/*===========================================================================*
 * bframe.c								     *
 *									     *
 *	Procedures concerned with the B-frame encoding			     *
 *									     *
 * EXPORTED PROCEDURES:							     *
 *	GenBFrame							     *
 *	ResetBFrameStats						     *
 *	ShowBFrameSummary						     *
 *	EstimateSecondsPerBFrame					     *
 *	ComputeBMotionLumBlock						     *
 *	SetBQScale							     *
 *	GetBQScale							     *
 *									     *
 *===========================================================================*/

/*
 * 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: /n/picasso/project/mpeg/mpeg_dist/mpeg_encode/RCS/bframe.c,v 1.20 1995/08/14 22:28:11 smoot Exp $
 *  $Log: bframe.c,v $
 *  Revision 1.20  1995/08/14 22:28:11  smoot
 *  renamed index to idx
 *  added option to not skip in B frames
 *
 *  Revision 1.19  1995/08/07 21:52:11  smoot
 *  added Color to skip routine
 *  fixed full/half bug in intial loop
 *  added comments
 *  removed buggy "extra skips" code
 *
 *  Revision 1.18  1995/06/21 22:22:24  smoot
 *  generalized time checking, fixed bug in specifics filesm
 *  and added TUNEing stuff
 *
 * Revision 1.17  1995/04/14  23:08:02  smoot
 * reorganized to ease rate control experimentation
 *
 * Revision 1.16  1995/02/24  23:49:10  smoot
 * added Spec version 2
 *
 * Revision 1.15  1995/01/30  19:45:45  smoot
 * Fixed a cr/cb screwup
 *
 * Revision 1.14  1995/01/23  02:46:43  darryl
 * initialized variable
 *
 * Revision 1.13  1995/01/19  23:07:12  eyhung
 * Changed copyrights
 *
 * Revision 1.12  1995/01/16  07:44:11  eyhung
 * Added realQuiet
 *
 * Revision 1.11  1994/12/07  00:40:36  smoot
 * Added seperate P and B search ranges
 *
 * Revision 1.10  1994/11/24  00:35:47  smoot
 * fixed bug (divide by 0) in B fram statsitics
 *
 * Revision 1.9  1994/11/14  22:26:48  smoot
 * Merged specifics and rate control.
 *
 * Revision 1.8  1994/11/01  05:01:16  darryl
 *  with rate control changes added
 *
 * Revision 2.0  1994/10/24  02:38:51  darryl
 * will be adding the experiment code
 *
 * Revision 1.1  1994/09/27  00:16:04  darryl
 * Initial revision
 *
 * Revision 1.7  1994/03/15  00:27:11  keving
 * nothing
 *
 * Revision 1.6  1993/12/22  19:19:01  keving
 * nothing
 *
 * Revision 1.5  1993/07/30  19:24:04  keving
 * nothing
 *
 * Revision 1.4  1993/07/22  22:23:43  keving
 * nothing
 *
 * Revision 1.3  1993/06/30  20:06:09  keving
 * nothing
 *
 * Revision 1.2  1993/06/03  21:08:08  keving
 * nothing
 *
 * Revision 1.1  1993/02/19  19:14:28  keving
 * nothing
 *
 */


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

#include "all.h"
//#include <sys/param.h>
#include <assert.h>
#include "mtypes.h"
#include "bitio.h"
#include "frames.h"
#include "prototypes.h"
#include "fsize.h"
#include "param.h"
#include "mheaders.h"
#include "postdct.h"
#include "rate.h"
#include "opts.h"

/*==================*
 * STATIC VARIABLES *
 *==================*/

static int numBIBlocks = 0;
static int numBBBlocks = 0;
static int numBSkipped = 0;
static int numBIBits = 0;
static int numBBBits = 0;
static int numFrames = 0;
static int numFrameBits = 0;
static int32 totalTime = 0;
static int qscaleB;
static float    totalSNR = 0.0;
static float	totalPSNR = 0.0;

static int numBFOBlocks = 0;    /* forward only */
static int numBBABlocks = 0;    /* backward only */
static int numBINBlocks = 0;    /* interpolate */
static int numBFOBits = 0;
static int numBBABits = 0;
static int numBINBits = 0;

/*====================*
 * EXTERNAL VARIABLES *
 *====================*/

extern Block **dct, **dctr, **dctb;
extern dct_data_type **dct_data;
#define NO_MOTION 0
#define MOTION 1
#define SKIP 2  /* used in useMotion in dct_data */

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

static boolean	MotionSufficient _ANSI_ARGS_((MpegFrame *curr, LumBlock currBlock, MpegFrame *prev, MpegFrame *next,
			 int by, int bx, int mode, int fmy, int fmx,
			 int bmy, int bmx));
static void	ComputeBMotionBlock _ANSI_ARGS_((MpegFrame *prev, MpegFrame *next,
			       int by, int bx, int mode, int fmy, int fmx,
			       int bmy, int bmx, Block motionBlock, int type));
static void	ComputeBDiffDCTs _ANSI_ARGS_((MpegFrame *current, MpegFrame *prev, MpegFrame *next,
			 int by, int bx, int mode, int fmy, int fmx, 
			 int bmy, int bmx, int *pattern));
static boolean	DoBIntraCode _ANSI_ARGS_((MpegFrame *current, MpegFrame *prev, MpegFrame *next,
		     int by, int bx, int mode, int fmy, int fmx, int bmy,
		     int bmx));

static int ComputeBlockColorDiff _ANSI_ARGS_((Block current, Block motionBlock));

