1/*
2 *  Copyright (c) 2012 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#ifndef WEBRTC_MODULES_AUDIO_CODING_NETEQ_TIME_STRETCH_H_
12#define WEBRTC_MODULES_AUDIO_CODING_NETEQ_TIME_STRETCH_H_
13
14#include <assert.h>
15#include <string.h>  // memset, size_t
16
17#include "webrtc/base/constructormagic.h"
18#include "webrtc/modules/audio_coding/neteq/audio_multi_vector.h"
19#include "webrtc/typedefs.h"
20
21namespace webrtc {
22
23// Forward declarations.
24class BackgroundNoise;
25
26// This is the base class for Accelerate and PreemptiveExpand. This class
27// cannot be instantiated, but must be used through either of the derived
28// classes.
29class TimeStretch {
30 public:
31  enum ReturnCodes {
32    kSuccess = 0,
33    kSuccessLowEnergy = 1,
34    kNoStretch = 2,
35    kError = -1
36  };
37
38  TimeStretch(int sample_rate_hz, size_t num_channels,
39              const BackgroundNoise& background_noise)
40      : sample_rate_hz_(sample_rate_hz),
41        fs_mult_(sample_rate_hz / 8000),
42        num_channels_(num_channels),
43        master_channel_(0),  // First channel is master.
44        background_noise_(background_noise),
45        max_input_value_(0) {
46    assert(sample_rate_hz_ == 8000 ||
47           sample_rate_hz_ == 16000 ||
48           sample_rate_hz_ == 32000 ||
49           sample_rate_hz_ == 48000);
50    assert(num_channels_ > 0);
51    assert(master_channel_ < num_channels_);
52    memset(auto_correlation_, 0, sizeof(auto_correlation_));
53  }
54
55  virtual ~TimeStretch() {}
56
57  // This method performs the processing common to both Accelerate and
58  // PreemptiveExpand.
59  ReturnCodes Process(const int16_t* input,
60                      size_t input_len,
61                      bool fast_mode,
62                      AudioMultiVector* output,
63                      size_t* length_change_samples);
64
65 protected:
66  // Sets the parameters |best_correlation| and |peak_index| to suitable
67  // values when the signal contains no active speech. This method must be
68  // implemented by the sub-classes.
69  virtual void SetParametersForPassiveSpeech(size_t input_length,
70                                             int16_t* best_correlation,
71                                             size_t* peak_index) const = 0;
72
73  // Checks the criteria for performing the time-stretching operation and,
74  // if possible, performs the time-stretching. This method must be implemented
75  // by the sub-classes.
76  virtual ReturnCodes CheckCriteriaAndStretch(
77      const int16_t* input,
78      size_t input_length,
79      size_t peak_index,
80      int16_t best_correlation,
81      bool active_speech,
82      bool fast_mode,
83      AudioMultiVector* output) const = 0;
84
85  static const size_t kCorrelationLen = 50;
86  static const size_t kLogCorrelationLen = 6;  // >= log2(kCorrelationLen).
87  static const size_t kMinLag = 10;
88  static const size_t kMaxLag = 60;
89  static const size_t kDownsampledLen = kCorrelationLen + kMaxLag;
90  static const int kCorrelationThreshold = 14746;  // 0.9 in Q14.
91
92  const int sample_rate_hz_;
93  const int fs_mult_;  // Sample rate multiplier = sample_rate_hz_ / 8000.
94  const size_t num_channels_;
95  const size_t master_channel_;
96  const BackgroundNoise& background_noise_;
97  int16_t max_input_value_;
98  int16_t downsampled_input_[kDownsampledLen];
99  // Adding 1 to the size of |auto_correlation_| because of how it is used
100  // by the peak-detection algorithm.
101  int16_t auto_correlation_[kCorrelationLen + 1];
102
103 private:
104  // Calculates the auto-correlation of |downsampled_input_| and writes the
105  // result to |auto_correlation_|.
106  void AutoCorrelation();
107
108  // Performs a simple voice-activity detection based on the input parameters.
109  bool SpeechDetection(int32_t vec1_energy, int32_t vec2_energy,
110                       size_t peak_index, int scaling) const;
111
112  RTC_DISALLOW_COPY_AND_ASSIGN(TimeStretch);
113};
114
115}  // namespace webrtc
116#endif  // WEBRTC_MODULES_AUDIO_CODING_NETEQ_TIME_STRETCH_H_
117