Super audio compact disc
The Super Audio Compact Disc, SACD or SA-CD for short , is a data carrier and physically a special form of the Digital Versatile Disc ( DVD ) that was developed by Philips and Sony . The SACD uses a higher digital resolution of the audio signal than the audio CD and also offers the option of storing multi-channel sound ( surround sound ) without data reduction. It was designed as the successor to the audio CD (CD-DA) and has been in competition with DVD-Audio , which has comparable properties, for several years .
The audio material on the SACD is available in Direct Stream Digital (DSD) format. This differs from the pulse code modulation technology (PCM technology) used in audio CD or DVD audio . The so-called delta-sigma modulation is used for the direct stream digital format . The word length of the digitized audio signal is only 1 bit here , but with a sampling rate of 2.8224 MHz (64 × 44.1 kHz). In contrast to this, the audio data on a conventional audio CD is available in pulse code modulation with 16-bit resolution at a sampling rate of 44.1 kHz. Even if today mainly delta-sigma analog-digital converters are used for both codings , the two methods differ fundamentally in the type of signal processing. The anti-aliasing filter required for analog-to-digital conversion - it can lead to the filter ringing effect , especially with the relatively low sampling rate of the audio CD - can be significant at the much higher sampling rates of delta-sigma modulation be interpreted less disruptive. Also, when using the usual delta-sigma converters for analog-digital conversion, decimation filters can be dispensed with and interpolation filters for digital-analog conversion in the terminal.
According to advertising statements from Sony / Philips, due to
- the significantly higher sampling frequency ,
- a higher upper frequency (approx. 50,000 Hertz instead of 20,000 Hertz) and
- a dynamic range of over 120 dB
the SACD already sound better than a conventional audio CD in stereo playback - provided a high-quality recording and a very high-quality stereo system. Assumptions from the high-end sector that DSD is fundamentally superior to the PCM format have not yet been proven. The sound properties of the SACD can also be achieved with PCM technology if the resolution that determines the dynamics and the sampling frequency that is decisive for the frequency range are increased accordingly, for example to 24 bit at 176.4 kHz.
If you compare the underlying process of pulse-code modulation with that of the delta-sigma modulator (conventional delta-sigma analog-digital converter), the only difference is the lack of the sampling rate converter (downsampling) at the output of the delta-sigma Modulator: In the DSD format, the audio signal is stored with a small word length (1 bit) and a high sampling rate. The band limitation, which also suppresses the higher-frequency noise components, is integrated in conventional delta-sigma analog-to-digital converters (with PCM output) by means of digital filters immediately after the delta-sigma modulator during the sample rate conversion, while with the DSD Technology is only made later, namely with audio playback.
In addition, the SACD supports multi-channel sound ( surround sound ) with up to six channels. The SACD can - like the DVD-Audio - store high-resolution multi-channel sound without loss. Compression methods such as Dolby Digital or DTS , which are used for example in DVD-Video , only master this in the Dolby TrueHD and DTS-HD Master Audio variants , which were introduced later and are only used on Blu-ray Disc and HD DVD . The multi-channel sound track on the SACD is optional: some SACDs only contain a high-resolution stereo track, so they do not use the multi-channel option.
There are some SACD players that can only play stereo SACDs, but not multi-channel SACDs.
Similar to the MLP process of DVD-Audio , a lossless compression algorithm is also used with SACD. Before the SACD image is finalized, the DSD audio material is converted to DST ( Direct Stream Transfer ) format . The compression rate - and thus the maximum possible playing time - depends on the audio material. In purely mathematical terms, the maximum playing time is around 110 minutes (single layer and hybrid disc) or around 200 minutes (double layer). (2.8224 MHz, one bit per channel, results in stereo 5.6 Mbit / s or 700 kByte / s, single layer (SL) SACD 4.7 GByte or double layer (DL) SACD 8.5 GByte = SL 110 minutes or DL 200 minutes).
There are three different types of Super Audio CDs:
- Single Layer: contains a high-density (HD) layer and can only be played on SACD players.
- Dual Layer: contains a second HD layer for additional recording time and can only be played on SACD players.
- Hybrid Layer: In addition to the HD layer, it also contains a CD layer that can be read by conventional CD players
In hybrid disc technology, a CD and a DVD layer are applied to the disc. The DVD (SACD) layer is in front of that for the CD when viewed from the laser; it is transparent to light with a wavelength of 780 nm, which is used for CD scanning, and only reflects light with a wavelength of 650 nm, which is used for DVD scanning. It contains the audio data in SACD quality. The CD layer below contains the audio data in the format of the audio CD (16-bit, 44.1 kHz) and can be read out by standard CD players. Most SACDs are currently made using this process.
Apart from the CD layer that is also present in hybrid SACDs, which can be played and copied without any problems just like any audio CD, the high-resolution content of an SACD is protected from unwanted distribution by copy protection .
The SACD's copy protection method is extremely effective. It consists of several levels of protection: Pit Signal Processing (PSP) is a digital, invisible watermark that ensures the authenticity of the SACD. In the case of the pits in which the data is encoded, not only is the length evaluated, as is the case with DVD, but also the width in which the watermark is encoded. PSP can only be created in the mastering process.
