📄 dtx.c
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/***************************************************************************
*
* File Name: dtx.c
*
* Purpose: DTX and comfort noise functions of the GSM half rate
* system
*
* Reference: Recommendation GSM 06.41 (DTX)
* Recommendation GSM 06.22 (Comfort Noise)
*
* Below is a listing of all the functions appearing in the file.
* The functions are arranged according to their purpose. Under
* each heading, the ordering is hierarchical.
*
* Evaluation of comfort noise parameters
* swComfortNoise()
* updateCNHist()
* avgGsHistQntz()
* gsQuant()
* avgCNHist()
* lpcCorrQntz()
* getPnBits()
*
* Interpolation of comfort noise parameters
* rxInterpR0Lpc()
* linInterpSid()
*
**************************************************************************/
/*________________________________________________________________________
| |
| Include Files |
|________________________________________________________________________|
*/
#include "typedefs.h"
#include "mathhalf.h"
#include "mathdp31.h"
#include "dtx.h"
#include "sp_dec.h"
#include "sp_rom.h"
#include "sp_frm.h"
/*________________________________________________________________________
| |
| Defines |
|________________________________________________________________________|
*/
#define PN_XOR_REG (Longword)0x00000005L
#define PN_XOR_ADD (Longword)0x40000000L
#define OH_SHIFT 3 /* shift corresponding to OVERHANG */
#define NP_AFLAT 4
#define LPC_VQ_SEG 3
#define ASHIFT 4
#define ASCALE 0x0800
/*________________________________________________________________________
| |
| Global Variables |
|________________________________________________________________________|
*/
Shortword swVadFrmCnt = 0; /* Indicates the number of sequential
* frames where VAD == 0 */
short int siUpdPointer = 0;
Shortword swNElapsed = 50;
Longword pL_GsHist[N_SUB * (OVERHANG - 1)];
/*________________________________________________________________________
| |
| Other External Variables |
|________________________________________________________________________|
*/
extern int iLimit;
extern Shortword swR0Dec,
swOldR0Dec,
swR0NewCN;
extern Shortword swCNR0,
pswCNLpc[],
pswCNGsp0Code[],
pswCNVSCode1[],
pswCNVSCode2[];
/*________________________________________________________________________
| |
| DTX Rom Tables |
|________________________________________________________________________|
*/
/* interpolation curve for comfort noise (i*1/12) i=1..12 */
Shortword psrCNNewFactor[12] = {0x0aaa, 0x1554, 0x1ffe, 0x2aa8, 0x3552,
0x3ffc, 0x4aa6, 0x5550, 0x5ffa, 0x6aa4,
0x754e, 0x7fff};
/* Values of GS for voicing state 0, all values shifted down by 2
shifts */
LongwordRom ppLr_gsTable[4][32] =
{
{
0x000011ab, 0x000038d2, 0x0000773e, 0x000144ef,
0x00035675, 0x000648c5, 0x000c3d65, 0x0017ae17,
0x002a3dbb, 0x005238e7, 0x00695c1a, 0x00a60d45,
0x00e4cc68, 0x01c3ba6a, 0x019e3c96, 0x02d1fbac,
0x030453ec, 0x0549a998, 0x05190298, 0x08258920,
0x08daff30, 0x0c3150e0, 0x0e45d850, 0x14c111a0,
0x0ff7e1c0, 0x18a06860, 0x13810400, 0x1abc9ee0,
0x28500940, 0x41f22800, 0x22fc5040, 0x2cd90180
},
{
0x00003ede, 0x00021fc9, 0x0013f0c3, 0x003a7be2,
0x007a6663, 0x00fe3773, 0x012fabf4, 0x02275cd0,
0x01c0ef14, 0x02c0b1d8, 0x0350fc70, 0x05505078,
0x04175f30, 0x052c1098, 0x08ed3310, 0x0a63b470,
0x05417870, 0x08995ee0, 0x07bbe018, 0x0a19fa10,
0x0b5818c0, 0x0fd96ea0, 0x0e5cad10, 0x13b40d40,
0x12d45840, 0x14577320, 0x2b2e5e00, 0x333e9640,
0x194c35c0, 0x1c30f8c0, 0x2d16db00, 0x2cc970ff
},
{
0x002f18e7, 0x00a47be0, 0x01222efe, 0x01c42df8,
0x024be794, 0x03424c40, 0x036950fc, 0x04973108,
