---
title: vDSP_biquad
framework: accelerate
role: symbol
role_heading: Function
path: accelerate/vdsp_biquad
---

# vDSP_biquad

Applies a single-precision single-channel biquadratic IIR filter.

## Declaration

```occ
extern void vDSP_biquad(const struct vDSP_biquad_SetupStruct *__Setup, float *__Delay, const float *__X, vDSP_Stride __IX, float *__Y, vDSP_Stride __IY, vDSP_Length __N);
```

## Parameters

- `__Setup`: The doc://com.apple.documentation/documentation/kernel/vdsp_biquad_setup object defining the filter to apply.
- `__Delay`: An array of single-precision values initialized with direct-form 1 “past” state data for each section of the biquad. The length of the array should be (2 * M) + 2, where M is the number of sections. For each section m, Delay[2*m:2*m+1] represent the two delayed input values for section m and Delay[2*M:2*M+1] represent the two delayed output values of the filter. After this function executes, this array contains the final state data of the filters.
- `__X`: An array of single-precision input data for the channel.
- `__IX`: Stride for X.
- `__Y`: An array to be filled with single-precision output data for the channel.
- `__IY`: Stride forY.
- `__N`: The number of elements to filter.

## Discussion

Discussion This function applies a cascaded biquad filter to the input values in X, and places the results in Y. The state contained in the setup object is updated upon return.

## See Also

### Applying a single-channel biquadratic filter

- [vDSP_biquadD](accelerate/vdsp_biquadd.md)