Editing Super Audio CD (section)

=== Direct Stream Digital ===
{{Main|Direct Stream Digital}}

SACD audio is stored in [[Direct Stream Digital]] (DSD) format using [[pulse-density modulation]] (PDM) where audio amplitude is determined by the varying proportion of 1s and 0s. This contrasts with [[compact disc]] and conventional computer audio systems using [[pulse-code modulation]] (PCM) where audio amplitude is determined by numbers encoded in the bit stream. Both modulations require neighboring samples to reconstruct the original waveform; the more neighboring samples, the lower the frequency that can be encoded.

DSD is [[1-bit DAC|1-bit]], has a sampling rate of 2.8224&nbsp;[[MHz]], and makes use of [[noise shaping]] [[Quantization (signal processing)|quantization]] techniques in order to push 1-bit quantization noise up to inaudible ultrasonic frequencies. This gives the format a greater [[dynamic range]] and wider frequency response than the CD. The SACD format is capable of delivering a dynamic range of 120&nbsp;[[decibel|dB]] from 20&nbsp;Hz to 20&nbsp;kHz and an extended frequency response up to 100&nbsp;kHz, although most available players list an upper limit of 70–90&nbsp;kHz,<ref name="Reefman"/> and practical limits reduce this to 50&nbsp;kHz.<ref name=extremetech2001/> Because of the nature of [[Delta-sigma modulation|sigma-delta converters]], DSD and PCM cannot be directly compared. DSD's frequency response can be as high as 100&nbsp;kHz, but frequencies that high compete with high levels of ultrasonic [[quantization noise]].<ref name="ambisonic2001"/> With appropriate [[low-pass filter]]ing, a [[frequency response]] of 20&nbsp;kHz can be achieved along with a dynamic range of nearly 120&nbsp;dB, which is about the same dynamic range as PCM audio with a resolution of 20 bits.{{citation needed|date=August 2013}}