FreeCalypso > hg > gsmhr-codec-ref
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README: punctuation fix
| author | Mychaela Falconia <falcon@freecalypso.org> |
|---|---|
| date | Tue, 20 Aug 2024 19:00:23 +0000 |
| parents | 9008dbc8ca74 |
| children |
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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). * * ppL_CorrHistory[OVERHANG][NP+1] - - history of the OVERHANG * frames worth of pL_UnqntzdCorr[]. * * RETURN VALUE: * * none * *************************************************************************/ void updateCNHist(Longword L_UnqntzdR0, Longword *pL_UnqntzdCorr, Longword pL_R0History[], Longword ppL_CorrHistory[OVERHANG][NP + 1]) { /*_________________________________________________________________________ | | | Automatic Variables | |_________________________________________________________________________| */ int i; /*_________________________________________________________________________ | | | Executable Code | |_________________________________________________________________________| */ /* update */ pL_R0History[siUpdPointer] = L_UnqntzdR0; for (i = 0; i < NP + 1; i++) ppL_CorrHistory[siUpdPointer][i] = pL_UnqntzdCorr[i]; siUpdPointer = (siUpdPointer + 1) % OVERHANG; } /************************************************************************* * * FUNCTION NAME: avgGsHistQntz * * PURPOSE: * * Average gs history, where history is of length OVERHANG-1 * frames. The last frame's (i.e. this frame) gs values are not * available since quantization would have occured only after the * VAD decision is made. * * INPUTS: * * pL_GsHistory[(OVERHANG-1)*N_SUB] - the GS of the past * OVERHANG-1 frames. The GS values are stored shifted down by 2 * shifts to avoid overflow (the largest GS is greater than 2.0). * * * OUTPUTS: * * *pL_GsAvgd - the average of pL_GsHistory[], also shifted down * by two shifts. * * RETURN VALUE: * * none. * * *************************************************************************/ void avgGsHistQntz(Longword pL_GsHistory[], Longword *pL_GsAvgd) { /*_________________________________________________________________________ | | | Automatic Variables | |_________________________________________________________________________| */ int i; Longword L_avg; /*_________________________________________________________________________ | | | Executable Code | |_________________________________________________________________________| */ L_avg = L_shift_r(pL_GsHistory[0], -(OH_SHIFT + 2)); for (i = 1; i < N_SUB * (OVERHANG - 1); i++) L_avg = L_add(L_shift_r(pL_GsHistory[i], -(OH_SHIFT + 2)), L_avg); /* avg number x/32 not x/28 */ *pL_GsAvgd = L_add(L_avg, L_mpy_ls(L_avg, 0x1249)); /* L_avg *= 32/28 */ } /************************************************************************* * * FUNCTION NAME: gsQuant * * PURPOSE: * * Quantize a value of gs in any of the voicing modes. Input GS * is a 32 bit number. The GSP0 index is returned. * * INPUTS: * * L_GsIn - 32 bit GS value, shifted down by 2 shifts. * * swVoicingMode - voicing level * * ppLr_gsTable[4][32] - Rom GS Table. (global), all GS values * have been shifted down by 2 from their true value. * * OUTPUTS: * * none * * RETURN VALUE: * * * GSP0 Index closest to the input value of GS. * * *************************************************************************/ Shortword gsQuant(Longword L_GsIn, Shortword swVoicingMode) { /*_________________________________________________________________________ | | | Automatic Variables | |_________________________________________________________________________| */ Shortword swGsIndex, swBestGs; Longword L_diff, L_min = LW_MAX; /*_________________________________________________________________________ | | | Executable Code | |_________________________________________________________________________| */ for (swGsIndex = 0; swGsIndex < 32; swGsIndex++) { L_diff = L_abs(L_sub(L_GsIn, ppLr_gsTable[swVoicingMode][swGsIndex])); if (L_sub(L_diff, L_min) < 0) { /* new minimum */ /* ----------- */ swBestGs = swGsIndex; L_min = L_diff; } } return (swBestGs); } /************************************************************************* * * FUNCTION NAME: avgCNHist * * PURPOSE: * * Average the unquantized R0 and LPC data stored at the encoder * to arrive at an average R0 and LPC frame for