1 /* 2 * Copyright (C) 2004-2010 NXP Software 3 * Copyright (C) 2010 The Android Open Source Project 4 * 5 * Licensed under the Apache License, Version 2.0 (the "License"); 6 * you may not use this file except in compliance with the License. 7 * You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18 /************************************************************************/ 19 /* */ 20 /* %created_by: sra % (CM/S)*/ 21 /* %name: dB_to_Lin32.c % (CM/S)*/ 22 /* %version: 2 % (CM/S)*/ 23 /* %date_created: Wed Jun 18 11:27:46 2008 % (CM/S)*/ 24 /* */ 25 /************************************************************************/ 26 27 /*######################################################################################*/ 28 /* Include files */ 29 /*######################################################################################*/ 30 31 #include "ScalarArithmetic.h" 32 #ifdef BUILD_FLOAT 33 #include <math.h> 34 #endif 35 36 37 /**************************************************************************************** 38 * Name : dB_to_Lin32() 39 * Input : Signed 16-bit integer 40 * MSB (16) = sign bit 41 * (15->05) = integer part 42 * (04->01) = decimal part 43 * Output : Signed 32-bit integer 44 * MSB (32) = sign bit 45 * (31->16) = integer part 46 * (15->01) = decimal part 47 * Returns : Lin value format 1.16.15 48 * Description : 49 * Remarks : Makes an approximation to the conversion by counting the number 50 * of 6dB steps for use as shifts and then interpolates with a remainder 51 * with the equation: 52 * 53 * Correction = (Remainder / 1.5029) - (Remainder^2 / 6) 54 * 55 * The two coefficients are scaled from 0x40000000 in 96 steps and calculated 56 * as follows: 57 * 58 * FIRST_COEF = 0x80000000 / (96 * 1.5029) 59 * SECOND_COEF = 0x80000000 / (96^2 * 6) 60 * 61 ****************************************************************************************/ 62 63 #define FOUR_OVER_SIX 21846 /* (4 / 6) * 2^15 */ 64 #define SIX_DB 96 /* 6 * 16 or 6dB in Q11.4 format */ 65 #define FIRST_COEF_NEG 14884305 66 #define FIRST_COEF_POS 7442152 /* FIRST_COEF_NEG / 2 */ 67 #define SECOND_COEF 38836 68 #define MAX_VALUE 1536 /* 96 * 16 */ 69 70 #ifdef BUILD_FLOAT dB_to_LinFloat(LVM_INT16 db_fix)71LVM_FLOAT dB_to_LinFloat(LVM_INT16 db_fix) 72 { 73 LVM_FLOAT dB_Float; 74 LVM_FLOAT LinFloat; 75 76 dB_Float = (LVM_FLOAT)((LVM_FLOAT)db_fix / 16.0f); 77 LinFloat = pow(10, dB_Float / 20.0); 78 79 return LinFloat; 80 } 81 #else dB_to_Lin32(LVM_INT16 db_fix)82LVM_INT32 dB_to_Lin32(LVM_INT16 db_fix) 83 { 84 LVM_INT32 Lin_val_32; 85 LVM_INT16 Shift; 86 LVM_INT32 Remain; 87 88 89 /* 90 * Check sign of the input 91 */ 92 if (db_fix<0) 93 { 94 if (db_fix > -MAX_VALUE) 95 { 96 Shift = (LVM_INT16)((((LVM_UINT32)(-db_fix) >> 4) * FOUR_OVER_SIX) >> 17); /* Number of 6dB steps in Q11.4 format */ 97 Remain = -db_fix - (Shift * SIX_DB); 98 Remain = (0x7FFFFFFF - (Remain * FIRST_COEF_NEG)) + (Remain * Remain * SECOND_COEF); 99 Lin_val_32 = (LVM_INT32)((LVM_UINT32)Remain >> (16 + Shift)); 100 } 101 else 102 { 103 Lin_val_32 = 0; 104 } 105 } 106 else 107 { 108 if (db_fix < MAX_VALUE) 109 { 110 Shift = (LVM_INT16)((((LVM_UINT32)db_fix >> 4) * FOUR_OVER_SIX) >> 17); /* Number of 6dB steps in Q11.4 format */ 111 Remain = db_fix - (Shift * SIX_DB); 112 Remain = 0x3FFFFFFF + (Remain * FIRST_COEF_POS) + (Remain * Remain * SECOND_COEF); 113 Lin_val_32 = (LVM_INT32)((LVM_UINT32)Remain >> (15 - Shift)); 114 } 115 else 116 { 117 Lin_val_32 = 0x7FFFFFFF; 118 } 119 } 120 121 122 return Lin_val_32; /* format 1.16.15 */ 123 } 124 #endif 125