API

Data Structures
struct	_xtract_function_descriptor
	Data structure containing useful information about functions provided by LibXtract. More...
struct	xtract_mel_filter_
	A structure to store a set of n_filters Mel filters. More...

Macros
#define	XTRACT_FEATURES   62

Typedefs
typedef enum type_	xtract_type_t
	Enumeration of data types.
typedef enum unit_	xtract_unit_t
	Enumeration of units.
typedef enum xtract_vector_	xtract_vector_t
	Enumeration of vector format types.
typedef struct _xtract_function_descriptor	xtract_function_descriptor_t
	Data structure containing useful information about functions provided by LibXtract.
typedef struct xtract_mel_filter_	xtract_mel_filter
	A structure to store a set of n_filters Mel filters.

Enumerations
enum	xtract_features_ {   XTRACT_MEAN, XTRACT_VARIANCE, XTRACT_STANDARD_DEVIATION, XTRACT_AVERAGE_DEVIATION,   XTRACT_SKEWNESS, XTRACT_KURTOSIS, XTRACT_SPECTRAL_MEAN, XTRACT_SPECTRAL_VARIANCE,   XTRACT_SPECTRAL_STANDARD_DEVIATION, XTRACT_SPECTRAL_SKEWNESS, XTRACT_SPECTRAL_KURTOSIS, XTRACT_SPECTRAL_CENTROID,   XTRACT_IRREGULARITY_K, XTRACT_IRREGULARITY_J, XTRACT_TRISTIMULUS_1, XTRACT_TRISTIMULUS_2,   XTRACT_TRISTIMULUS_3, XTRACT_SMOOTHNESS, XTRACT_SPREAD, XTRACT_ZCR,   XTRACT_ROLLOFF, XTRACT_LOUDNESS, XTRACT_FLATNESS, XTRACT_FLATNESS_DB,   XTRACT_TONALITY, XTRACT_CREST, XTRACT_NOISINESS, XTRACT_RMS_AMPLITUDE,   XTRACT_SPECTRAL_INHARMONICITY, XTRACT_POWER, XTRACT_ODD_EVEN_RATIO, XTRACT_SHARPNESS,   XTRACT_SPECTRAL_SLOPE, XTRACT_LOWEST_VALUE, XTRACT_HIGHEST_VALUE, XTRACT_SUM,   XTRACT_NONZERO_COUNT, XTRACT_HPS, XTRACT_F0, XTRACT_FAILSAFE_F0,   XTRACT_WAVELET_F0, XTRACT_MIDICENT, XTRACT_LNORM, XTRACT_FLUX,   XTRACT_ATTACK_TIME, XTRACT_DECAY_TIME, XTRACT_DIFFERENCE_VECTOR, XTRACT_AUTOCORRELATION,   XTRACT_AMDF, XTRACT_ASDF, XTRACT_BARK_COEFFICIENTS, XTRACT_PEAK_SPECTRUM,   XTRACT_SPECTRUM, XTRACT_AUTOCORRELATION_FFT, XTRACT_MFCC, XTRACT_DCT,   XTRACT_HARMONIC_SPECTRUM, XTRACT_LPC, XTRACT_LPCC, XTRACT_SUBBANDS,   XTRACT_WINDOWED, XTRACT_SMOOTHED }
	Enumeration of features, elements are used as indixes to an array of pointers to feature extracton functions.
enum	xtract_feature_init_ { XTRACT_INIT_MFCC = 100, XTRACT_INIT_BARK, XTRACT_INIT_WINDOWED }
	Enumeration of feature initialisation functions.
enum	xtract_feature_types_ { XTRACT_SCALAR, XTRACT_VECTOR, XTRACT_DELTA }
	Enumeration of feature types.
enum	xtract_mfcc_types_ { XTRACT_EQUAL_GAIN, XTRACT_EQUAL_AREA }
	Enumeration of mfcc types.
enum	xtract_lnorm_filter_types_ { XTRACT_NO_LNORM_FILTER, XTRACT_POSITIVE_SLOPE, XTRACT_NEGATIVE_SLOPE }
enum	xtract_return_codes_ {   XTRACT_SUCCESS, XTRACT_MALLOC_FAILED, XTRACT_BAD_ARGV, XTRACT_BAD_VECTOR_SIZE,   XTRACT_BAD_STATE, XTRACT_DENORMAL_FOUND, XTRACT_NO_RESULT, XTRACT_FEATURE_NOT_IMPLEMENTED,   XTRACT_ARGUMENT_ERROR }
	Enumeration of return codes.
enum	xtract_spectrum_ { XTRACT_MAGNITUDE_SPECTRUM, XTRACT_LOG_MAGNITUDE_SPECTRUM, XTRACT_POWER_SPECTRUM, XTRACT_LOG_POWER_SPECTRUM }
	Enumeration of spectrum types.
enum	xtract_subband_scales_ { XTRACT_OCTAVE_SUBBANDS, XTRACT_LINEAR_SUBBANDS }
	Subband scales.
enum	type_ { XTRACT_FLOAT, XTRACT_FLOATARRAY, XTRACT_INT, XTRACT_MEL_FILTER }
	Enumeration of data types.
enum	unit_ {   XTRACT_HERTZ = 2, XTRACT_ANY_AMPLITUDE_HERTZ, XTRACT_DBFS, XTRACT_DBFS_HERTZ,   XTRACT_PERCENT, XTRACT_BINS, XTRACT_SONE, XTRACT_MIDI_CENT }
	Enumeration of units.
enum	xtract_bool_t { XTRACT_FALSE, XTRACT_TRUE }
	Boolean.
enum	xtract_window_types_ {   XTRACT_GAUSS, XTRACT_HAMMING, XTRACT_HANN, XTRACT_BARTLETT,   XTRACT_TRIANGULAR, XTRACT_BARTLETT_HANN, XTRACT_BLACKMAN, XTRACT_KAISER,   XTRACT_BLACKMAN_HARRIS }
	Window types.
enum	xtract_vector_ {   XTRACT_SPECTRAL, XTRACT_SPECTRAL_MAGNITUDES, XTRACT_SPECTRAL_PEAKS, XTRACT_SPECTRAL_PEAKS_MAGNITUDES,   XTRACT_SPECTRAL_PEAKS_FREQUENCIES, XTRACT_SPECTRAL_HARMONICS, XTRACT_SPECTRAL_HARMONICS_MAGNITUDES, XTRACT_SPECTRAL_HARMONICS_FREQUENCIES,   XTRACT_AUTOCORRELATION_COEFFS, XTRACT_ARBITRARY_SERIES, XTRACT_AUDIO_SAMPLES, XTRACT_MEL_COEFFS,   XTRACT_LPC_COEFFS, XTRACT_LPCC_COEFFS, XTRACT_BARK_COEFFS, XTRACT_SUBFRAMES,   XTRACT_NO_DATA }
	Enumeration of vector format types.

