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/*
* 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 includes the implementation of the internal VAD call
* WebRtcVad_GaussianProbability. For function description, see vad_gmm.h.
*/
#include "vad_gmm.h"
#include "signal_processing_library.h"
#include "vad_const.h"
WebRtc_Word32 WebRtcVad_GaussianProbability(WebRtc_Word16 in_sample,
WebRtc_Word16 mean,
WebRtc_Word16 std,
WebRtc_Word16 *delta)
{
WebRtc_Word16 tmp16, tmpDiv, tmpDiv2, expVal, tmp16_1, tmp16_2;
WebRtc_Word32 tmp32, y32;
// Calculate tmpDiv=1/std, in Q10
tmp32 = (WebRtc_Word32)WEBRTC_SPL_RSHIFT_W16(std,1) + (WebRtc_Word32)131072; // 1 in Q17
tmpDiv = (WebRtc_Word16)WebRtcSpl_DivW32W16(tmp32, std); // Q17/Q7 = Q10
// Calculate tmpDiv2=1/std^2, in Q14
tmp16 = WEBRTC_SPL_RSHIFT_W16(tmpDiv, 2); // From Q10 to Q8
tmpDiv2 = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(tmp16, tmp16, 2); // (Q8 * Q8)>>2 = Q14
tmp16 = WEBRTC_SPL_LSHIFT_W16(in_sample, 3); // Q7
tmp16 = tmp16 - mean; // Q7 - Q7 = Q7
// To be used later, when updating noise/speech model
// delta = (x-m)/std^2, in Q11
*delta = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT(tmpDiv2, tmp16, 10); //(Q14*Q7)>>10 = Q11
// Calculate tmp32=(x-m)^2/(2*std^2), in Q10
tmp32 = (WebRtc_Word32)WEBRTC_SPL_MUL_16_16_RSFT(*delta, tmp16, 9); // One shift for /2
// Calculate expVal ~= exp(-(x-m)^2/(2*std^2)) ~= exp2(-log2(exp(1))*tmp32)
if (tmp32 < kCompVar)
{
// Calculate tmp16 = log2(exp(1))*tmp32 , in Q10
tmp16 = (WebRtc_Word16)WEBRTC_SPL_MUL_16_16_RSFT((WebRtc_Word16)tmp32,
kLog10Const, 12);
tmp16 = -tmp16;
tmp16_2 = (WebRtc_Word16)(0x0400 | (tmp16 & 0x03FF));
tmp16_1 = (WebRtc_Word16)(tmp16 ^ 0xFFFF);
tmp16 = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W16(tmp16_1, 10);
tmp16 += 1;
// Calculate expVal=log2(-tmp32), in Q10
expVal = (WebRtc_Word16)WEBRTC_SPL_RSHIFT_W32((WebRtc_Word32)tmp16_2, tmp16);
} else
{
expVal = 0;
}
// Calculate y32=(1/std)*exp(-(x-m)^2/(2*std^2)), in Q20
y32 = WEBRTC_SPL_MUL_16_16(tmpDiv, expVal); // Q10 * Q10 = Q20
return y32; // Q20
}
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