| /* ------------------------------------------------------------------ |
| * 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/div_32.c |
| |
| ------------------------------------------------------------------------------ |
| REVISION HISTORY |
| |
| Description: Updated template. Changed function interface to pass in a |
| pointer to overflow flag into the function instead of using a |
| global flag. Removed inclusion of unwanted header files. Changed |
| the name of input and output variables for clarity. |
| |
| Description: |
| 1. Eliminated unused include files. |
| 2. Replaced l_extract functionality, code size and speed |
| do not justify calling this function |
| 3. Eliminated sub() function call, replace by (-), this knowing |
| that the result will not saturate. |
| |
| Description: Added casting to eliminate warnings |
| |
| Who: Date: |
| Description: |
| |
| |
| ------------------------------------------------------------------------------ |
| */ |
| |
| /*---------------------------------------------------------------------------- |
| ; 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: div_32 |
| ------------------------------------------------------------------------------ |
| INPUT AND OUTPUT DEFINITIONS |
| |
| Inputs: |
| L_num = 32 bit signed integer (Word32) whose value falls in the |
| range : 0x0000 0000 < L_num < L_denom |
| L_denom_hi = 16 bit positive normalized integer whose value falls in |
| the range : 0x4000 < hi < 0x7fff |
| L_denom_lo = 16 bit positive integer whose value falls in the range : |
| 0 < lo < 0x7fff |
| |
| pOverflow = pointer to overflow (Flag) |
| |
| Outputs: |
| pOverflow -> 1 if the 32 bit divide operation resulted in overflow |
| |
| Returns: |
| result = 32-bit quotient of of the division of two 32 bit integers |
| L_num / L_denom (Word32) |
| |
| Global Variables Used: |
| None |
| |
| Local Variables Needed: |
| None |
| |
| ------------------------------------------------------------------------------ |
| FUNCTION DESCRIPTION |
| |
| This function is a fractional integer division of two 32 bit numbers, the |
| numerator L_num and the denominator L_denom. The denominator is formed by |
| combining denom_hi and denom_lo. Note that denom_hi is a normalized numbers. |
| The numerator and denominator must be positive and the numerator must be |
| less than the denominator. |
| |
| The division is done as follows: |
| 1. Find 1/L_denom by first approximating: approx = 1 / denom_hi. |
| 2. 1/L_denom = approx * (2.0 - L_denom * approx ). |
| 3. result = L_num * (1/L_denom). |
| |
| ------------------------------------------------------------------------------ |
| REQUIREMENTS |
| |
| None |
| |
| ------------------------------------------------------------------------------ |
| REFERENCES |
| |
| [1] div_32() function in oper_32b.c, UMTS GSM AMR speech codec, R99 - |
| Version 3.2.0, March 2, 2001 |
| |
| ------------------------------------------------------------------------------ |
| PSEUDO-CODE |
| |
| |
| ------------------------------------------------------------------------------ |
| 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 |
| ----------------------------------------------------------------------------*/ |
| Word32 Div_32(Word32 L_num, |
| Word16 L_denom_hi, |
| Word16 L_denom_lo, |
| Flag *pOverflow) |
| { |
| |
| Word16 approx; |
| Word16 hi; |
| Word16 lo; |
| Word16 n_hi; |
| Word16 n_lo; |
| Word32 result; |
| |
| /* First approximation: 1 / L_denom = 1/L_denom_hi */ |
| |
| approx = div_s((Word16) 0x3fff, L_denom_hi); |
| |
| /* 1/L_denom = approx * (2.0 - L_denom * approx) */ |
| |
| result = Mpy_32_16(L_denom_hi, L_denom_lo, approx, pOverflow); |
| /* result is > 0 , and less than 1.0 */ |
| result = 0x7fffffffL - result; |
| |
| hi = (Word16)(result >> 16); |
| lo = (result >> 1) - (hi << 15); |
| |
| result = Mpy_32_16(hi, lo, approx, pOverflow); |
| |
| /* L_num * (1/L_denom) */ |
| |
| hi = (Word16)(result >> 16); |
| lo = (result >> 1) - (hi << 15); |
| |
| n_hi = (Word16)(L_num >> 16); |
| n_lo = (L_num >> 1) - (n_hi << 15); |
| |
| result = Mpy_32(n_hi, n_lo, hi, lo, pOverflow); |
| result = L_shl(result, 2, pOverflow); |
| |
| return (result); |
| } |
| |