| /* |
| * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved. |
| * |
| * Use of this source code is governed by a BSD-style license |
| * that can be found in the LICENSE file in the root of the source |
| * tree. An additional intellectual property rights grant can be found |
| * in the file PATENTS. All contributing project authors may |
| * be found in the AUTHORS file in the root of the source tree. |
| */ |
| |
| /****************************************************************** |
| |
| iLBC Speech Coder ANSI-C Source Code |
| |
| WebRtcIlbcfix_Lsf2Poly.c |
| |
| ******************************************************************/ |
| |
| #include "defines.h" |
| #include "lsf_to_lsp.h" |
| #include "get_lsp_poly.h" |
| #include "constants.h" |
| |
| void WebRtcIlbcfix_Lsf2Poly( |
| WebRtc_Word16 *a, /* (o) predictor coefficients (order = 10) in Q12 */ |
| WebRtc_Word16 *lsf /* (i) line spectral frequencies in Q13 */ |
| ) { |
| WebRtc_Word32 f[2][6]; /* f[0][] and f[1][] corresponds to |
| F1(z) and F2(z) respectivly */ |
| WebRtc_Word32 *f1ptr, *f2ptr; |
| WebRtc_Word16 *a1ptr, *a2ptr; |
| WebRtc_Word32 tmpW32; |
| WebRtc_Word16 lsp[10]; |
| int i; |
| |
| /* Convert lsf to lsp */ |
| WebRtcIlbcfix_Lsf2Lsp(lsf, lsp, LPC_FILTERORDER); |
| |
| /* Get F1(z) and F2(z) from the lsp */ |
| f1ptr=f[0]; |
| f2ptr=f[1]; |
| WebRtcIlbcfix_GetLspPoly(&lsp[0],f1ptr); |
| WebRtcIlbcfix_GetLspPoly(&lsp[1],f2ptr); |
| |
| /* for i = 5 down to 1 |
| Compute f1[i] += f1[i-1]; |
| and f2[i] += f2[i-1]; |
| */ |
| f1ptr=&f[0][5]; |
| f2ptr=&f[1][5]; |
| for (i=5; i>0; i--) |
| { |
| (*f1ptr) += (*(f1ptr-1)); |
| (*f2ptr) -= (*(f2ptr-1)); |
| f1ptr--; |
| f2ptr--; |
| } |
| |
| /* Get the A(z) coefficients |
| a[0] = 1.0 |
| for i = 1 to 5 |
| a[i] = (f1[i] + f2[i] + round)>>13; |
| for i = 1 to 5 |
| a[11-i] = (f1[i] - f2[i] + round)>>13; |
| */ |
| a[0]=4096; |
| a1ptr=&a[1]; |
| a2ptr=&a[10]; |
| f1ptr=&f[0][1]; |
| f2ptr=&f[1][1]; |
| for (i=5; i>0; i--) |
| { |
| tmpW32 = (*f1ptr) + (*f2ptr); |
| (*a1ptr) = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32((tmpW32+4096),13); |
| |
| tmpW32 = (*f1ptr) - (*f2ptr); |
| (*a2ptr) = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32((tmpW32+4096),13); |
| |
| a1ptr++; |
| a2ptr--; |
| f1ptr++; |
| f2ptr++; |
| } |
| |
| return; |
| } |