/*=====================*
 * EXPORTED PROCEDURES *
 *=====================*/

/*===========================================================================*
 *
 * GenBFrame
 *
 *	generate a B-frame from previous and next frames, adding the result
 *	to the given bit bucket
 *
 * RETURNS:	frame appended to bb
 *
 * SIDE EFFECTS:    none
 *
 *===========================================================================*/
void
GenBFrame(bb, curr, prev, next)
    BitBucket *bb;
    MpegFrame *curr;
    MpegFrame *prev;
    MpegFrame *next;
{
    extern int **bfmvHistogram;
    extern int **bbmvHistogram;
    FlatBlock fba[6], fb[6];
    Block     dec[6];
    int32 y_dc_pred, cr_dc_pred, cb_dc_pred;
    int x, y;
    int	fMotionX = 0, fMotionY = 0;
    int bMotionX = 0, bMotionY = 0;
    int	oldFMotionX = 0, oldFMotionY = 0;
    int oldBMotionX = 0, oldBMotionY = 0;
    int	oldMode = MOTION_FORWARD;
    int	mode = MOTION_FORWARD;
    int	offsetX, offsetY;
    int	tempX, tempY;
    int	fMotionXrem = 0, fMotionXquot = 0;
    int	fMotionYrem = 0, fMotionYquot = 0;
    int	bMotionXrem = 0, bMotionXquot = 0;
    int	bMotionYrem = 0, bMotionYquot = 0;
    int	pattern;
    int	numIBlocks = 0, numBBlocks = 0;
    int numSkipped = 0, totalBits;
    int	numIBits = 0,   numBBits = 0;
    boolean	lastIntra = TRUE;
    boolean    motionForward, motionBackward;
    int	    totalFrameBits;
    int32    startTime, endTime;
    int lastX, lastY;
    int lastBlockX, lastBlockY;
    register int ix, iy;
    LumBlock currentBlock;
    int         fy, fx;
    boolean	make_skip_block;
    int	mbAddrInc = 1;
    int	mbAddress;
    int	    slicePos;
    float   snr[3], psnr[3];
    int	    idx;
    int     QScale;
    BlockMV *info;
    int     bitstreamMode, newQScale;
    int     rc_blockStart=0;
    boolean overflowChange=FALSE;
    int overflowValue = 0;

    if (collect_quant) {fprintf(collect_quant_fp, "# B\n");}
    if (dct == NULL) AllocDctBlocks();
    numFrames++;
    totalFrameBits = bb->cumulativeBits;
    startTime = time_elapsed();

    /*   Rate Control */
    bitstreamMode = getRateMode();
    if (bitstreamMode == FIXED_RATE) {
      targetRateControl(curr);
    }
 
    QScale = GetBQScale();
    Mhead_GenPictureHeader(bb, B_FRAME, curr->id, fCodeB);
    /* Check for Qscale change */
    if (specificsOn) {
      newQScale = SpecLookup(curr->id, 0, 0 /* junk */, &info, QScale);
      if (newQScale != -1) {
	QScale = newQScale;
      }
      /* check for slice */
      newQScale = SpecLookup(curr->id, 1, 1, &info, QScale);
      if (newQScale != -1) {
	QScale = newQScale;
      }
    }

    Mhead_GenSliceHeader(bb, 1, QScale, NULL, 0);

    Frame_AllocBlocks(curr);
    BlockifyFrame(curr);

    if ( printSNR ) {
	Frame_AllocDecoded(curr, FALSE);
    }

    /* for I-blocks */
    y_dc_pred = cr_dc_pred = cb_dc_pred = 128;

    totalBits = bb->cumulativeBits;

    if ( ! pixelFullSearch ) {
	if ( ! prev->halfComputed && (prev != NULL)) {
	    ComputeHalfPixelData(prev);
	}

	if ( ! next->halfComputed ) {
	    ComputeHalfPixelData(next);
	}
    }

    lastBlockX = Fsize_x>>3;
    lastBlockY = Fsize_y>>3;
    lastX = lastBlockX-2;
    lastY = lastBlockY-2;
    mbAddress = 0;

    /* find motion vectors and do dcts */
    /* In this first loop, all MVs are in half-pixel scope, (if FULL is set
       then they will be multiples of 2).  This is not true in the second loop. */
    for (y = 0;  y < lastBlockY;  y += 2) {
      for (x = 0;  x < lastBlockX;  x += 2) {
	slicePos = (mbAddress % blocksPerSlice);

	/* compute currentBlock */
	BLOCK_TO_FRAME_COORD(y, x, fy, fx);
	for ( iy = 0; iy < 16; iy++ ) {
	  for ( ix = 0; ix < 16; ix++ ) {
	    currentBlock[iy][ix] = (int16)curr->orig_y[fy+iy][fx+ix];
	  }
	}
	    
	if (slicePos == 0) {
	  oldFMotionX = 0;	oldFMotionY = 0;
	  oldBMotionX = 0;	oldBMotionY = 0;
	  oldMode = MOTION_FORWARD;
	  lastIntra = TRUE;
	}

