Direct Stream Digital

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2022-08-06 00:30:07

Direct Stream Digital (DSD) is a trademark used by Sony and Philips for their system for digitally encoding audio signals for the Super Audio CD (SACD).

DSD uses pulse-density modulation encoding - a technology to store audio signals on digital storage media which are used for the SACD. The signal is stored as delta-sigma modulated digital audio, which is 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 {\displaystyle {\tfrac {1}{32768}}} of its 16-bit resolution). Noise shaping occurs by use of the 64-times 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.[1]

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 first described by C.C. Cutler in 1954,[2] but was not named as such until a 1962 paper by Inose et al. Decimation did not initially exist and oversampled data was sent as-is. The proposal to decimate oversampled delta-sigma data before converting it into PCM audio was made by D. J. Goodman in 1969.[3]