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diff --git a/webrtc/modules/video_coding/decoding_state.h b/webrtc/modules/video_coding/decoding_state.h
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+/*
+ *  Copyright (c) 2011 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 WEBRTC_MODULES_VIDEO_CODING_DECODING_STATE_H_
+#define WEBRTC_MODULES_VIDEO_CODING_DECODING_STATE_H_
+
+#include "webrtc/typedefs.h"
+
+namespace webrtc {
+
+// Forward declarations
+class VCMFrameBuffer;
+class VCMPacket;
+
+class VCMDecodingState {
+ public:
+  // The max number of bits used to reference back
+  // to a previous frame when using flexible mode.
+  static const uint16_t kNumRefBits = 7;
+  static const uint16_t kFrameDecodedLength = 1 << kNumRefBits;
+
+  VCMDecodingState();
+  ~VCMDecodingState();
+  // Check for old frame
+  bool IsOldFrame(const VCMFrameBuffer* frame) const;
+  // Check for old packet
+  bool IsOldPacket(const VCMPacket* packet) const;
+  // Check for frame continuity based on current decoded state. Use best method
+  // possible, i.e. temporal info, picture ID or sequence number.
+  bool ContinuousFrame(const VCMFrameBuffer* frame) const;
+  void SetState(const VCMFrameBuffer* frame);
+  void CopyFrom(const VCMDecodingState& state);
+  bool UpdateEmptyFrame(const VCMFrameBuffer* frame);
+  // Update the sequence number if the timestamp matches current state and the
+  // sequence number is higher than the current one. This accounts for packets
+  // arriving late.
+  void UpdateOldPacket(const VCMPacket* packet);
+  void SetSeqNum(uint16_t new_seq_num);
+  void Reset();
+  uint32_t time_stamp() const;
+  uint16_t sequence_num() const;
+  // Return true if at initial state.
+  bool in_initial_state() const;
+  // Return true when sync is on - decode all layers.
+  bool full_sync() const;
+
+ private:
+  void UpdateSyncState(const VCMFrameBuffer* frame);
+  // Designated continuity functions
+  bool ContinuousPictureId(int picture_id) const;
+  bool ContinuousSeqNum(uint16_t seq_num) const;
+  bool ContinuousLayer(int temporal_id, int tl0_pic_id) const;
+  bool ContinuousFrameRefs(const VCMFrameBuffer* frame) const;
+  bool UsingPictureId(const VCMFrameBuffer* frame) const;
+  bool UsingFlexibleMode(const VCMFrameBuffer* frame) const;
+  bool AheadOfFramesDecodedClearedTo(uint16_t index) const;
+
+  // Keep state of last decoded frame.
+  // TODO(mikhal/stefan): create designated classes to handle these types.
+  uint16_t sequence_num_;
+  uint32_t time_stamp_;
+  int picture_id_;
+  int temporal_id_;
+  int tl0_pic_id_;
+  bool full_sync_;  // Sync flag when temporal layers are used.
+  bool in_initial_state_;
+
+  // Used to check references in flexible mode.
+  bool frame_decoded_[kFrameDecodedLength];
+  uint16_t frame_decoded_cleared_to_;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_VIDEO_CODING_DECODING_STATE_H_