1 /* 2 * Copyright (c) 2014 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 MODULES_AUDIO_PROCESSING_RMS_LEVEL_H_ 12 #define MODULES_AUDIO_PROCESSING_RMS_LEVEL_H_ 13 14 #include "api/array_view.h" 15 #include "api/optional.h" 16 #include "typedefs.h" // NOLINT(build/include) 17 18 namespace webrtc { 19 20 // Computes the root mean square (RMS) level in dBFs (decibels from digital 21 // full-scale) of audio data. The computation follows RFC 6465: 22 // https://tools.ietf.org/html/rfc6465 23 // with the intent that it can provide the RTP audio level indication. 24 // 25 // The expected approach is to provide constant-sized chunks of audio to 26 // Analyze(). When enough chunks have been accumulated to form a packet, call 27 // Average() to get the audio level indicator for the RTP header. 28 class RmsLevel { 29 public: 30 struct Levels { 31 int average; 32 int peak; 33 }; 34 35 static constexpr int kMinLevelDb = 127; 36 37 RmsLevel(); 38 ~RmsLevel(); 39 40 // Can be called to reset internal states, but is not required during normal 41 // operation. 42 void Reset(); 43 44 // Pass each chunk of audio to Analyze() to accumulate the level. 45 void Analyze(rtc::ArrayView<const int16_t> data); 46 47 // If all samples with the given |length| have a magnitude of zero, this is 48 // a shortcut to avoid some computation. 49 void AnalyzeMuted(size_t length); 50 51 // Computes the RMS level over all data passed to Analyze() since the last 52 // call to Average(). The returned value is positive but should be interpreted 53 // as negative as per the RFC. It is constrained to [0, 127]. Resets the 54 // internal state to start a new measurement period. 55 int Average(); 56 57 // Like Average() above, but also returns the RMS peak value. Resets the 58 // internal state to start a new measurement period. 59 Levels AverageAndPeak(); 60 61 private: 62 // Compares |block_size| with |block_size_|. If they are different, calls 63 // Reset() and stores the new size. 64 void CheckBlockSize(size_t block_size); 65 66 float sum_square_; 67 size_t sample_count_; 68 float max_sum_square_; 69 rtc::Optional<size_t> block_size_; 70 }; 71 72 } // namespace webrtc 73 74 #endif // MODULES_AUDIO_PROCESSING_RMS_LEVEL_H_ 75 76