The lead-in area of a SACD is encrypted and can only be decoded by a hardware component in SACD players. In addition, the audio data is encoded using content scrambling, and part of the key required for decoding is also here in the SACD hardware. Both measures prevent SACDs from being read out on standard DVD-ROM drives. Optionally, a visible watermark can be inserted on the data page using PSP.
The playback devices available up to now transmit the content stored on an SACD predominantly in analog form to the amplifier. However, the HDMI multimedia interface has also supported the digital transmission of DSD data since version 1.2.
The Super Audio Compact Disc (SACD) has been available on the market since 1999. The number of releases in pop and popular music is stagnating, there are hardly any new releases, and these are essentially remastered older albums. However, the SACD has been able to assert itself well as a high-quality audiophile sound carrier in the classical field to this day (2014). Every month albums with mostly multi-channel mixed new productions are released, for example from labels such as ARS Produktion, Audimax, Audite , BIS , Chandos , Cybele, EMI, Farao, Hänssler Classic , Harmonia Mundi , Hyperion , MDG , Musicaphon, Pentatone, Tacet and others . Sony, Marantz, Pioneer, Yamaha, T + A and Denon offer playback devices for SACDs, some in the form of SACD players, some as BD players.
The first generation players, which were presented to the public in the spring of 1999, were unsuitable for the mass market with retail prices of around US $ 5,000. It wasn't until a year later that audiophiles in Japan were able to acquire a player at affordable prices. It was not until a few years later that SACD technology became available and attractively priced for end customers worldwide.
In 2009, SACD players from numerous brands were available for less than 200 euros, some for less than 100 euros. There are now numerous so-called universal players that can handle most formats, including SACD. SACDs cannot be played on PC drives (with the exception of the CD layer of a hybrid SACD). The first revision of the PlayStation 3 from Sony played SACDs, newer models no longer do this.
The number of releases available on SACD was around 40 in the year of market launch and over 500 at the end of 2001. In 2009, around 4,500 to 5,000 titles were published on SACD, which is about five times the number of published DVD-Audio Title. Compared to the approximately 1,000 CD releases per month, this number is of little importance for the mass market.
This is confirmed by the sales in the first half of 2004, which were 100,000 copies across Germany. That's about 0.14% of total sales in any format. In the United States , the SACD is even less important, accounting for 0.09% of total sales, despite an absolute higher number of units sold (300,000) over the same period. (Sources: IFPI, RIAA)
The two formats SACD and DVD-Audio did not achieve a breakthrough, as was evident when switching from record to CD or from VHS cassette to DVD-Video . However, the SACD continues to play an important and growing role in the classical music sector due to its high-resolution multi-channel capability. Today almost all manufacturers equip their Blu-ray Disc multiplayer and many DVD players with the functions of DVD-Audio and SACD.
The first pure audio tracks have now been released on Blu-ray Disc (from the 2L label from Norway), and more such records are in the planning stage, for example from the CD sound critic Neil Young and the classic label MDG . However, the very high licensing requirements of the music rights holders currently prevent the widespread use of Blu-ray Disc as a pure audio format.
In the case of stereo recordings, objective listening tests show practically no differences between a high-quality conventional CD and a super audio CD, so that the better sound quality of super audio CDs compared to CDs, which was claimed due to the higher sampling rate and greater sampling depth , could not be confirmed . SACDs, however, offer the possibility of multi-channel recordings , with which an audible difference in the spatial sound reproduction can be achieved in a corresponding playback system.
- Rolf Seidelmann: Surround in the music studio . Wizoobooks, Bremen 2008, ISBN 978-3-934903-69-2 .
- Dominik Blech and Min-Chi Yang: Investigation into the auditory differentiability of digital recording methods. Aural comparison of direct stream digital and high-resolution PCM (24bit / 176.4kHz). Diploma thesis, reviewers: Rainer Maillard and Andreas Meyer, Erich-Thienhaus-Institut, Hochschule für Musik Detmold, 2004, online version at hfm-detmold.de
- E. Brad Meyer, David R. Moran: Audibility of a CD-Standard A / DA / A Loop Inserted into High-Resolution Audio Playback. Journal of the Audio Engineering Society, Volume 55, Issue 9, pp. 775-779; September 2007, AES E-Library
- ↑ Blech and Yang (2004), Section 2.3, http://old.hfm-detmold.de/eti/projekte/diplomarbeiten/2004/dsdpcm/23.htm
- ↑ Blech and Yang (2004), Section 7, http://old.hfm-detmold.de/eti/projekte/diplomarbeiten/2004/dsdpcm/fazit.htm
- ↑ http://www.dvddemystified.com/dvdfaq.html#3.6.1
- ↑ a b DVD Frequently Asked Questions, http://www.dvddemystified.com/dvdfaq.html#1.12 (as of 12/09)
- ↑ SA-CD.net http://www.sa-cd.net/faq#playback11
- ↑ Stiftung Warentest: There is simply no argument for it. Interview with Günther Theile. In: test 11/2003, test.de
- ↑ Stiftung Warentest: Super Audio: Only for bats. In: test 11/2003 , test.de
- General SACD FAQ
- HD audio FAQ
- The hi-fi magazine “Stereo” (August 2011): What will happen to the SACD?