy
, and Roxy Music
's Avalon, were released on SACD to take advantage of the format's multi-channel capability. All three albums were remixed in 5.1 surround, and released as hybrid SACDs with a stereo mix on the standard CD layer.
Some popular artists have released new recordings on SACD. Sales figures for Sting's Sacred Love
album reached number one on SACD sales charts in four European countries in June 2004.
As of May 2009, over 440 labels have released one or more SACDs. Instead of depending on major label support, some orchestras and artists have released SACDs on their own. For instance, the Chicago Symphony Orchestra
started the Chicago Resound label to provide full support for high-resolution SACD hybrid discs, and the London Symphony Orchestra
established their own 'LSO Live' label.
, 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 as a CD since there is no high-resolution layer.
The Sony SCD-1 was a player which was introduced concurrently with the SACD format in 1999, at a price of approximately US$5,000. It weighed over 26 kg
(57 lb
). The SCD-1, no longer produced, was introduced before multi-channel SACDs existed and played two channel SACDs and Red Book CDs only.
Many electronics manufacturers, including Denon, Marantz, Pioneer and Yamaha offer SACD players. 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.
Sony
has made in-car Super Audio CD players.
Several brands have introduced (mostly high-end) Blu-ray Disc
players that are SACD-compatible.
SACD players are not permitted to offer an output carrying an unencrypted stream of Direct Stream Digital
(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 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 specifications 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.
(PS3) game console were capable of reading SACD discs. Starting with the third generation (introduced October 2007), SACD playback was removed altogether.
For models that are capable of reading SACD, three output options exist:
PS3 was capable of converting surround DSD to lossy 1.5 Mbit/s DTS for playback over S/PDIF using the 2.00 system software
. The subsequent revision removed the feature. There is software available for creating a backup copy of a SACD using an older generation PlayStation 3.
(DSD), which differs from the conventional Pulse-code modulation
(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 70–90 kHz, and practical limits reduce this to 50 kHz.
Because of the nature of sigma-delta converters
, one cannot make a direct technical comparison between DSD and PCM. DSD's frequency response can be as high as 100 kHz, but frequencies that high compete with high levels of ultrasonic quantization noise
. With appropriate low-pass filter
ing, a frequency response
of 50 kHz can be achieved along with a dynamic range of 120 dB. This is about the same resolution as PCM audio with a bit depth of 20 bits and a sampling frequency of 96 kHz. Thus, DSD looks inferior to a "standard" PCM 24bit/96 kHz even using slightly more bandwidth than PCM (2.8224 Mbit/s vs 2.304 Mbit/s).
published the results of a year-long trial in which a range of subjects including professional recording engineers were asked to discern the difference between SACD and compact disc
audio (44.1 kHz/16 bit) under double blind test conditions. Out of 554 trials, there were 276 correct answers, a 49.8% success rate corresponding almost exactly to the 50% that would have been expected by chance guessing
alone. The authors commented:
This conclusion is contentious among a large segment of audio engineers who work with high resolution material and many within the audiophile community. Some have questioned the basic methodology and the equipment used in the AES study.
Double-blind listening tests
in 2004 between DSD and 24-bit, 176.4 kHz PCM recordings reported that among test subjects no significant differences could be heard. DSD advocates and equipment manufacturers continue to assert an improvement in sound quality above PCM 24-bit 176.4 kHz. Despite both formats' extended frequency responses, it has been shown people cannot distinguish audio with information above 21 kHz from audio without such high-frequency content.
(DSD), 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.
Direct Stream Transfer compression was also standardized as an amendment to MPEG-4 Audio standard (ISO/IEC
14496-3:2001/Amd 6:2005 - Lossless coding of oversampled audio) in 2005. It contains the DSD and DST definitions as described in the Super Audio CD Specification. The MPEG-4 DST provides lossless coding of oversampled audio signals. Target applications of DST is archiving and storage of 1-bit oversampled audio signals and SA-CD.
