---
title: vDSP_blkman_windowD
framework: accelerate
role: symbol
role_heading: Function
path: accelerate/vdsp_blkman_windowd
---

# vDSP_blkman_windowD

Creates a double-precision Blackman window.

## Declaration

```occ
extern void vDSP_blkman_windowD(double *__C, vDSP_Length __N, int __Flag);
```

## Parameters

- `__C`: The output vector.
- `__N`: The number of elements in the output vector.
- `__Flag`: A value that specifies whether the function creates a half window or a full window. Pass the doc://com.apple.documentation/documentation/kernel/1645052-anonymous/vdsp_half_window flag to create only the first (N+1)/2 points; pass 0 to create a full-size window.

## Discussion

Discussion The vDSP_blkman_window and vDSP_blkman_windowD functions create a Blackman window vector using the following operation: for (n=0; n < N; ++n) {     C[n] = 0.42 - (0.5 * cos(  2 * pi * n / N ) ) +              (0.08 * cos( 4 * pi * n / N) ); } The following code shows how to generate a Blackman window. let n = vDSP_Length(1024)

var c = [Float](repeating: 0,                 count: Int(n))

vDSP_blkman_window(&c,                    n,                    0) The following illustrates the values of the output vector, c:

## See Also

### Vector generation with window functions

- [Reducing spectral leakage with windowing](accelerate/reducing-spectral-leakage-with-windowing.md)
- [vDSP_blkman_window](accelerate/vdsp_blkman_window.md)
- [vDSP_hamm_window](accelerate/vdsp_hamm_window.md)
- [vDSP_hamm_windowD](accelerate/vdsp_hamm_windowd.md)
- [vDSP_hann_window](accelerate/vdsp_hann_window.md)
- [vDSP_hann_windowD](accelerate/vdsp_hann_windowd.md)
- [vDSP_HALF_WINDOW](accelerate/vdsp_half_window.md)
- [vDSP_HANN_DENORM](accelerate/vdsp_hann_denorm.md)
- [vDSP_HANN_NORM](accelerate/vdsp_hann_norm.md)