Functions
int	xtract_init_wavelet_f0_state (void)
	An array of pointers to functions that perform the extraction. More...
int	xtract_init_mfcc (int N, double nyquist, int style, double freq_min, double freq_max, int freq_bands, double **fft_tables)
	A function to initialise a mel filter bank. More...
int	xtract_init_bark (int N, double sr, int *band_limits)
	A function to initialise bark filter bounds. More...
int	xtract_init_fft (int N, int feature_name)
	An initialisation function for functions using FFT. More...
void	xtract_free_fft (void)
	Free memory used for fft plans. More...
double *	xtract_init_window (const int N, const int type)
	Make a window of a given type and return a pointer to it. More...
void	xtract_free_window (double *window)
	Free a window as allocated by xtract_make_window() More...
xtract_function_descriptor_t *	xtract_make_descriptors ()
int	xtract_free_descriptors (xtract_function_descriptor_t *fd)

Detailed Description

Defines a very simple API that provides access to the functions in the library

Function Documentation

void xtract_free_fft

(

void

)

Free memory used for fft plans.

This function should be used to explicitly free memory allocated for ffts by xtract_init_fft(). It is primarily intended for use if a new FFT needs to be taken with a different blocksize. If only one fft size is required then there is no need to call this function since it will be called when the program exits.

void xtract_free_window

(

double *

window

)

Free a window as allocated by xtract_make_window()

Parameters

*window

a pointer to an array of doubles as allocated by xtract_make_window()

int xtract_init_bark	(	int	N,
		double	sr,
		int *	band_limits
	)

A function to initialise bark filter bounds.

A pointer to an array of BARK_BANDS ints most be passed in, and is populated with BARK_BANDS fft bin numbers representing the limits of each band

Parameters

N	the audio block size
sr	The sample audio sample rate
*band_limits	a pointer to an array of BARK_BANDS ints

int xtract_init_fft	(	int	N,
		int	feature_name
	)

An initialisation function for functions using FFT.

This function initialises global data structures used by functions requiring FFT functionality. It can be called multiple times with different feature names. Calling it more than once with the same feature name is not a valid operation and will result in a memory leak.

Parameters

N	the size of the FFT
feature_name	the name of the feature the FFT is being used for, e.g. XTRACT_DCT

int xtract_init_mfcc	(	int	N,
		double	nyquist,
		int	style,
		double	freq_min,
		double	freq_max,
		int	freq_bands,
		double **	fft_tables
	)

A function to initialise a mel filter bank.

It is up to the caller to pass in a pointer to memory allocated for freq_bands arrays of length N. This function populates these arrays with magnitude coefficients representing the mel filterbank on a linear scale

int xtract_init_wavelet_f0_state

(

void

)

An array of pointers to functions that perform the extraction.

Parameters

*data	a pointer to the start of the input data (usually the first element in an array)
N	the number of elements to be processed
*argv	an abitrary number of additional arguments, used to pass additional parameters to the function being called. All arguments are compulsary!
*result	a pointer to the first element in the result

Each function will iterate over N array elements, the first of which is pointed to by *data. It is up to the calling function to ensure that the array is in the format expected by the function being called.

For scalar and delta features, *result will point to a single value.

For vector features it will point to the first element in an array.

Memory for this array must be allocated and freed by the calling function.

All functions return an integer error code as descibed in the enumeration return_codes_

The preprocessor macro: XTRACT must be defined before this can be used

example:

#include <stdio.h>
#define XTRACT
#include "libxtract.h"

main () {
double values[] = {1.0, 2.0, 3.0, 4.0, 5.0};
int N = 5;
double mean;

xtract[MEAN]((void *)values, N, NULL, &mean);

printf("Mean = %.2f\n", mean);
}

The calling function may additionally make some tests against the value returned by xtractA function to initialise wavelet f0 detector state

double* xtract_init_window	(	const int	N,
		const int	type
	)

Make a window of a given type and return a pointer to it.

Parameters

N	the size of the window
type	the type of the window as given in the enumeration window_types_