243 lines
7.2 KiB
C++
243 lines
7.2 KiB
C++
/* ------------------------------------------------------------------
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* Copyright (C) 1998-2009 PacketVideo
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
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* express or implied.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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* -------------------------------------------------------------------
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*/
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/****************************************************************************************
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Portions of this file are derived from the following 3GPP standard:
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3GPP TS 26.073
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ANSI-C code for the Adaptive Multi-Rate (AMR) speech codec
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Available from http://www.3gpp.org
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(C) 2004, 3GPP Organizational Partners (ARIB, ATIS, CCSA, ETSI, TTA, TTC)
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Permission to distribute, modify and use this file under the standard license
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terms listed above has been obtained from the copyright holder.
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****************************************************************************************/
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/*
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Pathname: ./audio/gsm-amr/c/src/lsfwt.c
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Functions: Lsf_wt
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------------------------------------------------------------------------------
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REVISION HISTORY
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Description: Updated to accept new parameter, Flag *pOverflow. Placed
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file in the proper PV Software template.
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Description:
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1. Eliminated unused include files.
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2. Replaced array addressing by pointers
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3. Eliminated math operations that unnecessary checked for
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saturation, by evaluating the operands
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4. Unrolled loops to speed up processing, use decrement loops
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Description: Replaced "int" and/or "char" with OSCL defined types.
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Who: Date:
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Description:
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------------------------------------------------------------------------------
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INPUT AND OUTPUT DEFINITIONS
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Inputs:
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lsf -- Pointer to Word16 -- LSF vector
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Outputs:
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wf -- Pointer to Word16 -- square of weighting factors
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pOverflow -- Pointer to type Flag -- Flag set when overflow occurs
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Returns:
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None
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Global Variables Used:
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None
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Local Variables Needed:
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None
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------------------------------------------------------------------------------
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FUNCTION DESCRIPTION
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Compute LSF weighting factors
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d[i] = lsf[i+1] - lsf[i-1]
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The weighting factors are approximated by two line segment
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First segment passes by the following 2 points:
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d[i] = 0Hz wf[i] = 3.347
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d[i] = 450Hz wf[i] = 1.8
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Second segment passes by the following 2 points:
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d[i] = 450Hz wf[i] = 1.8
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d[i] = 1500Hz wf[i] = 1.0
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if( d[i] < 450Hz )
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wf[i] = 3.347 - ( (3.347-1.8) / (450-0)) * d[i]
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else
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wf[i] = 1.8 - ( (1.8-1.0) / (1500-450)) * (d[i] - 450)
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if( d[i] < 1843)
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wf[i] = 3427 - (28160*d[i])>>15
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else
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wf[i] = 1843 - (6242*(d[i]-1843))>>15
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------------------------------------------------------------------------------
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REQUIREMENTS
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------------------------------------------------------------------------------
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REFERENCES
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lsfwt.c, UMTS GSM AMR speech codec, R99 - Version 3.2.0, March 2, 2001
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------------------------------------------------------------------------------
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PSEUDO-CODE
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------------------------------------------------------------------------------
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RESOURCES USED
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When the code is written for a specific target processor the
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the resources used should be documented below.
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STACK USAGE: [stack count for this module] + [variable to represent
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stack usage for each subroutine called]
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where: [stack usage variable] = stack usage for [subroutine
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name] (see [filename].ext)
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DATA MEMORY USED: x words
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PROGRAM MEMORY USED: x words
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CLOCK CYCLES: [cycle count equation for this module] + [variable
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used to represent cycle count for each subroutine
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called]
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where: [cycle count variable] = cycle count for [subroutine
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name] (see [filename].ext)
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------------------------------------------------------------------------------
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*/
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/*----------------------------------------------------------------------------
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; INCLUDES
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----------------------------------------------------------------------------*/
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#include "lsfwt.h"
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#include "cnst.h"
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/*----------------------------------------------------------------------------
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; MACROS
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; Define module specific macros here
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----------------------------------------------------------------------------*/
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/*----------------------------------------------------------------------------
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; DEFINES
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; Include all pre-processor statements here. Include conditional
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; compile variables also.
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----------------------------------------------------------------------------*/
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/*----------------------------------------------------------------------------
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; LOCAL FUNCTION DEFINITIONS
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; Function Prototype declaration
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----------------------------------------------------------------------------*/
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/*----------------------------------------------------------------------------
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; LOCAL STORE/BUFFER/POINTER DEFINITIONS
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; Variable declaration - defined here and used outside this module
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----------------------------------------------------------------------------*/
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/*----------------------------------------------------------------------------
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; EXTERNAL FUNCTION REFERENCES
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; Declare functions defined elsewhere and referenced in this module
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----------------------------------------------------------------------------*/
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/*----------------------------------------------------------------------------
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; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES
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; Declare variables used in this module but defined elsewhere
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----------------------------------------------------------------------------*/
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/*----------------------------------------------------------------------------
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; FUNCTION CODE
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----------------------------------------------------------------------------*/
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void Lsf_wt(
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Word16 *lsf, /* input : LSF vector */
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Word16 *wf, /* output: square of weighting factors */
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Flag *pOverflow
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)
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{
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Word16 temp;
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Word16 wgt_fct;
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Word16 i;
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Word16 *p_wf = wf;
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Word16 *p_lsf = &lsf[0];
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Word16 *p_lsf_2 = &lsf[1];
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OSCL_UNUSED_ARG(pOverflow);
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/* wf[0] = lsf[1] - 0 */
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*(p_wf++) = *(p_lsf_2++);
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for (i = 4; i != 0 ; i--)
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{
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*(p_wf++) = *(p_lsf_2++) - *(p_lsf++);
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*(p_wf++) = *(p_lsf_2++) - *(p_lsf++);
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}
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/*
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* wf[9] = 4000 - lsf[8]
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*/
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*(p_wf) = 16384 - *(p_lsf);
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p_wf = wf;
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for (i = 10; i != 0; i--)
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{
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/*
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* (wf[i] - 450);
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* 1843 == 450 Hz (Q15 considering 7FFF = 8000 Hz)
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*/
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wgt_fct = *p_wf;
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temp = wgt_fct - 1843;
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if (temp > 0)
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{
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temp = (Word16)(((Word32)temp * 6242) >> 15);
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wgt_fct = 1843 - temp;
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}
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else
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{
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temp = (Word16)(((Word32)wgt_fct * 28160) >> 15);
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wgt_fct = 3427 - temp;
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}
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*(p_wf++) = wgt_fct << 3;
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} /* for (i = 10; i != 0; i--) */
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return;
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} /* Lsf_wt() */
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