use in a SID * frame. * * INPUTS: * * pL_R0History[OVERHANG] - contains unquantized R(0) data from the * most recent OVERHANG frame (including this one). * * ppL_CorrHistory[OVERHANG][NP+1] - Unquantized correlation * coefficients from the most recent OVERHANG frame (including this * one). The data stored here is an output of FLAT. * * OUTPUTS: * * *pL_AvgdR0 - the average of pL_R0History[] * * pL_AvgdCorrSeq[NP+1] - the average of ppL_CorrHistory[][]. * * * RETURN VALUE: * * none * *************************************************************************/ void avgCNHist(Longword pL_R0History[], Longword ppL_CorrHistory[OVERHANG][NP + 1], Longword *pL_AvgdR0, Longword pL_AvgdCorrSeq[]) { /*_________________________________________________________________________ | | | Automatic Variables | |_________________________________________________________________________| */ int i, j; Longword L_avg; /*_________________________________________________________________________ | | | Executable Code | |_________________________________________________________________________| */ /* R0 Averaging */ /* ------------ */ for (L_avg = 0, i = 0; i < OVERHANG; i++) L_avg = L_add(L_shr(pL_R0History[i], OH_SHIFT), L_avg); *pL_AvgdR0 = L_avg; /* LPC: average the last OVERHANG frames */ /* ------------------------------------- */ for (j = 0; j < NP + 1; j++) { for (L_avg = 0, i = 0; i < OVERHANG; i++) { L_avg = L_add(L_shift_r(ppL_CorrHistory[i][j], -OH_SHIFT), L_avg); } pL_AvgdCorrSeq[j] = L_avg; } } /*************************************************************************** * * FUNCTION NAME: lpcCorrQntz * * PURPOSE: Quantize a correlation sequence * * * INPUT: * * pL_CorrelSeq[NP+1] * Correlation sequence to quantize. * * OUTPUTS: * * pswFinalRc[0:NP-1] * A quantized set of NP reflection coefficients. * * piVQCodewds[0:2] * An array containing the indices of the 3 reflection * coefficient vectors selected from the three segment * Rc-VQ. * * RETURN: * None. * * KEYWORDS: AFLAT,aflat,flat,vectorquantization, reflectioncoefficients * *************************************************************************/ void lpcCorrQntz(Longword pL_CorrelSeq[], Shortword pswFinalRc[], int piVQCodewds[]) { /*_________________________________________________________________________ | | | Automatic Variables | |_________________________________________________________________________| */ Shortword pswPOldSpace[NP_AFLAT], pswPNewSpace[NP_AFLAT], pswVOldSpace[2 * NP_AFLAT - 1], pswVNewSpace[2 * NP_AFLAT - 1], *ppswPAddrs[2], *ppswVAddrs[2], *pswVBar, pswPBar[NP_AFLAT], pswVBarSpace[2 * NP_AFLAT - 1], pswFlatsRc[NP], /* Unquantized Rc's computed by FLAT */ pswRc[NP + 1]; /* Temp list for the converted RC's */ Longword *pL_VBarFull, pL_PBarFull[NP], pL_VBarFullSpace[2 * NP - 1]; int i, iVec, iSeg, iCnt; /* Loop counter */ struct QuantList quantList, /* A list of vectors */ bestPql[4]; /* The four best vectors from * the PreQ */ struct QuantList bestQl[LPC_VQ_SEG + 1]; /* Best vectors for each of * the three segments */ /*_________________________________________________________________________ | | | Executable Code | |_________________________________________________________________________| */ /* Setup pointers temporary space */ /*--------------------------------*/ pswVBar = pswVBarSpace + NP_AFLAT - 1; pL_VBarFull = pL_VBarFullSpace + NP - 1; ppswPAddrs[0] = pswPOldSpace; ppswPAddrs[1] = pswPNewSpace; ppswVAddrs[0] = pswVOldSpace + NP_AFLAT - 1; ppswVAddrs[1] = pswVNewSpace + NP_AFLAT - 1; /* Set up pL_PBarFull and pL_VBarFull initial conditions, using the */ /* autocorrelation sequence derived from the optimal reflection */ /* coefficients computed by FLAT. The initial conditions are shifted */ /* right by RSHIFT bits. These initial conditions, stored as */ /* Longwords, are used to initialize PBar and VBar arrays for the */ /* next VQ segment. */ /*--------------------------------------------------------------------*/ initPBarFullVBarFullL(pL_CorrelSeq, pL_PBarFull, pL_VBarFull); /* Set up initial PBar and VBar initial conditions, using pL_PBarFull */ /* and pL_VBarFull arrays initialized above. These are the initial */ /* PBar and VBar conditions to be used by the AFLAT recursion at the */ /* 1-st Rc-VQ segment. */ /*--------------------------------------------------------------------*/ initPBarVBarL(pL_PBarFull, pswPBar, pswVBar); for (iSeg = 1; iSeg <= LPC_VQ_SEG; iSeg++) { /* initialize candidate list */ /*---------------------------*/ quantList.iNum = psrPreQSz[iSeg - 1]; quantList.iRCIndex = 0; /* do aflat for all vectors in the list */ /*--------------------------------------*/ setupPreQ(iSeg, quantList.iRCIndex); /* set up vector ptrs */ for (iCnt = 0; iCnt < quantList.iNum; iCnt++) { /* get a vector */ /*--------------*/ getNextVec(pswRc); /* clear the limiter flag */ /*------------------------*/ iLimit = 0; /* find the error values for each vector */ /*---------------------------------------*/ quantList.pswPredErr[iCnt] = aflatRecursion(&pswRc[psvqIndex[iSeg - 1].l], pswPBar, pswVBar, ppswPAddrs, ppswVAddrs, psvqIndex[iSeg - 1].len); /* check the limiter flag */ /*------------------------*/ if (iLimit) quantList.pswPredErr[iCnt] = 0x7fff; /* set error to bad value */ } /* done list loop */ /* find 4 best prequantizer levels */ /*---------------------------------*/ findBestInQuantList(quantList, 4, bestPql); for (iVec = 0; iVec < 4; iVec++) { /* initialize quantizer list */ /*---------------------------*/ quantList.iNum = psrQuantSz[iSeg - 1]; quantList.iRCIndex = bestPql[iVec].iRCIndex * psrQuantSz[iSeg - 1]; setupQuant(iSeg, quantList.iRCIndex); /* set up vector ptrs */ /* do aflat recursion on each element of list */ /*--------------------------------------------*/ for (iCnt = 0; iCnt < quantList.iNum; iCnt++) { /* get a vector */ /*--------------*/ getNextVec(pswRc); /* clear the limiter flag */ /*------------------------*/ iLimit = 0; /* find the error values for each vector */ /*---------------------------------------*/ quantList.pswPredErr[iCnt] = aflatRecursion(&pswRc[psvqIndex[iSeg - 1].l], pswPBar, pswVBar, ppswPAddrs, ppswVAddrs, psvqIndex[iSeg - 1].len); /* check the limiter flag */ /*------------------------*/ if (iLimit) quantList.pswPredErr[iCnt] = 0x7fff; /* set error to the worst * value */ } /* done list loop */ /* find best quantizer vector for this segment, and save it */ /*----------------------------------------------------------*/ findBestInQuantList(quantList, 1, bestQl); if (iVec == 0) bestQl[iSeg] = bestQl[0]; else if (sub(bestQl[iSeg].pswPredErr[0], bestQl[0].pswPredErr[0]) > 0) bestQl[iSeg] = bestQl[0]; } /* find the quantized reflection coefficients */ /*--------------------------------------------*/ setupQuant(iSeg, bestQl[iSeg].iRCIndex); /* set up vector ptrs */ getNextVec((Shortword *) (pswFinalRc - 1)); /* Update pBarFull and vBarFull for the next Rc-VQ segment, and */ /* update the pswPBar and pswVBar for the next Rc-VQ segment */ /*--------------------------------------------------------------*/ if (iSeg < LPC_VQ_SEG) aflatNewBarRecursionL(&pswFinalRc[psvqIndex[iSeg - 1].l - 1], iSeg, pL_PBarFull, pL_VBarFull, pswPBar, pswVBar); } /* find the quantizer index (the values to be output in the symbol file) */ /*-----------------------------------------------------------------*/ for (iSeg = 1; iSeg <= LPC_VQ_SEG; iSeg++) piVQCodewds[iSeg - 1] = bestQl[iSeg].iRCIndex; } /************************************************************************* * * FUNCTION NAME: getPnBits * * PURPOSE: * * Generate iBits pseudo-random bits using *pL_PNSeed as the * pn-generators seed. * * INPUTS: * * iBits - integer indicating how many random bits to return. * range [0,15], 0 yields 1 bit output * * *pL_PNSeed - 32 bit seed (changed by function) * * OUTPUTS: * * *pL_PNSeed - 32 bit seed, modified. * * RETURN VALUE: * * random bits in iBits LSB's. * * * IMPLEMENTATION: * * implementation of x**31 + x**3 + 1 == PN_XOR_REG | PN_XOR_ADD a * PN sequence generator using Longwords generating a 2**31 -1 * length pn-sequence. * *************************************************************************/ Shortword getPnBits(int iBits, Longword *pL_PNSeed) { /*_________________________________________________________________________ | | | Automatic Variables | |_________________________________________________________________________| */ Shortword swPnBits = 0; Longword L_Taps, L_FeedBack; int i; /*_________________________________________________________________________ | | | Executable Code | |_________________________________________________________________________| */ for (i = 0; i < iBits; i++) { /* update