FFTInterface Manual

内容表

关于
Classes
FFTInterface
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关于

The fast Fourier transform (FFT) is used to analyze a given signal in order to transform it into the frequency domain. The maxon::FFTInterface gives access to implementations of various algorithms.

Classes

Various implementations of the FFT are registered at maxon::FFTClasses :

maxon::FFTClasses::Generic: Generic Cinema 4D implementation.
maxon::FFTClasses::Kiss: Fast FFT algorithm using the KISS library.
maxon::FFTClasses::Cooley: Cooley Tukey algorithm.

FFTInterface

The maxon::FFTInterface provides the functions to perform the FFT:

maxon::FFTInterface::Transform1D() : Computes a one-dimensional FFT transformation.
maxon::FFTInterface::Transform2D() : Computes a two-dimensional FFT transformation.
maxon::FFTInterface::GetSupportOptions() : Returns the supported features of the implementation. See maxon::FFT_SUPPORT .

// This example shows how to use FFT to get the spectrum of a signal.

// synthesize a signal of one second

// signal parameters const maxon::Int sampleCount = 500; const maxon::Float sampleTime = 1.0; // seconds const maxon::Float samplingFrequency = maxon::Float (sampleCount) / sampleTime;

const maxon::Float step = (2 * maxon::PI ) / maxon::Float (sampleCount);

// create signal maxon::BaseArray<maxon::Float> signal; signal. EnsureCapacity (sampleCount) iferr_return ;

for ( maxon::Int i = 0; i < sampleCount; ++i) { const maxon::Float pos = maxon::Float (i) * step; maxon::Float sample = 0.0;

// 1Hz component sample += maxon::Sin (pos); // 2Hz component sample += maxon::Sin (pos * 2); // 4Hz component sample += maxon::Sin (pos * 4) * 0.5; // 8Hz component sample += maxon::Sin (pos * 8) * 0.5; signal. Append (sample) iferr_return ; }

// perform FFT

// create FFTRef const maxon::FFTRef genericFFT = maxon::FFTClasses::Generic().Create() iferr_return ;

// check if this FFT implementation supports Transform1D() const maxon::FFT_SUPPORT options = genericFFT.GetSupportOptions(); if (!(options & maxon::FFT_SUPPORT::TRANSFORM_1D )) return maxon::UnexpectedError( MAXON_SOURCE_LOCATION );

// transform signal maxon::BaseArray<maxon::Complex64> complexDFT; genericFFT.Transform1D(signal. ToArray (), complexDFT. ToArray ()) iferr_return ;

// convert to amplitude spectrum maxon::BaseArray<maxon::Float> spectrum; spectrum. EnsureCapacity (complexDFT. GetCount ()) iferr_return ; for ( const auto DFT : complexDFT) { const maxon::Float amplitude = DFT.GetLength(); spectrum. Append (amplitude) iferr_return ; }

// display spectrum

// spectrum resolution const maxon::Float resolution = samplingFrequency / sampleCount; const maxon::Float spectrumRange = maxon::Float (spectrum. GetCount ()); const maxon::Int maxFrequencyIndex = maxon::Int (spectrumRange * 0.5); for ( maxon::Int i = 0; i < maxFrequencyIndex; ++i) { const maxon::Float frequency = ( maxon::Float )i * resolution; const maxon::Float amplitude = spectrum[i]; const maxon::Float normalizedAmplitude = (amplitude / maxon::Float (sampleCount)); DiagnosticOutput ( "@ Hz: @" , frequency, normalizedAmplitude); }

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maxon::FFT_SUPPORT

FFT_SUPPORT

Flags for GetSupportOptions()

定义： fft.h:24

maxon::ArrayBase< BaseArray< T, BASEARRAY_DEFAULT_CHUNK_SIZE, BASEARRAYFLAGS::NONE, DefaultAllocator >, T, BaseArrayData< T, DefaultAllocator, STD_IS_REPLACEMENT(empty, DefaultAllocator)>, DefaultCompare >::ToArray

ArrayImpl< BaseArray< T, BASEARRAY_DEFAULT_CHUNK_SIZE, BASEARRAYFLAGS::NONE, DefaultAllocator > & > ToArray()

定义： array.h:1602

#define iferr_return

定义： resultbase.h:1434

MAXON_SOURCE_LOCATION

#define MAXON_SOURCE_LOCATION

定义： memoryallocationbase.h:66

Float64 Float

定义： apibase.h:193

maxon::BaseArray

定义： basearray.h:366

DiagnosticOutput

#define DiagnosticOutput(formatString,...)

定义： debugdiagnostics.h:166

static constexpr Float64 PI

floating point constant: PI

定义： apibasemath.h:139

maxon::BaseArray::GetCount

MAXON_ATTRIBUTE_FORCE_INLINE Int GetCount() const

定义： basearray.h:527

maxon::BaseArray::Append

MAXON_ATTRIBUTE_FORCE_INLINE ResultRef< T > Append()

定义： basearray.h:569

Int64 Int

signed 32/64 bit int, size depends on the platform

定义： apibase.h:184

MAXON_ATTRIBUTE_FORCE_INLINE Float32 Sin(Float32 val)

Calculates the sine of a value.

定义： apibasemath.h:198

maxon::FFT_SUPPORT::TRANSFORM_1D

@ TRANSFORM_1D

Component supports 1D transformation.

maxon::BaseArray::EnsureCapacity

ResultMem EnsureCapacity(Int requestedCapacity, COLLECTION_RESIZE_FLAGS resizeFlags=COLLECTION_RESIZE_FLAGS::ON_GROW_RESERVE_CAPACITY)

定义： basearray.h:1188