path: root/converter/ppm/ppmtompeg/rate.c

/*============================================================================*
 * rate.c								      *
 *									      *
 *	Procedures concerned with rate control                                *
 *									      *
 * EXPORTED PROCEDURES:							      *
 *      initRatecontrol()                                                     *
 *      targetRateControl()                                                   *
 *      updateRateControl()                                                   *
 *      MB_RateOut()                                                          *
 *      needQScaleChange()                                                    *
 *      incNumBlocks()                                                        *
 *      incQuant()                                                            *
 *	incMacroBlockBits()                                                   *
 *      setPictureRate()                                                      *
 *      setBitRate()                                                          *
 *      getBitRate()                                                          *
 *      setBufferSize()                                                       *
 *      getBufferSize()                                                       *
 *                                                                            *
 * NOTES:                                                                     *
 *	Naming conventions follow those of MPEG-2 draft algorithm (chap. 10)  *
 *============================================================================*/


/*
 * Copyright (c) 1995 The Regents of the University of California.
 * All rights reserved.
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose, without fee, and without written agreement is
 * hereby granted, provided that the above copyright notice and the following
 * two paragraphs appear in all copies of this software.
 *
 * IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT
 * OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF THE UNIVERSITY OF
 * CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
 * ON AN "AS IS" BASIS, AND THE UNIVERSITY OF CALIFORNIA HAS NO OBLIGATION TO
 * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
 */

/*==============*
 * HEADER FILES *
 *==============*/

#include <assert.h>
#include <sys/types.h>

#include "ppm.h"
#include "nstring.h"

#include "all.h"
#include "mtypes.h"
#include "bitio.h"
#include "frames.h"
#include "prototypes.h"
#include "param.h"
#include "mheaders.h"
#include "fsize.h"
#include "postdct.h"
#include "mpeg.h"
#include "parallel.h"
#include "dct.h"
#include "rate.h"


/*==================*
 * GLOBAL VARIABLES *
 *==================*/

#define MAX_BIT_RATE 104857600		/* 18 digit number in units of 400 */
#define MAX_BUFFER_SIZE 16760832        /* 10 digit number in units of 16k */
#define DEFAULT_BUFFER_SIZE 327680      /* maximum for "constrained" bitstream */
#define DEFAULT_VBV_FULLNESS 3          /* wait till 1/3 full */
#define DEFAULT_PICT_RATE_CODE 5        /* code for 30 Frames/sec */
#define DEFAULT_PICT_RATE 30            /* 30 frames per second */
#define MAX_VBV_DELAY 32768             /* 16 digits */


/*	  Variables from Parameter File */

static int	RateControlMode = VARIABLE_RATE;
static int32 buffer_size = DEFAULT_BUFFER_SIZE;
static int32 bit_rate = -1;

static bool wantVbvUnderflowWarning;
static bool wantVbvOverflowWarning;

/*   Variables for the VBV buffer defined in MPEG specs */
static unsigned int VBV_remainingDelay;
    /* delay in units of 1/90000 seconds */
static int32 VBV_buffer = 0;	  /* fullness of the theoretical VBV buffer */
static int32 bufferFillRate = 0;    /* constant rate at which buffer filled */
static int32 frameDelayIncrement = 0;	/* number of "delay" units/Frame */

/*  Global complexity measure variables */
static int Xi, Xp, Xb;  /*  Global complexity measure  */

static int Si, Sp, Sb;  /*  Total # bits for last pict of type (Overhead?) */

static float Qi, Qp, Qb; /* avg quantizaton for last picture of type  */

/*  Target bit allocations for each type of picture*/
int Ti, Tp, Tb;

int current_Tx;	/* allocation for current frame */

/*  Count of number of pictures of each type remaining */
int GOP_X;
int GOP_I;
int GOP_P;
int GOP_B;

int Nx = 0;
int Ni = 0;
int Np = 0;
int Nb = 0;

/*   Counters used while encoding frames   */

int rc_numBlocks = 0;
int rc_totalQuant = 0;
int rc_bitsThisMB;
int rc_totalMBBits;
int rc_totalFrameBits;
int rc_totalOverheadBits = 0;


