mlib_SignalCepstral_S16(3MLIB)				    mediaLib Library Functions				    mlib_SignalCepstral_S16(3MLIB)

NAME

       mlib_SignalCepstral_S16 - perform cepstral analysis

SYNOPSIS

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

       mlib_status mlib_SignalCepstral_S16(mlib_s16 *cepst, mlib_s32 cscale, const mlib_s16 *signal, void *state);

DESCRIPTION

       The  mlib_SignalCepstral_S16()  function  performs cepstral analysis.  The user supplied scaling factor will be used and the output will be
       saturated if necessary.

       The basic operations to compute the cepstrum is shown below.

	     +-----------+	+--------+	 +-----------+
	     |	Fourier  |	|	 |	 |  Inverse  |
       ----->|		 |----->| log|*| |------>|  Fourier  |----->
	x(n) | Transform | X(k) |	 | X'(k) | Transform | c(n)
	     +-----------+	+--------+	 +-----------+

       where x(n) is the input signal and c(n) is its cepstrum. In mathematics, they are

	      N-1		 2*PI*k*n
       X(k) = SUM x(n) * exp(-j*----------)
	      n=0		    N

       X'(k) = log|X(k)|

	       1  N-1		     2*PI*k*n
       c(n) = --- SUM X'(k) * exp(j*----------)
	       N  n=0			N

       Since X'(k) is real and even (symmetric), i.e.

       X'(k) = X'(N - k)

       the c(n) is real and the equation becomes Cosine transform.

	       1  N-1		   2*PI*k*n
       c(n) = --- SUM X'(k) * cos(----------)
	       N  n=0		      N

       The cepstral coefficients in LPC is a special case of the above.

       See Digital Signal Processing by Alan V. Oppenheim and Ronald W. Schafer, Prentice Hall, 1974.

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

PARAMETERS

       The function takes the following arguments:

       cepst	       The cepstral coefficients.

       cscale	       The scaling factor of cepstral coefficients, where actual_data = output_data * 2**(-scaling_factor).

       signal	       The input signal vector, the signal samples are in Q15 format.

       state	       Pointer to the internal state structure.

RETURN VALUES

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

ATTRIBUTES

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

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Evolving			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       mlib_SignalCepstralInit_S16(3MLIB), mlib_SignalCepstral_S16_Adp(3MLIB), mlib_SignalCepstralFree_S16(3MLIB), attributes(5)

SunOS 5.10							    10 Nov 2004 				    mlib_SignalCepstral_S16(3MLIB)