the state */ /* ---------------- */ L_Taps = *pL_PNSeed & PN_XOR_REG; L_FeedBack = L_Taps; /* Xor tap bits to yield * feedback bit */ L_Taps = L_shr(L_Taps, 1); while (L_Taps) { L_FeedBack = L_FeedBack ^ L_Taps; L_Taps = L_shr(L_Taps, 1); } /* LSB of L_FeedBack is next MSB of PN register */ *pL_PNSeed = L_shr(*pL_PNSeed, 1); if (L_FeedBack & 1) *pL_PNSeed = *pL_PNSeed | PN_XOR_ADD; /* State update complete. Get the output bit from the state, add/or it * into output */ swPnBits = shl(swPnBits, 1); swPnBits = swPnBits | (extract_l(*pL_PNSeed) & 0x0001); } return (swPnBits); } /************************************************************************* * * FUNCTION NAME: rxInterpR0Lpc * * PURPOSE: * * Perform part of the comfort noise algorithm at the decoder. * LPC and R0 are derived in this routine * * INPUTS: * * pswOldKs - Last frame's reflection coeffs. * * pswNewKs - This frame's decoded/received reflection coeffs. * This will serve a new endpoint in interpolation. * * swRxDTXState - primary DTX state variable (at the receiver). A * modulo 12 counter, which is 0 at SID frame. * * swDecoMode - actual mode the decoder: speech decoding mode * or comfort noise insertion mode (SPEECH = speech decoding; * CNIFIRSTSID = comfort noise, 1st SID received; CNICONT = comfort * noise, SID frame received, but not 1st SID; CNIBFI = comfort * noise, bad frame received) * * swFrameType - type of the received frame (VALIDSID, INVALIDSID * GOODSPEECH or UNUSABLE) * * swOldR0Dec - global variable, the decoded R0 value from the last * frame . This will be modified. * * swR0NewCN - global variable the decoded R0 value from the frame * just received. Valid information if current frame is a SID frame. * * * OUTPUTS: * * pswNewKs - This frames LPC coeffs. modified to reflect * interpolated correlation sequence pL_CorrSeq[]. * * swR0Dec - global variable, interpolated R0 value * * swR0OldCN - global variable, R0 interpolation point to * interpolate from. * * swR0NewCN - global variable, R0 interpolation point to * interpolate to. * * pL_OldCorrSeq[NP+1] - global variable, starting point for * interpolation of LPC information. * * pL_NewCorrSeq[NP+1] - global variable, end point for * interpolation of LPC information. * * pL_CorrSeq[NP+1] - global variable, interpolated value of LPC * information to be used in this frame. * * * RETURN VALUE: * * None. * * KEYWORDS: interpolation, comfort noise, SID, DTX * *************************************************************************/ void rxInterpR0Lpc(Shortword *pswOldKs, Shortword *pswNewKs, Shortword swRxDTXState, Shortword swDecoMode, Shortword swFrameType) { /*________________________________________________________________________ | | | Static Variables | |________________________________________________________________________| */ static Shortword swR0OldCN; static Longword pL_OldCorrSeq[NP + 1], pL_NewCorrSeq[NP + 1], pL_CorrSeq[NP + 1]; /*_________________________________________________________________________ | | | Automatic Variables | |_________________________________________________________________________| */ int i; /*_________________________________________________________________________ | | | Executable Code | |_________________________________________________________________________| */ if (swDecoMode == CNIFIRSTSID) { /* first SID frame arrived */ /* ----------------------- */ /* use tx'd R0 frame as both endpoints of interp curve. */ /* i.e. no interpolation for the first frames */ /* ---------------------------------------------------- */ swR0OldCN = swOldR0Dec; /* last non-SID, received R0 */ swR0Dec = linInterpSidShort(swR0NewCN, swR0OldCN, swRxDTXState); /* generate the LPC end points for interpolation */ /* --------------------------------------------- */ rcToCorrDpL(ASHIFT, ASCALE, pswOldKs, pL_OldCorrSeq); rcToCorrDpL(ASHIFT, ASCALE, pswNewKs, pL_NewCorrSeq); /* linearly interpolate between the two sets of correlation coefs */ /* -------------------------------------------------------------- */ for (i = 0; i < NP + 1; i++) { pL_CorrSeq[i] = linInterpSid(pL_NewCorrSeq[i], pL_OldCorrSeq[i], swRxDTXState); } /* Generate this frames K's (overwrite input) */ /* ------------------------------------------ */ aFlatRcDp(pL_CorrSeq, pswNewKs); } else if ((swDecoMode == CNICONT) && (swFrameType == VALIDSID)) { /* new (not the first) SID frame arrived */ /* ------------------------------------- */ swR0OldCN = swOldR0Dec; /* move current state of R0 to old */ swR0Dec = linInterpSidShort(swR0NewCN, swR0OldCN, swRxDTXState); /* LPC: generate new endpoints for interpolation */ /* --------------------------------------------- */ for (i = 0; i < NP + 1; i++) { pL_OldCorrSeq[i] = pL_CorrSeq[i]; } rcToCorrDpL(ASHIFT, ASCALE, pswNewKs, pL_NewCorrSeq); /* linearly interpolate between the two sets of correlation coefs */ /* -------------------------------------------------------------- */ for (i = 0; i < NP + 1; i++) { pL_CorrSeq[i] = linInterpSid(pL_NewCorrSeq[i], pL_OldCorrSeq[i], swRxDTXState); } /* Use interpolated LPC for this frame, overwrite the input K's */ /* ------------------------------------------------------------ */ aFlatRcDp(pL_CorrSeq, pswNewKs); } else { /* in between SID frames / invalid SID frames */ /* ------------------------------------------ */ swR0Dec = linInterpSidShort(swR0NewCN, swR0OldCN, swRxDTXState); /* linearly interpolate between the two sets of correlation coefs */ /* -------------------------------------------------------------- */ for (i = 0; i < NP + 1; i++) { pL_CorrSeq[i] = linInterpSid(pL_NewCorrSeq[i], pL_OldCorrSeq[i], swRxDTXState); } /* Use interpolated LPC for this frame, overwrite the input K's */ /* ------------------------------------------------------------ */ aFlatRcDp(pL_CorrSeq, pswNewKs); } } /************************************************************************* * * FUNCTION NAME: linInterpSid * * PURPOSE: * * Linearly interpolate between two input numbers based on what the * current DtxState is. * * INPUTS: * * L_New - longword more current value * * L_Old - longword oldest value * * swDtxState - state is 0 at the transmitted SID Frame. * * * OUTPUTS: * * none * * RETURN VALUE: * * A value between old and new inputs with dtxState+1/12 of the new * (dtxState+1)-12/12 of the old * * *************************************************************************/ Longword linInterpSid(Longword L_New, Longword L_Old, Shortword swDtxState) { /*_________________________________________________________________________ | | | Automatic Variables | |_________________________________________________________________________| */ Shortword swOldFactor; /*_________________________________________________________________________ | | | Executable Code | |_________________________________________________________________________| */ /* old factor = (1.0 - newFactor) */ /* ------------------------------ */ swOldFactor = sub(0x7fff, psrCNNewFactor[swDtxState]); swOldFactor = add(0x1, swOldFactor); /* contributions from new and old */ /* ------------------------------ */ L_New = L_mpy_ls(L_New, psrCNNewFactor[swDtxState]); L_Old = L_mpy_ls(L_Old, swOldFactor); return (L_add(L_New, L_Old)); } /************************************************************************* * * FUNCTION NAME: linInterpSidShort * * PURPOSE: * * Linearly interpolate between two input numbers based on what * the current DtxState is. * * INPUTS: * * swNew - 16 bit, more current value * * swOld - 16 bit, oldest value * * swDtxState - state is 0 at the transmitted SID Frame. * * * OUTPUTS: * * none * * RETURN VALUE: * * A value between old and new inputs with dtxState+1/12 of the new * (dtxState+1)-12/12 of the old * *************************************************************************/ Shortword linInterpSidShort(Shortword swNew, Shortword swOld, Shortword swDtxState) { /*_________________________________________________________________________ | | | Automatic Variables | |_________________________________________________________________________| */ Shortword swOldFactor; Longword L_New, L_Old; /*_________________________________________________________________________ | | | Executable Code | |_________________________________________________________________________| */ /* old factor = (1.0 - newFactor) */ /* ------------------------------ */ swOldFactor = sub(0x7fff, psrCNNewFactor[swDtxState]); swOldFactor = add(0x1, swOldFactor); /* contributions from new and old */ /* ------------------------------ */ L_New = L_mult(swNew, psrCNNewFactor[swDtxState]); L_Old = L_mult(swOld, swOldFactor); return (round(L_add(L_New, L_Old))); }