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# vDSP_biquadD

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

```
extern void vDSP_biquadD(const struct vDSP_biquad_SetupStructD *__Setup, double *__Delay, const double *__X, vDSP_Stride __IX, double *__Y, vDSP_Stride __IY, vDSP_Length __N);
```

## Parameters

`__Setup`

The <doc://com.apple.documentation/documentation/kernel/vdsp_biquad_setupd> object defining the filter to apply.

`__Delay`

An array of double-precision values initialized with “past” state data (elements -2 and -1) for each section of the biquad. After this function executes, this array contains the final state data of the filters. See Discussion below.

`__X`

An array of double-precision input data for the channel.

`__IX`

Stride for `X`.

`__Y`

An array to be filled with double-precision output data for the channel.

`__IY`

Stride for `Y`.

`__N`

The number of elements to filter.

## Discussion

This function is the same as [`vDSP_biquad`](/documentation/Accelerate/vDSP_biquad), except for the types of arrays `Delay`, `X`, and `Y`.

---

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