| /* ------------------------------------------------------------------ |
| * 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/log2.c |
| |
| ------------------------------------------------------------------------------ |
| REVISION HISTORY |
| |
| Description: Updated template used to PV coding template. Moved Log2_norm |
| function to its own file. |
| |
| Description: Changed l_shl.c to l_shl.h in Include section. |
| |
| Description: Updated template. Changed function interface to pass in a |
| pointer to overflow flag into the function instead of using a |
| global flag. Changed input pointer names for clarity. |
| |
| Description: |
| 1. Eliminated l_shl function knowing that after normalization |
| the left shift factor will not saturate. |
| 2. Eliminated unused include files typedef.h and l_shl.h. |
| |
| |
| Who: Date: |
| Description: |
| |
| ------------------------------------------------------------------------------ |
| */ |
| |
| /*---------------------------------------------------------------------------- |
| ; INCLUDES |
| ----------------------------------------------------------------------------*/ |
| #include "log2.h" |
| #include "basic_op.h" |
| #include "log2_norm.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: log2() |
| ------------------------------------------------------------------------------ |
| INPUT AND OUTPUT DEFINITIONS |
| |
| Inputs: |
| L_x = input value of type Word32 |
| pExponent = pointer to the integer part of Log2 of type Word16 whose |
| valid range is: 0 <= value <= 30 |
| pFraction = pointer to the fractional part of Log2 of type Word16 |
| whose valid range is: 0 <= value < 1 |
| pOverflow = pointer to overflow flag |
| |
| |
| Outputs: |
| pExponent -> integer part of the newly calculated Log2 |
| pFraction -> fractional part of the newly calculated Log2 |
| pOverflow -> 1 if the log2() operation resulted in saturation |
| |
| Returns: |
| None |
| |
| Global Variables Used: |
| None |
| |
| Local Variables Needed: |
| None |
| |
| ------------------------------------------------------------------------------ |
| FUNCTION DESCRIPTION |
| |
| This function computes logarithm (base2) of the input L_x, where L_x is |
| positive. If L_x is negative or zero, the result is 0. |
| |
| This function first normalizes the input L_x and calls the function Log2_norm |
| to calculate the logarithm. |
| |
| ------------------------------------------------------------------------------ |
| REQUIREMENTS |
| |
| None |
| |
| ------------------------------------------------------------------------------ |
| REFERENCES |
| |
| [1] log2.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 |
| ----------------------------------------------------------------------------*/ |
| void Log2( |
| Word32 L_x, /* (i) : input value */ |
| Word16 *pExponent, /* (o) : Integer part of Log2. (range: 0<=val<=30)*/ |
| Word16 *pFraction, /* (o) : Fractional part of Log2. (range: 0<=val<1) */ |
| Flag *pOverflow /* (i/o) : overflow flag */ |
| ) |
| { |
| Word16 exp; |
| Word32 result; |
| OSCL_UNUSED_ARG(pOverflow); |
| |
| exp = norm_l(L_x); |
| result = L_x << exp; |
| Log2_norm(result, exp, pExponent, pFraction); |
| |
| return; |
| } |