A reference implementation of MPEG-4 DST was published as ISO/IEC 14496-5:2001/Amd.10:2007 in 2007.
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 are 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 is legitimate. Because the majority of DVD players and all DVD-ROM drives use an optical pickup that lacks this specialized watermark detection circuitry, although they can read the data on the SACD layer, they cannot decode the audio of a protected SACD disc.
On hybrid SACD discs, PSP is only applied to the SACD layer, not to the CD layer.
features at the physical level which, for the moment, appear to make SACD discs difficult 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
. But there is software available which allows ripping/copying a SACD using an early Sony PlayStation 3 Console.
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.
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.
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
optical disc
Optical disc
In computing and optical disc recording technologies, an optical disc is a flat, usually circular disc which encodes binary data in the form of pits and lands on a special material on one of its flat surfaces...
for audio storage. Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
and Philips Electronics
Philips
Koninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....
jointly developed the technology, and publicized it in 1999. It is designated as the Scarlet Book
Rainbow Books
The Rainbow Books are a collection of standards defining the formats of Compact Discs.Red BookYellow BookThe Rainbow Books are a collection of standards defining the formats of Compact Discs.Red Book...
standard. Sony and Philips previously collaborated to define the Compact Disc
Compact Disc
The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...
standard (as well as the S/PDIF
S/PDIF
S/PDIF is a digital audio interconnect used in consumer audio equipment over relatively short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fiber optic cable with TOSLINK connectors. S/PDIF interconnects components in home theaters and other digital high...
digital audio cable specification). SACDs allow greater dynamic range
Dynamic range
Dynamic range, abbreviated DR or DNR, is the ratio between the largest and smallest possible values of a changeable quantity, such as in sound and light. It is measured as a ratio, or as a base-10 or base-2 logarithmic value.-Dynamic range and human perception:The human senses of sight and...
and may hold more playing time than CDs.
Super Audio CD technology
SACD is capable of encoding recorded audio in either stereophonic soundStereophonic sound
The term Stereophonic, commonly called stereo, sound refers to any method of sound reproduction in which an attempt is made to create an illusion of directionality and audible perspective...
or surround sound
Surround sound
Surround sound encompasses a range of techniques such as for enriching the sound reproduction quality of an audio source with audio channels reproduced via additional, discrete speakers. Surround sound is characterized by a listener location or sweet spot where the audio effects work best, and...
. Although SACD audio streams are encoded in a pulse-density modulation
Pulse-density modulation
Pulse-density modulation, or PDM, is a form of modulation used to represent an analog signal with digital data. In a PDM signal, specific amplitude values are not encoded into pulses of different size as they would be in PCM. Instead, it is the relative density of the pulses that corresponds to...
(PDM) scheme called Direct Stream Digital
Direct Stream Digital
Direct-Stream Digital is the trademark name used by Sony and Philips for their system of recreating audible signals which uses pulse-density modulation encoding, a technology to store audio signals on digital storage media which is used for the Super Audio CD .The signal is stored as delta-sigma...
(DSD), a manufacturer may also write a Pulse-code modulation
Pulse-code modulation
Pulse-code modulation is a method used to digitally represent sampled analog signals. It is the standard form for digital audio in computers and various Blu-ray, Compact Disc and DVD formats, as well as other uses such as digital telephone systems...
(PCM) "layer" compatible with conventional Compact Disc player
Compact disc player
A Compact Disc player , or CD player, is an electronic device that plays audio Compact Discs. CD players are often a part of home stereo systems, car audio systems, and personal computers. They are also manufactured as portable devices...
s.
SACD is a disc of identical physical dimensions to a standard compact disc; the density of the disc is the same as a DVD
DVD
A DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than Compact Discs while having the same dimensions....
and it encodes audio using a process known as Direct Stream Digital
Direct Stream Digital
Direct-Stream Digital is the trademark name used by Sony and Philips for their system of recreating audible signals which uses pulse-density modulation encoding, a technology to store audio signals on digital storage media which is used for the Super Audio CD .The signal is stored as delta-sigma...