	/* STEP 1:  Select Forward, Backward, or Interpolated motion vectors */
	/* see if old motion is good enough */
	/* but force last block to be non-skipped */
	/* can only skip if:
	 *     1)  not the last block in frame
	 *     2)  not the last block in slice
	 *     3)  not the first block in slice
	 *     4)  previous block was not intra-coded
	 */
	if ( ((y < lastY) || (x < lastX)) &&
	    (slicePos+1 != blocksPerSlice) &&
	    (slicePos != 0) &&
	    (! lastIntra) &&
	    (BSkipBlocks) ) {
	  make_skip_block = MotionSufficient(curr, currentBlock, prev, next, y, x, oldMode,
					     oldFMotionY, oldFMotionX,
					     oldBMotionY, oldBMotionX);
	} else {
	  make_skip_block = FALSE;
	}

	if ( make_skip_block ) {
	skip_it:
	  /* skipped macro block */
	  dct_data[y][x].useMotion = SKIP;
	} else {
	  if (specificsOn) {
	    (void) SpecLookup(curr->id, 2, mbAddress, &info, QScale);
	    if (info == (BlockMV*)NULL) goto gosearch;
	    else {
	      switch (info->typ) {
	      case TYP_SKIP:
		goto skip_it;
	      case TYP_FORW:
		fMotionX = info->fx;
		fMotionY = info->fy;
		mode = MOTION_FORWARD;
		break;
	      case TYP_BACK:
		bMotionX = info->bx;
		bMotionY = info->by;
		mode = MOTION_BACKWARD;
		break;
	      case TYP_BOTH:
		fMotionX = info->fx;
		fMotionY = info->fy;
		bMotionX = info->bx;
		bMotionY = info->by;
		mode = MOTION_INTERPOLATE;
		break;
	      default:
		fprintf(stderr,"Unreachable code in GenBFrame!\n");
		goto gosearch;
	      }
	      goto skipsearch;
	    }}
	gosearch:		/* do bsearch */
	  mode = BMotionSearch(currentBlock, prev, next, y, x, &fMotionY,
			       &fMotionX, &bMotionY, &bMotionX, mode);
	skipsearch:	      
	      
	  /* STEP 2:  INTRA OR NON-INTRA CODING */
	  if ( IntraPBAllowed && DoBIntraCode(curr, prev, next, y, x, mode, fMotionY,
			    fMotionX, bMotionY, bMotionX) ) {
	    /* output I-block inside a B-frame */
	    numIBlocks++;
	    oldFMotionX = 0;	oldFMotionY = 0;
	    oldBMotionX = 0;	oldBMotionY = 0;
	    lastIntra = TRUE;
	    dct_data[y][x].useMotion = NO_MOTION;
	    oldMode = MOTION_FORWARD;
	    /* calculate forward dct's */
	    if (collect_quant && (collect_quant_detailed & 1)) fprintf(collect_quant_fp, "l\n");
	    mp_fwd_dct_block2(curr->y_blocks[y][x], dct[y][x]);
	    mp_fwd_dct_block2(curr->y_blocks[y][x+1], dct[y][x+1]);
	    mp_fwd_dct_block2(curr->y_blocks[y+1][x], dct[y+1][x]);
	    mp_fwd_dct_block2(curr->y_blocks[y+1][x+1], dct[y+1][x+1]);
	    if (collect_quant && (collect_quant_detailed & 1)) {fprintf(collect_quant_fp, "c\n");}
	    mp_fwd_dct_block2(curr->cb_blocks[y>>1][x>>1], dctb[y>>1][x>>1]);
	    mp_fwd_dct_block2(curr->cr_blocks[y>>1][x>>1], dctr[y>>1][x>>1]);

	  } else { /* dct P/Bi/B block */

	    pattern = 63;
	    lastIntra = FALSE;
	    numBBlocks++;
	    dct_data[y][x].mode = mode;
	    oldMode = mode;
	    dct_data[y][x].fmotionX = fMotionX;
	    dct_data[y][x].fmotionY = fMotionY;
	    dct_data[y][x].bmotionX = bMotionX;
	    dct_data[y][x].bmotionY = bMotionY;
	    switch (mode) {
	    case MOTION_FORWARD:
	      numBFOBlocks++;
	      oldFMotionX = fMotionX;		oldFMotionY = fMotionY;
	      break;
	    case MOTION_BACKWARD:
	      numBBABlocks++;
	      oldBMotionX = bMotionX;		oldBMotionY = bMotionY;
	      break;
	    case MOTION_INTERPOLATE:
	      numBINBlocks++;
	      oldFMotionX = fMotionX;		oldFMotionY = fMotionY;
	      oldBMotionX = bMotionX;		oldBMotionY = bMotionY;
	      break;
	    default:
	      fprintf(stderr, "PROGRAMMER ERROR:  Illegal mode: %d\n", mode);
	      exit(1);
	    }
	    
