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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.
+ */
+
+// Gaussian probability calculations internally used in vad_core.c.
+
+#ifndef WEBRTC_COMMON_AUDIO_VAD_VAD_GMM_H_
+#define WEBRTC_COMMON_AUDIO_VAD_VAD_GMM_H_
+
+#include "typedefs.h"
+
+// Calculates the probability for |input|, given that |input| comes from a
+// normal distribution with mean and standard deviation (|mean|, |std|).
+//
+// Inputs:
+// - input : input sample in Q4.
+// - mean : mean input in the statistical model, Q7.
+// - std : standard deviation, Q7.
+//
+// Output:
+//
+// - delta : input used when updating the model, Q11.
+// |delta| = (|input| - |mean|) / |std|^2.
+//
+// Return:
+// (probability for |input|) =
+// 1 / |std| * exp(-(|input| - |mean|)^2 / (2 * |std|^2));
+int32_t WebRtcVad_GaussianProbability(int16_t input,
+ int16_t mean,
+ int16_t std,
+ int16_t* delta);
+
+#endif // WEBRTC_COMMON_AUDIO_VAD_VAD_GMM_H_