 | |
 Reverse side of a hybrid SACD. Unlike a CD, the reflection has a gold hue. | |
| Media type | Optical disc |
|---|---|
| Encoding | Digital (DSD) |
| Capacity | 4.38 GiB (4.7 GB) single layer and hybrid 7.92 GiB (8.5 GB) dual layer |
| Read mechanism | 650 nm laser (780 nm for the CD layer of a hybrid disc) |
| Standard | Scarlet Book |
| Developed by | Sony andPhilips |
| Usage | Audio storage |
| Extended from | Compact Disc Digital Audio |
| Released | 1999; 27 years ago (1999) |
Super Audio CD (SACD) is anoptical disc format foraudio storage introduced in 1999. It was developed jointly bySony andPhilips Electronics and intended to be the successor to thecompact disc (CD) format.
The SACD format allows multiple audio channels (i.e.,surround sound or multichannel sound). It also provides a higher bit rate and longer playing time than a conventional CD.
An SACD is designed to be played on an SACD player. Ahybrid SACD contains aCompact Disc Digital Audio (CDDA) layer and can also be played on a standard CD player.
The Super Audio CD format was introduced in 1999,[1] and is defined by theScarlet Book standard document.Philips andCrest Digital partnered in May 2002 to develop and install the first SACD hybrid disc production line in the United States, with a production capacity of up to three million discs per year.[2] SACD did not achieve the level of growth that compact discs enjoyed in the 1980s,[3] and was not accepted by the mainstream market.[4][5][6]
By 2007, SACD had failed to make a significant impact in the marketplace; consumers were increasingly downloading low-resolution music files over the internet rather than buying music on physical disc formats.[1] A small and niche market for SACD has remained, serving theaudiophile community.[7]
Many popular artists have released some or all of their back catalog on SACD.Pink Floyd's albumThe Dark Side of the Moon (1973) sold over 800,000 copies by June 2004 in its SACD Surround Sound edition.[8]The Who's rock operaTommy (1969), andRoxy Music'sAvalon (1982), were released on SACD to take advantage of the format's multi-channel capability. All three albums were remixed in5.1 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 forSting'sSacred Love (2003) album reached number one on SACD sales charts in four European countries in June 2004.[8]
Between 2007 and 2008, the rock bandGenesis re-released all of their studio albums across three SACD box sets. Each album in these sets contains both new stereo and 5.1 mixes. The original stereo mixes were not included. The US and Canada versions do not use SACD but CD instead.
By August 2009, 443 labels had released one or more SACDs.[9]
Many SACD discs that were released from 2000 to 2005 are now out of print and available only on the used market.[7][10] By 2009, the major record companies were no longer regularly releasing discs in the format, with new releases confined to the smaller labels.[11]
| Characteristic | CD layer (optional) | SACD layer |
|---|---|---|
| Disc capacity | 700 MB[12] | 4.7 GB[13] |
| Audio encoding | 16-bitpulse-code modulation | 1-bitDirect Stream Digital |
| Sampling frequency | 44.1 kHz | 2,822.4 kHz (2.8224 MHz) |
| Audio channels | 2 (stereo) | Up to 6 (discrete surround) |
| Playback time if stereo | 80 minutes[14] | 110 minutes without DST compression[13] |
SACD discs have identical physical dimensions as standard compact discs. Theareal density of the disc is the same as aDVD. There are three types of disc:[13]
A stereo SACD recording has an uncompressed rate of 5.6 Mbit/s, four times the rate forRed Book CD stereo audio.[13]
Commercial releases commonly include both surround sound (five full-range plusLFE multi-channel) and stereo (dual-channel) mixes on the SACD layer.[citation needed] Some reissues retain the mixes of earlier multi-channel formats (examples include the 1973quadraphonic mix ofMike Oldfield'sTubular Bells and the 1957 three-channel stereo recording by theChicago Symphony Orchestra ofMussorgsky'sPictures at an Exhibition, reissued on SACD in 2001 and 2004 respectively).
Objective lenses in conventional CD players have a longer working distance, orfocal length, than lenses designed for SACD players. In SACD-capable DVD, Blu-ray and Ultra HD Blu-ray players, the red DVD laser is used for reading SACDs.[citation needed] This means that when a hybrid SACD is placed into a conventional CD player, the infrared laser beam passes through the SACD layer and is reflected by the CD layer at the standard 1.2 mm distance, and the SACD layer is out of focus. When the same disc is placed into an SACD player, the red laser is reflected by the SACD layer (at 0.6 mm distance) before it can reach the CD 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 SACD layer.[13][16]
SACD audio is stored inDirect Stream Digital (DSD) format usingpulse-density modulation (PDM), where audio amplitude is determined by the varying proportion of 1s and 0s. This contrasts withcompact disc and conventional computer audio systems usingpulse-code modulation (PCM,) where audio amplitude is determined by numbers encoded in the bit stream. Both modulations require neighboring samples to reconstruct the original waveform; the more neighboring samples, the lower the frequency that can be encoded.
