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 31 Filename: /audio/gsm_amr/c/src/mult_r.c 32 33 ------------------------------------------------------------------------------ 34 REVISION HISTORY 35 36 Description: Created separate file for the mult_r function. Sync'ed up 37 with the current template and fixed tabs. 38 39 Description: Passing in a pointer to the overflow flag instead of using 40 a global flag. 41 42 Description: Made the following changes based on P2/P3 review: 43 1) Simplified test to determine if sign extension is necessary 44 2) Changed the name of pointer "overflow" to "Poverflow" 45 3) Removed code that updates MOPS counter 46 4) Updated template and reference section 47 48 Who: Date: 49 Description: 50 51 52 ------------------------------------------------------------------------------ 53 MODULE DESCRIPTION 54 55 Multiplication function with rounding and overflow control 56 57 ------------------------------------------------------------------------------ 58 */ 59 60 /*---------------------------------------------------------------------------- 61 ; INCLUDES 62 ----------------------------------------------------------------------------*/ 63 #include "basic_op.h" 64 65 /*---------------------------------------------------------------------------- 66 ; MACROS 67 ; [Define module specific macros here] 68 ----------------------------------------------------------------------------*/ 69 70 /*---------------------------------------------------------------------------- 71 ; DEFINES 72 ; [Include all pre-processor statements here. Include conditional 73 ; compile variables also.] 74 ----------------------------------------------------------------------------*/ 75 76 /*---------------------------------------------------------------------------- 77 ; LOCAL FUNCTION DEFINITIONS 78 ; [List function prototypes here] 79 ----------------------------------------------------------------------------*/ 80 81 /*---------------------------------------------------------------------------- 82 ; LOCAL VARIABLE DEFINITIONS 83 ; [Variable declaration - defined here and used outside this module] 84 ----------------------------------------------------------------------------*/ 85 86 87 /* 88 ------------------------------------------------------------------------------ 89 FUNCTION NAME: mult_r 90 ------------------------------------------------------------------------------ 91 INPUT AND OUTPUT DEFINITIONS 92 93 Inputs: 94 var1 = 16 bit short signed integer (Word16) whose value falls in 95 the range : 0xffff 8000 <= var1 <= 0x0000 7fff. 96 97 var2 = 16 bit short signed integer (Word16) whose value falls in 98 the range : 0xffff 8000 <= var2 <= 0x0000 7fff. 99 100 pOverflow = pointer to overflow (Flag) 101 102 Outputs: 103 pOverflow -> 1 if the add operation resulted in overflow 104 105 Returns: 106 L_product_arr = 16-bit limited product of var1 and var2 (Word16) 107 108 Global Variables Used: 109 None 110 111 Local Variables Needed: 112 None 113 114 ------------------------------------------------------------------------------ 115 FUNCTION DESCRIPTION 116 117 This function performs the multiplication of var1 by var2 with rounding, and 118 gives a 16 bit result which is scaled, i.e.: 119 mult_r(var1,var2) = extract_l(L_shr(((var1 * var2) + 16384),15)) and | 120 mult_r(-32768,-32768) = 32767 121 122 ------------------------------------------------------------------------------ 123 REQUIREMENTS 124 125 None 126 127 ------------------------------------------------------------------------------ 128 REFERENCES 129 130 [1] mult_r() function in basicop2.c, UMTS GSM AMR speech codec, R99 - 131 Version 3.2.0, March 2, 2001 132 133 ------------------------------------------------------------------------------ 134 PSEUDO-CODE 135 136 Word16 mult_r (Word16 var1, Word16 var2) 137 { 138 Word16 var_out; 139 Word32 L_product_arr; 140 141 L_product_arr = (Word32) var1 *(Word32) var2; 142 L_product_arr += (Word32) 0x00004000L; 143 L_product_arr &= (Word32) 0xffff8000L; 144 L_product_arr >>= 15; 145 146 if (L_product_arr & (Word32) 0x00010000L) 147 { 148 L_product_arr |= (Word32) 0xffff0000L; 149 } 150 * The reference ETSI code uses a global flag for Overflow inside the function 151 * saturate(). In the actual implementation a pointer to Overflow flag is passed in 152 * as a parameter to the function 153 154 var_out = saturate (L_product_arr); 155 156 #if (WMOPS) 157 multiCounter[currCounter].mult_r++; 158 #endif 159 160 return (var_out); 161 } 162 163 ------------------------------------------------------------------------------ 164 RESOURCES USED [optional] 165 166 When the code is written for a specific target processor the 167 the resources used should be documented below. 168 169 HEAP MEMORY USED: x bytes 170 171 STACK MEMORY USED: x bytes 172 173 CLOCK CYCLES: (cycle count equation for this function) + (variable 174 used to represent cycle count for each subroutine 175 called) 176 where: (cycle count variable) = cycle count for [subroutine 177 name] 178 179 ------------------------------------------------------------------------------ 180 CAUTION [optional] 181 [State any special notes, constraints or cautions for users of this function] 182 183 ------------------------------------------------------------------------------ 184 */ 185 186 /*---------------------------------------------------------------------------- 187 ; FUNCTION CODE 188 ----------------------------------------------------------------------------*/ 189 190 Word16 mult_r(Word16 var1, Word16 var2, Flag *pOverflow) 191 { 192 193 Word32 L_product_arr; 194 195 L_product_arr = ((Word32) var1) * var2; /* product */ 196 L_product_arr += (Word32) 0x00004000L; /* round */ 197 L_product_arr >>= 15; /* shift */ 198 199 /* sign extend when necessary */ 200 L_product_arr |= (Word32) - (L_product_arr & (Word32) 0x00010000L); 201 202 /* Saturate result (if necessary). */ 203 /* Replaced function call with in-line code to conserve MIPS, */ 204 /* i.e., var_out = saturate (L_product_arr) */ 205 206 if (L_product_arr > 0X00007fffL) 207 { 208 *pOverflow = 1; 209 L_product_arr = MAX_16; 210 } 211 else if (L_product_arr < (Word32) 0xffff8000L) 212 { 213 *pOverflow = 1; 214 L_product_arr = MIN_16; 215 } 216 217 return ((Word16) L_product_arr); 218 } 219