	    ComputeBDiffDCTs(curr, prev, next, y, x, mode, fMotionY,
			     fMotionX, bMotionY, bMotionX, &pattern);
	    
	    dct_data[y][x].pattern = pattern;
	    dct_data[y][x].useMotion = MOTION;
	    if ( computeMVHist ) {
	      assert(fMotionX+searchRangeB+1 >= 0);
	      assert(fMotionY+searchRangeB+1 >= 0);
	      assert(fMotionX+searchRangeB+1 <= 2*searchRangeB+2);
	      assert(fMotionY+searchRangeB+1 <= 2*searchRangeB+2);
	      assert(bMotionX+searchRangeB+1 >= 0);
	      assert(bMotionY+searchRangeB+1 >= 0);
	      assert(bMotionX+searchRangeB+1 <= 2*searchRangeB+2);
	      assert(bMotionY+searchRangeB+1 <= 2*searchRangeB+2);

	      bfmvHistogram[fMotionX+searchRangeB+1][fMotionY+searchRangeB+1]++;
	      bbmvHistogram[bMotionX+searchRangeB+1][bMotionY+searchRangeB+1]++;
	    }
	  } /* motion-block */
	} /* not skipped */
	mbAddress++;
      }}

    /* reset everything */
    oldFMotionX = 0;	oldFMotionY = 0;
    oldBMotionX = 0;	oldBMotionY = 0;
    oldMode = MOTION_FORWARD;
    lastIntra = TRUE;
    y_dc_pred = cr_dc_pred = cb_dc_pred = 128;
    mbAddress = 0;

    /* Now generate the frame */
    for (y = 0; y < lastBlockY; y += 2) {
      for (x = 0; x < lastBlockX; x += 2) {
	slicePos = (mbAddress % blocksPerSlice);

	if ( (slicePos == 0) && (mbAddress != 0) ) {
	  if (specificsOn) {
	    /* Make sure no slice Qscale change */
	    newQScale = SpecLookup(curr->id,1,mbAddress/blocksPerSlice, &info, QScale);
	    if (newQScale != -1) QScale = newQScale;
	  }
	  Mhead_GenSliceEnder(bb);
	  Mhead_GenSliceHeader(bb, 1+(y>>1), QScale, NULL, 0);

	  /* reset everything */
	  oldFMotionX = 0;	oldFMotionY = 0;
	  oldBMotionX = 0;	oldBMotionY = 0;
	  oldMode = MOTION_FORWARD;
	  lastIntra = TRUE;
	  y_dc_pred = cr_dc_pred = cb_dc_pred = 128;

	  mbAddrInc = 1+(x>>1);
	}

	/*  Determine if new Qscale needed for Rate Control purposes */
	if (bitstreamMode == FIXED_RATE) {
	  rc_blockStart =  bb->cumulativeBits;
	  newQScale = needQScaleChange(QScale,
				       curr->y_blocks[y][x],
				       curr->y_blocks[y][x+1],
				       curr->y_blocks[y+1][x],
				       curr->y_blocks[y+1][x+1]);
	  if (newQScale > 0) {
	    QScale = newQScale;
	  }
	}
 
	if (specificsOn) {
	  newQScale = SpecLookup(curr->id, 2, mbAddress, &info, QScale);
	  if (newQScale != -1) {
	    QScale = newQScale;
	  }}

	if (dct_data[y][x].useMotion == NO_MOTION) {

	  GEN_I_BLOCK(B_FRAME, curr, bb, mbAddrInc, QScale);
	  mbAddrInc = 1;
	  numIBits += (bb->cumulativeBits-totalBits);
	  totalBits = bb->cumulativeBits;
	      
	  /* reset because intra-coded */
	  oldFMotionX = 0;		oldFMotionY = 0;
	  oldBMotionX = 0;		oldBMotionY = 0;
	  oldMode = MOTION_FORWARD;
	  lastIntra = TRUE;
	      
	  if ( printSNR ) {
	    /* need to decode block we just encoded */
	    /* and reverse the DCT transform */
	    for ( idx = 0; idx < 6; idx++ ) {
	      Mpost_UnQuantZigBlock(fb[idx], dec[idx], QScale, TRUE);
	      mpeg_jrevdct((int16 *)dec[idx]);
	    }

	    /* now, unblockify */
	    BlockToData(curr->decoded_y, dec[0], y, x);
	    BlockToData(curr->decoded_y, dec[1], y, x+1);
	    BlockToData(curr->decoded_y, dec[2], y+1, x);
	    BlockToData(curr->decoded_y, dec[3], y+1, x+1);
	    BlockToData(curr->decoded_cb, dec[4], y>>1, x>>1);
	    BlockToData(curr->decoded_cr, dec[5], y>>1, x>>1);
	  }
	} else if (dct_data[y][x].useMotion == SKIP) {
	skip_block:
	  numSkipped++;
	  mbAddrInc++;
	      
	  /* decode skipped block */
	  if ( printSNR ) {
	    int	fmy, fmx, bmy, bmx;
		
	    for ( idx = 0; idx < 6; idx++ ) {
	      memset((char *)dec[idx], 0, sizeof(Block)); 
	    }
	    
	    if ( pixelFullSearch ) {
	      fmy = 2*oldFMotionY;
	      fmx = 2*oldFMotionX;
	      bmy = 2*oldBMotionY;
	      bmx = 2*oldBMotionX;
	    } else {
	      fmy = oldFMotionY;
	      fmx = oldFMotionX;
	      bmy = oldBMotionY;
	      bmx = oldBMotionX;
	    }
	    