/*	Want to print out Macroblock info every Nth MB */
int RC_MB_SAMPLE_RATE = 0;

static float Ki = .7;
static float Kp = 1;
static float Kb = 1.4;
static int rc_R;
static int rc_G;

/*   Rate Control variables   */

/*   Virtual buffers for each frame type */
static int d0_i;   /* Initial fullnesses */
static int d0_p;
static int d0_b;

static int lastFrameVirtBuf;   /* fullness after last frame of this type */
static int currentVirtBuf;     /* fullness during current encoding*/

static int MB_cnt = -1;	       /* Number of MB's in picture */

static int rc_Q;               /* reference quantization parameter */

static int reactionParameter;  /*  Reaction parameter */

/*	Adaptive Quantization variables */
static int act_j;              /*  spatial activity measure */
static float N_act;            /*  Normalized spacial activity */
static int avg_act;	   /*  average activity value in last picture encoded */
static int total_act_j;	       /*  Sum of activity values in current frame */

static int var_sblk;	       /* sub-block activity */
static int P_mean;	       /* Mean value of pixels in 8x8 sub-block */

static int mquant;	       /* Raw Quantization value */
static int Qscale;	       /* Clipped, truncated quantization value */



/*  Output-related variables */
#ifdef RC_STATS_FILE
static FILE *RC_FILE;
#endif

static char rc_buffer[101];

/*	EXTERNAL Variables  */
extern char *framePattern;
extern int framePatternLen;


/*===============================*
 * INTERNAL PROCEDURE prototypes *
 *===============================*/

int initGOPRateControl (void);
int determineMBCount (void);
void checkBufferFullness (int count);
void checkSpatialActivity (Block blk0, Block blk1, Block blk2, Block blk3);
void incNumBlocks (int num);
void calculateVBVDelay (int num);
int BlockExperiments  (int16 *OrigBlock, int16 *NewBlock, int control);



static void
analyzePattern(const char *  const framePattern,
               int           const framePatternLen,
               int *         const gop_xP,
               int *         const gop_iP,
               int *         const gop_pP,
               int *         const gop_bP,
               const char ** const errorP) {

    unsigned int i;

    /*  Initialize Pattern info */
    *gop_xP = framePatternLen;

    for (i = 0, *gop_iP = 0, *gop_pP = 0, *gop_bP = 0, *errorP = NULL;
         i < framePatternLen && !*errorP;
         ++i) {
        switch(framePattern[i]) {
        case 'i': ++*gop_iP; break;
        case 'p': ++*gop_pP; break;
        case 'b': ++*gop_bP; break;
        default:
            pm_asprintf(errorP, "Bad pattern - not composed of i, p, and b");
        }
    }
    assert(*gop_xP == *gop_iP + *gop_pP + *gop_bP);
}



/*===========================================================================*
 *
 * initRateControl
 *
 *	initialize the allocation parameters.
 *
 * RETURNS:	nothing
 *
 * SIDE EFFECTS:   many global variables
 *
 * NOTES:  Get rid of the redundant pattern stuff!!
 *===========================================================================*/
int
initRateControl(bool const wantUnderflowWarning,
                bool const wantOverflowWarning) {
    int result;
    const char * error;

    wantVbvUnderflowWarning = wantUnderflowWarning;
    wantVbvOverflowWarning  = wantOverflowWarning;

    DBG_PRINT(("Initializing Allocation Data\n"));

#ifdef RC_STATS_FILE
    RC_FILE = fopen("RC_STATS_FILE", "w");
    if ( RC_FILE  == NULL) {
        DBG_PRINT(("Open of RC file failed, using stderr\n"));
        RC_FILE = stderr;
        fprintf(RC_FILE, "Open of RC file failed, using stderr\n");
        fflush(RC_FILE);
    }
#endif

    VBV_remainingDelay = 0;

    analyzePattern(framePattern, framePatternLen,
                   &GOP_X, &GOP_I, &GOP_P, &GOP_B, &error);

    if (error) {
        pm_message("Unable to set up rate control.  Switching to variable.  "
                   "%s", error);
        pm_strfree(error);
        RateControlMode = VARIABLE_RATE;
        return -1;
    }


    /* Initializing GOP bit allocation */
    rc_R = 0;
    rc_G = (bit_rate * GOP_X/frameRateRounded);

