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/* ------------------------------------------------------------------
* 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.
****************************************************************************************/
/*
Pathname: ./audio/gsm-amr/c/src/lsfwt.c
Functions: Lsf_wt
------------------------------------------------------------------------------
REVISION HISTORY
Description: Updated to accept new parameter, Flag *pOverflow. Placed
file in the proper PV Software template.
Description:
1. Eliminated unused include files.
2. Replaced array addressing by pointers
3. Eliminated math operations that unnecessary checked for
saturation, by evaluating the operands
4. Unrolled loops to speed up processing, use decrement loops
Description: Replaced "int" and/or "char" with OSCL defined types.
Who: Date:
Description:
------------------------------------------------------------------------------
INPUT AND OUTPUT DEFINITIONS
Inputs:
lsf -- Pointer to Word16 -- LSF vector
Outputs:
wf -- Pointer to Word16 -- square of weighting factors
pOverflow -- Pointer to type Flag -- Flag set when overflow occurs
Returns:
None
Global Variables Used:
None
Local Variables Needed:
None
------------------------------------------------------------------------------
FUNCTION DESCRIPTION
Compute LSF weighting factors
d[i] = lsf[i+1] - lsf[i-1]
The weighting factors are approximated by two line segment
First segment passes by the following 2 points:
d[i] = 0Hz wf[i] = 3.347
d[i] = 450Hz wf[i] = 1.8
Second segment passes by the following 2 points:
d[i] = 450Hz wf[i] = 1.8
d[i] = 1500Hz wf[i] = 1.0
if( d[i] < 450Hz )
wf[i] = 3.347 - ( (3.347-1.8) / (450-0)) * d[i]
else
wf[i] = 1.8 - ( (1.8-1.0) / (1500-450)) * (d[i] - 450)
if( d[i] < 1843)
wf[i] = 3427 - (28160*d[i])>>15
else
wf[i] = 1843 - (6242*(d[i]-1843))>>15
------------------------------------------------------------------------------
REQUIREMENTS
------------------------------------------------------------------------------
REFERENCES
lsfwt.c, UMTS GSM AMR speech codec, R99 - Version 3.2.0, March 2, 2001
------------------------------------------------------------------------------
PSEUDO-CODE
------------------------------------------------------------------------------
RESOURCES USED
When the code is written for a specific target processor the
the resources used should be documented below.
STACK USAGE: [stack count for this module] + [variable to represent
stack usage for each subroutine called]
where: [stack usage variable] = stack usage for [subroutine
name] (see [filename].ext)
DATA MEMORY USED: x words
PROGRAM MEMORY USED: x words
CLOCK CYCLES: [cycle count equation for this module] + [variable
used to represent cycle count for each subroutine
called]
where: [cycle count variable] = cycle count for [subroutine
name] (see [filename].ext)
------------------------------------------------------------------------------
*/
/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/
#include "lsfwt.h"
#include "cnst.h"
/*----------------------------------------------------------------------------
; MACROS
; Define module specific macros here
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; DEFINES
; Include all pre-processor statements here. Include conditional
; compile variables also.
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; LOCAL FUNCTION DEFINITIONS
; Function Prototype declaration
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; LOCAL STORE/BUFFER/POINTER DEFINITIONS
; Variable declaration - defined here and used outside this module
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; EXTERNAL FUNCTION REFERENCES
; Declare functions defined elsewhere and referenced in this module
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; EXTERNAL GLOBAL STORE/BUFFER/POINTER REFERENCES
; Declare variables used in this module but defined elsewhere
----------------------------------------------------------------------------*/
/*----------------------------------------------------------------------------
; FUNCTION CODE
----------------------------------------------------------------------------*/
void Lsf_wt(
Word16 *lsf, /* input : LSF vector */
Word16 *wf, /* output: square of weighting factors */
Flag *pOverflow
)
{
Word16 temp;
Word16 wgt_fct;
Word16 i;
Word16 *p_wf = wf;
Word16 *p_lsf = &lsf[0];
Word16 *p_lsf_2 = &lsf[1];
OSCL_UNUSED_ARG(pOverflow);
/* wf[0] = lsf[1] - 0 */
*(p_wf++) = *(p_lsf_2++);
for (i = 4; i != 0 ; i--)
{
*(p_wf++) = *(p_lsf_2++) - *(p_lsf++);
*(p_wf++) = *(p_lsf_2++) - *(p_lsf++);
}
/*
* wf[9] = 4000 - lsf[8]
*/
*(p_wf) = 16384 - *(p_lsf);
p_wf = wf;
for (i = 10; i != 0; i--)
{
/*
* (wf[i] - 450);
* 1843 == 450 Hz (Q15 considering 7FFF = 8000 Hz)
*/
wgt_fct = *p_wf;
temp = wgt_fct - 1843;
if (temp > 0)
{
temp = (Word16)(((Word32)temp * 6242) >> 15);
wgt_fct = 1843 - temp;
}
else
{
temp = (Word16)(((Word32)wgt_fct * 28160) >> 15);
wgt_fct = 3427 - temp;
}
*(p_wf++) = wgt_fct << 3;
} /* for (i = 10; i != 0; i--) */
return;
} /* Lsf_wt() */
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