---
title: vDSP_fft_zrip
framework: Kernel
role: symbol
role_heading: Function
platforms: [macOS 10.0+]
path: kernel/1579997-vdsp_fft_zrip
---

# vDSP_fft_zrip

Computes a forward or inverse in-place, single-precision real FFT.

## Declaration

```occ
void vDSP_fft_zrip(FFTSetup __Setup, const DSPSplitComplex *__C, vDSP_Stride __IC, vDSP_Length __Log2N, FFTDirection __Direction);
```

## Parameters

- `__Setup`: The FFT setup structure for this transform. The setup’s structure Log2N must be greater than or equal to this function’s Log2N.
- `__C`: A pointer to the input-output data.
- `__IC`: The stride between the elements in C, set to 1 for best performance.
- `__Log2N`: The base 2 exponent of the number of elements to process. For example, to process 1024 elements, specify 10 for parameter Log2N.
- `__Direction`: A flag that specifies the transform direction. Pass doc://com.apple.documentation/documentation/kernel/1645049-anonymous/kfftdirection_forward to transform from the time domain to the frequency domain. Pass doc://com.apple.documentation/documentation/kernel/1645049-anonymous/kfftdirection_inverse to transform from the frequency domain to the time domain.

## Discussion

Discussion Forward transforms read real input and write packed complex output. Inverse transforms read packed complex input and write real output. As a result of packing the frequency-domain data, time-domain data and its equivalent frequency-domain data have the same storage requirements. You can find more details on the packing format in Data Packing for Real FFTs in vDSP Programming Guide.

where F is Direction, C is C, and N is two raised to the power of Log2N. See also functions vDSP_create_fftsetup and vDSP_destroy_fftsetup.