DSD is1-bit, has a sampling rate of 2.8224 MHz, and makes use ofnoise shapingquantization techniques in order to push 1-bit quantization noise up to inaudible ultrasonic frequencies. This gives the format a greaterdynamic 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 available players list an upper limit of 70–90 kHz,[17] and practical limits reduce this to 50 kHz.[13] Because of the nature ofsigma-delta converters, DSD and PCM cannot be directly compared. DSD's frequency response can be as high as 100 kHz, but frequencies that high compete with high levels of ultrasonicquantization noise.[18] With appropriatelow-pass filtering, afrequency response of 20 kHz can be achieved along with a dynamic range of nearly 120 dB, which is about the same dynamic range as PCM audio with a resolution of 20 bits.[citation needed]
To reduce the space and bandwidth requirements of DSD, alossless data compression method calledDirect Stream Transfer (DST) is used. DST compression is compulsory for multi-channel regions and optional for stereo regions. It 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.[19]
Direct Stream Transfer compression was standardized as an amendment to theMPEG-4 Audio standard,ISO/IEC 14496-3:2001/Amd 6:2005 (Lossless coding of oversampled audio), in 2005.[20][21] It contains the DSD and DST definitions as described in the Super Audio CD Specification.[22] The MPEG-4 DST provides lossless coding of oversampled audio signals. Target applications of DST are archiving and storage of1-bit oversampled audio signals and SA-CD.[23][24][25]
Areference implementation of MPEG-4 DST was published as ISO/IEC 14496-5:2001/Amd.10:2007 in 2007.[26][27]
SACD has severalcopy protection features at the physical level, which made the digital content of SACD discs difficult to copy until thejailbreak of the PlayStation 3. The content may be copyable without SACD quality by resorting to theanalog hole, or ripping the conventional 700 MB layer on hybrid discs. Copy protection schemes include physical pit modulation and 80-bitencryption of the audio data, with a key encoded on a special area of the disc 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, and SACDs can only be manufactured at the disc replication facilities inShizuoka andSalzburg.[28][29]
Nonetheless, very early versions of thePlayStation 3 with an SACD-compatible drive and appropriate firmware[30] and certain Blu-ray players[31][32] can use specialized software to extract aDSD copy of the HD stream.
Sound quality parameters achievable by the Red BookCD-DA and SACD formats compared with the limits of human hearing are as follows:
In September 2007, the Audio Engineering Society published the results of a year-long trial, in which a range of subjects—including professional recording engineers—were asked to discern the difference betweenhigh-resolution audio sources (including SACD andDVD-Audio) and a compact disc audio (44.1 kHz/16 bit) conversion of the same source material underdouble-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 bychance guessing alone.[36] When the level of the signal was elevated by 14 dB or more, the test subjects were able to detect the highernoise floor of the CD-quality loop easily. The authors commented:[37]
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.
Following criticism that the original published results of the study were not sufficiently detailed, the AES published a list of the audio equipment and recordings used during the tests.[38] Since the Meyer–Moran study in 2007,[39] approximately 80 studies have been published on high-resolution audio, about half of which included blind tests.Joshua Reiss performed a meta-analysis on 20 of the published tests that included sufficient experimental detail and data. In a paper published in the July 2016 issue of the AES Journal,[40] Reiss says that, although the individual tests had mixed results, and that the effect was "small and difficult to detect," the overall result was that trained listeners could distinguish between high-resolution recordings and their CD equivalents under blind conditions: "Overall, there was a small but statistically significant ability to discriminate between standard-quality audio (44.1 or 48 kHz, 16 bit) and high-resolution audio (beyond standard quality). When subjects were trained, the ability to discriminate was far more significant." Hiroshi Nittono pointed out that the results in Reiss's paper showed that the ability to distinguish high-resolution audio from CD-quality audio was "only slightly better than chance."[41]
Contradictory results have been found when comparing DSD and high-resolution PCM formats.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.[42] DSD advocates and equipment manufacturers continue to assert an improvement in sound quality above PCM 24-bit 176.4 kHz.[43] A 2003 study found that despite both formats' extended frequency responses, people could not distinguish audio with information above 21 kHz from audio without such high-frequency content.[44] In a 2014 study, however, Marui et al. found that under double-blind conditions, listeners were able to distinguish between PCM (192 kHz/24 bits) and DSD (2.8 MHz) or DSD (5.6 MHz) recording formats, preferring the qualitative features of DSD, but could not discriminate between the two DSD formats.[45]
In 1999, the Sony SCD-1 player was introduced concurrently with the SACD format, at a price of approximately US$5,000 (equivalent to $9,400 in 2024).[46] It weighed over 26 kilograms (57 lb; 4.1 st) and played two-channel SACDs andRed Book CDs only. Electronics manufacturers, includingOnkyo,[47]Denon,[48]Marantz,[49][50]Pioneer,[51][52] andYamaha,[53] offer or offered SACD players.Sony has made in-car SACD players.[54]
In order to play back SACD content digitally without any conversion, some players are able to offer an output carrying encrypted streams of DSD, either viaIEEE 1394[55] or more commonly,HDMI.[56]
SACD players are not permitted to offer an output carrying an unencrypted stream of DSD.[57]
The first two generations of Sony's PlayStation 3 game console were capable of reading SACD discs. Starting with the third generation (introduced October 2007), SACD playback was removed.[58] All PlayStation 3 models, however, will play DSD Disc format. The PlayStation 3 was capable of converting multi-channel DSD tolossy 1.5 Mbit/sDTS for playback overS/PDIF using the 2.00system software. The subsequent revision removed the feature.[59]
Several brands have introduced (mostlyhigh-end)Blu-ray Disc andUltra HD Blu-ray players that can play SACD discs.[60]
Unofficial playback of SACDdisc images on a PC is possible throughfreewareaudio playerfoobar2000 forWindows using theopen source plug-in extension SACDDecoder.[61]macOS music software Audirvana also supports playback of SACD disc images.[62]
{{citation}}: CS1 maint: numeric names: authors list (link){{cite web}}: CS1 maint: numeric names: authors list (link){{cite web}}: CS1 maint: numeric names: authors list (link)i.LINK section, Format (output)
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