Physical Modelling Swift Library

• Author: Alexandros Gounis

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Filters: (declared in filters.swift)

This class implements the standard difference equation that defines how the output signal is calculated both from current and previous samples from the input and the output signal.

Difference Equation

• y[n] : output signal
• x[n] : input signal
  • n ⋲ {0, 1, 2, ...}

y[n] = 1/a[0]*(b[0]*x[n] + b[1]*x[n-1]... + b[nb]*x[n-nb]
- a[1]*y[n-1] - a[2]*y[n-2]... - a[na]*y[n-na])

Functions:

• PassThrough(): trivial function for pass through filtering, x[n] = y[n]
• SetFilter: For setting the filter's coefficients
• Clear(): For clearing the filter's coefficients by setting 0 everywhere
• Compute: For computing the current output sample

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Delay lines: (declared in DelayLines.swift)

This class creates, modifies and processes fractional delay lines. By using linear interpolation between two successive samples, one can use this class for accurate physical modelling of musical instruments.

• Author: Alexandros Gounis

Functions:

• Create: create a delay line of Maximum delay, SetDelay is used automatically
• Clear: clear the delay line by placing 0 everywhere
• SetDelay: provide a delay and a Maximum and set or change the delay
• Compute: calculate the next output, that is to feed the delay line with a sample (float) and return the delayed output

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Files	Functionality
Filters.swift	Create IIR filters defining the standard difference equation
DelayLines.swift	Create fractional delay lines by linear interpolation
FFT.swift	(to be added)