Infinite Impulse Response (IIR) digital filter with
a single-stage polynomial (numerator-denominator) internal structure.
The filter can be designed off-line using a third-party application
(such as
MATLAB®
or
QEDesign®
), then imported to WaveWarp via a simple dialog box in the Parameter Window
(refer to the
WaveWarp Users' Guide
for
a detailed description of the specific IIR
single-stage polynomial
structure implemented in WaveWarp, and the
associated ASCII file format for storing the coefficients). For MATLAB users in
particular, the "wwmatlab" sub-directory of the WaveWarp root directory contains
the necessary function m-files (plus example scripts) for exporting
filters from MATLAB, enabling the seamless integration of
MATLAB's powerful filter design tools with WaveWarp's real-time audio engine.
Likewise, m-files are supplied for importing filters designed by WaveWarp into MATLAB
for off-line analysis (refer to the
WaveWarp Users' Guide
for
a summary of all bundled m-files for working with MATLAB
in a variety of areas in addition to digital filter design).
The controls available in the Parameter Window, are summarised in the following table.
Parameter
Purpose
"Load filter design from file" dialog
Imports an
arbitrary IIR filter (in polynomial format) from an ASCII file.
"Output gain" slider
Adjusts the amplitude of the output signal.
"Save filter design to file" dialog
Exports the
filter coefficients to an ASCII file (in polynomial format) for off-line analysis or for future import.
If the application specifically requires selective filtering at low frequencies, it is recommended to
employ multirate techniques, whereby the signal is downsampled before filtering.
The Multirate
category of the Component Library contains a wide range of downsamplers (and upsamplers) for this purpose.
All WaveWarp components automatically adapt to the sample rate of the incoming signal, so it is straightforward
to connect a digital filter component after a downsampler in order to realise the significant performance
gains inherent to multirate techniques
(refer to the
WaveWarp Users' Guide
for more information on WaveWarp's multirate signal processing functionality; and see
[CrRa]
and
[StNg]
for a detailed treatment
of multirate filtering.)
The mono audio input is filtered and sent to the mono audio output.
Single input single output mono-stereo
n/a
The mono audio input is filtered and sent (in duplicate) to the stereo audio output channels.
Single input single output stereo-mono
n/a
Each audio input channel is filtered separately (but with the same filter coefficients). The filtered channels are then averaged and sent to the mono audio output.
Single input single output stereo-stereo
n/a
Each audio input channel is filtered separately (but with the same filter coefficients) and sent to the separate stereo output channels.
