LPC_Analyses(3SP)

NAME
LPC_Analyses - Linear Predictive analysis.

SYNOPSIS

#include <speech.h>

int LPC_Analyses(short *speech, int length, float window, float step,
	         float fSamp, float ***Ri, float ***Ai, float ***RFi,
	         float ***Ci, float ***DelCi, int m, int n, int p)

DESCRIPTION

The Linear Predictive (LP) speech analysis technique estimates an all-pole (autoregressive) model of the short-term speech spectrum.

The 16-bit speech data is pointed to by speech. The number of samples is length. The speech sample rate is given by fSamp, which should be the number of samples per second. The analysis window width is specified in milliseconds by win_size . The frame increment is specified in milliseconds by step_size.

The model order is given by p. The number of auto correlation coefficients is given by m. The total number of Cepstal coefficients is given by n. Space for the output is created with Alloc2d and assigned to

*Ri Auto Correlation coefficients

*Ai Linear Predictive coefficients

*RFi
    Reflection coefficients

*Ci Linear Predictive Cepstal coefficients

*DelCi
    Linear Predictive Delta cepstral coefficients

These can be treated as a two-dimensional array with the first index giving the time and the second giving the coefficient. The number of frames computed is returned on exit.

EXAMPLE
    short *speech;
    int length;
    float **R, **A, **RF, **C, **DelC;
    int numberofwindows;

    numberofwindows = LPC_Analyses(speech, length, 20.0, 10.0, 8000.0,
                            &R, &A, &RF, &C, &DelC, 13, 16, 10);
    if (numberofwindows<0)
      fprintf(stderr,"ComputePLP error: %s",ErrorString);

    This example computes the 10'th order LPC model at each 10 millisecond interval, using a window width of 20 milliseconds. Using this model the AutoCorrelation, Reflection, Cepstral and Delta Cepstral coefficients are computed and returned in the specified arrays. The total number of windows calculated is denoted by numberofwindows.

DIAGNOSTICS
LPC_Analyses returns a negative number on error and sets ErrorString. If successful LPC-Analyses returns the total number of frames computed.

SEE ALSO
ErrorString(3SP), Alloc2d(3SP)

AUTHORS
Johan Schalkwyk
Center for Spoken Language Understanding
Department of Computer Science and Engineering
Oregon Graduate Institute of Science & Technology