mlib_SignalLSP2LPC_S16

, mlib_SignalLSP2LPC_S16_Adp

- convert line spectral pair coefficients to linear prediction coefficients

Synopsis

cc [ flag... ] file... -lmlib [ library... ]
#include <mlib.h>

mlib_status mlib_SignalLSP2LPC_S16(mlib_s16 *lpc,
     mlib_s32 lscale, const mlib_s16 *lsp, mlib_s32 order);

mlib_status mlib_SignalLSP2LPC_S16_Adp(mlib_s16 *lpc,
     mlib_s32 *lscale, const mlib_s16 *lsp, mlib_s32 order);

Description

Each of the functions in this group converts line spectral pair coefficients to linear prediction coefficients.

The line spectral pair (LPS) coefficients are defined as the roots of the following two polynomials:

                   -(M+1)     -1
    P(z) = A(z) + z      * A(z  )

                   -(M+1)     -1
    Q(z) = A(z) - z      * A(z  )

where A(z) is the inverse filter

               M          -i
    A(z) = 1- SUM a(i) * z
              i=1

Note that since P(z) is symmetric and Q(z) is antisymmetric all roots of these polynomials are on the unit circle and they alternate each other. P(z) has a root at z = -1 (w = PI) and Q(z) has a root at z = 1 (w = 0).

The line spectral frequency (LPF) are the angular frequency of the line spectral pair (LPS) coefficients.

    q = cos(w)

where q is the LPS and w is the LPF.

See Fundamentals of Speech Recognition by Lawrence Rabiner and Biing-Hwang Juang, Prentice Hall, 1993.

Note for functions with adaptive scaling (with _Adp postfix), the scaling factor of the output data will be calculated based on the actual data; for functions with non-adaptive scaling (without _Adp postfix), the user supplied scaling factor will be used and the output will be saturated if necessary.

Parameters

Each function takes the following arguments:

lpc

The linear prediction coefficients.

lscale

The scaling factor of the line spectral pair coefficients, where actual_data = output_data * 2**(-scaling_factor).

lsp

The line spectral pair coefficients in Q15 format.

order

The order of the linear prediction filter.

Return Values

Each function returns MLIB_SUCCESS if successful. Otherwise it returns MLIB_FAILURE.

Attributes

See attributes(5) for descriptions of the following attributes:

See Also

mlib_SignalLPC2LSP_S16(3MLIB), attributes(5)