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diff --git a/modules/rtp_rtcp/source/capture_clock_offset_updater.h b/modules/rtp_rtcp/source/capture_clock_offset_updater.h
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+++ b/modules/rtp_rtcp/source/capture_clock_offset_updater.h
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+/*
+ *  Copyright (c) 2021 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_RTP_RTCP_SOURCE_CAPTURE_CLOCK_OFFSET_UPDATER_H_
+#define MODULES_RTP_RTCP_SOURCE_CAPTURE_CLOCK_OFFSET_UPDATER_H_
+
+#include <stdint.h>
+
+#include "absl/types/optional.h"
+
+namespace webrtc {
+
+//
+// Helper class for calculating the clock offset against the capturer's clock.
+//
+// This is achieved by adjusting the estimated capture clock offset in received
+// Absolute Capture Time RTP header extension (see
+// https://webrtc.org/experiments/rtp-hdrext/abs-capture-time/), which
+// represents the clock offset between a remote sender and the capturer, by
+// adding local-to-remote clock offset.
+
+class CaptureClockOffsetUpdater {
+ public:
+  // Adjusts remote_capture_clock_offset, which originates from Absolute Capture
+  // Time RTP header extension, to get the local clock offset against the
+  // capturer's clock.
+  absl::optional<int64_t> AdjustEstimatedCaptureClockOffset(
+      absl::optional<int64_t> remote_capture_clock_offset) const;
+
+  // Sets the NTP clock offset between the sender system (which may be different
+  // from the capture system) and the local system. This information is normally
+  // provided by passing half the value of the Round-Trip Time estimation given
+  // by RTCP sender reports (see DLSR/DLRR).
+  //
+  // Note that the value must be in Q32.32-formatted fixed-point seconds.
+  void SetRemoteToLocalClockOffset(absl::optional<int64_t> offset_q32x32);
+
+ private:
+  absl::optional<int64_t> remote_to_local_clock_offset_;
+};
+
+}  // namespace webrtc
+
+#endif  // MODULES_RTP_RTCP_SOURCE_CAPTURE_CLOCK_OFFSET_UPDATER_H_