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// This file includes specific signal processing tools used in vad_core.c.
13
14#ifndef WEBRTC_COMMON_AUDIO_VAD_VAD_SP_H_
15#define WEBRTC_COMMON_AUDIO_VAD_VAD_SP_H_
16
17#include "webrtc/common_audio/vad/vad_core.h"
18#include "webrtc/typedefs.h"
19
20// Downsamples the signal by a factor 2, eg. 32->16 or 16->8.
21//
22// Inputs:
23//      - signal_in     : Input signal.
24//      - in_length     : Length of input signal in samples.
25//
26// Input & Output:
27//      - filter_state  : Current filter states of the two all-pass filters. The
28//                        |filter_state| is updated after all samples have been
29//                        processed.
30//
31// Output:
32//      - signal_out    : Downsampled signal (of length |in_length| / 2).
33void WebRtcVad_Downsampling(const int16_t* signal_in,
34                            int16_t* signal_out,
35                            int32_t* filter_state,
36                            int in_length);
37
38// Updates and returns the smoothed feature minimum. As minimum we use the
39// median of the five smallest feature values in a 100 frames long window.
40// As long as |handle->frame_counter| is zero, that is, we haven't received any
41// "valid" data, FindMinimum() outputs the default value of 1600.
42//
43// Inputs:
44//      - feature_value : New feature value to update with.
45//      - channel       : Channel number.
46//
47// Input & Output:
48//      - handle        : State information of the VAD.
49//
50// Returns:
51//                      : Smoothed minimum value for a moving window.
52int16_t WebRtcVad_FindMinimum(VadInstT* handle,
53                              int16_t feature_value,
54                              int channel);
55
56#endif  // WEBRTC_COMMON_AUDIO_VAD_VAD_SP_H_
57