The Scarlet Book is Philips and Sony's 1999 specification document for Super Audio Compact Disc ( SACD ), a high-resolution audio format that features complex six-channel sound. SACD discs can contain three different versions of the same material.
SACD uses Direct Stream Digital (DSD) recording, a proprietary Sony technology that converts an analog waveform to a 1-bit signal for direct recording, instead of the pulse code modulation ( PCM ) and filtering used by standard CDs. DSD uses lossless compression (so-called because none of the data is lost in the compression process) and a sampling rate of 2.8 MHz to improve the complexity and realism of sound. DSD enables a frequency response of 100 kHz and a dynamic range of 120 dB (the ratio of the softest to the loudest sound - 120 db is also the approximate dynamic range of human hearing) on all channels.
Scarlet Book specifications include three separate options for disk format: single-layer DSD, dual-layer DSD, or dual-layer hybrid, which includes a Red Book layer that can be played on any existing CD player in addition to the high-density layer that has the capacity to deliver eight channels of DSD. In addition to DSD and the hybrid disk technology, Scarlet Book specifications include: Super Bit Mapping Direct , a proprietary downconversion method that enables improved audio when the disks are played on an ordinary CD player; Direct Stream Transfer, a type of coding that increases data capacity; and a digital watermark to protect against piracy.
According to some, SACD is a hybrid CD/DVD format, since Scarlet Book specifications are identical to those for DVD disks for the file system, sector size, error correction, and modultation . SACD is in competition with a similar product, DVD-Audio , as the format that will replace standard audio CD.