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 includes the implementation of the internal VAD call 14 * WebRtcVad_GaussianProbability. For function description, see vad_gmm.h. 15 */ 16 17 #include "vad_gmm.h" 18 #include "signal_processing_library.h" 19 #include "vad_const.h" 20 21 WebRtc_Word32 WebRtcVad_GaussianProbability(WebRtc_Word16 in_sample, 22 WebRtc_Word16 mean, 23 WebRtc_Word16 std, 24 WebRtc_Word16 *delta) 25 { 26 WebRtc_Word16 tmp16, tmpDiv, tmpDiv2, expVal, tmp16_1, tmp16_2; 27 WebRtc_Word32 tmp32, y32; 28 29 // Calculate tmpDiv=1/std, in Q10 30 tmp32 = (WebRtc_Word32)WEBRTC_SPL_RSHIFT_W16(std,1) + (WebRtc_Word32)131072; // 1 in Q17 31 tmpDiv = (WebRtc_Word16)WebRtcSpl_DivW32W16(tmp32, std); // Q17/Q7 = Q10 32 33 // Calculate tmpDiv2=1/std^2, in Q14 34 tmp16 = WEBRTC_SPL_RSHIFT_W16(tmpDiv, 2); // From Q10 to Q8 35 tmpDiv2 = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(tmp16, tmp16, 2); // (Q8 * Q8)>>2 = Q14 36 37 tmp16 = WEBRTC_SPL_LSHIFT_W16(in_sample, 3); // Q7 38 tmp16 = tmp16 - mean; // Q7 - Q7 = Q7 39 40 // To be used later, when updating noise/speech model 41 // delta = (x-m)/std^2, in Q11 42 *delta = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(tmpDiv2, tmp16, 10); //(Q14*Q7)>>10 = Q11 43 44 // Calculate tmp32=(x-m)^2/(2*std^2), in Q10 45 tmp32 = (WebRtc_Word32)WEBRTC_SPL_MUL_16_16_RSFT(*delta, tmp16, 9); // One shift for /2 46 47 // Calculate expVal ~= exp(-(x-m)^2/(2*std^2)) ~= exp2(-log2(exp(1))*tmp32) 48 if (tmp32 < kCompVar) 49 { 50 // Calculate tmp16 = log2(exp(1))*tmp32 , in Q10 51 tmp16 = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT((WebRtc_Word16)tmp32, 52 kLog10Const, 12); 53 tmp16 = -tmp16; 54 tmp16_2 = (WebRtc_Word16)(0x0400 | (tmp16 & 0x03FF)); 55 tmp16_1 = (WebRtc_Word16)(tmp16 ^ 0xFFFF); 56 tmp16 = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W16(tmp16_1, 10); 57 tmp16 += 1; 58 // Calculate expVal=log2(-tmp32), in Q10 59 expVal = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32((WebRtc_Word32)tmp16_2, tmp16); 60 61 } else 62 { 63 expVal = 0; 64 } 65 66 // Calculate y32=(1/std)*exp(-(x-m)^2/(2*std^2)), in Q20 67 y32 = WEBRTC_SPL_MUL_16_16(tmpDiv, expVal); // Q10 * Q10 = Q20 68 69 return y32; // Q20 70 } 71
