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DSD(Direct Stream Digital) The sampling technique used in Sony's high-resolution SACD music format. Although SACD discs never took off and new ones are few and far between, the DSD format is used to encode music for high-quality downloads. Increasingly, Blu-ray players and music servers can decode the format. Digital DSD files use DFF and DSF extensions, the latter holding meta-data.
From 44 Thousand to Millions of Samples
For standard CDs, music is digitized 44.1 thousand times per second, producing 16-bit PCM samples. In contrast, DSD uses pulse density modulation (PDM) to encode 2,822,400 1-bit samples per second (64 times the CD sampling rate). Each DSD sample is a 1 or 0 (either up or down from the previous sample). Compared to CDs, DSD boosts frequency response from 20 kHz to 100 kHz and dynamic range from 96 to 120 db. See PCM, PDM and CD.
Even Higher Sampling Rates
No longer confined to a physical disc, DSD resolutions have gone beyond SACD (see table below). The DSD's one-bit sampling generates a very low signal-to-noise ratio, and "noise shaping" shifts the noise to a high frequency that is filtered out before the final output. The advantage to higher sampling is that the noise is spread out over a wider frequency band, and the filtering can be relaxed. High-end DSD players offer multiple filtering modes to accommodate high-res DSD files. See SACD, DSD DAC, DXD, signal-to-noise ratio and high-resolution audio.
MultiplesDSD of CD Number ofFormat Samples ---1-Bit Samples--- SACD (DSD64) 64 2,822,400 (2.8 MHz) Double-rate (DSD128) 128 5,644,800 (5.6 MHz) Quad-rate (DSD256) 256 11,289,600 (11.2 MHz) Octuple-rate (DSD512) 512 22,579,920 (22.5 MHz)