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      1 /*
      2  *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
      3  *
      4  *  Use of this source code is governed by a BSD-style license
      5  *  that can be found in the LICENSE file in the root of the source
      6  *  tree. An additional intellectual property rights grant can be found
      7  *  in the file PATENTS.  All contributing project authors may
      8  *  be found in the AUTHORS file in the root of the source tree.
      9  */
     10 
     11 #ifndef WEBRTC_MODULES_VIDEO_CODING_UTILITY_INCLUDE_FRAME_DROPPER_H_
     12 #define WEBRTC_MODULES_VIDEO_CODING_UTILITY_INCLUDE_FRAME_DROPPER_H_
     13 
     14 #include "webrtc/base/exp_filter.h"
     15 #include "webrtc/typedefs.h"
     16 
     17 namespace webrtc
     18 {
     19 
     20 // The Frame Dropper implements a variant of the leaky bucket algorithm
     21 // for keeping track of when to drop frames to avoid bit rate
     22 // over use when the encoder can't keep its bit rate.
     23 class FrameDropper
     24 {
     25 public:
     26     FrameDropper();
     27     explicit FrameDropper(float max_time_drops);
     28     virtual ~FrameDropper() {}
     29 
     30     // Resets the FrameDropper to its initial state.
     31     // This means that the frameRateWeight is set to its
     32     // default value as well.
     33     virtual void Reset();
     34 
     35     virtual void Enable(bool enable);
     36     // Answers the question if it's time to drop a frame
     37     // if we want to reach a given frame rate. Must be
     38     // called for every frame.
     39     //
     40     // Return value     : True if we should drop the current frame
     41     virtual bool DropFrame();
     42     // Updates the FrameDropper with the size of the latest encoded
     43     // frame. The FrameDropper calculates a new drop ratio (can be
     44     // seen as the probability to drop a frame) and updates its
     45     // internal statistics.
     46     //
     47     // Input:
     48     //          - frameSizeBytes    : The size of the latest frame
     49     //                                returned from the encoder.
     50     //          - deltaFrame        : True if the encoder returned
     51     //                                a key frame.
     52     virtual void Fill(uint32_t frameSizeBytes, bool deltaFrame);
     53 
     54     virtual void Leak(uint32_t inputFrameRate);
     55 
     56     void UpdateNack(uint32_t nackBytes);
     57 
     58     // Sets the target bit rate and the frame rate produced by
     59     // the camera.
     60     //
     61     // Input:
     62     //          - bitRate       : The target bit rate
     63     virtual void SetRates(float bitRate, float incoming_frame_rate);
     64 
     65     // Return value     : The current average frame rate produced
     66     //                    if the DropFrame() function is used as
     67     //                    instruction of when to drop frames.
     68     virtual float ActualFrameRate(uint32_t inputFrameRate) const;
     69 
     70 private:
     71     void FillBucket(float inKbits, float outKbits);
     72     void UpdateRatio();
     73     void CapAccumulator();
     74 
     75     rtc::ExpFilter _keyFrameSizeAvgKbits;
     76     rtc::ExpFilter _keyFrameRatio;
     77     float _keyFrameSpreadFrames;
     78     int32_t _keyFrameCount;
     79     float _accumulator;
     80     float _accumulatorMax;
     81     float _targetBitRate;
     82     bool _dropNext;
     83     rtc::ExpFilter _dropRatio;
     84     int32_t _dropCount;
     85     float _windowSize;
     86     float _incoming_frame_rate;
     87     bool _wasBelowMax;
     88     bool _enabled;
     89     bool _fastMode;
     90     float _cap_buffer_size;
     91     float _max_time_drops;
     92 }; // end of VCMFrameDropper class
     93 
     94 }  // namespace webrtc
     95 
     96 #endif // WEBRTC_MODULES_VIDEO_CODING_UTILITY_INCLUDE_FRAME_DROPPER_H_
     97