FFmpeg: FFT functions

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FFT functions

Utility functions

Files

file avfft.h

FFT functions.

Data Structures

struct FFTComplex

Typedefs

typedef float FFTSample

Enumerations

enum RDFTransformType { DFT_R2C, IDFT_C2R, IDFT_R2C, DFT_C2R }

enum DCTTransformType { DCT_II = 0, DCT_III, DCT_I, DST_I }

Functions

FFTContext * av_fft_init (int nbits, int inverse)

Set up a complex FFT.

void av_fft_permute (FFTContext *s, FFTComplex *z)

Do the permutation needed BEFORE calling ff_fft_calc().

void av_fft_calc (FFTContext *s, FFTComplex *z)

Do a complex FFT with the parameters defined in av_fft_init().

void av_fft_end (FFTContext *s)

FFTContext * av_mdct_init (int nbits, int inverse, double scale)

void av_imdct_calc (FFTContext *s, FFTSample *output, const FFTSample *input)

void av_imdct_half (FFTContext *s, FFTSample *output, const FFTSample *input)

void av_mdct_calc (FFTContext *s, FFTSample *output, const FFTSample *input)

void av_mdct_end (FFTContext *s)

RDFTContext * av_rdft_init (int nbits, enum RDFTransformType trans)

Set up a real FFT.

void av_rdft_calc (RDFTContext *s, FFTSample *data)

void av_rdft_end (RDFTContext *s)

DCTContext * av_dct_init (int nbits, enum DCTTransformType type)

Set up DCT.

void av_dct_calc (DCTContext *s, FFTSample *data)

void av_dct_end (DCTContext *s)

Detailed Description

Typedef Documentation

typedef float FFTSample

Definition at line 35 of file avfft.h.

Enumeration Type Documentation

enum RDFTransformType

Enumerator:: DFT_R2C

IDFT_C2R

IDFT_R2C

DFT_C2R

Definition at line 71 of file avfft.h.

enum DCTTransformType

Enumerator:: DCT_II

DCT_III

DCT_I

DST_I

Definition at line 93 of file avfft.h.

Function Documentation

FFTContext* av_fft_init ( int nbits,

int inverse

)

Set up a complex FFT.

Parameters: nbits log2 of the length of the input array

inverse if 0 perform the forward transform, if 1 perform the inverse

Definition at line 27 of file avfft.c.

void av_fft_permute ( FFTContext * s,

FFTComplex * z

)

Do the permutation needed BEFORE calling ff_fft_calc().

Definition at line 37 of file avfft.c.

void av_fft_calc ( FFTContext * s,

FFTComplex * z

)

Do a complex FFT with the parameters defined in av_fft_init().

The input data must be permuted before. No 1.0/sqrt(n) normalization is done.

Definition at line 42 of file avfft.c.

void av_fft_end ( FFTContext * s )

Definition at line 47 of file avfft.c.

FFTContext* av_mdct_init ( int nbits,

int inverse,

double scale

)

void av_imdct_calc ( FFTContext * s,

FFTSample * output,

const FFTSample * input

)

void av_imdct_half ( FFTContext * s,

FFTSample * output,

const FFTSample * input

)

void av_mdct_calc ( FFTContext * s,

FFTSample * output,

const FFTSample * input

)

void av_mdct_end ( FFTContext * s )

RDFTContext* av_rdft_init ( int nbits,

enum RDFTransformType trans

)

Set up a real FFT.

Parameters: nbits log2 of the length of the input array

trans the type of transform

Referenced by config_output(), video_audio_display(), and yae_reset().

void av_rdft_calc ( RDFTContext * s,

FFTSample * data

)

Referenced by plot_spectrum_column(), video_audio_display(), yae_apply(), yae_flush(), and yae_xcorr_via_rdft().

void av_rdft_end ( RDFTContext * s )

Referenced by config_output(), stream_component_close(), uninit(), video_audio_display(), yae_release_buffers(), and yae_reset().

DCTContext* av_dct_init ( int nbits,

enum DCTTransformType type

)

Set up DCT.

Parameters: nbits size of the input array: (1 << nbits) for DCT-II, DCT-III and DST-I (1 << nbits) + 1 for DCT-I

Note: the first element of the input of DST-I is ignored

void av_dct_calc ( DCTContext * s,

FFTSample * data

)

void av_dct_end ( DCTContext * s )

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