78 lines
2.5 KiB
C
78 lines
2.5 KiB
C
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/*
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* Copyright (c) 2014 The WebRTC project authors. All Rights Reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef MODULES_AUDIO_PROCESSING_RMS_LEVEL_H_
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#define MODULES_AUDIO_PROCESSING_RMS_LEVEL_H_
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#include <stddef.h>
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#include <stdint.h>
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#include "absl/types/optional.h"
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#include "api/array_view.h"
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namespace webrtc {
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// Computes the root mean square (RMS) level in dBFs (decibels from digital
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// full-scale) of audio data. The computation follows RFC 6465:
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// https://tools.ietf.org/html/rfc6465
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// with the intent that it can provide the RTP audio level indication.
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//
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// The expected approach is to provide constant-sized chunks of audio to
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// Analyze(). When enough chunks have been accumulated to form a packet, call
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// Average() to get the audio level indicator for the RTP header.
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class RmsLevel {
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public:
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struct Levels {
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int average;
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int peak;
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};
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enum : int { kMinLevelDb = 127, kInaudibleButNotMuted = 126 };
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RmsLevel();
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~RmsLevel();
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// Can be called to reset internal states, but is not required during normal
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// operation.
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void Reset();
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// Pass each chunk of audio to Analyze() to accumulate the level.
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void Analyze(rtc::ArrayView<const int16_t> data);
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void Analyze(rtc::ArrayView<const float> data);
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// If all samples with the given `length` have a magnitude of zero, this is
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// a shortcut to avoid some computation.
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void AnalyzeMuted(size_t length);
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// Computes the RMS level over all data passed to Analyze() since the last
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// call to Average(). The returned value is positive but should be interpreted
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// as negative as per the RFC. It is constrained to [0, 127]. Resets the
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// internal state to start a new measurement period.
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int Average();
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// Like Average() above, but also returns the RMS peak value. Resets the
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// internal state to start a new measurement period.
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Levels AverageAndPeak();
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private:
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// Compares `block_size` with `block_size_`. If they are different, calls
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// Reset() and stores the new size.
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void CheckBlockSize(size_t block_size);
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float sum_square_;
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size_t sample_count_;
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float max_sum_square_;
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absl::optional<size_t> block_size_;
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};
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} // namespace webrtc
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#endif // MODULES_AUDIO_PROCESSING_RMS_LEVEL_H_
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