Spectral Transformers:

IMPORTANT: this spectral shaping is crude but computationally efficient. It can introduce significant distortion, depending on the spectral and temporal nature of the audio material being processed. This can lead to interesting audio effects, but may be unacceptable for a given application. If accurate filtering is required, refer to the Digital Filters category of the Component Library.

The attributes of the spectral shaper are adjustable via the Parameter Window, as summarised in the following table.

Parameter	Purpose
"Load shaping profile as wavetable from file" dialog	The shaping profile is imported in wavetable format from an ASCII file containing an arbitrary user-defined profile, and interpolated (to the appropriate length) via the selected "Interpolation" method. The shaping profile is displayed, versus frequency, in the plot window. The ASCII file format is described in the WaveWarp Users' Guide. This simple file structure enables files to be written by hand (e.g. via a text editor). For MATLAB® users, the process of creating shaping profiles is particularly straightforward. The "wwmatlab" sub-directory of the WaveWarp root directory contains the necessary function m-files (plus example scripts) for exporting wavetables from MATLAB, thereby providing ready access to MATLAB's powerful mathematical tools for creating elaborate waveforms. (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 waveform design).
"Depth" slider	Only activated when "Enable depth modulation" is selected, whereby the spectral weighting gains are confined to the range from 0 to 1. The "Depth" determines the fraction of this range over which the shaping profile is mapped. Maximum "Depth" (a value of 1) implies that the shaping profile will be mapped on to the entire range from 0 to 1, thereby maximising the spectral modifications. Minimum "Depth" (a value of 0) implies no mapping, thereby suppressing the spectral modifications. An intermediate value, say 0.2, implies that the shaping profile will be mapped on to the upper 20% of the output range, and so forth. The plot is automatically adjusted to reflect the selected "Depth". When "Enable depth modulation" is not selected, the shaping profile is used "as is" from the file (also reflected in the plot).
"Buffer length" slider	Adjusts the length of the input data buffer, which also defines the "Latency" (overall delay) of the process. The FFT buffer size is computed from the "Buffer length" rounded up to the nearest power of 2 (for efficient FFT computation). If "double zero-padding" is selected, the FFT buffer size is doubled (after the rounding) to improve the smoothness of the spectrum between successive FFT bins (but without increasing the underlying frequency resolution). The input data buffer is windowed (using a selected profile), then extended to the length of the FFT buffer by padding with zeros (on either side). Successive input data buffers are overlapped by a factor of 2, and the ouputs of the overlapped inverse transformed buffers are summed, in order to avoid discontinuities at the window boundaries.
"Window type" selection	Selects the profile of the windowing function applied to the input data.
"Output gain" slider	Adjusts the overall gain of the output signal, after the spectral manipulations have been applied.
"Save shaping profile as wavetable to file" dialog	Exports the current shaping profile to an ASCII file (in wavetable format) for future import or off-line analysis.

Algorithm

For an introduction to the Discrete Fourier Transform and the FFT, see, for example, [St] sections 4.1 and 4.2. For further introductory information (with emphasis on audio applications), and for discussions on spectral measurements, zero-padding, windowing, the overlap-add re-synthesis method, and the Short Time Fourier Transform (STFT) for audio applications, see [Roa] p. 1084-1112 and [Moore] p. 61-111.

Signal Implementations

• Brick Wall 1
• Brick Wall 2
• Brick Wall 3
• Brick Wall 4
• Controllable Brick Wall 1
• Controllable Brick Wall 2
• Controllable Brick Wall 3
• Controllable Brick Wall 4
• Controllable Spectral Morph 1
• Controllable Spectral Shift 1
• Convolution
• Spectral 3-Peak Detector
• Spectral Averaging
• Spectral Compressor
• Spectral Expander
• Spectral Gate
• Spectral Morph 1
• Spectral Peak Detector
• Spectral Shift 1
• Spectral Shift 2
• Spectral X-Synth 1
• Tracking 3-Peak Detector
• Tracking Peak Detector

• UserProgrammableSpectralShapingExample