1 /* ------------------------------------------------------------------ 2 * Copyright (C) 1998-2009 PacketVideo 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 13 * express or implied. 14 * See the License for the specific language governing permissions 15 * and limitations under the License. 16 * ------------------------------------------------------------------- 17 */ 18 /**************************************************************************************** 19 Portions of this file are derived from the following 3GPP standard: 20 21 3GPP TS 26.073 22 ANSI-C code for the Adaptive Multi-Rate (AMR) speech codec 23 Available from http://www.3gpp.org 24 25 (C) 2004, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC) 26 Permission to distribute, modify and use this file under the standard license 27 terms listed above has been obtained from the copyright holder. 28 ****************************************************************************************/ 29 /* 30 Filename: /audio/gsm_amr/c/src/log2.c 31 32 ------------------------------------------------------------------------------ 33 REVISION HISTORY 34 35 Description: Updated template used to PV coding template. Moved Log2_norm 36 function to its own file. 37 38 Description: Changed l_shl.c to l_shl.h in Include section. 39 40 Description: Updated template. Changed function interface to pass in a 41 pointer to overflow flag into the function instead of using a 42 global flag. Changed input pointer names for clarity. 43 44 Description: 45 1. Eliminated l_shl function knowing that after normalization 46 the left shift factor will not saturate. 47 2. Eliminated unused include files typedef.h and l_shl.h. 48 49 50 Who: Date: 51 Description: 52 53 ------------------------------------------------------------------------------ 54 */ 55 56 /*---------------------------------------------------------------------------- 57 ; INCLUDES 58 ----------------------------------------------------------------------------*/ 59 #include "log2.h" 60 #include "basic_op.h" 61 #include "log2_norm.h" 62 63 /*---------------------------------------------------------------------------- 64 ; MACROS 65 ; [Define module specific macros here] 66 ----------------------------------------------------------------------------*/ 67 68 /*---------------------------------------------------------------------------- 69 ; DEFINES 70 ; [Include all pre-processor statements here. Include conditional 71 ; compile variables also.] 72 ----------------------------------------------------------------------------*/ 73 74 /*---------------------------------------------------------------------------- 75 ; LOCAL FUNCTION DEFINITIONS 76 ; [List function prototypes here] 77 ----------------------------------------------------------------------------*/ 78 79 /*---------------------------------------------------------------------------- 80 ; LOCAL VARIABLE DEFINITIONS 81 ; [Variable declaration - defined here and used outside this module] 82 ----------------------------------------------------------------------------*/ 83 84 85 /* 86 ------------------------------------------------------------------------------ 87 FUNCTION NAME: log2() 88 ------------------------------------------------------------------------------ 89 INPUT AND OUTPUT DEFINITIONS 90 91 Inputs: 92 L_x = input value of type Word32 93 pExponent = pointer to the integer part of Log2 of type Word16 whose 94 valid range is: 0 <= value <= 30 95 pFraction = pointer to the fractional part of Log2 of type Word16 96 whose valid range is: 0 <= value < 1 97 pOverflow = pointer to overflow flag 98 99 100 Outputs: 101 pExponent -> integer part of the newly calculated Log2 102 pFraction -> fractional part of the newly calculated Log2 103 pOverflow -> 1 if the log2() operation resulted in saturation 104 105 Returns: 106 None 107 108 Global Variables Used: 109 None 110 111 Local Variables Needed: 112 None 113 114 ------------------------------------------------------------------------------ 115 FUNCTION DESCRIPTION 116 117 This function computes logarithm (base2) of the input L_x, where L_x is 118 positive. If L_x is negative or zero, the result is 0. 119 120 This function first normalizes the input L_x and calls the function Log2_norm 121 to calculate the logarithm. 122 123 ------------------------------------------------------------------------------ 124 REQUIREMENTS 125 126 None 127 128 ------------------------------------------------------------------------------ 129 REFERENCES 130 131 [1] log2.c, UMTS GSM AMR speech codec, R99 - Version 3.2.0, March 2, 2001 132 133 ------------------------------------------------------------------------------ 134 PSEUDO-CODE 135 136 137 ------------------------------------------------------------------------------ 138 RESOURCES USED [optional] 139 140 When the code is written for a specific target processor the 141 the resources used should be documented below. 142 143 HEAP MEMORY USED: x bytes 144 145 STACK MEMORY USED: x bytes 146 147 CLOCK CYCLES: (cycle count equation for this function) + (variable 148 used to represent cycle count for each subroutine 149 called) 150 where: (cycle count variable) = cycle count for [subroutine 151 name] 152 153 ------------------------------------------------------------------------------ 154 CAUTION [optional] 155 [State any special notes, constraints or cautions for users of this function] 156 157 ------------------------------------------------------------------------------ 158 */ 159 160 /*---------------------------------------------------------------------------- 161 ; FUNCTION CODE 162 ----------------------------------------------------------------------------*/ 163 void Log2( 164 Word32 L_x, /* (i) : input value */ 165 Word16 *pExponent, /* (o) : Integer part of Log2. (range: 0<=val<=30)*/ 166 Word16 *pFraction, /* (o) : Fractional part of Log2. (range: 0<=val<1) */ 167 Flag *pOverflow /* (i/o) : overflow flag */ 168 ) 169 { 170 Word16 exp; 171 Word32 result; 172 OSCL_UNUSED_ARG(pOverflow); 173 174 exp = norm_l(L_x); 175 result = L_x << exp; 176 Log2_norm(result, exp, pExponent, pFraction); 177 178 return; 179 } 180