	    /* now add the motion block */
	    AddBMotionBlock(dec[0], prev->decoded_y,
			    next->decoded_y, y, x, mode,
			    fmy, fmx, bmy, bmx);
	    AddBMotionBlock(dec[1], prev->decoded_y,
			    next->decoded_y, y, x+1, mode,
			    fmy, fmx, bmy, bmx);
	    AddBMotionBlock(dec[2], prev->decoded_y,
			    next->decoded_y, y+1, x, mode,
			    fmy, fmx, bmy, bmx);
	    AddBMotionBlock(dec[3], prev->decoded_y,
			    next->decoded_y, y+1, x+1, mode,
			    fmy, fmx, bmy, bmx);
	    AddBMotionBlock(dec[4], prev->decoded_cb,
			    next->decoded_cb, y>>1, x>>1, mode,
			    fmy/2, fmx/2,
			    bmy/2, bmx/2);
	    AddBMotionBlock(dec[5], prev->decoded_cr,
			    next->decoded_cr, y>>1, x>>1, mode,
			    fmy/2, fmx/2,
			    bmy/2, bmx/2);
	    
	    /* now, unblockify */
	    BlockToData(curr->decoded_y, dec[0], y, x);
	    BlockToData(curr->decoded_y, dec[1], y, x+1);
	    BlockToData(curr->decoded_y, dec[2], y+1, x);
	    BlockToData(curr->decoded_y, dec[3], y+1, x+1);
	    BlockToData(curr->decoded_cb, dec[4], y>>1, x>>1);
	    BlockToData(curr->decoded_cr, dec[5], y>>1, x>>1);
	  }
	} else   /* B block */ {
	  int fCode = fCodeB;	

	  pattern = dct_data[y][x].pattern;
	  fMotionX = dct_data[y][x].fmotionX;
	  fMotionY = dct_data[y][x].fmotionY;
	  bMotionX = dct_data[y][x].bmotionX;
	  bMotionY = dct_data[y][x].bmotionY;

	  if ( pixelFullSearch ) {
	    fMotionX /= 2;	    fMotionY /= 2;
	    bMotionX /= 2;	    bMotionY /= 2;
	  }
	      
	  /* create flat blocks and update pattern if necessary */
	calc_blocks:
	/* Note DoQuant references QScale, overflowChange, overflowValue,
           pattern, and the calc_blocks label                 */
	  DoQuant(0x20, dct[y][x], fba[0]);
	  DoQuant(0x10, dct[y][x+1], fba[1]);
	  DoQuant(0x08, dct[y+1][x], fba[2]);
	  DoQuant(0x04, dct[y+1][x+1], fba[3]);
	  DoQuant(0x02, dctb[y>>1][x>>1], fba[4]);
	  DoQuant(0x01, dctr[y>>1][x>>1], fba[5]);

	  motionForward  = (dct_data[y][x].mode != MOTION_BACKWARD);
	  motionBackward = (dct_data[y][x].mode != MOTION_FORWARD);

#ifdef BUGGY_CODE
	  /*
	  send us mail if you can tell me why this code
          doesnt work.  Generates some bad vectors.
          I suspect 'cuz oldMode/motions aren't being set right,
          but am unsure.
	  */
	  /* Check to see if we should have skipped */
	  if ((pattern == 0) &&
	      ((y < lastY) || (x < lastX)) &&
	      (slicePos+1 != blocksPerSlice) &&
	      (slicePos != 0) &&
	      (!lastIntra) &&
	      ( (!motionForward) || 
	       (motionForward && 
		fMotionX == oldFMotionX && fMotionY == oldFMotionY)) &&
	      ( (!motionBackward) || 
	       (motionBackward && 
		bMotionX == oldBMotionX && bMotionY == oldBMotionY))
	      ) {
	    /* Now *thats* an if statement! */
	    goto skip_block; 
	  }
#endif
	  /* Encode Vectors */
	  if ( motionForward ) {
	    /* transform the fMotion vector into the appropriate values */
	    offsetX = fMotionX - oldFMotionX;
	    offsetY = fMotionY - oldFMotionY;

	    ENCODE_MOTION_VECTOR(offsetX, offsetY, fMotionXquot,
				 fMotionYquot, fMotionXrem, fMotionYrem,
				 FORW_F);
	    oldFMotionX = fMotionX;		oldFMotionY = fMotionY;
	  }
	      
	  if ( motionBackward ) {
	    /* transform the bMotion vector into the appropriate values */
	    offsetX = bMotionX - oldBMotionX;
	    offsetY = bMotionY - oldBMotionY;
	    ENCODE_MOTION_VECTOR(offsetX, offsetY, bMotionXquot,
				 bMotionYquot, bMotionXrem, bMotionYrem,
				 BACK_F);
	    oldBMotionX = bMotionX;		oldBMotionY = bMotionY;
	  }
	      
	  oldMode = dct_data[y][x].mode;
	      
	  if ( printSNR ) { /* Need to decode */
	    if ( pixelFullSearch ) {
	      fMotionX *= 2;	fMotionY *= 2;
	      bMotionX *= 2;	bMotionY *= 2;
	    }
	    for ( idx = 0; idx < 6; idx++ ) {
	      if ( pattern & (1 << (5-idx)) ) {
		Mpost_UnQuantZigBlock(fba[idx], dec[idx], QScale, FALSE);
		mpeg_jrevdct((int16 *)dec[idx]);
	      } else {
		memset((char *)dec[idx], 0, sizeof(Block));
	      }
	    }

