Direct stream number? (? DSD？ ) are trademarks used by Sony and Philips for their systems, for super audio CDs? (SACD) is digitally encoded.

The signal itself is stored as digital audio modulated by Δ σ, and the continuous single-bit sequence is sampled at the frequency of 64 times the CD sampling rate (44. 1 kHz), that is, 2.8224 MHz.

Noise shaping is realized by 64 times oversampling, thus reducing the noise and loss caused by inaccurate quantization of acoustic and audio signals to an error of less than one bit. Whether sigma-delta operation of 1 bit can really solve the loss problem is debatable.

Because of the operation mode of 1 bit sigma-delta transform, the resolution of DSD-encoded sound is better than PCM in low and medium frequency bands, and the phase error at high frequency is extremely low, but the dynamics at high frequency are worse than PCM.

DSD and PCM?

There has been a great controversy between supporters of DSD and PCM about which coding system is better. In 200 1, Lipshitz and Vanderkooy said that the one-bit converter used in DSD is not suitable for high-end applications because of its high distortion. In 2002, Philips published a paper and put forward the opposite view.

Angus further criticized the papers of Lipshits and Van der Kuyt. Lipshitz and Vanderkooy responded to the criticism. Stuart also defined sigma-delta modulation as a "completely inappropriate choice" for high-resolution digital audio.

The traditional implementation of DSD has inherent high distortion. Using multi-bit DAC can reduce distortion to some extent. The most advanced ADC is based on sigma-delta modulation design. Oversampling converters are usually used in linear PCM format, where the output of ADC or DAC is affected by bandwidth limitation and jitter.

Most modern ADC and DAC converters adopt oversampling and multi-bit design; In other words, although DSD is in 1 bit format, modern converters use 2-bit to 6-bit format internally.