H D C D
P R O C E S S O V E R V I E W
HDCD Encoding Process
Analog to Digital Conversion
Signal Analysis and Delay Memory
Decimation Filter Selection, Reduction to 44.1 kHz
Thus, fixed-filter 44.1-kHz decimation often sounds very different from the original analog or high sampling frequency digital master. In contrast, the HDCD processors' real-time analysis allows the anti-alias filter's transition band characteristics to be dynamically optimized to preserve the program signal's content—reducing distortion and producing a more sonically accurate 44.1-kHz signal.
Amplitude Encoding/Gain Structure
- Peak Extend is a reversible soft limiter that allows the engineer to increase the peak signal level by up to 6 dB without "overs." These peaks are precisely reconstructed when decoded, increasing dynamic range by 6 dB. For undecoded playback, Peak Extend provides all the advantages of an excellent limiter.
- Low Level Range Extend gradually increases the gain on low-level signals (starting at -45 dBfs) by 4 dB over a 20-dB range. Decoded playback reverses the added gain, providing low-level resolution beyond 16 bits. For undecoded playback, the increased gain compensates for the lack of low-level resolution in inexpensive CD playback systems, producing a sound more like the original high-resolution master.