webrtc/modules/video_coding/utility/frame_dropper.h

/*
 *  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_UTILITY_FRAME_DROPPER_H_
#define WEBRTC_MODULES_VIDEO_CODING_UTILITY_FRAME_DROPPER_H_

#include <cstddef>

#include "webrtc/base/exp_filter.h"
#include "webrtc/typedefs.h"

namespace webrtc {

// 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 FrameDropper {
 public:
    FrameDropper();
    explicit FrameDropper(float max_time_drops);
    virtual ~FrameDropper() {}

    // Resets the FrameDropper to its initial state.
    // This means that the frameRateWeight is set to its
    // default value as well.
    virtual void Reset();

    virtual 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
    virtual 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.
    virtual void Fill(size_t frameSizeBytes, bool deltaFrame);

    virtual void Leak(uint32_t inputFrameRate);

    void UpdateNack(uint32_t nackBytes);

    // Sets the target bit rate and the frame rate produced by
    // the camera.
    //
    // Input:
    //          - bitRate       : The target bit rate
    virtual void SetRates(float bitRate, float incoming_frame_rate);

    // Return value     : The current average frame rate produced
    //                    if the DropFrame() function is used as
    //                    instruction of when to drop frames.
    virtual float ActualFrameRate(uint32_t inputFrameRate) const;

 private:
    void FillBucket(float inKbits, float outKbits);
    void UpdateRatio();
    void CapAccumulator();

    rtc::ExpFilter _keyFrameSizeAvgKbits;
    rtc::ExpFilter _keyFrameRatio;
    float _keyFrameSpreadFrames;
    int32_t _keyFrameCount;
    float _accumulator;
    float _accumulatorMax;
    float _targetBitRate;
    bool _dropNext;
    rtc::ExpFilter _dropRatio;
    int32_t _dropCount;
    float _windowSize;
    float _incoming_frame_rate;
    bool _wasBelowMax;
    bool _enabled;
    bool _fastMode;
    float _cap_buffer_size;
    float _max_time_drops;
};  // end of VCMFrameDropper class

}  // namespace webrtc

#endif  // WEBRTC_MODULES_VIDEO_CODING_UTILITY_FRAME_DROPPER_H_