andrew@webrtc.org | 8ec46c6 | 2014-05-05 18:22:21 +0000 | [diff] [blame] | 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 | |
andrew@webrtc.org | 5ec8fee | 2014-05-14 19:00:59 +0000 | [diff] [blame^] | 11 | #ifndef WEBRTC_MODULES_AUDIO_PROCESSING_RMS_LEVEL_H_ |
| 12 | #define WEBRTC_MODULES_AUDIO_PROCESSING_RMS_LEVEL_H_ |
| 13 | |
andrew@webrtc.org | 8ec46c6 | 2014-05-05 18:22:21 +0000 | [diff] [blame] | 14 | #include "webrtc/typedefs.h" |
| 15 | |
| 16 | namespace webrtc { |
| 17 | |
| 18 | // Computes the root mean square (RMS) level in dBFs (decibels from digital |
| 19 | // full-scale) of audio data. The computation follows RFC 6465: |
| 20 | // https://tools.ietf.org/html/rfc6465 |
| 21 | // with the intent that it can provide the RTP audio level indication. |
| 22 | // |
| 23 | // The expected approach is to provide constant-sized chunks of audio to |
| 24 | // Process(). When enough chunks have been accumulated to form a packet, call |
| 25 | // RMS() to get the audio level indicator for the RTP header. |
| 26 | class RMSLevel { |
| 27 | public: |
| 28 | static const int kMinLevel = 127; |
| 29 | |
| 30 | RMSLevel(); |
| 31 | ~RMSLevel(); |
| 32 | |
| 33 | // Can be called to reset internal states, but is not required during normal |
| 34 | // operation. |
| 35 | void Reset(); |
| 36 | |
| 37 | // Pass each chunk of audio to Process() to accumulate the level. |
| 38 | void Process(const int16_t* data, int length); |
| 39 | |
| 40 | // If all samples with the given |length| have a magnitude of zero, this is |
| 41 | // a shortcut to avoid some computation. |
| 42 | void ProcessMuted(int length); |
| 43 | |
| 44 | // Computes the RMS level over all data passed to Process() since the last |
| 45 | // call to RMS(). The returned value is positive but should be interpreted as |
| 46 | // negative as per the RFC. It is constrained to [0, 127]. |
| 47 | int RMS(); |
| 48 | |
| 49 | private: |
| 50 | float sum_square_; |
| 51 | int sample_count_; |
| 52 | }; |
| 53 | |
| 54 | } // namespace webrtc |
andrew@webrtc.org | 5ec8fee | 2014-05-14 19:00:59 +0000 | [diff] [blame^] | 55 | |
| 56 | #endif // WEBRTC_MODULES_AUDIO_PROCESSING_RMS_LEVEL_H_ |
| 57 | |