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diff --git a/third_party/libwebrtc/modules/audio_processing/agc2/rnn_vad/common.h b/third_party/libwebrtc/modules/audio_processing/agc2/rnn_vad/common.h
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+/*
+ *  Copyright (c) 2018 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_AGC2_RNN_VAD_COMMON_H_
+#define MODULES_AUDIO_PROCESSING_AGC2_RNN_VAD_COMMON_H_
+
+#include <stddef.h>
+
+namespace webrtc {
+namespace rnn_vad {
+
+constexpr double kPi = 3.14159265358979323846;
+
+constexpr int kSampleRate24kHz = 24000;
+constexpr int kFrameSize10ms24kHz = kSampleRate24kHz / 100;
+constexpr int kFrameSize20ms24kHz = kFrameSize10ms24kHz * 2;
+
+// Pitch buffer.
+constexpr int kMinPitch24kHz = kSampleRate24kHz / 800;   // 0.00125 s.
+constexpr int kMaxPitch24kHz = kSampleRate24kHz / 62.5;  // 0.016 s.
+constexpr int kBufSize24kHz = kMaxPitch24kHz + kFrameSize20ms24kHz;
+static_assert((kBufSize24kHz & 1) == 0, "The buffer size must be even.");
+
+// 24 kHz analysis.
+// Define a higher minimum pitch period for the initial search. This is used to
+// avoid searching for very short periods, for which a refinement step is
+// responsible.
+constexpr int kInitialMinPitch24kHz = 3 * kMinPitch24kHz;
+static_assert(kMinPitch24kHz < kInitialMinPitch24kHz, "");
+static_assert(kInitialMinPitch24kHz < kMaxPitch24kHz, "");
+static_assert(kMaxPitch24kHz > kInitialMinPitch24kHz, "");
+// Number of (inverted) lags during the initial pitch search phase at 24 kHz.
+constexpr int kInitialNumLags24kHz = kMaxPitch24kHz - kInitialMinPitch24kHz;
+// Number of (inverted) lags during the pitch search refinement phase at 24 kHz.
+constexpr int kRefineNumLags24kHz = kMaxPitch24kHz + 1;
+static_assert(
+    kRefineNumLags24kHz > kInitialNumLags24kHz,
+    "The refinement step must search the pitch in an extended pitch range.");
+
+// 12 kHz analysis.
+constexpr int kSampleRate12kHz = 12000;
+constexpr int kFrameSize10ms12kHz = kSampleRate12kHz / 100;
+constexpr int kFrameSize20ms12kHz = kFrameSize10ms12kHz * 2;
+constexpr int kBufSize12kHz = kBufSize24kHz / 2;
+constexpr int kInitialMinPitch12kHz = kInitialMinPitch24kHz / 2;
+constexpr int kMaxPitch12kHz = kMaxPitch24kHz / 2;
+static_assert(kMaxPitch12kHz > kInitialMinPitch12kHz, "");
+// The inverted lags for the pitch interval [`kInitialMinPitch12kHz`,
+// `kMaxPitch12kHz`] are in the range [0, `kNumLags12kHz`].
+constexpr int kNumLags12kHz = kMaxPitch12kHz - kInitialMinPitch12kHz;
+
+// 48 kHz constants.
+constexpr int kMinPitch48kHz = kMinPitch24kHz * 2;
+constexpr int kMaxPitch48kHz = kMaxPitch24kHz * 2;
+
+// Spectral features.
+constexpr int kNumBands = 22;
+constexpr int kNumLowerBands = 6;
+static_assert((0 < kNumLowerBands) && (kNumLowerBands < kNumBands), "");
+constexpr int kCepstralCoeffsHistorySize = 8;
+static_assert(kCepstralCoeffsHistorySize > 2,
+              "The history size must at least be 3 to compute first and second "
+              "derivatives.");
+
+constexpr int kFeatureVectorSize = 42;
+
+}  // namespace rnn_vad
+}  // namespace webrtc
+
+#endif  // MODULES_AUDIO_PROCESSING_AGC2_RNN_VAD_COMMON_H_