    /*   Initialize the "global complexity measures" */
    Xi = (160 * bit_rate/115);
    Xp = (60 * bit_rate/115);
    Xb = (42 * bit_rate/115);

    /*   Initialize MB counters */
    rc_totalMBBits= rc_bitsThisMB= rc_totalFrameBits=rc_totalOverheadBits = 0;
    rc_numBlocks = rc_totalQuant = 0;

    /*   init virtual buffers  */
    reactionParameter = (2 * bit_rate / frameRateRounded);
    d0_i = (10 * reactionParameter / 31);
    d0_p = (Kp * d0_i);
    d0_b = (Kb * d0_i);

    lastFrameVirtBuf = d0_i;	/*  start with I Frame */
    rc_Q = lastFrameVirtBuf  * 31 / reactionParameter;

    /*   init spatial activity measures */
    avg_act = 400;		/* Suggested initial value */
    N_act = 1;

    mquant = rc_Q * N_act;

    frameDelayIncrement = (90000 / frameRateRounded);
        /* num of "delay" units per frame */
    bufferFillRate = bit_rate / frameRateRounded;
        /* VBV buf fills at constant rate */
    VBV_buffer = buffer_size;
    DBG_PRINT(("VBV- delay: %d, fill rate: %d, delay/Frame: %d units, "
               "buffer size: %d\n",
               VBV_remainginDelay, bufferFillRate, frameDelayIncrement,
               buffer_size));

    result = initGOPRateControl();

    return result;
}

/*===========================================================================*
 *
 * initGOPRateControl
 *
 *		(re)-initialize the RC for the a new Group of Pictures.
 *	New bit allocation, but carry over complexity measures.
 *
 * RETURNS:	nothing
 *
 * SIDE EFFECTS:   many global variables
 *
 *===========================================================================*/
int
initGOPRateControl()
{
    DBG_PRINT(("Initializing new GOP\n"));

    Nx = GOP_X;
    Ni = GOP_I;
    Np = GOP_P;
    Nb = GOP_B;

    rc_R += rc_G;

    DBG_PRINT(("bufsize: %d, bitrate: %d, pictrate: %d, GOP bits: %d\n",
               buffer_size, bit_rate, frameRateRounded, rc_R));
    DBG_PRINT(("Xi: %d, Xp: %d, Xb: %d Nx: %d, Ni: %d, Np: %d, Nb: %d\n",
               Xi, Xp, Xb, Nx,Ni,Np,Nb));
    DBG_PRINT(("d0_i: %d, d0_p: %d, d0_b: %d, avg_act: %d, rc_Q: %d, "
               "mquant: %d\n",
               d0_i, d0_p, d0_b, avg_act, rc_Q, mquant));
    return 1;
}



/*===========================================================================*
 *
 * targetRateControl
 *
 *      Determine the target allocation for given picture type, initiates
 *  variables for rate control process.
 *
 * RETURNS:     nothing.
 *
 * SIDE EFFECTS:   many global variables
 *
 *===========================================================================*/
void
targetRateControl(MpegFrame * const frame) {

    float temp1, minimumBits;
    float tempX, tempY, tempZ;
    int result;
    int frameType;

    minimumBits = (bit_rate / (8 * frameRateRounded));

    /*   Check if new GOP */
    if (Nx == 0) {
        initGOPRateControl();
    }

    if (MB_cnt < 0) {MB_cnt = determineMBCount();}

    switch (frame->type) {
    case TYPE_IFRAME:
        frameType = 'I';

        tempX = ( (Np * Ki * Xp) / (Xi * Kp) );
        tempY = ( (Nb * Ki * Xb) / (Xi*Kb) );
        tempZ = Ni + tempX + tempY;
        temp1 = (rc_R / tempZ);
        result = (int) (temp1 > minimumBits ? temp1 :  minimumBits);
        current_Tx = Ti = result;
        lastFrameVirtBuf = d0_i;
        break;

    case TYPE_PFRAME:
        frameType = 'P';
        tempX =  ( (Ni * Kp * Xi) / (Ki * Xp) );
        tempY =  ( (Nb * Kp * Xb) / (Kb * Xp) );
        tempZ = Np + tempX + tempY;
        temp1 = (rc_R/ tempZ);
        result = (int) (temp1 > minimumBits ? temp1 :  minimumBits);
        current_Tx = Tp = result;
        lastFrameVirtBuf = d0_p;
        break;

