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 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 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 89 90 91 92