. The SACD sampling rate is 2.8224 MHz and the resolution is one bit. A stereo SACD recording can stream data at an uncompressed rate of 5.6 Mbit/s, four times the rate for Red Book
Red Book (audio CD standard)
Red Book is the standard for audio CDs . It is named after one of the Rainbow Books, a series of books that contain the technical specifications for all CD and CD-ROM formats.The first edition of the Red Book was released in 1980 by Philips and Sony; it was adopted by the Digital Audio Disc...
CD stereo audio. SACD recordings can have a wider frequency and dynamic range than conventional CDs.
| CD | SACD | |
|---|---|---|
| Format | 16 bit PCM Pulse-code modulation Pulse-code modulation is a method used to digitally represent sampled analog signals. It is the standard form for digital audio in computers and various Blu-ray, Compact Disc and DVD formats, as well as other uses such as digital telephone systems... |
1 bit DSD Direct Stream Digital Direct-Stream Digital is the trademark name used by Sony and Philips for their system of recreating audible signals which uses pulse-density modulation encoding, a technology to store audio signals on digital storage media which is used for the Super Audio CD .The signal is stored as delta-sigma... |
| Sampling frequency | 44.1 kHz | 2.8224 MHz |
| Dynamic range | 96 dB | 120 dB |
| Frequency range | 20 Hz – 20 kHz | 20 Hz – 50 kHz |
| Disc capacity | 700 MB | 7.95 GB |
| Stereo | Yes | Yes |
| Discrete surround | Never implemented Four-channel compact disc digital audio Compact Disc recordings contain two channels of 44.1-kHz 16-bit linear PCM audio. However, creators of the CD originally contemplated a four-channel, or quadraphonic, mode as well.... |
Yes |
There are three types of SACDs:
- Hybrid: Hybrid SACDs are encoded with a 4.7 GB DSD layer (also known as the HD layer), as well as a PCM (Red Book) audio layer readable by most conventional Compact Disc players.
- Single-layer: A DVD-5 encoded with one 4.7 GB DSD layer. Single-layer SACDs are not backward-compatible with conventional CD players.
- Dual-layer: A DVD-9 encoded with two DSD layers, totaling 8.5 GB, and no PCM layer. Dual-layer SACDs can store nearly twice as much data as a single-layer SACD. Like single-layer SACDs, dual-layer discs are not backward-compatible with conventional CD players.
Almost all commercially released SACDs have included both stereo (dual-channel) and surround sound (multi-channel) mixes. A multi-channel mix need not be surround, however; some of the Living Stereo reissues (such as the RCA
RCA
RCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. The RCA trademark is currently owned by the French conglomerate Technicolor SA through RCA Trademark Management S.A., a company owned by Technicolor...
reissue of the 1957 Chicago Symphony Orchestra
Chicago Symphony Orchestra
The Chicago Symphony Orchestra is an American orchestra based in Chicago, Illinois. It is one of the five American orchestras commonly referred to as the "Big Five". Founded in 1891, the Symphony makes its home at Orchestra Hall in Chicago and plays a summer season at the Ravinia Festival...
recording of Mussorgsky
Mussorgsky
Mussorgsky can refer to:*The Mussorgsky family of Russian nobility;*Modest Mussorgsky, a Russian composer belonging to that family.*Mussorgsky , a 1950 Soviet film about the composer...
's Pictures at an Exhibition
Pictures at an Exhibition
Pictures at an Exhibition is a suite in ten movements composed for piano by Russian composer Modest Mussorgsky in 1874.The suite is Mussorgsky's most famous piano composition, and has become a showpiece for virtuoso pianists...