    case TYPE_BFRAME:
        frameType = 'B';
        tempX =  ( (Ni * Kb * Xi) / (Ki * Xb) );
        tempY =  ( (Np * Kb * Xp) / (Kp * Xb) );
        tempZ = Nb + tempX + tempY;
        temp1 = (rc_R/ tempZ);
        result = (int) (temp1 > minimumBits ? temp1 :  minimumBits);
        current_Tx = Tb = result;
        lastFrameVirtBuf = d0_b;
        break;

    default:
        frameType = 'X';
    }

    N_act = 1;
    rc_Q = lastFrameVirtBuf  * 31 / reactionParameter;
    mquant = rc_Q * N_act;
    Qscale = (mquant > 31 ? 31 : mquant);
    Qscale = (Qscale < 1 ? 1 : Qscale);

#ifdef HEINOUS_DEBUG_MODE
    {
        const char * strPtr;
        /*   Print headers for Frame info */
        strPtr = Frame_header1;
        DBG_PRINT(("%s\n",strPtr));
        strPtr = Frame_header2;
        DBG_PRINT(("%s\n",strPtr));
        strPtr = Frame_header3;
        DBG_PRINT(("%s\n",strPtr));
    }
#endif
    /*   Print Frame info */
    sprintf(rc_buffer, "%4d     %1c  %4d  %6d %7d  "
            "%2d %2d %2d   %2.2f  %6d %4d    %3d",
            frame->id,frameType,MB_cnt,current_Tx,rc_R,Ni,Np,Nb,
            N_act, lastFrameVirtBuf, rc_Q, Qscale);

#ifdef RC_STATS_FILE
    fprintf(RC_FILE,"%s\n", rc_buffer);
    fflush(RC_FILE);
#endif
    DBG_PRINT(("%s\n",rc_buffer));

    /*  Print headers for Macroblock info */
    if (RC_MB_SAMPLE_RATE) {
#ifdef HEINOUS_DEBUG_MODE
        const char * strPtr;
        strPtr = MB_header1;
        DBG_PRINT(("%s\n",strPtr));
        strPtr = MB_header2;
        DBG_PRINT(("%s\n",strPtr));
#endif
    }
}




static void
updateVBVBuffer(int const frameBits) {
/*----------------------------------------------------------------------------
  Update the VBV buffer after each frame.  This theoretical buffer is
  being filled at constant rate 'bufferFillRate' from an mpeg stream.
  It is emptied as each frame is grabbed by the decoder.  Exception is
  that the decoder will wait until the "delay" is over.

  We mark the passing of one unit of time, in which 'frameBits' bits of
  mpeg data were grabbed from the buffer by the decoder.
-----------------------------------------------------------------------------*/
    if (VBV_remainingDelay)
        VBV_remainingDelay -= MIN(frameDelayIncrement, VBV_remainingDelay);
    else
        VBV_buffer -= frameBits;

    VBV_buffer += bufferFillRate;
    if (VBV_buffer < 0 && wantVbvUnderflowWarning)
        pm_message("WARNING - VBV buffer underflow (%d)", VBV_buffer);
    if (VBV_buffer > buffer_size && wantVbvOverflowWarning)
        pm_message("WARNING - VBV buffer overflow (%d > %d)",
                   VBV_buffer, buffer_size);
}



/*===========================================================================*
 *
 * updateRateControl
 *
 *      Update the statistics kept, after end of frame.  Resets
 *  various global variables
 *
 * RETURNS:     nothing
 *
 * SIDE EFFECTS:   many global variables
 *
 *===========================================================================*/
void
updateRateControl(int const type) {
    int totalBits, frameComplexity, pctAllocUsed, pctGOPUsed;
    float avgQuant;

    totalBits = rc_totalFrameBits;
    avgQuant = ((float) rc_totalQuant / (float) rc_numBlocks);
    frameComplexity = totalBits * avgQuant;
    pctAllocUsed = (totalBits *100 / current_Tx);
    rc_R -= totalBits;
    pctGOPUsed = (rc_R *100/ rc_G);

    avg_act = (total_act_j / MB_cnt);

    updateVBVBuffer(totalBits);

