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The DirectX SDK (June 2010) release includes a little utility header, XDSP.H. This contains CPU-based functions for computing the Fast Fourier Transform (FFT) as well as some related multi-channel audio interleave/deinterleave functionality primarily used in writing custom xAPOs for XAUDIO2. The DirectX SDK version makes use of SSE intrinsics, which means it supports Windows x86 and x64 native code generation. This header is not included in the Windows SDK 8.0 (see “Where is the DirectX SDK?“). If writing a custom xAPO for Metro style applications, you also likely want to support the Windows on ARM platform as well.

Attached to this post is a version of XDSP.H that uses DirectXMath and compiles for x86, x64, and Windows on ARM. It can be used with either Visual Studio 11 or VS 2010 with the Windows 8.0 SDK, and compiles for both Win32 desktop applications and Metro style applications.

This release of XDSP.H is bound to the Microsoft Public License (Ms-PL).

Full documentation for XDSP can be found in the offline help for the DirectX SDK (June 2010) release. These functions are in the XDSP C++ namespace, and memory buffers provided to these functions must be 16-byte aligned.

Note that vmulComplex, ButterflyDIT4_1, and ButterflyDIT4_4 are internal implementation functions and not intended for direct use.