---
title: vDSP_biquadD
framework: accelerate
role: symbol
role_heading: Function
path: accelerate/vdsp_biquadd
---

# vDSP_biquadD

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

## Declaration

```occ
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

Discussion This function is the same as vDSP_biquad, except for the types of arrays Delay, X, and Y.

## See Also

### Applying a single-channel biquadratic filter

- [vDSP_biquad](accelerate/vdsp_biquad.md)