    switch (type) {
    case TYPE_IFRAME:
        Ti = current_Tx;
        d0_i = currentVirtBuf;
        Ni--;
        Si = totalBits;
        Qi = avgQuant;
        Xi = frameComplexity;
        break;
    case TYPE_PFRAME:
        Tp = current_Tx;
        d0_p = currentVirtBuf;
        Np--;
        Sp = totalBits;
        Qp = avgQuant;
        Xp = frameComplexity;
        break;
    case TYPE_BFRAME:
        Tb = current_Tx;
        d0_b = currentVirtBuf;
        Nb--;
        Sb = totalBits;
        Qb = avgQuant;
        Xb = frameComplexity;
        break;
    }

#ifdef HEINOUS_DEBUG_MODE
    {
        /*  Print Frame info */
        const char * strPtr;
        strPtr = Frame_trailer1;
        DBG_PRINT(("%s\n",strPtr));
        strPtr = Frame_trailer2;
        DBG_PRINT(("%s\n",strPtr));
        strPtr = Frame_trailer3;
        DBG_PRINT(("%s\n",strPtr));
    }
#endif
    sprintf(rc_buffer, "%6d  %2.2f  %6d  %3d  %2.2f %7d   "
            "%3d %7d   %3d  %6d %6d",
            totalBits, avgQuant, frameComplexity, avg_act, N_act,
            currentVirtBuf, pctAllocUsed, rc_R, pctGOPUsed,
            VBV_buffer, VBV_remainingDelay);
#ifdef RC_STATS_FILE
    fprintf(RC_FILE,"%s\n", rc_buffer);
    fflush(RC_FILE);
#endif
    DBG_PRINT(("%s\n",rc_buffer));

    Nx--;
    rc_totalMBBits= rc_bitsThisMB= rc_totalFrameBits=rc_totalOverheadBits = 0;
    rc_numBlocks = rc_totalQuant = total_act_j = currentVirtBuf = 0;

    DBG_PRINT(("GOP now has %d bits remaining (%3d%%) for %d frames .. , "
               "Ni= %d, Np= %d, Nb= %d\n",
               rc_R, (rc_R*100/rc_G), (Ni+Np+Nb), Ni, Np, Nb));

}


/*===========================================================================*
 *
 * MB_RateOut
 *
 *      Prints out sampling of MB rate control data.  Every "nth" block
 *	stats are printed, with "n" controlled by global RC_MB_SAMPLE_RATE
 *	(NB. "skipped" blocks do not go through this function and thus do not
 *		show up in the sample )
 *
 * RETURNS:     nothing
 *
 * SIDE EFFECTS:   none
 *
 * NOTES:
 *
 *===========================================================================*/
void
  MB_RateOut(type)
int type;
{
  int totalBits;
  int pctUsed, pctDone;
  int bitsThisMB;
  int bitsPerMB;

  bitsThisMB = rc_bitsThisMB;
  totalBits = rc_totalFrameBits;
  bitsPerMB = (totalBits / rc_numBlocks);
  pctDone = (rc_numBlocks * 100/ MB_cnt);
  pctUsed = (totalBits *100/current_Tx);

  sprintf(rc_buffer, "%3d  %5d %2d %3d %6d  %3d %6d   %2.2f   %6d %4d    %3d   %3d\n",
	  (rc_numBlocks - 1), bitsThisMB, Qscale, mquant, currentVirtBuf,
	  rc_Q, act_j, N_act, totalBits, bitsPerMB, pctUsed, pctDone);
#ifdef RC_STATS_FILE
  fprintf(RC_FILE, "%s", rc_buffer);
  fflush(RC_FILE);
#endif

  if ( (RC_MB_SAMPLE_RATE) && ((rc_numBlocks -1) % RC_MB_SAMPLE_RATE)) {
    DBG_PRINT(("%s\n", rc_buffer));
  } else {
    return;
  }
}



/*===========================================================================*
 *
 * incNumBlocks()
 *
 *
 * RETURNS:   nothing
 *
 * SIDE EFFECTS:  rc_numBlocks
 *
 * NOTES:
 *
 *===========================================================================*/
void incNumBlocks(num)
     int num;
{
  rc_numBlocks += num;
}