	    /* now add the motion block */
	    AddBMotionBlock(dec[0], prev->decoded_y,
			    next->decoded_y, y, x, mode,
			    fMotionY, fMotionX, bMotionY, bMotionX);
	    AddBMotionBlock(dec[1], prev->decoded_y,
			    next->decoded_y, y, x+1, mode,
			    fMotionY, fMotionX, bMotionY, bMotionX);
	    AddBMotionBlock(dec[2], prev->decoded_y,
			    next->decoded_y, y+1, x, mode,
			    fMotionY, fMotionX, bMotionY, bMotionX);
	    AddBMotionBlock(dec[3], prev->decoded_y,
			    next->decoded_y, y+1, x+1, mode,
			    fMotionY, fMotionX, bMotionY, bMotionX);
	    AddBMotionBlock(dec[4], prev->decoded_cb,
			    next->decoded_cb, y>>1, x>>1, mode,
			    fMotionY/2, fMotionX/2,
			    bMotionY/2, bMotionX/2);
	    AddBMotionBlock(dec[5], prev->decoded_cr,
			    next->decoded_cr, y>>1, x>>1, mode,
			    fMotionY/2, fMotionX/2,
			    bMotionY/2, bMotionX/2);

	    /* now, unblockify */
	    BlockToData(curr->decoded_y,  dec[0], y,    x);
	    BlockToData(curr->decoded_y,  dec[1], y,    x+1);
	    BlockToData(curr->decoded_y,  dec[2], y+1,  x);
	    BlockToData(curr->decoded_y,  dec[3], y+1,  x+1);
	    BlockToData(curr->decoded_cb, dec[4], y>>1, x>>1);
	    BlockToData(curr->decoded_cr, dec[5], y>>1, x>>1);
	  }

	  /* reset because non-intra-coded */
	  y_dc_pred = cr_dc_pred = cb_dc_pred = 128;
	  lastIntra = FALSE;
	  mode = dct_data[y][x].mode;

	  /*      DBG_PRINT(("MB Header(%d,%d)\n", x, y));  */
	  Mhead_GenMBHeader(bb, 3 /* pict_code_type */, mbAddrInc /* addr_incr */,
	    QScale /* q_scale */,
	    fCodeB /* forw_f_code */, fCodeB /* back_f_code */,
	    fMotionXrem /* horiz_forw_r */, fMotionYrem /* vert_forw_r */,
	    bMotionXrem /* horiz_back_r */, bMotionYrem /* vert_back_r */,
	    motionForward /* motion_forw */, fMotionXquot /* m_horiz_forw */,
	    fMotionYquot /* m_vert_forw */, motionBackward /* motion_back */,
	    bMotionXquot /* m_horiz_back */, bMotionYquot /* m_vert_back */,
	    pattern /* mb_pattern */, FALSE /* mb_intra */);
	  mbAddrInc = 1;
	      
	  /* now output the difference */
	  for ( tempX = 0; tempX < 6; tempX++ ) {
	    if ( GET_ITH_BIT(pattern, 5-tempX) ) {
	      Mpost_RLEHuffPBlock(fba[tempX], bb);
	    }
	  }
	      
	  
	  switch (mode) {
	  case MOTION_FORWARD:
	    numBFOBits += (bb->cumulativeBits-totalBits);
	    break;
	  case MOTION_BACKWARD:
	    numBBABits += (bb->cumulativeBits-totalBits);
	    break;
	  case MOTION_INTERPOLATE:
	    numBINBits += (bb->cumulativeBits-totalBits);
	    break;
	  default:
	    fprintf(stderr, "PROGRAMMER ERROR:  Illegal mode: %d\n",
		    mode);
	    exit(1);
	  }
	  
	  numBBits += (bb->cumulativeBits-totalBits);
	  totalBits = bb->cumulativeBits;
	
	  if (overflowChange) {
	    /* undo an overflow-caused Qscale change */
	    overflowChange = FALSE;
	    QScale -= overflowValue;
	    overflowValue = 0;
	  }
	} /* if I-block, skip, or B */

	mbAddress++;
	/*   Rate Control  */
	if (bitstreamMode == FIXED_RATE) {
	  incMacroBlockBits( bb->cumulativeBits - rc_blockStart);
	  rc_blockStart = bb->cumulativeBits;
	  MB_RateOut(TYPE_BFRAME);
	}
	
      }
    }

    if ( printSNR ) {
      BlockComputeSNR(curr,snr,psnr);
      totalSNR += snr[0];
      totalPSNR += psnr[0];
    }
    
