msamr/opencore-amr/opencore/codecs_v2/audio/gsm_amr/amr_nb/dec/src/dec_lag3.cpp
/* ------------------------------------------------------------------
* 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: dec_lag3.cpp
Functions: Dec_lag3
------------------------------------------------------------------------------
INPUT AND OUTPUT DEFINITIONS
Inputs:
index -- Word16 -- received pitch index
t0_min -- Word16 -- minimum of search range
t0_max -- Word16 -- maximum of search range
i_subfr -- Word16 -- subframe flag
T0_prev -- Word16 -- integer pitch delay of last subframe
used in 2nd and 4th subframes
flag4 -- Word16 -- flag for encoding with 4 bits
Outputs:
T0 -- Pointer to type Word16 -- integer part of pitch lag
T0_frac -- Pointer to type Word16 -- fractional part of pitch lag
pOverflow -- Pointer to type Flag -- Flag set when overflow occurs
Returns:
None.
Global Variables Used:
None
Local Variables Needed:
None
)
------------------------------------------------------------------------------
FUNCTION DESCRIPTION
PURPOSE: Decoding of fractional pitch lag with 1/3 resolution.
Extract the integer and fraction parts of the pitch lag from
the received adaptive codebook index.
See "Enc_lag3.c" for more details about the encoding procedure.
The fractional lag in 1st and 3rd subframes is encoded with 8 bits
while that in 2nd and 4th subframes is relatively encoded with 4, 5
and 6 bits depending on the mode.
------------------------------------------------------------------------------
REQUIREMENTS
------------------------------------------------------------------------------
REFERENCES
dec_lag3.c, UMTS GSM AMR speech codec, R99 - Version 3.2.0, March 2, 2001
------------------------------------------------------------------------------
PSEUDO-CODE
------------------------------------------------------------------------------
*/
/*----------------------------------------------------------------------------
; INCLUDES
----------------------------------------------------------------------------*/
#include "dec_lag3.h"
#include "typedef.h"
#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
; 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 Dec_lag3(Word16 index, /* i : received pitch index */
Word16 t0_min, /* i : minimum of search range */
Word16 t0_max, /* i : maximum of search range */
Word16 i_subfr, /* i : subframe flag */
Word16 T0_prev, /* i : integer pitch delay of last subframe
used in 2nd and 4th subframes */
Word16 * T0, /* o : integer part of pitch lag */
Word16 * T0_frac, /* o : fractional part of pitch lag */
Word16 flag4, /* i : flag for encoding with 4 bits */
Flag *pOverflow /* o : Flag set when overflow occurs */
)
{
Word16 i;
Word16 tmp_lag;
if (i_subfr == 0) /* if 1st or 3rd subframe */
{
if (index < 197)
{
tmp_lag = index + 2;
tmp_lag =
mult(
tmp_lag,
10923,
pOverflow);
i = tmp_lag + 19;
*T0 = i;
/* i = 3 * (*T0) */
i <<= 1;
i += *T0;
tmp_lag = index - i;
*T0_frac = tmp_lag + 58;
}
else
{
*T0 = index - 112;
*T0_frac = 0;
}
}
else
{ /* 2nd or 4th subframe */
if (flag4 == 0)
{
/* 'normal' decoding: either with 5 or 6 bit resolution */
i = index + 2;
i = ((Word32) i * 10923) >> 15;
i -= 1;
*T0 = i + t0_min;
/* i = 3* (*T0) */
i = i + (i << 1);
tmp_lag = index - 2;
*T0_frac = tmp_lag - i;
}
else
{
/* decoding with 4 bit resolution */
tmp_lag = T0_prev;
i =
sub(
tmp_lag,
t0_min,
pOverflow);
if (i > 5)
{
tmp_lag = t0_min + 5;
}
i = t0_max - tmp_lag;
if (i > 4)
{
tmp_lag = t0_max - 4;
}
if (index < 4)
{
i = tmp_lag - 5;
*T0 = i + index;
*T0_frac = 0;
}
else
{
/* 4 >= index < 12 */
if (index < 12)
{
i = index - 5;
i = ((Word32) i * 10923) >> 15;
i--;
*T0 = i + tmp_lag;
i = i + (i << 1);
tmp_lag = index - 9;
*T0_frac = tmp_lag - i;
}
else
{
i = index - 12;
i = i + tmp_lag;
*T0 = i + 1;
*T0_frac = 0;
}
}
} /* end if (decoding with 4 bit resolution) */
}
return;
}