/*===========================================================================*
 *
 * incMacroBlockBits()
 *
 *	Increments the number of Macro Block bits and the total of Frame
 *  bits by the number passed.
 *
 * RETURNS:   nothing
 *
 * SIDE EFFECTS:  rc_totalMBBits
 *
 * NOTES:
 *
 *===========================================================================*/
void incMacroBlockBits(num)
     int num;
{
  rc_bitsThisMB = num;
  rc_totalMBBits += num;
  rc_totalFrameBits += num;
}


/*===========================================================================*
 *
 *   	needQScaleChange(current Q scale, 4 luminance blocks)
 *
 *
 * RETURNS:     new Qscale
 *
 * SIDE EFFECTS:
 *
 *===========================================================================*/
int needQScaleChange(oldQScale, blk0, blk1, blk2, blk3)
     int oldQScale;
     Block blk0;
     Block blk1;
     Block blk2;
     Block blk3;
{

  /*   One more MacroBlock seen */
  rc_numBlocks++;		/* this notes each block num in MB */

  checkBufferFullness(oldQScale);

  checkSpatialActivity(blk0, blk1, blk2, blk3);

  mquant = rc_Q * N_act;
  Qscale = (mquant > 31 ? 31 : mquant);
  Qscale = (Qscale < 1 ? 1 : Qscale);
  rc_totalQuant += Qscale;

  if (oldQScale == Qscale)
    return -1;
  else
    return Qscale;
}


/*===========================================================================*
 *
 * determineMBCount()
 *
 *      Determines number of Macro Blocks in frame from the frame sizes
 *	passed.
 *
 * RETURNS:     nothing
 *
 * SIDE EFFECTS:   sets the count passed
 *
 *===========================================================================*/
int
  determineMBCount ()
{
  int y,x;

  x = (Fsize_x +15)/16;
  y = (Fsize_y +15)/16;
  return  (x * y);
}



/*===========================================================================*
 *
 * void checkBufferFullness ()
 *
 *      Calculates the fullness of the virtual buffer for each
 *  frame type.  Called before encoding each macro block.  Along
 *  with the normalized spatial activity measure (N_act), it
 *  determine the quantization factor for the next macroblock.
 *
 * RETURNS:     nothing
 *
 * SIDE EFFECTS:   the "currentVirtBuf" variable
 *
 * NOTES:
 *
 *===========================================================================*/
void checkBufferFullness (oldQScale)
     int oldQScale;
{
  int temp;

  temp = lastFrameVirtBuf + rc_totalFrameBits;
  temp -=  (current_Tx * rc_numBlocks / MB_cnt);
  currentVirtBuf = temp;

  rc_Q = (currentVirtBuf * 31 / reactionParameter);
  return;
}


/*===========================================================================*
 *
 * void checkSpatialActivity()
 *
 *      Calculates the spatial activity for the four luminance blocks of the
 *	macroblock.  Along with the normalized reference quantization parameter
 *  (rc_Q) , it determines the quantization factor for the next macroblock.
 *
 * RETURNS:     nothing
 *
 * SIDE EFFECTS:   the Adaptive quantization variables- act_j, N_act.
 *
 * NOTES:
 *
 *===========================================================================*/
void checkSpatialActivity(blk0, blk1, blk2, blk3)
     Block blk0;
     Block blk1;
     Block blk2;
     Block blk3;
{
  int temp;
  int16 *blkArray[4];
  int16 *curBlock;
  int16 *blk_ptr;
  int var[4];
  int i, j;


  blkArray[0] = (int16 *) blk0;
  blkArray[1] = (int16 *) blk1;
  blkArray[2] = (int16 *) blk2;
  blkArray[3] = (int16 *) blk3;


  for (i =0; i < 4; i++) {	/* Compute the activity in each block */
    curBlock = blkArray[i];
    blk_ptr = curBlock;
    P_mean = 0;
    /*  Find the mean pixel value */
    for (j=0; j < DCTSIZE_SQ; j ++) {
      P_mean += *(blk_ptr++);
      /*			P_mean += curBlock[j];
				if (curBlock[j] != *(blk_ptr++)) {
				printf("ARRAY ERROR: block %d\n", j);
				}
				*/
    }
    P_mean /= DCTSIZE_SQ;