) use only the three front channels to reproduce the original three-track (3.0) stereo recordings. Nor is a surround mix obliged to use all six SACD channels (five full-range plus LFE). For example, the 2001 SACD release of Mike Oldfield
Mike Oldfield
Michael Gordon Oldfield is an English multi-instrumentalist musician and composer, working a style that blends progressive rock, folk, ethnic or world music, classical music, electronic music, New Age, and more recently, dance. His music is often elaborate and complex in nature...
's Tubular Bells
Tubular Bells
Tubular Bells is the debut record album of English musician Mike Oldfield, released in 1973. It was the first album released by Virgin Records and an early cornerstone of the company's success...
remains in the quadraphonic
Quadraphonic
Quadraphonic sound – the most widely used early term for what is now called 4.0 surround sound – uses four channels in which speakers are positioned at the four corners of the listening space, reproducing signals that are independent of one another...
4.0 mix.
The CD layer exists primarily for backward compatibility, but is not required. If the CD layer is omitted, the SACD need not be limited to an 80-minute playing time. For stereo material, the space that would have been taken by the multi-channel program can be used to extend playing time to four hours or more. BIS
BIS Records
BIS Records is a record label founded in 1973 by Robert von Bahr. It is located in Åkersberga, Sweden.BIS focuses on classical music, both contemporary and early, especially works that are not already well represented by existing recordings....
has taken advantage of this to put all of Bach's organ music on five SACD-only disks.
SACD adoption
The Super Audio CD format was originally introduced in 1999. Royal Philips Electronics and Crest DigitalCrest Digital
Crest Digital is a privately owned company specializing in post production and DVD/CD replication. Crest Digital provides editing, DVD and Blu-Ray authoring, digital asset management, audio mixing, language dubbing and subtitling, and DVD/CD optical media replication services...
partnered in May 2002 to develop and install the first SACD hybrid disc production line in the USA, with a production capacity of 3 million discs per year. But SACD did not achieve the same explosive growth that Compact Discs enjoyed in the 1980s, and was not accepted by the mainstream market. By 2008, some considered the Super Audio CD a complete failure. However, the format continues to thrive in the audiophile community, and new SACD recordings and players continue to be made.
Despite the global decline in Compact Disc sales, sales of Super Audio CDs and players increased in 2010.
Content
By October 2009, record companies had published more than 6,000 SACD releases, slightly more than half of which were European classical music. JazzJazz
Jazz is a musical style that originated at the beginning of the 20th century in African American communities in the Southern United States. It was born out of a mix of African and European music traditions. From its early development until the present, jazz has incorporated music from 19th and 20th...
and popular music albums, mainly remastered previous releases, were the next two most numerous genres represented.
Record companies issue most SACDs as backward-compatible hybrid discs. Such a disc can be played in high-resolution audio on a SACD player and conventional Red Book CD or DVD video players (albeit just with standard CD quality). The SACD format is thus backward compatible. SACD machines can play CDs and SACD discs; CD players can play SACD hybrid discs as audio CDs.
Artist releases
Many popular artists have released some or all of their back catalog on SACD. Pink FloydPink Floyd
Pink Floyd were an English rock band that achieved worldwide success with their progressive and psychedelic rock music. Their work is marked by the use of philosophical lyrics, sonic experimentation, innovative album art, and elaborate live shows. Pink Floyd are one of the most commercially...
's album The Dark Side of the Moon
The Dark Side of the Moon
The Dark Side of the Moon is the eighth studio album by English progressive rock band Pink Floyd, released in March 1973. It built on ideas explored in the band's earlier recordings and live shows, but lacks the extended instrumental excursions that characterised their work following the departure...
sold over 800,000 copies by June 2004 in its SACD Surround Sound edition. The Who
The Who
The Who are an English rock band formed in 1964 by Roger Daltrey , Pete Townshend , John Entwistle and Keith Moon . They became known for energetic live performances which often included instrument destruction...
