FrameRate.h

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// FrameRate.h
//
//
// Copyright (c) 2002 David Ward
//

#ifndef __FrameRate_h__
#define __FrameRate_h__

#include "MSVC_Unannoy.h"

// keeps track of framerate
// computes the Steps parameter
// computes RXmax - which controls the maximum rate of zooming in

const double LN2= log(2);

class CFrameRate {
        public:
                CFrameRate() ;
                ~CFrameRate() {};
                const double Rxmax() const {return m_dRXmax;}
                const int Steps() const {return m_iSteps;}
                const double Framerate() const {return m_dFr;}
                void Reset(unsigned long Time);
                void NewFrame(unsigned long Time);
                
                // TODO: These two shouldn't be the same thing:
                void SetBitrate(double TargetRate);
                void SetMaxBitrate(double MaxRate);
        private:
                double m_dFr;
                double m_dMaxbitrate;    // the maximum rate of entering information
                double m_dRXmax;         // the maximum zoomin per frame
                int m_iFrames,m_iTime,m_iTime2,m_iSamples;
                int m_iSteps;            // the 'Steps' parameter. See djw thesis.
};
        
inline CFrameRate::CFrameRate() {

 // maxbitrate should be user-defined and/or adaptive. Currently it is not.
#if defined(_WIN32_WCE)
        m_dMaxbitrate=5;
#else
        m_dMaxbitrate=5.5;
#endif

        m_dRXmax=2;  // only a transient effect
        m_iFrames=0;
        m_iSamples=1;

        // we dont know the framerate yet - play it safe by setting it high
        m_dFr=1<<5;

        // start off very slow until we have sampled framerate adequately
        m_iSteps=2000;
        m_iTime=0; // Hmmm, User must reset framerate before starting.
}

inline void CFrameRate::NewFrame(unsigned long Time) 
        // compute framerate if we have sampled enough frames
{
        
        m_iFrames++;

        if (m_iFrames==m_iSamples) {
                m_iTime2=Time;
                if (m_iTime2-m_iTime < 50) 
                        m_iSamples++;      // increase sample size
                else if (m_iTime2-m_iTime > 80) {
                        m_iSamples--;
                        if (m_iSamples <2)
                                m_iSamples=2;
                }
                if (m_iTime2-m_iTime) {
                                m_dFr=m_iFrames*1000.0/(m_iTime2-m_iTime);
                                m_iTime=m_iTime2;
                                m_iFrames=0;

                        }
                m_dRXmax=exp(m_dMaxbitrate*LN2/m_dFr);
                m_iSteps=m_iSteps/2+(int)(-log(0.2)*m_dFr/LN2/m_dMaxbitrate)/2;
        //      dchar debug[256];
        //              _stprintf(debug,TEXT("fr %f Steps %d samples %d time2 %d rxmax %f\n"),fr,Steps,samples,time2,RXmax);
        //      OutputDebugString(debug);
        
        }
}

inline void CFrameRate::Reset(unsigned long Time)
{
        m_iFrames=0;
        m_iTime=Time;
}


inline void CFrameRate::SetBitrate(double TargetRate)
{
        m_dMaxbitrate = TargetRate;
}


inline void CFrameRate::SetMaxBitrate(double MaxRate)
{
        m_dMaxbitrate = MaxRate;
}



#endif /* #ifndef __FrameRate_h__ */

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