    Mhead_GenSliceEnder(bb);
    /*   Rate Control  */
    if (bitstreamMode == FIXED_RATE) {
      updateRateControl(TYPE_BFRAME);
    }
    
    endTime = time_elapsed();
    totalTime += (endTime-startTime);
    
    if ( ( ! childProcess) && showBitRatePerFrame ) {
      /* ASSUMES 30 FRAMES PER SECOND */
      fprintf(bitRateFile, "%5d\t%8d\n", curr->id,
	      30*(bb->cumulativeBits-totalFrameBits));
    }
    
    if ( (! childProcess) && frameSummary && !realQuiet) {
      fprintf(stdout, "FRAME %d (B):  I BLOCKS:  %d;  B BLOCKS:  %d   SKIPPED:  %d (%ld seconds)\n",
	      curr->id, numIBlocks, numBBlocks, numSkipped, (long)((endTime-startTime)/TIME_RATE));
      if ( printSNR )
	fprintf(stdout, "FRAME %d:  SNR:  %.1f\t%.1f\t%.1f\tPSNR:  %.1f\t%.1f\t%.1f\n",
		curr->id, snr[0], snr[1], snr[2],
		psnr[0], psnr[1], psnr[2]);
    }
    
    numFrameBits += (bb->cumulativeBits-totalFrameBits);
    numBIBlocks += numIBlocks;
    numBBBlocks += numBBlocks;
    numBSkipped += numSkipped;
    numBIBits += numIBits;
    numBBBits += numBBits;
  }


/*===========================================================================*
 *
 * SetBQScale
 *
 *	set the B-frame Q-scale
 *
 * RETURNS:	nothing
 *
 * SIDE EFFECTS:    qscaleB
 *
 *===========================================================================*/
void
SetBQScale(qB)
    int qB;
{
    qscaleB = qB;
}


/*===========================================================================*
 *
 * GetBQScale
 *
 *	get the B-frame Q-scale
 *
 * RETURNS:	the Q-scale
 *
 * SIDE EFFECTS:    none
 *
 *===========================================================================*/
int
GetBQScale()
{
    return qscaleB;
}


/*===========================================================================*
 *
 * ResetBFrameStats
 *
 *	reset the B-frame stats
 *
 * RETURNS:	nothing
 *
 * SIDE EFFECTS:    none
 *
 *===========================================================================*/
void
ResetBFrameStats()
{
    numBIBlocks = 0;
    numBBBlocks = 0;
    numBSkipped = 0;
    numBIBits = 0;
    numBBBits = 0;
    numFrames = 0;
    numFrameBits = 0;
    totalTime = 0;
}


/*===========================================================================*
 *
 * ShowBFrameSummary
 *
 *	print out statistics on all B-frames
 *
 * RETURNS:	time taken for B-frames (in seconds)
 *
 * SIDE EFFECTS:    none
 *
 *===========================================================================*/
float
ShowBFrameSummary(inputFrameBits, totalBits, fpointer)
    int inputFrameBits;
    int32 totalBits;
    FILE *fpointer;
{
    if ( numFrames == 0 ) {
	return 0.0;
    }

    fprintf(fpointer, "-------------------------\n");
    fprintf(fpointer, "*****B FRAME SUMMARY*****\n");
    fprintf(fpointer, "-------------------------\n");

    if ( numBIBlocks != 0 ) {
	fprintf(fpointer, "  I Blocks:  %5d     (%6d bits)     (%5d bpb)\n",
		numBIBlocks, numBIBits, numBIBits/numBIBlocks);
    } else {
	fprintf(fpointer, "  I Blocks:  %5d\n", 0);
    }

    if ( numBBBlocks != 0 ) {
	fprintf(fpointer, "  B Blocks:  %5d     (%6d bits)     (%5d bpb)\n",
		numBBBlocks, numBBBits, numBBBits/numBBBlocks);
	fprintf(fpointer, "  B types:   %5d     (%4d bpb) forw  %5d (%4d bpb) back   %5d (%4d bpb) bi\n",
		numBFOBlocks, (numBFOBlocks==0)?0:numBFOBits/numBFOBlocks,
		numBBABlocks, (numBBABlocks==0)?0:numBBABits/numBBABlocks,
		numBINBlocks, (numBINBlocks==0)?0:numBINBits/numBINBlocks);
    } else {
	fprintf(fpointer, "  B Blocks:  %5d\n", 0);
    }

    fprintf(fpointer, "  Skipped:   %5d\n", numBSkipped);

    fprintf(fpointer, "  Frames:    %5d     (%6d bits)     (%5d bpf)     (%2.1f%% of total)\n",
	    numFrames, numFrameBits, numFrameBits/numFrames,
	    100.0*(float)numFrameBits/(float)totalBits);	    
    fprintf(fpointer, "  Compression:  %3d:1     (%9.4f bpp)\n",
	    numFrames*inputFrameBits/numFrameBits,
	    24.0*(float)numFrameBits/(float)(numFrames*inputFrameBits));
    if ( printSNR )
	fprintf(fpointer, "  Avg Y SNR/PSNR:  %.1f     %.1f\n",
		totalSNR/(float)numFrames, totalPSNR/(float)numFrames);
    if ( totalTime == 0 ) {
	fprintf(fpointer, "  Seconds:  NONE\n");
    } else {
	fprintf(fpointer, "  Seconds:  %9ld     (%9.4f fps)  (%9ld pps)  (%9ld mps)\n",
		(long)(totalTime/TIME_RATE),
		(float)((float)(TIME_RATE*numFrames)/(float)totalTime),
		(long)((float)TIME_RATE*(float)numFrames*(float)inputFrameBits/(24.0*(float)totalTime)),
		(long)((float)TIME_RATE*(float)numFrames*(float)inputFrameBits/(256.0*24.0*(float)totalTime)));
    }

