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- /*
- ==============================================================================
-
- This file is part of the JUCE library.
- Copyright (c) 2017 - ROLI Ltd.
-
- JUCE is an open source library subject to commercial or open-source
- licensing.
-
- The code included in this file is provided under the terms of the ISC license
- http://www.isc.org/downloads/software-support-policy/isc-license. Permission
- To use, copy, modify, and/or distribute this software for any purpose with or
- without fee is hereby granted provided that the above copyright notice and
- this permission notice appear in all copies.
-
- JUCE IS PROVIDED "AS IS" WITHOUT ANY WARRANTY, AND ALL WARRANTIES, WHETHER
- EXPRESSED OR IMPLIED, INCLUDING MERCHANTABILITY AND FITNESS FOR PURPOSE, ARE
- DISCLAIMED.
-
- ==============================================================================
- */
-
- /**
- A very minimal FFT class.
-
- This is only a simple low-footprint implementation and isn't tuned for speed - it may
- be useful for simple applications where one of the more complex FFT libraries would be
- overkill. (But in the future it may end up becoming optimised of course...)
-
- The FFT class itself contains lookup tables, so there's some overhead in creating
- one, you should create and cache an FFT object for each size/direction of transform
- that you need, and re-use them to perform the actual operation.
- */
- class JUCE_API FFT
- {
- public:
- /** Initialises an object for performing either a forward or inverse FFT with the given size.
- The the number of points the FFT will operate on will be 2 ^ order.
- */
- FFT (int order, bool isInverse);
-
- /** Destructor. */
- ~FFT();
-
- /** A complex number, for the purposes of the FFT class. */
- struct Complex
- {
- float r; /**< Real part. */
- float i; /**< Imaginary part. */
- };
-
- /** Performs an out-of-place FFT, either forward or inverse depending on the mode
- that was passed to this object's constructor.
-
- The arrays must contain at least getSize() elements.
- */
- void perform (const Complex* input, Complex* output) const noexcept;
-
- /** Performs an in-place forward transform on a block of real data.
-
- The size of the array passed in must be 2 * getSize(), and the first half
- should contain your raw input sample data. On return, the array will contain
- complex frequency + phase data, and can be passed to performRealOnlyInverseTransform()
- in order to convert it back to reals.
- */
- void performRealOnlyForwardTransform (float* inputOutputData) const noexcept;
-
- /** Performs a reverse operation to data created in performRealOnlyForwardTransform().
-
- The size of the array passed in must be 2 * getSize(), containing complex
- frequency and phase data. On return, the first half of the array will contain
- the reconstituted samples.
- */
- void performRealOnlyInverseTransform (float* inputOutputData) const noexcept;
-
- /** Takes an array and simply transforms it to the frequency spectrum.
- This may be handy for things like frequency displays or analysis.
- */
- void performFrequencyOnlyForwardTransform (float* inputOutputData) const noexcept;
-
- /** Returns the number of data points that this FFT was created to work with. */
- int getSize() const noexcept { return size; }
-
- private:
- JUCE_PUBLIC_IN_DLL_BUILD (struct FFTConfig)
- ScopedPointer<FFTConfig> config;
- const int size;
-
- void performRealOnlyForwardTransform (Complex*, float*) const noexcept;
- void performRealOnlyInverseTransform (Complex*, float*) const noexcept;
-
- JUCE_DECLARE_NON_COPYABLE_WITH_LEAK_DETECTOR (FFT)
- };
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