's rock opera Tommy
Tommy
Tommy is a given name that is usually the English diminutive of Thomas. The name also could refer to:- People with the given name Tommy :* Tommy Alcedo , Venezuelan road cyclist* Tommy G...
, and Roxy Music
Roxy Music
Roxy Music was a British art rock band formed in 1971 by Bryan Ferry, who became the group's lead vocalist and chief songwriter, and bassist Graham Simpson. The other members are Phil Manzanera , Andy Mackay and Paul Thompson . Former members include Brian Eno , and Eddie Jobson...
's Avalon, were released on SACD to take advantage of the format's multi-channel capability. All three albums were remixed in 5.1 surround, and released as hybrid SACDs with a stereo mix on the standard CD layer.
Some popular artists have released new recordings on SACD. Sales figures for Sting's Sacred Love
Sacred Love
Sacred Love is the seventh studio album by Sting. The album was released on 30 September 2003. The album featured smoother, R&B-style beats and experiments collaborating with hip-hop artist Mary J. Blige and sitar player Anoushka Shankar...
album reached number one on SACD sales charts in four European countries in June 2004.
As of May 2009, over 440 labels have released one or more SACDs. Instead of depending on major label support, some orchestras and artists have released SACDs on their own. For instance, the Chicago Symphony Orchestra
Chicago Symphony Orchestra
The Chicago Symphony Orchestra is an American orchestra based in Chicago, Illinois. It is one of the five American orchestras commonly referred to as the "Big Five". Founded in 1891, the Symphony makes its home at Orchestra Hall in Chicago and plays a summer season at the Ravinia Festival...
started the Chicago Resound label to provide full support for high-resolution SACD hybrid discs, and the London Symphony Orchestra
London Symphony Orchestra
The London Symphony Orchestra is a major orchestra of the United Kingdom, as well as one of the best-known orchestras in the world. Since 1982, the LSO has been based in London's Barbican Centre.-History:...
established their own 'LSO Live' label.
Disc reading
Objective lenses in conventional CD players have a longer working distance, or focal lengthFocal length
The focal length of an optical system is a measure of how strongly the system converges or diverges light. For an optical system in air, it is the distance over which initially collimated rays are brought to a focus...
, 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 as a CD since there is no high-resolution layer.
Playback hardware
Hybrid Super Audio CDs (which include both CD and Super Audio CD layers) can be played on CD players. The SACD layer can be played only on a player that supports the SACD format. Not all SACD players support multi-channel playback—some are simply stereo.The Sony SCD-1 was a player which was introduced concurrently with the SACD format in 1999, at a price of approximately US$5,000. It weighed over 26 kg
Kilogram
The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...
(57 lb
Pound (mass)
The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...
). The SCD-1, no longer produced, was introduced before multi-channel SACDs existed and played two channel SACDs and Red Book CDs only.
Many electronics manufacturers, including Denon, Marantz, Pioneer and Yamaha offer SACD players. 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.
Sony
Sony
, commonly referred to as Sony, is a Japanese multinational conglomerate corporation headquartered in Minato, Tokyo, Japan and the world's fifth largest media conglomerate measured by revenues....
has made in-car Super Audio CD players.
Several brands have introduced (mostly high-end) Blu-ray Disc
Blu-ray Disc
Blu-ray Disc is an optical disc storage medium designed to supersede the DVD format. The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Blu-ray Discs contain 25 GB per layer, with dual layer discs being the norm for feature-length video discs...
players that are SACD-compatible.
SACD players are not permitted to offer an output carrying an unencrypted stream of Direct Stream Digital
Direct Stream Digital
Direct-Stream Digital is the trademark name used by Sony and Philips for their system of recreating audible signals which uses pulse-density modulation encoding, a technology to store audio signals on digital storage media which is used for the Super Audio CD .The signal is stored as delta-sigma...
(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
HDMI
HDMI is a compact audio/video interface for transmitting uncompressed digital data. It is a digital alternative to consumer analog standards, such as radio frequency coaxial cable, composite video, S-Video, SCART, component video, D-Terminal, or VGA...
