Hdcd Indicator; Peak Extension And Hdcd Limiting - Pacific Microsonics HDCD Model Two User Manual

Reference
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Model Two HDCD User's Manual
resolution signal, which is then output in the correct form for the D/A converter being
used. Decoding can be performed by the Pacific Microsonics PMD-200 HDCD decoder DSP
ASIC, other ASIC's including a one chip HDCD decoder and 24-bit D/A converter from Burr-
Brown, and HDCD coded DSP based chips from Motorola, Analog Devices, Zoran, Mediamatics,
Crystal Semiconductor and others.
There are two subsets to the HDCD process, 16-bit amplitude domain encoding and time
domain encoding. The Model Two provides the option of turning off decoding of the 16-bit
amplitude domain functions of the HDCD process for monitoring purposes. This is done in
either the Second Operating Menu, Levels Menu, or Monitor Setup Menu. See pages 41 -
43, and 61 for additional information. Time domain decoding is automatic with HDCD
decoder filtering and cannot be turned off.

HDCD Indicator

The HDCD Indicator on the Model Two consists of a blue or amber LED back lit HDCD logo.
For additional information, see the HDCD Indicator description on page 18.

Peak Extension and HDCD Limiting

Peak Extension is normally used when converting analog or high resolution 24-bit or 20-
bit digital signals to HDCD 16-bit amplitude encoded signals. Peak Extension is a digital
soft limiter, with a curve that mimics analog tape saturation, except that on decoding the
peaks are restored. Peak Extension can be used for several purposes: to provide headroom
to capture occasional peaks or as a method to raise the average signal level to create a
"hot" recording. Peak extension allows raising the average level of a recording as much as
6 dB without overload. Of course, like any limiter, if overused it can produce audible
distortion when not decoded. Decoding restores the limited peaks, eliminating any distor-
tion that might be audible. Therefore, whenever peak extension is used, the output should
be monitored with HDCD 16-bit amplitude decoding both on and off to determine how
much peak extension is appropriate. Peak Extension does not need to be used when the
original program material has limited dynamic range.
HDCD Limiting is identical to Peak Extension except HDCD Limiting is not undone by HDCD
playback decoding, and is used for its limiting effect with all types of playback.
The Model Two HDCD Processor has Peak Extension Meters which indicate the extended
dynamic range available when in HDCD Peak Extension or HDCD Limiting modes. The Peak
Extension meters are only active when monitoring HDCD 16-bit amplitude encoded signals
that contain peak extension. With HDCD Limiting, the Peak Extension Meters only indicate
during recording. Peak Extension and HDCD Limiting can be turned On or Off in the Second
Operating Menu or the Digital Output HDCD Setup Menu. The default is Off. See pages 35,
P A C I F I C M I C R O S O N I C S I N C .
Rev. C - January 2002
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