DSBuffer

public class DSBuffer

Fixed-length buffer for windowed signal processing

Initializer and deinitializer

  • Initializer

    Tips:

    • If you do not need to perform FFT on the buffer, set fftIsSupperted to be false could save 50% memory.
    • If you need to perform FFT, set buffer size to power of 2 could accelerate more.

    Declaration

    Swift

    init(_ size: Int, fftIsSupported: Bool = true)

    Parameters

    size

    Buffer length. If you set fftIsSupperted to be true, the size should be number
    fftIsSupported

    Whether FFT will be performed on the buffer

    Return Value

    DSBuffer object

Regular operations

  • Push new value to buffer (and the foremost will be dropped)

    Declaration

    Swift

    func push(_ value: Float)

    Parameters

    value

    New value to be added

  • Get data by index

    Declaration

    Swift

    func dataAt(_ index: Int) -> Float

  • Get Buffer size

    Declaration

    Swift

    var bufferSize: Int

  • Dump buffer as array

    Declaration

    Swift

    var data: [Float]

  • Reset buffer to be zero filled

    Declaration

    Swift

    func clear()

  • Print buffer

    Declaration

    Swift

    func printBuffer(dataFormat: String)

Vector-like operations

  • Add value to each buffer data

    Declaration

    Swift

    func add(value: Float) -> [Float]

  • Multiply each buffer data with value

    Declaration

    Swift

    func multiply(value: Float) -> [Float]

  • Modulus by value of each buffer data

    Declaration

    Swift

    func mod(value: Float) -> [Float]

  • Remove mean value

    Declaration

    Swift

    var centralized: [Float]

  • Normalize vector to have unit length

    Declaration

    Swift

    func normalizedToUnitLength(centralized: Bool) -> [Float]

    Parameters

    centralized

    Should remove mean?

  • Normalize vector to have unit variance

    Declaration

    Swift

    func normalizedToUnitVariance(centralized: Bool) -> [Float]

    Parameters

    centralized

    Should remove mean?

  • Perform dot production with array

    Declaration

    Swift

    func dotProduct(with: [Float]) -> Float

Time-domain features

  • Mean value

    Declaration

    Swift

    var mean: Float
  • sum

    Mean value

    Declaration

    Swift

    var sum: Float

  • Vector length

    Declaration

    Swift

    var length: Float

  • Square of length

    Declaration

    Swift

    var energy: Float
  • max

    Max value

    Declaration

    Swift

    var max: Float
  • min

    Min value

    Declaration

    Swift

    var min: Float

  • Variance

    Declaration

    Swift

    var variance: Float
  • std

    Standard deviation

    Declaration

    Swift

    var std: Float

FFT

  • Perform FFT

    Note for FFT related methods:

    • Set fftIsSupported to true when creating the buffer.
    • Buffer size should be even. If you pass odd size when creating the buffer, it is automatically increased by 1.
    • Only results in nfft/2+1 complex frequency bins from DC to Nyquist are returned.

    Declaration

    Swift

    func fft() -> (real: [Float], imaginary: [Float])

  • FFT sample frequencies

    Declaration

    Swift

    func fftFrequencies(fs: Float) -> [Float]

    Return Value

    array of size nfft/2+1

  • FFT magnitudes, i.e. abs(fft())

    Declaration

    Swift

    func fftMagnitudes() -> [Float]

    Return Value

    array of size nfft/2+1

  • Square of FFT magnitudes, i.e. (abs(fft()))^2

    Declaration

    Swift

    func squaredPowerSpectrum() -> [Float]

    Return Value

    array of size nfft/2+1

  • Mean-squared power spectrum, i.e. (abs(fft()))^2 / N

    Declaration

    Swift

    func meanSquaredPowerSpectrum() -> [Float]

    Return Value

    array of size nfft/2+1

  • Power spectral density (PSD), i.e. (abs(fft()))^2 / (fs*N)

    Declaration

    Swift

    func powerSpectralDensity(fs: Float) -> [Float]

    Return Value

    array of size nfft/2+1

  • Average power over specific frequency band, i.e. mean(abs(fft(from…to))^2)

    Declaration

    Swift

    func averageBandPower(fromFreq: Float = 0, toFreq: Float, fs: Float) -> Float

FIR filter

  • Undocumented

    Declaration

    Swift

    public class DSBuffer

  • Get latest FIR output

    Declaration

    Swift

    func latestFIROutput() -> Float

  • FIR filtered buffer

    Declaration

    Swift

    func FIRFiltered() -> [Float]