1 /* 2 * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved. 3 * 4 * Use of this source code is governed by a BSD-style license 5 * that can be found in the LICENSE file in the root of the source 6 * tree. An additional intellectual property rights grant can be found 7 * in the file PATENTS. All contributing project authors may 8 * be found in the AUTHORS file in the root of the source tree. 9 */ 10 11 /****************************************************************** 12 13 iLBC Speech Coder ANSI-C Source Code 14 15 WebRtcIlbcfix_SimpleLpcAnalysis.c 16 17 ******************************************************************/ 18 19 #include "defines.h" 20 #include "window32_w32.h" 21 #include "bw_expand.h" 22 #include "poly_to_lsf.h" 23 #include "constants.h" 24 25 /*----------------------------------------------------------------* 26 * lpc analysis (subrutine to LPCencode) 27 *---------------------------------------------------------------*/ 28 29 void WebRtcIlbcfix_SimpleLpcAnalysis( 30 int16_t *lsf, /* (o) lsf coefficients */ 31 int16_t *data, /* (i) new block of speech */ 32 iLBC_Enc_Inst_t *iLBCenc_inst 33 /* (i/o) the encoder state structure */ 34 ) { 35 int k; 36 int scale; 37 int16_t is; 38 int16_t stability; 39 /* Stack based */ 40 int16_t A[LPC_FILTERORDER + 1]; 41 int32_t R[LPC_FILTERORDER + 1]; 42 int16_t windowedData[BLOCKL_MAX]; 43 int16_t rc[LPC_FILTERORDER]; 44 45 is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl; 46 WEBRTC_SPL_MEMCPY_W16(iLBCenc_inst->lpc_buffer+is,data,iLBCenc_inst->blockl); 47 48 /* No lookahead, last window is asymmetric */ 49 50 for (k = 0; k < iLBCenc_inst->lpc_n; k++) { 51 52 is = LPC_LOOKBACK; 53 54 if (k < (iLBCenc_inst->lpc_n - 1)) { 55 56 /* Hanning table WebRtcIlbcfix_kLpcWin[] is in Q15-domain so the output is right-shifted 15 */ 57 WebRtcSpl_ElementwiseVectorMult(windowedData, iLBCenc_inst->lpc_buffer, WebRtcIlbcfix_kLpcWin, BLOCKL_MAX, 15); 58 } else { 59 60 /* Hanning table WebRtcIlbcfix_kLpcAsymWin[] is in Q15-domain so the output is right-shifted 15 */ 61 WebRtcSpl_ElementwiseVectorMult(windowedData, iLBCenc_inst->lpc_buffer+is, WebRtcIlbcfix_kLpcAsymWin, BLOCKL_MAX, 15); 62 } 63 64 /* Compute autocorrelation */ 65 WebRtcSpl_AutoCorrelation(windowedData, BLOCKL_MAX, LPC_FILTERORDER, R, &scale); 66 67 /* Window autocorrelation vector */ 68 WebRtcIlbcfix_Window32W32(R, R, WebRtcIlbcfix_kLpcLagWin, LPC_FILTERORDER + 1 ); 69 70 /* Calculate the A coefficients from the Autocorrelation using Levinson Durbin algorithm */ 71 stability=WebRtcSpl_LevinsonDurbin(R, A, rc, LPC_FILTERORDER); 72 73 /* 74 Set the filter to {1.0, 0.0, 0.0,...} if filter from Levinson Durbin algorithm is unstable 75 This should basically never happen... 76 */ 77 if (stability!=1) { 78 A[0]=4096; 79 WebRtcSpl_MemSetW16(&A[1], 0, LPC_FILTERORDER); 80 } 81 82 /* Bandwidth expand the filter coefficients */ 83 WebRtcIlbcfix_BwExpand(A, A, (int16_t*)WebRtcIlbcfix_kLpcChirpSyntDenum, LPC_FILTERORDER+1); 84 85 /* Convert from A to LSF representation */ 86 WebRtcIlbcfix_Poly2Lsf(lsf + k*LPC_FILTERORDER, A); 87 } 88 89 is=LPC_LOOKBACK+BLOCKL_MAX-iLBCenc_inst->blockl; 90 WEBRTC_SPL_MEMCPY_W16(iLBCenc_inst->lpc_buffer, 91 iLBCenc_inst->lpc_buffer+LPC_LOOKBACK+BLOCKL_MAX-is, is); 92 93 return; 94 } 95