0x038405b4, 0x05d8c8f0, 0x05063e08, 0x070cdea0,
0x05812be8, 0x06da5fc8, 0x088fcd60, 0x0a013cb0,
0x0909a460, 0x09e6cf40, 0x0ee581d0, 0x0ec99f20,
0x0b4e7470, 0x0c730e80, 0x0ff39d20, 0x105d0d80,
0x158b0b00, 0x172babe0, 0x14576460, 0x181a6720,
0x26126e80, 0x1f590180, 0x1fdaad60, 0x2e0e8000
},
{
0x00c7f603, 0x01260cda, 0x01b3926a, 0x026d82bc,
0x0228fba0, 0x036ec5b0, 0x034bf4cc, 0x043a55d0,
0x044f9c20, 0x05c66f50, 0x0515f890, 0x06065300,
0x0665dc00, 0x0802b630, 0x0737a1c0, 0x087294e0,
0x09253fc0, 0x0a619760, 0x097bd060, 0x0a6d4e50,
0x0d19e520, 0x0e15c420, 0x0c4e4eb0, 0x0e8880e0,
0x11cdf480, 0x12c85800, 0x10f4c0a0, 0x13e51b00,
0x189dbaa0, 0x18a6bb60, 0x22e31500, 0x21615240
}
};
/*************************************************************************
*
* FUNCTION NAME: swComfortNoise
*
* PURPOSE:
*
* This routine perform the following tasks:
* - generation of the speech flag (swSP)
* - averaging and encoding of the comfort noise parameters
* - randomization of the codebook indices
*
*
* INPUTS:
*
* swVadFrmCnt (global) - swVadFlag=0 frame counter.
* If swVadFlag=1 then this counter is 0, the first frame with
* swVadFlag=0 will set this counter to 1, with each additional
* swVadFlag=0 frame the counter is incremented.
*
* swVadFlag - voise activity flag. swVadFlag=0 frame with
* no voice activity, swVadFlag=0 frame with voice activity
*
* L_UnqntzdR0 - unquantized R(0), 32 bit value, output of
* FLAT.
*
* pL_UnqntzdCorr[NP+1] - unquantized correlation sequence,
* also an output of FLAT.
*
*
* OUTPUTS:
*
* swCNR0 - global variable, the output quantized R0 index
*
* pswCNLpc[3] - global variable, the output quantized LPC to the
* transmitted in the SID frame
*
* pswCNGsp0Code[N_SUB] - global variable, the output quantized GSP0 indices
*
* pswCNVSCode1[N_SUB] - global variable, the output quantized codevector 1
* indices.
*
* pswCNVSCode2[N_SUB] - global variable, the output quantized codevector 2
* indices.
*
*
* RETURN VALUE:
*
* swSP - speech flag, swSP=1 speech frames are generated, swSP=0
* SID frames are generated.
*
*************************************************************************/
Shortword swComfortNoise(Shortword swVadFlag,
Longword L_UnqntzdR0, Longword *pL_UnqntzdCorr)
{
/*________________________________________________________________________
| |
| Static Variables |
|________________________________________________________________________|
*/
/* history of unquantized parameters */
static Longword pL_R0Hist[OVERHANG];
static Longword ppL_CorrHist[OVERHANG][NP + 1];
/* quantized reference parameters */
static Shortword swQntRefR0,
swRefGsIndex;
static int piRefVqCodewds[3];
/* handling of short speech bursts */
static Shortword swShortBurst;
/* state value of random generator */
static Longword L_TxPNSeed;
/*_________________________________________________________________________
| |
| Automatic Variables |
|_________________________________________________________________________|
*/
Shortword swSP;
Shortword pswFinalRc[NP];
/* unquantized reference parameters */
Longword L_RefR0;
Longword pL_RefCorr[NP + 1];
Longword L_RefGs;
int i;
/*_________________________________________________________________________
| |
| Executable Code |
|_________________________________________________________________________|
*/
swSP = 1;
/* VadFrmCnt will indicate the number of sequential frames where */
/* swVadFlag == 0 */
/* ------------------------------------------------------------- */
if (swVadFlag)
swVadFrmCnt = 0; /* Voice acitvity present */
else
swVadFrmCnt = add(swVadFrmCnt, 1); /* no voice activity */
