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diff --git a/third_party/libwebrtc/test/testsupport/fixed_fps_video_frame_writer_adapter.h b/third_party/libwebrtc/test/testsupport/fixed_fps_video_frame_writer_adapter.h
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+/*
+ *  Copyright (c) 2022 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 TEST_TESTSUPPORT_FIXED_FPS_VIDEO_FRAME_WRITER_ADAPTER_H_
+#define TEST_TESTSUPPORT_FIXED_FPS_VIDEO_FRAME_WRITER_ADAPTER_H_
+
+#include <memory>
+
+#include "absl/types/optional.h"
+#include "api/test/video/video_frame_writer.h"
+#include "api/video/video_sink_interface.h"
+#include "system_wrappers/include/clock.h"
+#include "test/testsupport/video_frame_writer.h"
+
+namespace webrtc {
+namespace test {
+
+// Writes video to the specified video writer with specified fixed frame rate.
+// If at the point in time X no new frames are passed to the writer, the
+// previous frame is used to fill the gap and preserve frame rate.
+//
+// This adaptor uses next algorithm:
+// There are output "slots" at a fixed frame rate (starting at the time of the
+// first received frame). Each incoming frame is assigned to the closest output
+// slot. Then empty slots are filled by repeating the closest filled slot before
+// empty one. If there are multiple frames closest to the same slot, the latest
+// received one is used.
+//
+// The frames are outputted for the whole duration of the class life after the
+// first frame was written or until it will be closed.
+//
+// For example if frames from A to F were received, then next output sequence
+// will be generated:
+// Received frames:  A            B       C      D  EF        Destructor called
+//                   |            |       |      |  ||          |
+//                   v            v       v      v  vv          v
+//                   X----X----X----X----X----X----X----X----X----+----+--
+//                   |    |    |    |    |    |    |    |    |
+// Produced frames:  A    A    A    B    C    C    F    F    F
+//
+// This class is not thread safe.
+class FixedFpsVideoFrameWriterAdapter : public VideoFrameWriter {
+ public:
+  FixedFpsVideoFrameWriterAdapter(int fps,
+                                  Clock* clock,
+                                  std::unique_ptr<VideoFrameWriter> delegate);
+  ~FixedFpsVideoFrameWriterAdapter() override;
+
+  bool WriteFrame(const webrtc::VideoFrame& frame) override;
+
+  // Closes adapter and underlying delegate. User mustn't call to the WriteFrame
+  // after calling this method.
+  void Close() override;
+
+ private:
+  // Writes `last_frame_` for each "slot" from `last_frame_time_` up to now
+  // excluding the last one.
+  // Updates `last_frame_time_` to the position of the last NOT WRITTEN frame.
+  // Returns true if all writes were successful, otherwise retuns false. In such
+  // case it is not guranteed how many frames were actually written.
+  bool WriteMissedSlotsExceptLast(Timestamp now);
+  Timestamp Now() const;
+
+  // Because `TimeDelta` stores time with microseconds precision
+  // `last_frame_time_` may have a small drift and for very long streams it
+  // must be updated to use double for time.
+  const TimeDelta inter_frame_interval_;
+  Clock* const clock_;
+  std::unique_ptr<VideoFrameWriter> delegate_;
+  bool is_closed_ = false;
+
+  // Expected time slot for the last frame.
+  Timestamp last_frame_time_ = Timestamp::MinusInfinity();
+  absl::optional<VideoFrame> last_frame_ = absl::nullopt;
+};
+
+}  // namespace test
+}  // namespace webrtc
+
+#endif  // TEST_TESTSUPPORT_FIXED_FPS_VIDEO_FRAME_WRITER_ADAPTER_H_