# vDSP_deq22 Performs two-pole two-zero recursive filtering on a single-precision vector. ``` extern void vDSP_deq22(const float *__A, vDSP_Stride __IA, const float *__B, float *__C, vDSP_Stride __IC, vDSP_Length __N); ``` ## Parameters `__A` Single-precision real input vector. `__IA` Stride for `A`. `__B` 5 single-precision inputs (filter coefficients), with stride 1. `__C` Single-precision real output vector. `__IC` Stride for `C`. `__N` Number of new output elements to produce. ## Discussion This function creates `N` new values in output vector `C`, beginning with its third element. It performs two-pole two-zero recursive filtering on input vector `A`, which must contain at least `N` + 2 values; `C` must also contain at least `N` + 2 values. Since the computation is recursive, the first two elements in `C` must be initialized prior to calling this function. This function can only be done out of place.  --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)