1 /*
2 ** Copyright 2003-2010, VisualOn, Inc.
3 **
4 ** Licensed under the Apache License, Version 2.0 (the "License");
5 ** you may not use this file except in compliance with the License.
6 ** You may obtain a copy of the License at
7 **
8 ** http://www.apache.org/licenses/LICENSE-2.0
9 **
10 ** Unless required by applicable law or agreed to in writing, software
11 ** distributed under the License is distributed on an "AS IS" BASIS,
12 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 ** See the License for the specific language governing permissions and
14 ** limitations under the License.
15 */
16
17 /***********************************************************************
18 * File: isp_isf.c *
19 * *
20 * Description: *
21 * Isp_isf Transformation isp to isf *
22 * Isf_isp Transformation isf to isp *
23 * *
24 * The transformation from isp[i] to isf[i] and isf[i] to isp[i] *
25 * are approximated by a look-up table and interpolation *
26 * *
27 ************************************************************************/
28
29 #include "typedef.h"
30 #include "basic_op.h"
31 #include "isp_isf.tab" /* Look-up table for transformations */
32
Isp_isf(Word16 isp[],Word16 isf[],Word16 m)33 void Isp_isf(
34 Word16 isp[], /* (i) Q15 : isp[m] (range: -1<=val<1) */
35 Word16 isf[], /* (o) Q15 : isf[m] normalized (range: 0.0<=val<=0.5) */
36 Word16 m /* (i) : LPC order */
37 )
38 {
39 Word32 i, ind;
40 Word32 L_tmp;
41 ind = 127; /* beging at end of table -1 */
42 for (i = (m - 1); i >= 0; i--)
43 {
44 if (i >= (m - 2))
45 { /* m-2 is a constant */
46 ind = 127; /* beging at end of table -1 */
47 }
48 /* find value in table that is just greater than isp[i] */
49 while (table[ind] < isp[i])
50 ind--;
51 /* acos(isp[i])= ind*128 + ( ( isp[i]-table[ind] ) * slope[ind] )/2048 */
52 L_tmp = vo_L_mult(vo_sub(isp[i], table[ind]), slope[ind]);
53 isf[i] = vo_round((L_tmp << 4)); /* (isp[i]-table[ind])*slope[ind])>>11 */
54 isf[i] = add1(isf[i], (ind << 7));
55 }
56 isf[m - 1] = (isf[m - 1] >> 1);
57 return;
58 }
59
60
Isf_isp(Word16 isf[],Word16 isp[],Word16 m)61 void Isf_isp(
62 Word16 isf[], /* (i) Q15 : isf[m] normalized (range: 0.0<=val<=0.5) */
63 Word16 isp[], /* (o) Q15 : isp[m] (range: -1<=val<1) */
64 Word16 m /* (i) : LPC order */
65 )
66 {
67 Word16 offset;
68 Word32 i, ind, L_tmp;
69
70 for (i = 0; i < m - 1; i++)
71 {
72 isp[i] = isf[i];
73 }
74 isp[m - 1] = (isf[m - 1] << 1);
75
76 for (i = 0; i < m; i++)
77 {
78 ind = (isp[i] >> 7); /* ind = b7-b15 of isf[i] */
79 offset = (Word16) (isp[i] & 0x007f); /* offset = b0-b6 of isf[i] */
80
81 /* isp[i] = table[ind]+ ((table[ind+1]-table[ind])*offset) / 128 */
82 L_tmp = vo_L_mult(vo_sub(table[ind + 1], table[ind]), offset);
83 isp[i] = add1(table[ind], (Word16)((L_tmp >> 8)));
84 }
85
86 return;
87 }
88
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92