/* swNElapsed will indicate the number of frames that have elapsed */
/* since the last SID frame with updated comfort noise parameters */
/* was generated */
/* --------------------------------------------------------------- */
swNElapsed = add(swNElapsed, 1);
/* If no voice activity was detected. */
/* ----------------------------------- */
if (swVadFrmCnt)
{
/* Short speech burst ? */
/* -------------------- */
if (swVadFrmCnt == 1)
{
if (sub(swNElapsed, 24) < 0)
swShortBurst = 1; /* short speech burst detected */
else
swShortBurst = 0; /* long speech burst detected */
}
/* Update history, with this frames data */
/* ------------------------------------- */
updateCNHist(L_UnqntzdR0, pL_UnqntzdCorr,
pL_R0Hist, ppL_CorrHist);
/* first SID frame */
/* --------------- */
if (((swShortBurst == 0) && (swVadFrmCnt == OVERHANG)) ||
((swShortBurst == 1) && (swVadFrmCnt == 1)))
{
/* init. random generator */
/* ---------------------- */
L_TxPNSeed = PN_INIT_SEED;
/* average GS */
/* ---------- */
avgGsHistQntz(pL_GsHist, &L_RefGs);
/* GS quantization */
/* --------------- */
swRefGsIndex = gsQuant(L_RefGs, 0);
}
/* No Overhang in case of short speech bursts, */
/* generate SID frames with repeated comfort noise parameters */
/* ---------------------------------------------------------- */
if ((swShortBurst == 1) && (swVadFrmCnt < OVERHANG))
{
/* generate a SID frame with repeated parameters */
/* --------------------------------------------- */
swSP = 0;
/* repeat data: r0, LPC, GS */
/* ------------------------ */
swCNR0 = swQntRefR0;
for (i = 0; i < 3; i++)
pswCNLpc[i] = piRefVqCodewds[i];
for (i = 0; i < N_SUB; i++)
pswCNGsp0Code[i] = swRefGsIndex;
}
/* generate SID frames with updated comfort noise parameters */
/* --------------------------------------------------------- */
if (swVadFrmCnt >= OVERHANG)
{
/* A SID frame with updated parameters */
/* ----------------------------------- */
swSP = 0;
swNElapsed = 0;
/* average R0 and correlation values */
/* --------------------------------- */
avgCNHist(pL_R0Hist, ppL_CorrHist, &L_RefR0,
pL_RefCorr);
/* now quantize the averaged R(0) */
/* ------------------------------ */
swQntRefR0 = r0Quant(L_RefR0);
/* Quantize the averaged correlation */
/* --------------------------------- */
lpcCorrQntz(pL_RefCorr,
pswFinalRc,
piRefVqCodewds);
/* update frame data: r0, LPC */
/* -------------------------- */
swCNR0 = swQntRefR0;
for (i = 0; i < 3; i++)
pswCNLpc[i] = piRefVqCodewds[i];
/* update subframe data (unvoiced mode): GSP0 */
/* ------------------------------------------ */
for (i = 0; i < N_SUB; i++)
pswCNGsp0Code[i] = swRefGsIndex;
}
/* random codevectors */
/* ------------------ */
if (swSP == 0)
{
for (i = 0; i < N_SUB; i++)
{
pswCNVSCode1[i] = getPnBits(7, &L_TxPNSeed);
pswCNVSCode2[i] = getPnBits(7, &L_TxPNSeed);
}
}
}
return (swSP);
}
/*************************************************************************
*
* FUNCTION NAME: updateCNHist
*
* PURPOSE:
*
* Add current frame's unquantized R(0) and LPC information to the
* comfort noise history, so that it will be available for
* averaging.
*
* INPUTS:
*
* Unquantized values from the coder:
*
*
* L_UnqntzdR0 - unquantized frame energy R(0), an output of FLAT
*
* pL_UnqntzdCorr[NP+1] - unquantized correlation coefficient
* array. Also an output of FLAT.
*
* siUpdPointer (global) - A modulo counter which counts up from
* 0 to OVERHANG-1.
*
* OUTPUTS:
*
* pL_R0History[OVERHANG] - history of the OVERHANG frames worth of
* R(0).
*
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