(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 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 specifications DSD over HDMI feature. Most boutique manufacturers
Boutique Manufacturing
Boutique manufacturing is a method used for the custom production of certain products in limited quantities by hand or with a restricted level of automation. Products produced this way often include ceramics, furniture, amplifiers, yachts, boats, leather goods or watches and jewellery among others...
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.
PlayStation 3 and SACD playback
The first two generations of Sony's PlayStation 3PlayStation 3
The is the third home video game console produced by Sony Computer Entertainment and the successor to the PlayStation 2 as part of the PlayStation series. The PlayStation 3 competes with Microsoft's Xbox 360 and Nintendo's Wii as part of the seventh generation of video game consoles...
(PS3) game console were capable of reading SACD discs. Starting with the third generation (introduced October 2007), SACD playback was removed altogether.
For models that are capable of reading SACD, three output options exist:
- Using the AV output will give an analog stereo sound for SACD's that include a stereo track.
- Using HDMI will give access to multi-channel high-resolution PCM audio (converted from DSD).
- Using S/PDIFS/PDIFS/PDIF is a digital audio interconnect used in consumer audio equipment over relatively short distances. The signal is transmitted over either a coaxial cable with RCA connectors or a fiber optic cable with TOSLINK connectors. S/PDIF interconnects components in home theaters and other digital high...
will give digital stereo sound (of either the stereo track, or a subset of the multi-channel mix)
PS3 was capable of converting surround DSD to lossy 1.5 Mbit/s DTS for playback over S/PDIF using the 2.00 system software
PlayStation 3 system software
The PlayStation 3 system software is the updateable software and operating system of the PlayStation 3. The process of updating is almost identical to that of the PSP...
. The subsequent revision removed the feature. There is software available for creating a backup copy of a SACD using an older generation PlayStation 3.
Technical background
SACD audio is stored in a format called Direct Stream DigitalDirect Stream Digital
Direct-Stream Digital is the trademark name used by Sony and Philips for their system of recreating audible signals which uses pulse-density modulation encoding, a technology to store audio signals on digital storage media which is used for the Super Audio CD .The signal is stored as delta-sigma...
(DSD), which differs from the conventional Pulse-code modulation
Pulse-code modulation
Pulse-code modulation is a method used to digitally represent sampled analog signals. It is the standard form for digital audio in computers and various Blu-ray, Compact Disc and DVD formats, as well as other uses such as digital telephone systems...
(PCM) used by the compact disc
Compact Disc
The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...
or conventional computer audio systems.
DSD is 1-bit
Bit
A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...
, has a sampling rate of 2.8224 MHz, and makes use of noise shaping
Noise shaping
Noise shaping is a technique typically used in digital audio, image, and video processing, usually in combination with dithering, as part of the process of quantization or bit-depth reduction of a digital signal...
quantization
Quantization (sound processing)
In signal processing and digital audio, quantization is the process of approximating a continuous range of values by a relatively small set of discrete symbols or integer values...
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
Decibel
The decibel is a logarithmic unit that indicates the ratio of a physical quantity relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities...
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 70–90 kHz, and practical limits reduce this to 50 kHz.
Because of the nature of sigma-delta converters
Delta-sigma modulation
Delta-sigma modulation is a method for encoding high-resolution or analog signals into lower-resolution digital signals. The conversion is done using error feedback, where the difference between the two signals is measured and used to improve the conversion...
, one cannot make a direct technical comparison between DSD and PCM. DSD's frequency response can be as high as 100 kHz, but frequencies that high compete with high levels of ultrasonic quantization noise
Quantization error
In analog-to-digital conversion, the difference between the actual analog value and quantized digital value is called quantization error or quantization distortion. This error is either due to rounding or truncation...
