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author | andrew@webrtc.org <andrew@webrtc.org@4adac7df-926f-26a2-2b94-8c16560cd09d> | 2012-10-22 18:19:23 +0000 |
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committer | andrew@webrtc.org <andrew@webrtc.org@4adac7df-926f-26a2-2b94-8c16560cd09d> | 2012-10-22 18:19:23 +0000 |
commit | b015cbede88899f67a53fbbe581b02ce8e327949 (patch) | |
tree | 530a64a3cfdbbabacab974c183326517d49e761e /common_audio/signal_processing/lpc_to_refl_coef.c | |
download | webrtc-b015cbede88899f67a53fbbe581b02ce8e327949.tar.gz |
Move src/ -> webrtc/
TBR=niklas.enbom@webrtc.org
Review URL: https://webrtc-codereview.appspot.com/915006
git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@2963 4adac7df-926f-26a2-2b94-8c16560cd09d
Diffstat (limited to 'common_audio/signal_processing/lpc_to_refl_coef.c')
-rw-r--r-- | common_audio/signal_processing/lpc_to_refl_coef.c | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/common_audio/signal_processing/lpc_to_refl_coef.c b/common_audio/signal_processing/lpc_to_refl_coef.c new file mode 100644 index 00000000..2cb83c2e --- /dev/null +++ b/common_audio/signal_processing/lpc_to_refl_coef.c @@ -0,0 +1,57 @@ +/* + * 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. + */ + + +/* + * This file contains the function WebRtcSpl_LpcToReflCoef(). + * The description header can be found in signal_processing_library.h + * + */ + +#include "signal_processing_library.h" + +#define SPL_LPC_TO_REFL_COEF_MAX_AR_MODEL_ORDER 50 + +void WebRtcSpl_LpcToReflCoef(WebRtc_Word16* a16, int use_order, WebRtc_Word16* k16) +{ + int m, k; + WebRtc_Word32 tmp32[SPL_LPC_TO_REFL_COEF_MAX_AR_MODEL_ORDER]; + WebRtc_Word32 tmp_inv_denom32; + WebRtc_Word16 tmp_inv_denom16; + + k16[use_order - 1] = WEBRTC_SPL_LSHIFT_W16(a16[use_order], 3); //Q12<<3 => Q15 + for (m = use_order - 1; m > 0; m--) + { + // (1 - k^2) in Q30 + tmp_inv_denom32 = ((WebRtc_Word32)1073741823) - WEBRTC_SPL_MUL_16_16(k16[m], k16[m]); + // (1 - k^2) in Q15 + tmp_inv_denom16 = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32(tmp_inv_denom32, 15); + + for (k = 1; k <= m; k++) + { + // tmp[k] = (a[k] - RC[m] * a[m-k+1]) / (1.0 - RC[m]*RC[m]); + + // [Q12<<16 - (Q15*Q12)<<1] = [Q28 - Q28] = Q28 + tmp32[k] = WEBRTC_SPL_LSHIFT_W32((WebRtc_Word32)a16[k], 16) + - WEBRTC_SPL_LSHIFT_W32(WEBRTC_SPL_MUL_16_16(k16[m], a16[m-k+1]), 1); + + tmp32[k] = WebRtcSpl_DivW32W16(tmp32[k], tmp_inv_denom16); //Q28/Q15 = Q13 + } + + for (k = 1; k < m; k++) + { + a16[k] = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32(tmp32[k], 1); //Q13>>1 => Q12 + } + + tmp32[m] = WEBRTC_SPL_SAT(8191, tmp32[m], -8191); + k16[m - 1] = (WebRtc_Word16)WEBRTC_SPL_LSHIFT_W32(tmp32[m], 2); //Q13<<2 => Q15 + } + return; +} |