Direct Stream Digital

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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
Usage	Audio recording
Extended to	present
Released	1999

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 delta-sigma modulation, a form of pulse-density modulation encoding, a technique to represent audio signals in digital format, a sequence of single-bit values at a sampling rate of 2.8224 MHz. This is 64 times the CD audio sampling rate of 44.1 kHz, but with 1-bit samples instead of 16-bit samples. Noise shaping of the 64-times oversampled signal provides low quantization noise and low distortion in the audible bandwidth necessary for high resolution audio.

DSD is simply a format for storing a delta-sigma signal without applying a decimation process that converts the signal to a PCM signal.