1 /*
2
3 * Revision 1.1 1996/08/19 22:31:53 jaf
4 * Initial revision
5 *
6
7 */
8
9 /* -- translated by f2c (version 19951025).
10 You must link the resulting object file with the libraries:
11 -lf2c -lm (in that order)
12 */
13
14 #include "f2c.h"
15
16 extern int ivfilt_(real *lpbuf, real *ivbuf, integer *len, integer *nsamp, real *ivrc);
17
18 /* ********************************************************************* */
19
20 /* IVFILT Version 48 */
21
22 /*
23 * Revision 1.1 1996/08/19 22:31:53 jaf
24 * Initial revision
25 * */
26 /* Revision 1.3 1996/03/15 21:36:29 jaf */
27 /* Just added a few comments about which array indices of the arguments */
28 /* are used, and mentioning that this subroutine has no local state. */
29
30 /* Revision 1.2 1996/03/13 00:01:00 jaf */
31 /* Comments added explaining that none of the local variables of this */
32 /* subroutine need to be saved from one invocation to the next. */
33
34 /* Revision 1.1 1996/02/07 14:47:34 jaf */
35 /* Initial revision */
36
37
38 /* ********************************************************************* */
39
40 /* 2nd order inverse filter, speech is decimated 4:1 */
41
42 /* Input: */
43 /* LEN - Length of speech buffers */
44 /* NSAMP - Number of samples to filter */
45 /* LPBUF - Low pass filtered speech buffer */
46 /* Indices LEN-NSAMP-7 through LEN read. */
47 /* Output: */
48 /* IVBUF - Inverse filtered speech buffer */
49 /* Indices LEN-NSAMP+1 through LEN written. */
50 /* IVRC - Inverse filter reflection coefficients (for voicing) */
51 /* Indices 1 and 2 both written (also read, but only after writing).
52 */
53
54 /* This subroutine has no local state. */
55
ivfilt_(real * lpbuf,real * ivbuf,integer * len,integer * nsamp,real * ivrc)56 /* Subroutine */ int ivfilt_(real *lpbuf, real *ivbuf, integer *len, integer *
57 nsamp, real *ivrc)
58 {
59 /* System generated locals */
60 integer i__1;
61
62 /* Local variables */
63 integer i__, j, k;
64 real r__[3], pc1, pc2;
65
66 /* Arguments */
67 /* Local variables that need not be saved */
68 /* Local state */
69 /* None */
70 /* Calculate Autocorrelations */
71 /* Parameter adjustments */
72 --ivbuf;
73 --lpbuf;
74 --ivrc;
75
76 /* Function Body */
77 for (i__ = 1; i__ <= 3; ++i__) {
78 r__[i__ - 1] = 0.f;
79 k = (i__ - 1) << 2;
80 i__1 = *len;
81 for (j = (i__ << 2) + *len - *nsamp; j <= i__1; j += 2) {
82 r__[i__ - 1] += lpbuf[j] * lpbuf[j - k];
83 }
84 }
85 /* Calculate predictor coefficients */
86 pc1 = 0.f;
87 pc2 = 0.f;
88 ivrc[1] = 0.f;
89 ivrc[2] = 0.f;
90 if (r__[0] > 1e-10f) {
91 ivrc[1] = r__[1] / r__[0];
92 ivrc[2] = (r__[2] - ivrc[1] * r__[1]) / (r__[0] - ivrc[1] * r__[1]);
93 pc1 = ivrc[1] - ivrc[1] * ivrc[2];
94 pc2 = ivrc[2];
95 }
96 /* Inverse filter LPBUF into IVBUF */
97 i__1 = *len;
98 for (i__ = *len + 1 - *nsamp; i__ <= i__1; ++i__) {
99 ivbuf[i__] = lpbuf[i__] - pc1 * lpbuf[i__ - 4] - pc2 * lpbuf[i__ - 8];
100 }
101 return 0;
102 } /* ivfilt_ */
103
104