mlib_SignalFFTW_4_S16_S16(3mlib)

1mlib_SignalFFTW_4(3MLIB)  mediaLib Library Functions  mlib_SignalFFTW_4(3MLIB)
2
3
4

NAME

6       mlib_SignalFFTW_4,         mlib_SignalFFTW_4_S16_S16,         mlib_Sig‐
7       nalFFTW_4_S16C_S16C, mlib_SignalFFTW_4_S16C_S16, mlib_SignalFFTW_4_S16,
8       mlib_SignalFFTW_4_S16C  -  signal Fast Fourier Transform with windowing
9       (FFTW)
10

SYNOPSIS

12       cc [ flag... ] file... -lmlib [ library... ]
13       #include <mlib.h>
14
15       mlib_status mlib_SignalFFTW_4_S16_S16(mlib_s16 *dstr, mlib_s16 *dsti,
16            const mlib_s16 *srcr, const mlib_s16 *srci, const mlib_s16 *window,
17            mlib_s32 order, mlib_s32 *scale);
18
19
20       mlib_status mlib_SignalFFTW_4_S16C_S16C(mlib_s16 *dstc,
21            const mlib_s16 *srcc,const mlib_s16 *window, mlib_s32 order,
22            mlib_s32 *scale);
23
24
25       mlib_status mlib_SignalFFTW_4_S16C_S16(mlib_s16 *dstc,
26            const mlib_s16 *srcr,const mlib_s16 *window, mlib_s32 order,
27            mlib_s32 *scale);
28
29
30       mlib_status mlib_SignalFFTW_4_S16(mlib_s16 *srcdstr,
31            mlib_s16 *srcdsti,const mlib_s16 *window, mlib_s32 order,
32            mlib_s32 *scale);
33
34
35       mlib_status mlib_SignalFFTW_4_S16C(mlib_s16 *srcdstc,
36            const mlib_s16 *window,mlib_s32 order, mlib_s32 *scale);
37
38

DESCRIPTION

40       Each of the functions in this group  performs  Fast  Fourier  Transform
41       with windowing (FFTW).
42
43
44       The FFTW functions use the following equation:
45
46                   1   N-1
47         dst[k] = ---- SUM {src[n] * window[n] * exp(-j2*PI*n*k/N)}
48                   C1  n=0
49
50
51
52       and the IFFTW functions use the following equation:
53
54                   1   N-1
55         dst[n] = ---- SUM {src[k] * window[k] * exp(j2*PI*n*k/N)}
56                   C2  k=0
57
58
59
60       where
61
62         k = 0, 1, ..., (N - 1)
63         n = 0, 1, ..., (N - 1)
64         N = 2**order
65
66
67
68       The  signal  FFTW/IFFTW  functions  can be categorized into four groups
69       according to the ScaleMode in the function names in the following form:
70
71         mlib_Signal[FFTW|IFFTW]_ScaleMode_OutType_InType_OpMode()
72         mlib_Signal[FFTW|IFFTW]_ScaleMode_DataType_OpMode()
73
74
75
76       The scaling factors C1 and C2 used in the equations are defined as fol‐
77       lows:
78
79           o      For ScaleMode = 1, C1 = 1 and C2 = 2**order.
80
81           o      For ScaleMode = 2, C1 = 2**order and C2 = 1.
82
83           o      For  ScaleMode  =  3,  C1  = C2 = 2**(order/2) when order is
84                  even, or C1 = 2**((order+1)/2)  and  C2  =  2**((order-1)/2)
85                  when order is odd.
86
87           o      For  ScaleMode  =  4, C1 = 2**P and C2 = 2**Q, where P and Q
88                  are adaptive scaling factors and are generated by the  func‐
89                  tions.
90
91
92       For functions with only real parts for the source signal, the imaginary
93       parts are assumed to be all zero. For functions with  only  real  parts
94       for  the  destination  signal,  the  imaginary parts are discarded. The
95       functions with only one data type in their names perform the  operation
96       in place.
97

PARAMETERS

99       Each function takes some of the following arguments:
100
101       dstr       Destination signal array that contains the real parts.
102
103
104       dsti       Destination signal array that contains the imaginary parts.
105
106
107       srcr       Source signal array that contains the real parts.
108
109
110       srci       Source signal array that contains the imaginary parts.
111
112
113       dstc       Complex  destination  signal  array.  dstc[2*i] contains the
114                  real parts, and dstc[2*i+1] contains the imaginary parts.
115
116
117       srcc       Complex source signal array.  srcc[2*i]  contains  the  real
118                  parts, and srcc[2*i+1] contains the imaginary parts.
119
120
121       srcdstr    Source  and  destination signal array that contains the real
122                  parts.
123
124
125       srcdsti    Source and destination signal array that contains the imagi‐
126                  nary parts.
127
128
129       srcdstc    Complex  source  and  destination signal array. srcdstc[2*i]
130                  contains the real parts,  and  srcdstc[2*i+1]  contains  the
131                  imaginary parts.
132
133
134       window     Window  coefficient  array  with 2**order real elements. The
135                  window coefficients are in Q15 format for the S16 data type,
136                  or in float format for the F32 data type.
137
138
139       order      Order  of  the  transformation.  The base-2 logarithm of the
140                  number of data samples.
141
142
143       scale      Adaptive scaling factor.
144
145

RETURN VALUES

147       Each function returns MLIB_SUCCESS if successful. Otherwise it  returns
148       MLIB_FAILURE.
149

ATTRIBUTES

151       See attributes(5) for descriptions of the following attributes:
152
153
154
155
156       ┌─────────────────────────────┬─────────────────────────────┐
157       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
158       ├─────────────────────────────┼─────────────────────────────┤
159       │Interface Stability          │Committed                    │
160       ├─────────────────────────────┼─────────────────────────────┤
161       │MT-Level                     │MT-Safe                      │
162       └─────────────────────────────┴─────────────────────────────┘
163

NAME

SYNOPSIS

DESCRIPTION

PARAMETERS

RETURN VALUES

ATTRIBUTES

SEE ALSO