Voxengo Correlometer User Guide
Version 1.2
https://www.voxengo.com/product/correlometer/
Voxengo Correlometer User Guide
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Contents
Introduction 3
Features 3
Compatibility 3
User Interface Elements 4
Parameters 4
What is Correlation? 4
Credits 6
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Introduction
Correlometer is a free analog-style stereo multi-band correlation meter plug-in for
professional music production applications. It is based on correlation meter found in
PHA-979 phase-alignment plugin.
Multi-band correlation meter is an advanced way to check for presence of out-ofphase elements in the mix. Broadband correlation metering reports overall phase
issues and may misrepresent problems present in select spectral bands, while multiband correlation meter easily highlights problems present in mid to high frequencies
that are not easily heard by ear, but may still reduce clarity of the mix. Another
application of multi-band correlation metering is phase- and time-aligning of
channels and tracks, especially bass and bass-drum pairs, guitar mic and D.I. source
pairs, two-microphone stereo recordings, etc.
Correlometer can display 4 to 64 individual spectral bands, with adjustable band
quality factor that controls the degree of band’s selectivity. Averaging time of
correlation estimator can be adjusted. Correlometer supports side-chain inputs for
easy correlation estimation between separate audio tracks.
Features
4 to 64 band correlation meter
Adjustable band quality factor
Adjustable averaging time
Side-chain input
Resizable user interface
All sample rates support
Zero processing latency
Compatibility
This audio plug-in can be loaded into any audio host application that conforms to the
AAX, AudioUnit, VST or VST3 plug-in specification.
This plug-in is compatible with Windows (32- and 64-bit Windows XP, Vista, 7, 8, 10
and later versions, if not announced otherwise) and macOS (10.8 and later versions,
if not announced otherwise, 64-bit Intel processor-based) computers (2.5 GHz dualcore or faster processor with at least 4 GB of system RAM required). A separate
binary distribution file is available for each target computer platform and audio plugin specification.
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User Interface Elements
Note: Most interface elements (buttons, labels) located on the top of the user
interface and on the bottom are standard among all Voxengo plug-ins and do not
require much learning effort. For an in-depth description of these and other
standard user interface elements and features please refer to the “Voxengo Primary
User Guide”. Learned once it will allow you to feel comfortable with all pro audio
plug-ins from Voxengo.
Parameters
Correlation meter works by splitting the incoming signal into bands. Band-splitting
is performed by means of an array of band-pass filters (the Q factor of the filters
depends on the number of bands and the “B/width” parameter). This correlation
meter can be called an “analog-style” correlation meter.
The “Pri” parameter selects primary signal source.
The “Sec” parameter selects secondary signal source. You may select side-chain
inputs here.
If either “Pri” or “Sec” parameter refers to a non-existent or equal channel the
correlation meter will display 1.0 constant for all bands.
The “Scale” selector chooses vertical (correlation value) scale range. The “Full”
option displays the full correlation range (-1.0 to 1.0), the “Pos” option focuses on
positive correlation values (0.0 to 1.0), the “Neg” option focuses on negative
correlation values (-1.0 to 0.0), the “Null” option focuses on null-correlation values (-
0.25 to 0.25).
The “Avg Time” parameter specifies correlation estimation averaging or “window”
time in milliseconds. Note that this is full time required to change from one
stationary correlation value to another. Correlation value changes by 80% in half of
this time period.
The “Bands” parameter selects the number of spectral bands to split the signal into.
The “B/width” parameter adjusts the quality factor (bandwidth) of each band, affects
signal selectivity of the bands. The “Wide” setting is the widest width and least
selectivity, the “Narrow” setting is the narrowest width and most selectivity.
What is Correlation?
As you probably already know, correlation between two independent signals is
defined in the range between -1.0 and 1.0, inclusive. If correlation is close to 1.0
between any two signals, it can be said that signals are “in-phase” (0 degree phase
difference). If correlation is close to -1.0 the signals are “out of phase” (180 degree
phase difference). Correlation values close to 0.0 usually tell that any two signals
have no correlation and so they may either be 90 degree apart or significantly delayed
relative to each other, or both.
Correlation between two sinusoidal signals is equal to mathematical cosine of the
phase difference between these signals.
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Note that while simple sinusoidal stationary (constant) signals require only phase
rotation to change correlation value, musical signals and signals which are complex in
their nature may require time alignment (delaying) as well. Correlation of any signal
with any independent (uncorrelated) noise signal is always 0.0 and cannot be
changed with phase nor time alignment.
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Credits
DSP algorithms, internal signal routing code, user interface layout by Aleksey Vaneev.
Graphics user interface code by Vladimir Stolypko. Graphics elements by Vladimir
Stolypko and Scott Kane.
This plug-in is implemented in multi-platform C++ code form and uses “zlib”
compression library (written by Jean-loup Gailly and Mark Adler), “LZ4”
compression library by Yann Collet, filter design equations by Magnus Jonsson, VST
plug-in technology by Steinberg, AudioUnit plug-in SDK by Apple, Inc., AAX plug-in
SDK by Avid Technology, Inc., Intel IPP and run-time library by Intel Corporation
(used under the corresponding licenses granted by these parties).
Voxengo Correlometer Copyright © 2019 Aleksey Vaneev.
VST is a trademark and software of Steinberg Media Technologies GmbH.
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