PLParEQ is a 10-band Phase-Linear Parametric Equalizer of the highest
quality. Each filter may assume any of many different filter
characteristics, and operate in either traditional phase-warping mode,
or our phase-linear mode. It uses the same internal DSP core as all of
our other high-end products. Audio streams are treated in either stereo
or mono. Individual filters can be applied to either both stereo
channels, middle only, or side only.

This PC VST plugin can operate in traditional 32-bit mode (24-bit
audio) or as a 64-bit plugin for Cakewalks new Sonar 5. All internal
processing is carried out in double-precision 64-bit floating point,
regardless of external host mode.

For audio streams at sample rates below 80 kHz the DSP engine
internally upsamples with high-quality Sinc interpolation, applies its
filtering, and then downsamples back to your system sample rate.


Available filter types include all of the conventional resonant 2-pole
lowpass, highpass, bandpass, band-reject, all-pass, high and low
shelving, and the three Oxford variants of peaking/dipping filters.
Also included are 1-pole lowpass and highpass, 4-pole resonant
Butterworth lowpass and highpass, 6-pole notch for killing 50/60 Hz and
other troublesome spurs (very tight and narrow), 1/F pinking filter,
tunable 1/F lowpass (-3 dB/octave), tunable F-highpass (+3 dB/octave),
and A, B, and C weighting filters. The list of filters continues to
grow as we identify more useful variations.

You can run all of the filters at native sample rates higher than 80
kHz, and forego the internal upsampling conversions. Upper limits on
the sample rate (> 96 kHz) are dicted primarily by your computer's
capacity, and your need for high quality at the very lowest frequencies
(below 100 Hz).

Individual filters can be operated as either traditional phase-warping,
or phase-linear. Our algorithms employ blocked processing for phase
-linear operation, and produce phase linearity by sending the signal
through each filter twice - once in the forward time direction, and
then again the the time reversed direction, thereby unwinding the phase
back to zero.

The blocks are reassembled using very high-quality windowing and 8-fold
temporal overlap. IMD resulting from phase-linear operation has been
measured as -120 dB from peak signal levels. (IMD test measurements*)
Corner frequencies for filters can be adjusted from 10 Hz to 30 kHz at
all sample rates.

Computation proceeds in double-precision floating point throughout the
entire DSP core, which uses 56-bit mantissas and 80-bit intermediate
products and sums. At the last stage of conversion back to 24-bit
audio, we dither with a carefully crafted white-Gaussian dither from
the 56-bit mantissas to the 24-bit mantissas utilized thorughout by VST
hosts. Our noise floor is typically measured at around -180
dB/Root(Hz). The Gaussian dither distribution is provably more
preserving than more commonly used triangular distributions.

Our tests indicate that PLParEQ requires about 5-6% of our computer
speed capacity, with each additional filter enabled requiring an
additional 0.5-1% at the highest quality levels. These tests were
performed on a 3 GHz Pentium-4 computer with HyperThreading enabled.
Different VST hosts will show varying requirements. Our tests were
performed with Mackie's Tracktion 2 as the VST host. Performance on a
more modern Pentium IV are likely to show improvements upon these
results.

*(IMD test measurement statistics - The signal was a -0.5 dBFS 1 kHz
sinewave at 44.1 kHz SR. The filtering was performed as a Q=20 phase
-linear bandpass filter centered at 1 kHz with unity gain, and using
the highest quality setting = largest resampling blocksize.

The test chart exhibits a spectral resolution of 0.67 Hz, with the IMD
spurs spaced by 43.1 Hz. The signal was internally upsampled to 88.2
kHz for filter application, then downsampled back to 44.1 kHz for final
output.)





more info available at:

http://refinedaudiometrics.com

Download File Size:3.63 MB

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