mlib_SignalCepstral_S16(3MmediaLib Library Functmlib_SignalCepstral_S16(3MLIB)NAMEmlib_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 satu‐
rated 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 mathemat‐
ics, 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 for‐
mat.
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 │Committed │
├─────────────────────────────┼─────────────────────────────┤
│MT-Level │MT-Safe │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOmlib_SignalCepstralInit_S16(3MLIB), mlib_SignalCepstral_S16_Adp(3MLIB),
mlib_SignalCepstralFree_S16(3MLIB), attributes(5)SunOS 5.10 2 Mar 2007 mlib_SignalCepstral_S16(3MLIB)