. With appropriate low-pass filter
Low-pass filter
A low-pass filter is an electronic filter that passes low-frequency signals but attenuates signals with frequencies higher than the cutoff frequency. The actual amount of attenuation for each frequency varies from filter to filter. It is sometimes called a high-cut filter, or treble cut filter...
ing, a frequency response
Frequency response
Frequency response is the quantitative measure of the output spectrum of a system or device in response to a stimulus, and is used to characterize the dynamics of the system. It is a measure of magnitude and phase of the output as a function of frequency, in comparison to the input...
of 50 kHz can be achieved along with a dynamic range of 120 dB. This is about the same resolution as PCM audio with a bit depth of 20 bits and a sampling frequency of 96 kHz. Thus, DSD looks inferior to a "standard" PCM 24bit/96 kHz even using slightly more bandwidth than PCM (2.8224 Mbit/s vs 2.304 Mbit/s).
Audible differences compared to PCM/CD
In the audiophile community, the sound from the SACD format is thought to be significantly better compared to older format Red Book CD recordings. However, In September 2007, the Audio Engineering SocietyAudio Engineering Society
Established in 1948, the Audio Engineering Society draws its membership from amongst engineers, scientists, other individuals with an interest or involvement in the professional audio industry. The membership largely comprises engineers developing devices or products for audio, and persons working...
published the results of a year-long trial in which a range of subjects including professional recording engineers were asked to discern the difference between SACD and compact disc
Compact Disc
The Compact Disc is an optical disc used to store digital data. It was originally developed to store and playback sound recordings exclusively, but later expanded to encompass data storage , write-once audio and data storage , rewritable media , Video Compact Discs , Super Video Compact Discs ,...
audio (44.1 kHz/16 bit) under double blind test conditions. Out of 554 trials, there were 276 correct answers, a 49.8% success rate corresponding almost exactly to the 50% that would have been expected by chance guessing
Statistical significance
In statistics, a result is called statistically significant if it is unlikely to have occurred by chance. The phrase test of significance was coined by Ronald Fisher....
alone. The authors commented:
Now, it is very difficult to use negative results to prove the inaudibility of any given phenomenon or process.
There is always the remote possibility that a different system or more finely attuned pair of ears would reveal a difference. But we have gathered enough data, using sufficiently varied and capable systems and listeners, to state that the burden of proof has now shifted. Further claims that careful 16/44.1 encoding audibly degrades high resolution signals must be supported by properly controlled double-blind tests.
This conclusion is contentious among a large segment of audio engineers who work with high resolution material and many within the audiophile community. Some have questioned the basic methodology and the equipment used in the AES study.
Double-blind listening tests
ABX test
An ABX test is a method of comparing two kinds of sensory stimuli to identify detectable differences. A subject is presented with two known samples , and one unknown sample X, for three samples total. X is randomly selected from A and B, and the subject identifies X as being either A or B...
in 2004 between DSD and 24-bit, 176.4 kHz PCM recordings reported that among test subjects no significant differences could be heard. DSD advocates and equipment manufacturers continue to assert an improvement in sound quality above PCM 24-bit 176.4 kHz. Despite both formats' extended frequency responses, it has been shown people cannot distinguish audio with information above 21 kHz from audio without such high-frequency content.
DST
To reduce the space and bandwidth requirements of Direct Stream DigitalDirect Stream Digital
Direct-Stream Digital is the trademark name used by Sony and Philips for their system of recreating audible signals which uses pulse-density modulation encoding, a technology to store audio signals on digital storage media which is used for the Super Audio CD .The signal is stored as delta-sigma...
(DSD), a lossless data compression
Lossless data compression
Lossless data compression is a class of data compression algorithms that allows the exact original data to be reconstructed from the compressed data. The term lossless is in contrast to lossy data compression, which only allows an approximation of the original data to be reconstructed, in exchange...
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.
Direct Stream Transfer compression was also standardized as an amendment to MPEG-4 Audio standard (ISO/IEC
International Electrotechnical Commission
The International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...
