File: rms_level.h

package info (click to toggle)
chromium 138.0.7204.183-1
  • links: PTS, VCS
  • area: main
  • in suites: trixie
  • size: 6,071,908 kB
  • sloc: cpp: 34,937,088; ansic: 7,176,967; javascript: 4,110,704; python: 1,419,953; asm: 946,768; xml: 739,971; pascal: 187,324; sh: 89,623; perl: 88,663; objc: 79,944; sql: 50,304; cs: 41,786; fortran: 24,137; makefile: 21,806; php: 13,980; tcl: 13,166; yacc: 8,925; ruby: 7,485; awk: 3,720; lisp: 3,096; lex: 1,327; ada: 727; jsp: 228; sed: 36
file content (78 lines) | stat: -rw-r--r-- 2,511 bytes parent folder | download | duplicates (5)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
/*
 *  Copyright (c) 2014 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.
 */

#ifndef MODULES_AUDIO_PROCESSING_RMS_LEVEL_H_
#define MODULES_AUDIO_PROCESSING_RMS_LEVEL_H_

#include <stddef.h>
#include <stdint.h>

#include <optional>

#include "api/array_view.h"

namespace webrtc {

// Computes the root mean square (RMS) level in dBFs (decibels from digital
// full-scale) of audio data. The computation follows RFC 6465:
// https://tools.ietf.org/html/rfc6465
// with the intent that it can provide the RTP audio level indication.
//
// The expected approach is to provide constant-sized chunks of audio to
// Analyze(). When enough chunks have been accumulated to form a packet, call
// Average() to get the audio level indicator for the RTP header.
class RmsLevel {
 public:
  struct Levels {
    int average;
    int peak;
  };

  enum : int { kMinLevelDb = 127, kInaudibleButNotMuted = 126 };

  RmsLevel();
  ~RmsLevel();

  // Can be called to reset internal states, but is not required during normal
  // operation.
  void Reset();

  // Pass each chunk of audio to Analyze() to accumulate the level.
  void Analyze(ArrayView<const int16_t> data);
  void Analyze(ArrayView<const float> data);

  // If all samples with the given `length` have a magnitude of zero, this is
  // a shortcut to avoid some computation.
  void AnalyzeMuted(size_t length);

  // Computes the RMS level over all data passed to Analyze() since the last
  // call to Average(). The returned value is positive but should be interpreted
  // as negative as per the RFC. It is constrained to [0, 127]. Resets the
  // internal state to start a new measurement period.
  int Average();

  // Like Average() above, but also returns the RMS peak value. Resets the
  // internal state to start a new measurement period.
  Levels AverageAndPeak();

 private:
  // Compares `block_size` with `block_size_`. If they are different, calls
  // Reset() and stores the new size.
  void CheckBlockSize(size_t block_size);

  float sum_square_;
  size_t sample_count_;
  float max_sum_square_;
  std::optional<size_t> block_size_;
};

}  // namespace webrtc

#endif  // MODULES_AUDIO_PROCESSING_RMS_LEVEL_H_