git-svn-id: http://webrtc.googlecode.com/svn/trunk@4 4adac7df-926f-26a2-2b94-8c16560cd09d

modules/video_coding/main/source/frame_dropper.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_FRAME_DROPPER_H_
+#define WEBRTC_MODULES_VIDEO_CODING_FRAME_DROPPER_H_
+
+#include "exp_filter.h"
+#include "typedefs.h"
+
+namespace webrtc
+{
+
+/******************************/
+/* VCMFrameDropper class     */
+/****************************/
+// The Frame Dropper implements a variant of the leaky bucket algorithm
+// for keeping track of when to drop frames to avoid bit rate
+// over use when the encoder can't keep its bit rate.
+class VCMFrameDropper
+{
+public:
+    VCMFrameDropper(WebRtc_Word32 vcmId = 0);
+    // Resets the FrameDropper to its initial state.
+    // This means that the frameRateWeight is set to its
+    // default value as well.
+    void Reset();
+
+    void Enable(bool enable);
+    // Answers the question if it's time to drop a frame
+    // if we want to reach a given frame rate. Must be
+    // called for every frame.
+    //
+    // Return value     : True if we should drop the current frame
+    bool DropFrame();
+    // Updates the FrameDropper with the size of the latest encoded
+    // frame. The FrameDropper calculates a new drop ratio (can be
+    // seen as the probability to drop a frame) and updates its
+    // internal statistics.
+    //
+    // Input:
+    //          - frameSizeBytes    : The size of the latest frame
+    //                                returned from the encoder.
+    //          - deltaFrame        : True if the encoder returned
+    //                                a key frame.
+    void Fill(WebRtc_UWord32 frameSizeBytes, bool deltaFrame);
+
+    void Leak(WebRtc_UWord32 inputFrameRate);
+
+    void UpdateNack(WebRtc_UWord32 nackBytes);
+
+    // Sets the target bit rate and the frame rate produced by
+    // the camera.
+    //
+    // Input:
+    //          - bitRate       : The target bit rate
+    void SetRates(float bitRate, float userFrameRate);
+
+    // Return value     : The current average frame rate produced
+    //                    if the DropFrame() function is used as
+    //                    instruction of when to drop frames.
+    float ActualFrameRate(WebRtc_UWord32 inputFrameRate) const;
+
+private:
+    void FillBucket(float inKbits, float outKbits);
+    void UpdateRatio();
+
+    WebRtc_Word32     _vcmId;
+    VCMExpFilter       _keyFrameSizeAvgKbits;
+    VCMExpFilter       _keyFrameRatio;
+    float           _keyFrameSpreadFrames;
+    WebRtc_Word32     _keyFrameCount;
+    float           _accumulator;
+    float           _accumulatorMax;
+    float           _targetBitRate;
+    bool            _dropNext;
+    VCMExpFilter       _dropRatio;
+    WebRtc_Word32     _dropCount;
+    float           _windowSize;
+    float           _userFrameRate;
+    bool            _wasBelowMax;
+    bool            _enabled;
+    bool            _fastMode;
+}; // end of VCMFrameDropper class
+
+} // namespace webrtc
+
+#endif // WEBRTC_MODULES_VIDEO_CODING_FRAME_DROPPER_H_