14496-3:2001/Amd 6:2005 - Lossless coding of oversampled audio) in 2005. It contains the DSD and DST definitions as described in the Super Audio CD Specification. The MPEG-4 DST provides lossless coding of oversampled audio signals. Target applications of DST is archiving and storage of 1-bit oversampled audio signals and SA-CD.
A reference implementation of MPEG-4 DST was published as ISO/IEC 14496-5:2001/Amd.10:2007 in 2007.
Pit Signal Processing
SACD includes various copy protectionCopy protection
Copy protection, also known as content protection, copy obstruction, copy prevention and copy restriction, refer to techniques used for preventing the reproduction of software, films, music, and other media, usually for copyright reasons.- Terminology :Media corporations have always used the term...
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 are 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 is legitimate. Because the majority of DVD players and all DVD-ROM drives use an optical pickup that lacks this specialized watermark detection circuitry, although they can read the data on the SACD layer, they cannot decode the audio of a protected SACD disc.
On hybrid SACD discs, PSP is only applied to the SACD layer, not to the CD layer.
Copy protection
SACD has several copy protectionCopy protection
Copy protection, also known as content protection, copy obstruction, copy prevention and copy restriction, refer to techniques used for preventing the reproduction of software, films, music, and other media, usually for copyright reasons.- Terminology :Media corporations have always used the term...
features at the physical level which, for the moment, appear to make SACD discs difficult to copy without resorting to the analog hole
Analog hole
The analog hole is a fundamental and inevitable vulnerability in copy protection schemes for noninteractive works in digital formats which can be exploited to duplicate copy-protected works that are ultimately reproduced using analog means...
, or ripping of the conventional 700MB layer on hybrid discs. These include physical pit modulation and 80-bit encryption
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
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
Shizuoka Prefecture
is a prefecture of Japan located in the Chūbu region on Honshu island. The capital is the city of Shizuoka.- History :Shizuoka prefecture was formed from the former Tōtōmi, Suruga and Izu provinces.The area was the home of the first Tokugawa Shogun...
and Salzburg
Salzburg
-Population development:In 1935, the population significantly increased when Salzburg absorbed adjacent municipalities. After World War II, numerous refugees found a new home in the city. New residential space was created for American soldiers of the postwar Occupation, and could be used for...
. But there is software available which allows ripping/copying a SACD using an early Sony PlayStation 3 Console.
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
Digital Transmission Content Protection
Digital Transmission Content Protection, or DTCP, is a digital rights management technology that aims to restrict "digital home" technologies including DVD players and televisions by encrypting interconnections between devices...
(DTCP), which can be used in "Copy Once" or "Copy Never" modes.
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 formatAudio formatAn audio format is a medium for storing sound and music. The term is applied to both the physical recording media and the recording formats of the audio content – in computer science it is often limited to the audio file format, but its wider use usually refers to the physical method used to...
- Audio storage
- DualDiscDualDiscDualDisc was a type of double-sided optical disc product developed by a group of record companies including EMI Music, Universal Music Group, Sony/BMG Music Entertainment, Warner Music Group, and 5.1 Entertainment Group and later under the aegis of the Recording Industry Association of America...
- DVD-AudioDVD-AudioDVD-Audio is a digital format for delivering high-fidelity audio content on a DVD. DVD-Audio is not intended to be a video delivery format and is not the same as video DVDs containing concert films or music videos....
- 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 CDBlu-spec CDBlu-spec CD describes an Audio CD manufactured by a proprietary process introduced by Sony Music Entertainment Japan in late 2008. Its name derives from the similar manufacturing process to that used to create Blu-ray Discs. Instead of a traditional infra-red laser, a blue laser is used for...
.
External links
- Super Audio Compact Disc: A Technical Proposal, Sony (archived PDF)
- SA-CD.net Reviews of SACD releases and a discussion forum.
- SA-CD Faq
- New SACD releases Sony website.