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# vDSP_biquad

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

```
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 for`Y`.

`__N`

The number of elements to filter.

## 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.

---

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