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Diffstat (limited to 'third_party/webrtc/src/webrtc/common_audio/signal_processing/levinson_durbin.c')
| -rw-r--r-- | third_party/webrtc/src/webrtc/common_audio/signal_processing/levinson_durbin.c | 246 |
1 files changed, 246 insertions, 0 deletions
diff --git a/third_party/webrtc/src/webrtc/common_audio/signal_processing/levinson_durbin.c b/third_party/webrtc/src/webrtc/common_audio/signal_processing/levinson_durbin.c new file mode 100644 index 00000000..d46e5513 --- /dev/null +++ b/third_party/webrtc/src/webrtc/common_audio/signal_processing/levinson_durbin.c @@ -0,0 +1,246 @@ +/* + * 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_LevinsonDurbin(). + * The description header can be found in signal_processing_library.h + * + */ + +#include "webrtc/common_audio/signal_processing/include/signal_processing_library.h" + +#define SPL_LEVINSON_MAXORDER 20 + +int16_t WebRtcSpl_LevinsonDurbin(const int32_t* R, int16_t* A, int16_t* K, + size_t order) +{ + size_t i, j; + // Auto-correlation coefficients in high precision + int16_t R_hi[SPL_LEVINSON_MAXORDER + 1], R_low[SPL_LEVINSON_MAXORDER + 1]; + // LPC coefficients in high precision + int16_t A_hi[SPL_LEVINSON_MAXORDER + 1], A_low[SPL_LEVINSON_MAXORDER + 1]; + // LPC coefficients for next iteration + int16_t A_upd_hi[SPL_LEVINSON_MAXORDER + 1], A_upd_low[SPL_LEVINSON_MAXORDER + 1]; + // Reflection coefficient in high precision + int16_t K_hi, K_low; + // Prediction gain Alpha in high precision and with scale factor + int16_t Alpha_hi, Alpha_low, Alpha_exp; + int16_t tmp_hi, tmp_low; + int32_t temp1W32, temp2W32, temp3W32; + int16_t norm; + + // Normalize the autocorrelation R[0]...R[order+1] + + norm = WebRtcSpl_NormW32(R[0]); + + for (i = 0; i <= order; ++i) + { + temp1W32 = WEBRTC_SPL_LSHIFT_W32(R[i], norm); + // Put R in hi and low format + R_hi[i] = (int16_t)(temp1W32 >> 16); + R_low[i] = (int16_t)((temp1W32 - ((int32_t)R_hi[i] << 16)) >> 1); + } + + // K = A[1] = -R[1] / R[0] + + temp2W32 = WEBRTC_SPL_LSHIFT_W32((int32_t)R_hi[1],16) + + WEBRTC_SPL_LSHIFT_W32((int32_t)R_low[1],1); // R[1] in Q31 + temp3W32 = WEBRTC_SPL_ABS_W32(temp2W32); // abs R[1] + temp1W32 = WebRtcSpl_DivW32HiLow(temp3W32, R_hi[0], R_low[0]); // abs(R[1])/R[0] in Q31 + // Put back the sign on R[1] + if (temp2W32 > 0) + { + temp1W32 = -temp1W32; + } + + // Put K in hi and low format + K_hi = (int16_t)(temp1W32 >> 16); + K_low = (int16_t)((temp1W32 - ((int32_t)K_hi << 16)) >> 1); + + // Store first reflection coefficient + K[0] = K_hi; + + temp1W32 >>= 4; // A[1] in Q27. + + // Put A[1] in hi and low format + A_hi[1] = (int16_t)(temp1W32 >> 16); + A_low[1] = (int16_t)((temp1W32 - ((int32_t)A_hi[1] << 16)) >> 1); + + // Alpha = R[0] * (1-K^2) + + temp1W32 = ((K_hi * K_low >> 14) + K_hi * K_hi) << 1; // = k^2 in Q31 + + temp1W32 = WEBRTC_SPL_ABS_W32(temp1W32); // Guard against <0 + temp1W32 = (int32_t)0x7fffffffL - temp1W32; // temp1W32 = (1 - K[0]*K[0]) in Q31 + + // Store temp1W32 = 1 - K[0]*K[0] on hi and low format + tmp_hi = (int16_t)(temp1W32 >> 16); + tmp_low = (int16_t)((temp1W32 - ((int32_t)tmp_hi << 16)) >> 1); + + // Calculate Alpha in Q31 + temp1W32 = (R_hi[0] * tmp_hi + (R_hi[0] * tmp_low >> 15) + + (R_low[0] * tmp_hi >> 15)) << 1; + + // Normalize Alpha and put it in hi and low format + + Alpha_exp = WebRtcSpl_NormW32(temp1W32); + temp1W32 = WEBRTC_SPL_LSHIFT_W32(temp1W32, Alpha_exp); + Alpha_hi = (int16_t)(temp1W32 >> 16); + Alpha_low = (int16_t)((temp1W32 - ((int32_t)Alpha_hi << 16)) >> 1); + + // Perform the iterative calculations in the Levinson-Durbin algorithm + + for (i = 2; i <= order; i++) + { + /* ---- + temp1W32 = R[i] + > R[j]*A[i-j] + / + ---- + j=1..i-1 + */ + + temp1W32 = 0; + + for (j = 1; j < i; j++) + { + // temp1W32 is in Q31 + temp1W32 += (R_hi[j] * A_hi[i - j] << 1) + + (((R_hi[j] * A_low[i - j] >> 15) + + (R_low[j] * A_hi[i - j] >> 15)) << 1); + } + + temp1W32 = WEBRTC_SPL_LSHIFT_W32(temp1W32, 4); + temp1W32 += (WEBRTC_SPL_LSHIFT_W32((int32_t)R_hi[i], 16) + + WEBRTC_SPL_LSHIFT_W32((int32_t)R_low[i], 1)); + + // K = -temp1W32 / Alpha + temp2W32 = WEBRTC_SPL_ABS_W32(temp1W32); // abs(temp1W32) + temp3W32 = WebRtcSpl_DivW32HiLow(temp2W32, Alpha_hi, Alpha_low); // abs(temp1W32)/Alpha + + // Put the sign of temp1W32 back again + if (temp1W32 > 0) + { + temp3W32 = -temp3W32; + } + + // Use the Alpha shifts from earlier to de-normalize + norm = WebRtcSpl_NormW32(temp3W32); + if ((Alpha_exp <= norm) || (temp3W32 == 0)) + { + temp3W32 = WEBRTC_SPL_LSHIFT_W32(temp3W32, Alpha_exp); + } else + { + if (temp3W32 > 0) + { + temp3W32 = (int32_t)0x7fffffffL; + } else + { + temp3W32 = (int32_t)0x80000000L; + } + } + + // Put K on hi and low format + K_hi = (int16_t)(temp3W32 >> 16); + K_low = (int16_t)((temp3W32 - ((int32_t)K_hi << 16)) >> 1); + + // Store Reflection coefficient in Q15 + K[i - 1] = K_hi; + + // Test for unstable filter. + // If unstable return 0 and let the user decide what to do in that case + + if ((int32_t)WEBRTC_SPL_ABS_W16(K_hi) > (int32_t)32750) + { + return 0; // Unstable filter + } + + /* + Compute updated LPC coefficient: Anew[i] + Anew[j]= A[j] + K*A[i-j] for j=1..i-1 + Anew[i]= K + */ + + for (j = 1; j < i; j++) + { + // temp1W32 = A[j] in Q27 + temp1W32 = WEBRTC_SPL_LSHIFT_W32((int32_t)A_hi[j],16) + + WEBRTC_SPL_LSHIFT_W32((int32_t)A_low[j],1); + + // temp1W32 += K*A[i-j] in Q27 + temp1W32 += (K_hi * A_hi[i - j] + (K_hi * A_low[i - j] >> 15) + + (K_low * A_hi[i - j] >> 15)) << 1; + + // Put Anew in hi and low format + A_upd_hi[j] = (int16_t)(temp1W32 >> 16); + A_upd_low[j] = (int16_t)( + (temp1W32 - ((int32_t)A_upd_hi[j] << 16)) >> 1); + } + + // temp3W32 = K in Q27 (Convert from Q31 to Q27) + temp3W32 >>= 4; + + // Store Anew in hi and low format + A_upd_hi[i] = (int16_t)(temp3W32 >> 16); + A_upd_low[i] = (int16_t)( + (temp3W32 - ((int32_t)A_upd_hi[i] << 16)) >> 1); + + // Alpha = Alpha * (1-K^2) + + temp1W32 = ((K_hi * K_low >> 14) + K_hi * K_hi) << 1; // K*K in Q31 + + temp1W32 = WEBRTC_SPL_ABS_W32(temp1W32); // Guard against <0 + temp1W32 = (int32_t)0x7fffffffL - temp1W32; // 1 - K*K in Q31 + + // Convert 1- K^2 in hi and low format + tmp_hi = (int16_t)(temp1W32 >> 16); + tmp_low = (int16_t)((temp1W32 - ((int32_t)tmp_hi << 16)) >> 1); + + // Calculate Alpha = Alpha * (1-K^2) in Q31 + temp1W32 = (Alpha_hi * tmp_hi + (Alpha_hi * tmp_low >> 15) + + (Alpha_low * tmp_hi >> 15)) << 1; + + // Normalize Alpha and store it on hi and low format + + norm = WebRtcSpl_NormW32(temp1W32); + temp1W32 = WEBRTC_SPL_LSHIFT_W32(temp1W32, norm); + + Alpha_hi = (int16_t)(temp1W32 >> 16); + Alpha_low = (int16_t)((temp1W32 - ((int32_t)Alpha_hi << 16)) >> 1); + + // Update the total normalization of Alpha + Alpha_exp = Alpha_exp + norm; + + // Update A[] + + for (j = 1; j <= i; j++) + { + A_hi[j] = A_upd_hi[j]; + A_low[j] = A_upd_low[j]; + } + } + + /* + Set A[0] to 1.0 and store the A[i] i=1...order in Q12 + (Convert from Q27 and use rounding) + */ + + A[0] = 4096; + + for (i = 1; i <= order; i++) + { + // temp1W32 in Q27 + temp1W32 = WEBRTC_SPL_LSHIFT_W32((int32_t)A_hi[i], 16) + + WEBRTC_SPL_LSHIFT_W32((int32_t)A_low[i], 1); + // Round and store upper word + A[i] = (int16_t)(((temp1W32 << 1) + 32768) >> 16); + } + return 1; // Stable filters +} |