| /* ------------------------------------------------------------------ |
| * Copyright (C) 1998-2009 PacketVideo |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either |
| * express or implied. |
| * See the License for the specific language governing permissions |
| * and limitations under the License. |
| * ------------------------------------------------------------------- |
| */ |
| /**************************************************************************************** |
| Portions of this file are derived from the following 3GPP standard: |
| |
| 3GPP TS 26.073 |
| ANSI-C code for the Adaptive Multi-Rate (AMR) speech codec |
| Available from http://www.3gpp.org |
| |
| (C) 2004, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC) |
| Permission to distribute, modify and use this file under the standard license |
| terms listed above has been obtained from the copyright holder. |
| ****************************************************************************************/ |
| /* |
| |
| Filename: /audio/gsm_amr/c/src/mult_r.c |
| |
| ------------------------------------------------------------------------------ |
| REVISION HISTORY |
| |
| Description: Created separate file for the mult_r function. Sync'ed up |
| with the current template and fixed tabs. |
| |
| Description: Passing in a pointer to the overflow flag instead of using |
| a global flag. |
| |
| Description: Made the following changes based on P2/P3 review: |
| 1) Simplified test to determine if sign extension is necessary |
| 2) Changed the name of pointer "overflow" to "Poverflow" |
| 3) Removed code that updates MOPS counter |
| 4) Updated template and reference section |
| |
| Who: Date: |
| Description: |
| |
| |
| ------------------------------------------------------------------------------ |
| MODULE DESCRIPTION |
| |
| Multiplication function with rounding and overflow control |
| |
| ------------------------------------------------------------------------------ |
| */ |
| |
| /*---------------------------------------------------------------------------- |
| ; INCLUDES |
| ----------------------------------------------------------------------------*/ |
| #include "basic_op.h" |
| |
| /*---------------------------------------------------------------------------- |
| ; MACROS |
| ; [Define module specific macros here] |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; DEFINES |
| ; [Include all pre-processor statements here. Include conditional |
| ; compile variables also.] |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; LOCAL FUNCTION DEFINITIONS |
| ; [List function prototypes here] |
| ----------------------------------------------------------------------------*/ |
| |
| /*---------------------------------------------------------------------------- |
| ; LOCAL VARIABLE DEFINITIONS |
| ; [Variable declaration - defined here and used outside this module] |
| ----------------------------------------------------------------------------*/ |
| |
| |
| /* |
| ------------------------------------------------------------------------------ |
| FUNCTION NAME: mult_r |
| ------------------------------------------------------------------------------ |
| INPUT AND OUTPUT DEFINITIONS |
| |
| Inputs: |
| var1 = 16 bit short signed integer (Word16) whose value falls in |
| the range : 0xffff 8000 <= var1 <= 0x0000 7fff. |
| |
| var2 = 16 bit short signed integer (Word16) whose value falls in |
| the range : 0xffff 8000 <= var2 <= 0x0000 7fff. |
| |
| pOverflow = pointer to overflow (Flag) |
| |
| Outputs: |
| pOverflow -> 1 if the add operation resulted in overflow |
| |
| Returns: |
| L_product_arr = 16-bit limited product of var1 and var2 (Word16) |
| |
| Global Variables Used: |
| None |
| |
| Local Variables Needed: |
| None |
| |
| ------------------------------------------------------------------------------ |
| FUNCTION DESCRIPTION |
| |
| This function performs the multiplication of var1 by var2 with rounding, and |
| gives a 16 bit result which is scaled, i.e.: |
| mult_r(var1,var2) = extract_l(L_shr(((var1 * var2) + 16384),15)) and | |
| mult_r(-32768,-32768) = 32767 |
| |
| ------------------------------------------------------------------------------ |
| REQUIREMENTS |
| |
| None |
| |
| ------------------------------------------------------------------------------ |
| REFERENCES |
| |
| [1] mult_r() function in basicop2.c, UMTS GSM AMR speech codec, R99 - |
| Version 3.2.0, March 2, 2001 |
| |
| ------------------------------------------------------------------------------ |
| PSEUDO-CODE |
| |
| Word16 mult_r (Word16 var1, Word16 var2) |
| { |
| Word16 var_out; |
| Word32 L_product_arr; |
| |
| L_product_arr = (Word32) var1 *(Word32) var2; |
| L_product_arr += (Word32) 0x00004000L; |
| L_product_arr &= (Word32) 0xffff8000L; |
| L_product_arr >>= 15; |
| |
| if (L_product_arr & (Word32) 0x00010000L) |
| { |
| L_product_arr |= (Word32) 0xffff0000L; |
| } |
| * The reference ETSI code uses a global flag for Overflow inside the function |
| * saturate(). In the actual implementation a pointer to Overflow flag is passed in |
| * as a parameter to the function |
| |
| var_out = saturate (L_product_arr); |
| |
| #if (WMOPS) |
| multiCounter[currCounter].mult_r++; |
| #endif |
| |
| return (var_out); |
| } |
| |
| ------------------------------------------------------------------------------ |
| RESOURCES USED [optional] |
| |
| When the code is written for a specific target processor the |
| the resources used should be documented below. |
| |
| HEAP MEMORY USED: x bytes |
| |
| STACK MEMORY USED: x bytes |
| |
| CLOCK CYCLES: (cycle count equation for this function) + (variable |
| used to represent cycle count for each subroutine |
| called) |
| where: (cycle count variable) = cycle count for [subroutine |
| name] |
| |
| ------------------------------------------------------------------------------ |
| CAUTION [optional] |
| [State any special notes, constraints or cautions for users of this function] |
| |
| ------------------------------------------------------------------------------ |
| */ |
| |
| /*---------------------------------------------------------------------------- |
| ; FUNCTION CODE |
| ----------------------------------------------------------------------------*/ |
| |
| Word16 mult_r(Word16 var1, Word16 var2, Flag *pOverflow) |
| { |
| |
| Word32 L_product_arr; |
| |
| L_product_arr = ((Word32) var1) * var2; /* product */ |
| L_product_arr += (Word32) 0x00004000L; /* round */ |
| L_product_arr >>= 15; /* shift */ |
| |
| /* sign extend when necessary */ |
| L_product_arr |= (Word32) - (L_product_arr & (Word32) 0x00010000L); |
| |
| /* Saturate result (if necessary). */ |
| /* Replaced function call with in-line code to conserve MIPS, */ |
| /* i.e., var_out = saturate (L_product_arr) */ |
| |
| if (L_product_arr > 0X00007fffL) |
| { |
| *pOverflow = 1; |
| L_product_arr = MAX_16; |
| } |
| else if (L_product_arr < (Word32) 0xffff8000L) |
| { |
| *pOverflow = 1; |
| L_product_arr = MIN_16; |
| } |
| |
| return ((Word16) L_product_arr); |
| } |