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diff --git a/third_party/libwebrtc/modules/audio_processing/rms_level.h b/third_party/libwebrtc/modules/audio_processing/rms_level.h
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+/*
+ *  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 "absl/types/optional.h"
+#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(rtc::ArrayView<const int16_t> data);
+  void Analyze(rtc::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_;
+  absl::optional<size_t> block_size_;
+};
+
+}  // namespace webrtc
+
+#endif  // MODULES_AUDIO_PROCESSING_RMS_LEVEL_H_