Direct Stream Digital
 |
|
| Media type | Audio recording process Disc format |
|---|---|
| Encoding | Digital |
| Read mechanism | DSD |
| Write mechanism | Super Audio CD |
| Standard | ISO/IEC 14496-3 |
| Developed by |
Sony Philips |
| Usage | Audio recording |
| Extended from | 1999 |
| Extended to | present |
DSD Records (DSD) is the name of a trademark used by Sony and Philips for their system of digitally recreating audible signals for the Super Audio CD (SACD).
DSD uses pulse-density modulation encoding—a technology to store audio signals on digital storage media that are used for the SACD. The signal is stored as delta-sigma modulated digital audio; a sequence of single-bit values at a sampling rate of 2.8224 MHz (64 times the CD audio sampling rate of 44.1 kHz, but only at 1/32768 of its 16-bit resolution). Noise shaping occurs by use of the 64-timed oversampled signal to reduce noise and distortion caused by the inaccuracy of quantization of the audio signal to a single bit. Therefore, it is a topic of discussion whether it is possible to eliminate distortion in one-bit delta-sigma conversion.
DSD is a method of storing a delta-sigma signal before applying a "decimation" process that converts the signal to a PCM signal. Delta-sigma conversion was originally described in patent 2,927,962, filed by C.C. Cutler in 1954, but was not named as such until a 1962 paper by Inose et al. Previously, decimation had not existed and the intention was to have oversampled data sent as-is. Indeed, the first proposal to decimate oversampled delta-sigma data to convert it into PCM audio did not appear until 1969, in D.J. Goodman's paper "The Application of Delta Modulation of Analog-to-PCM encoding".
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