'\" te
.\" Copyright (c) 2007, Sun Microsystems, Inc.  All Rights Reserved 
.TH mlib_SignalMelCepstral_F32 3MLIB "2 Mar 2007" "SunOS 5.11" "mediaLib Library Functions"
.SH NAME
mlib_SignalMelCepstral_F32 \- perform cepstral analysis in mel frequency scale
.SH SYNOPSIS
.LP
.nf
cc [ \fIflag\fR... ] \fIfile\fR... \fB-lmlib\fR [ \fIlibrary\fR... ]
#include <mlib.h>

\fBmlib_status\fR \fBmlib_SignalMelCepstral_F32\fR(\fBmlib_f32 *\fR\fIcepst\fR,
     \fBconst mlib_f32 *\fR\fIsignal\fR, \fBvoid *\fR\fIstate\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBmlib_SignalMelCepstral_F32()\fR function performs cepstral analysis in mel frequency scale.
.sp
.LP
The first two steps of mel scale cepstral analysis is the same as in general cepstral anaysis. After the logarithm of the spectrum magnitude is obtained, it is converted into mel frequency scale before the inverse Fourier transform.
.sp
.in +2
.nf
           +-----------+        +-----------+
           |  Linear   |        |  Inverse  |
\&... ------>|    to     |------->|  Fourier  |----->
     X'(k) | Mel Scale | X''(m) | Transform | c(n)
           +-----------+        +-----------+
.fi
.in -2

.sp
.LP
where \fBX'(k)\fR is defined in linear frequency scale and \fBX''(m)\fR is defined in mel frequency scale.
.sp
.LP
The mel frequency scale is defined as following.
.sp
.in +2
.nf
freq_mel = melmul * LOG10(1 + freq_linear / meldiv)
.fi
.in -2

.sp
.LP
where \fBfreq_mel\fR is the frequency in mel scale, \fBfreq_linear\fR is the frequency in linear scale, \fBmelmul\fR is the multiplying factor, \fBmuldiv\fR is the dividing factor.
.sp
.LP
Optionally, a bank of band pass filters in linear frequency scale can be used below the bank of band pass filters in mel frequency scale, as shown below in linear frequency scale.
.sp
.in +2
.nf
0   f1  f2  f3    fp  fp+1 fp+2  fp+3  fp+q
|---|---|---| ... |---|----|-----| ... | ... -> freq
.fi
.in -2

.sp
.LP
where \fBfp = melbgn\fR, \fBfp+q = melend\fR, \fBp = nlinear\fR, \fBq = nmel\fR; the filters number \fB1\fR to \fBp\fR are defined in linear frequency scale which have equal bandwidth in linear frequency scale; the filters number \fBp+1\fR to \fBp+q\fR are defined in mel frequency scale which have equal bandwidth in mel frequency scale and increasing bandwidth in linear frequency scale.
.sp
.LP
See \fIDigital Signal Processing\fR by Alan V. Oppenheim and Ronald W. Schafer, Prentice Hall, 1974.
.sp
.LP
See \fIFundamentals of Speech Recognition\fR by Lawrence Rabiner and Biing-Hwang Juang, Prentice Hall, 1993.
.SH PARAMETERS
.sp
.LP
The function takes the following arguments:
.sp
.ne 2
.mk
.na
\fB\fIcepst\fR\fR
.ad
.RS 10n
.rt  
The cepstral coefficients.
.RE

.sp
.ne 2
.mk
.na
\fB\fIsignal\fR\fR
.ad
.RS 10n
.rt  
The input signal vector.
.RE

.sp
.ne 2
.mk
.na
\fB\fIstate\fR\fR
.ad
.RS 10n
.rt  
Pointer to the internal state structure.
.RE

.SH RETURN VALUES
.sp
.LP
The function returns \fBMLIB_SUCCESS\fR if successful. Otherwise it returns \fBMLIB_FAILURE\fR.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Interface StabilityCommitted
_
MT-LevelMT-Safe
.TE

.SH SEE ALSO
.sp
.LP
\fBmlib_SignalMelCepstralInit_F32\fR(3MLIB), \fBmlib_SignalMelCepstralFree_F32\fR(3MLIB), \fBattributes\fR(5)