andrew@webrtc.org | a7b57da | 2012-10-22 18:19:23 +0000 | [diff] [blame] | 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 | * This file contains the function WebRtcSpl_LpcToReflCoef(). |
| 14 | * The description header can be found in signal_processing_library.h |
| 15 | * |
| 16 | */ |
| 17 | |
pbos@webrtc.org | abf0cd8 | 2013-05-27 09:49:58 +0000 | [diff] [blame] | 18 | #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h" |
andrew@webrtc.org | a7b57da | 2012-10-22 18:19:23 +0000 | [diff] [blame] | 19 | |
| 20 | #define SPL_LPC_TO_REFL_COEF_MAX_AR_MODEL_ORDER 50 |
| 21 | |
pbos@webrtc.org | 1727dc7 | 2013-04-09 16:40:28 +0000 | [diff] [blame] | 22 | void WebRtcSpl_LpcToReflCoef(int16_t* a16, int use_order, int16_t* k16) |
andrew@webrtc.org | a7b57da | 2012-10-22 18:19:23 +0000 | [diff] [blame] | 23 | { |
| 24 | int m, k; |
pbos@webrtc.org | 1727dc7 | 2013-04-09 16:40:28 +0000 | [diff] [blame] | 25 | int32_t tmp32[SPL_LPC_TO_REFL_COEF_MAX_AR_MODEL_ORDER]; |
| 26 | int32_t tmp_inv_denom32; |
| 27 | int16_t tmp_inv_denom16; |
andrew@webrtc.org | a7b57da | 2012-10-22 18:19:23 +0000 | [diff] [blame] | 28 | |
| 29 | k16[use_order - 1] = WEBRTC_SPL_LSHIFT_W16(a16[use_order], 3); //Q12<<3 => Q15 |
| 30 | for (m = use_order - 1; m > 0; m--) |
| 31 | { |
| 32 | // (1 - k^2) in Q30 |
pbos@webrtc.org | 1727dc7 | 2013-04-09 16:40:28 +0000 | [diff] [blame] | 33 | tmp_inv_denom32 = ((int32_t)1073741823) - WEBRTC_SPL_MUL_16_16(k16[m], k16[m]); |
andrew@webrtc.org | a7b57da | 2012-10-22 18:19:23 +0000 | [diff] [blame] | 34 | // (1 - k^2) in Q15 |
pbos@webrtc.org | 1727dc7 | 2013-04-09 16:40:28 +0000 | [diff] [blame] | 35 | tmp_inv_denom16 = (int16_t)WEBRTC_SPL_RSHIFT_W32(tmp_inv_denom32, 15); |
andrew@webrtc.org | a7b57da | 2012-10-22 18:19:23 +0000 | [diff] [blame] | 36 | |
| 37 | for (k = 1; k <= m; k++) |
| 38 | { |
| 39 | // tmp[k] = (a[k] - RC[m] * a[m-k+1]) / (1.0 - RC[m]*RC[m]); |
| 40 | |
| 41 | // [Q12<<16 - (Q15*Q12)<<1] = [Q28 - Q28] = Q28 |
pbos@webrtc.org | 1727dc7 | 2013-04-09 16:40:28 +0000 | [diff] [blame] | 42 | tmp32[k] = WEBRTC_SPL_LSHIFT_W32((int32_t)a16[k], 16) |
andrew@webrtc.org | a7b57da | 2012-10-22 18:19:23 +0000 | [diff] [blame] | 43 | - WEBRTC_SPL_LSHIFT_W32(WEBRTC_SPL_MUL_16_16(k16[m], a16[m-k+1]), 1); |
| 44 | |
| 45 | tmp32[k] = WebRtcSpl_DivW32W16(tmp32[k], tmp_inv_denom16); //Q28/Q15 = Q13 |
| 46 | } |
| 47 | |
| 48 | for (k = 1; k < m; k++) |
| 49 | { |
pbos@webrtc.org | 1727dc7 | 2013-04-09 16:40:28 +0000 | [diff] [blame] | 50 | a16[k] = (int16_t)WEBRTC_SPL_RSHIFT_W32(tmp32[k], 1); //Q13>>1 => Q12 |
andrew@webrtc.org | a7b57da | 2012-10-22 18:19:23 +0000 | [diff] [blame] | 51 | } |
| 52 | |
| 53 | tmp32[m] = WEBRTC_SPL_SAT(8191, tmp32[m], -8191); |
pbos@webrtc.org | 1727dc7 | 2013-04-09 16:40:28 +0000 | [diff] [blame] | 54 | k16[m - 1] = (int16_t)WEBRTC_SPL_LSHIFT_W32(tmp32[m], 2); //Q13<<2 => Q15 |
andrew@webrtc.org | a7b57da | 2012-10-22 18:19:23 +0000 | [diff] [blame] | 55 | } |
| 56 | return; |
| 57 | } |