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_Lsf2Poly.c 16 17 ******************************************************************/ 18 19 #include "defines.h" 20 #include "lsf_to_lsp.h" 21 #include "get_lsp_poly.h" 22 #include "constants.h" 23 24 void WebRtcIlbcfix_Lsf2Poly( 25 int16_t *a, /* (o) predictor coefficients (order = 10) in Q12 */ 26 int16_t *lsf /* (i) line spectral frequencies in Q13 */ 27 ) { 28 int32_t f[2][6]; /* f[0][] and f[1][] corresponds to 29 F1(z) and F2(z) respectivly */ 30 int32_t *f1ptr, *f2ptr; 31 int16_t *a1ptr, *a2ptr; 32 int32_t tmpW32; 33 int16_t lsp[10]; 34 int i; 35 36 /* Convert lsf to lsp */ 37 WebRtcIlbcfix_Lsf2Lsp(lsf, lsp, LPC_FILTERORDER); 38 39 /* Get F1(z) and F2(z) from the lsp */ 40 f1ptr=f[0]; 41 f2ptr=f[1]; 42 WebRtcIlbcfix_GetLspPoly(&lsp[0],f1ptr); 43 WebRtcIlbcfix_GetLspPoly(&lsp[1],f2ptr); 44 45 /* for i = 5 down to 1 46 Compute f1[i] += f1[i-1]; 47 and f2[i] += f2[i-1]; 48 */ 49 f1ptr=&f[0][5]; 50 f2ptr=&f[1][5]; 51 for (i=5; i>0; i--) 52 { 53 (*f1ptr) += (*(f1ptr-1)); 54 (*f2ptr) -= (*(f2ptr-1)); 55 f1ptr--; 56 f2ptr--; 57 } 58 59 /* Get the A(z) coefficients 60 a[0] = 1.0 61 for i = 1 to 5 62 a[i] = (f1[i] + f2[i] + round)>>13; 63 for i = 1 to 5 64 a[11-i] = (f1[i] - f2[i] + round)>>13; 65 */ 66 a[0]=4096; 67 a1ptr=&a[1]; 68 a2ptr=&a[10]; 69 f1ptr=&f[0][1]; 70 f2ptr=&f[1][1]; 71 for (i=5; i>0; i--) 72 { 73 tmpW32 = (*f1ptr) + (*f2ptr); 74 (*a1ptr) = (int16_t)WEBRTC_SPL_RSHIFT_W32((tmpW32+4096),13); 75 76 tmpW32 = (*f1ptr) - (*f2ptr); 77 (*a2ptr) = (int16_t)WEBRTC_SPL_RSHIFT_W32((tmpW32+4096),13); 78 79 a1ptr++; 80 a2ptr--; 81 f1ptr++; 82 f2ptr++; 83 } 84 85 return; 86 } 87
