vDSP_conv

Declaration

void vDSP_conv(const float *__A, vDSP_Stride __IA, const float *__F, vDSP_Stride __IF, float *__C, vDSP_Stride __IC, vDSP_Length __N, vDSP_Length __P);

Parameters

• __A:

  The real single-precision input signal vector. The length of this vector must be at least N + P - 1.

• __IA:

  The stride through the input signal vector, A.

• __F:

  The real single-precision filter vector.

• __IF:

  The stride through the filter vector, F.

• __C:

  The real single-precision output signal vector.

• __IC:

  The stride through the output signal vector, C.

• __N:

  The number of elements in the output signal vector, C.

• __P:

  The number of elements in the filter vector, F.

Discussion

Use this function to compute either the convolution or the correlation of an input signal and a filter vector. Both operations compute the sliding dot product of the filter and the section of the input signal that the filter is over. Specify a positive stride through the filter to perform correlation and a negative stride through the filter to perform convolution. When you perform convolution, the __F parameter must point to the last element in the filter.

The function can run in place, but C can’t be in place with F. For example, the following code defines an input signal, a filter, and the number of output elements:

let signal: [Float] = [1, 2, 3, 4, 5, 6, 7, 8]

let filter: [Float] = [10, 20, 30]

let outputCount = signal.count - filter.count + 1