    /*  Now find the variance  */
    curBlock = blkArray[i];
    blk_ptr = curBlock;
    var[i] = 0;
    for (j=0; j < DCTSIZE_SQ; j++) {
#ifdef notdef
      if (curBlock[j] != *(blk_ptr++)) {
	printf("ARRAY ERROR: block %d\n", j);
      }
      temp = curBlock[j] - P_mean;
#endif
      temp = *(blk_ptr++) - P_mean;
      var[i] += (temp * temp);
    }
    var[i] /= DCTSIZE_SQ;
  }

  /*  Choose the minimum variance from the 4 blocks and use as the activity */
  var_sblk  = var[0];
  for (i=1; i < 4; i++) {
    var_sblk = (var_sblk < var[i] ? var_sblk : var[i]);
  }


  act_j = 1 + var_sblk;
  total_act_j += act_j;
  temp = (2 * act_j + avg_act);
  N_act = ( (float) temp / (float) (act_j + 2*avg_act) );

  return;
}




/*============================================================================*
 *
 * getRateMode ()
 *
 *      Returns the rate mode- interpreted as either Fixed or Variable
 *
 * RETURNS:     integer
 *
 * SIDE EFFECTS:   none
 *
 *
 *==========================================================================*/
int getRateMode()
{
  return RateControlMode;
}


/*===========================================================================*
 *
 * setBitRate ()
 *
 *      Checks the string parsed from the parameter file.  Verifies
 *  number and sets global values. MPEG standard specifies that bit rate
 *	be rounded up to nearest 400 bits/sec.
 *
 * RETURNS:     nothing
 *
 * SIDE EFFECTS:   global variables
 *
 * NOTES:	Should this be in the 400-bit units used in sequence header?
 *
 *===========================================================================*/
void setBitRate (const char * const charPtr)
{
  int rate, rnd;

  rate = atoi(charPtr);
  if (rate > 0) {
    RateControlMode = FIXED_RATE;
  } else {
    printf("Parameter File Error:  invalid BIT_RATE: \"%s\", defaults to Variable ratemode\n",
	   charPtr);
    RateControlMode = VARIABLE_RATE;
    bit_rate = -1;
  }
  rnd = (rate % 400);
  rate += (rnd ? 400 -rnd : 0); /* round UP to nearest 400 bps */
  rate = (rate > MAX_BIT_RATE ? MAX_BIT_RATE : rate);
  bit_rate = rate;
  DBG_PRINT(("Bit rate is: %d\n", bit_rate));
}



/*===========================================================================*
 *
 * getBitRate ()
 *
 *      Returns the bit rate read from the parameter file.  This is the
 *  real rate in bits per second, not in 400 bit units as is written to
 *  the sequence header.
 *
 * RETURNS:     int (-1 if Variable mode operation)
 *
 * SIDE EFFECTS:   none
 *
 *===========================================================================*/
int getBitRate ()
{
  return bit_rate;
}




/*===========================================================================*
 *
 * setBufferSize ()
 *
 *      Checks the string parsed from the parameter file.  Verifies
 *  number and sets global values.
 *
 * RETURNS:     nothing
 *
 * SIDE EFFECTS:   buffer_size global variable.
 *
 * NOTES:	The global is in bits, NOT the 16kb units used in sequence header
 *
 *===========================================================================*/
void setBufferSize (const char * const charPtr)
{
  int size;

  size = atoi(charPtr);
  size = (size > MAX_BUFFER_SIZE ? MAX_BUFFER_SIZE : size);
  if (size > 0) {
    size = (16*1024) * ((size + (16*1024 - 1)) / (16*1024));
    buffer_size = size;
  } else {
    buffer_size = DEFAULT_BUFFER_SIZE;
    printf("Parameter File Error:  invalid BUFFER_SIZE: \"%s\", defaults to : %d\n",
	   charPtr, buffer_size);
  }
  DBG_PRINT(("Buffer size is: %d\n", buffer_size));
}


/*===========================================================================*
 *
 * getBufferSize ()
 *
 *      returns the buffer size read from the parameter file.  Size is
 *  in bits- not in units of 16k as written to the sequence header.
 *
 * RETURNS:     int (or -1 if invalid)
 *
 * SIDE EFFECTS:   none
 *
 *===========================================================================*/
int getBufferSize ()
{
  return buffer_size;
}