    return (float)totalTime/TIME_RATE;
}


/*===========================================================================*
 *
 * ComputeBMotionLumBlock
 *
 *	compute the luminance block resulting from motion compensation
 *
 * RETURNS:	motionBlock modified
 *
 * SIDE EFFECTS:    none
 *
 * PRECONDITION:	the motion vectors must be valid!
 *
 *===========================================================================*/
void
ComputeBMotionLumBlock(prev, next, by, bx, mode, fmy, fmx, bmy, bmx, motionBlock)
    MpegFrame *prev;
    MpegFrame *next;
    int by;
    int bx;
    int mode;
    int fmy;
    int fmx;
    int bmy;
    int bmx;
    LumBlock motionBlock;
{
    LumBlock	prevBlock, nextBlock;
    register int	y, x;

    switch(mode) {
    case MOTION_FORWARD:
      ComputeMotionLumBlock(prev, by, bx, fmy, fmx, motionBlock);
      break;
    case MOTION_BACKWARD:
      ComputeMotionLumBlock(next, by, bx, bmy, bmx, motionBlock);
      break;
    case MOTION_INTERPOLATE:
      ComputeMotionLumBlock(prev, by, bx, fmy, fmx, prevBlock);
      ComputeMotionLumBlock(next, by, bx, bmy, bmx, nextBlock);
      
      for ( y = 0; y < 16; y++ ) {
	for ( x = 0; x < 16; x++ ) {
	  motionBlock[y][x] = (prevBlock[y][x]+nextBlock[y][x]+1)/2;
	}
      }
      break;
    default:
      fprintf(stderr, "Bad mode!\nProgrammer error!\n");
      break;
      
    }
}


/*===========================================================================*
 *
 * EstimateSecondsPerBFrame
 *
 *	estimate the seconds to compute a B-frame
 *
 * RETURNS:	the time, in seconds
 *
 * SIDE EFFECTS:    none
 *
 *===========================================================================*/
float
EstimateSecondsPerBFrame()
{
    if ( numFrames == 0 ) {
	return 20.0;
    } else {
	return (float)totalTime/((float)TIME_RATE*(float)numFrames);
    }
}


/*=====================*
 * INTERNAL PROCEDURES *
 *=====================*/

/*===========================================================================*
 *
 * ComputeBMotionBlock
 *
 *	compute the block resulting from motion compensation
 *
 * RETURNS:	motionBlock is modified
 *
 * SIDE EFFECTS:    none
 *
 * PRECONDITION:	the motion vectors must be valid!
 *
 *===========================================================================*/
static void
ComputeBMotionBlock(prev, next, by, bx, mode, fmy, fmx, bmy, bmx, motionBlock, type)
    MpegFrame *prev;
    MpegFrame *next;
    int by;
    int bx;
    int mode;
    int fmy;
    int fmx;
    int bmy;
    int bmx;
    Block motionBlock;
    int type;
{
    Block	prevBlock, nextBlock;
    register int	y, x;

    switch(mode) {
	case MOTION_FORWARD:
	    if ( type == LUM_BLOCK ) {
		ComputeMotionBlock(prev->ref_y, by, bx, fmy, fmx, motionBlock);
	    } else if ( type == CB_BLOCK ) {
		ComputeMotionBlock(prev->ref_cb, by, bx, fmy, fmx, motionBlock);
	    } else if ( type == CR_BLOCK ) {
		ComputeMotionBlock(prev->ref_cr, by, bx, fmy, fmx, motionBlock);
	    }
	    break;
	case MOTION_BACKWARD:
	    if ( type == LUM_BLOCK ) {
		ComputeMotionBlock(next->ref_y, by, bx, bmy, bmx, motionBlock);
	    } else if ( type == CB_BLOCK ) {
		ComputeMotionBlock(next->ref_cb, by, bx, bmy, bmx, motionBlock);
	    } else if ( type == CR_BLOCK ) {
		ComputeMotionBlock(next->ref_cr, by, bx, bmy, bmx, motionBlock);
	    }
	    break;
	case MOTION_INTERPOLATE:
	    if ( type == LUM_BLOCK ) {
		ComputeMotionBlock(prev->ref_y, by, bx, fmy, fmx, prevBlock);
		ComputeMotionBlock(next->ref_y, by, bx, bmy, bmx, nextBlock);
	    } else if ( type == CB_BLOCK ) {
		ComputeMotionBlock(prev->ref_cb, by, bx, fmy, fmx, prevBlock);
		ComputeMotionBlock(next->ref_cb, by, bx, bmy, bmx, nextBlock);
	    } else if ( type == CR_BLOCK ) {
		ComputeMotionBlock(prev->ref_cr, by, bx, fmy, fmx, prevBlock);
		ComputeMotionBlock(next->ref_cr, by, bx, bmy, bmx, nextBlock);
	    }

	    for ( y = 0; y < 8; y++ ) {
		for ( x = 0; x < 8; x++ ) {
		    motionBlock[y][x] = (prevBlock[y][x]+nextBlock[y][x]+1)/2;
		}
	    }
	    break;
    }
}


/*===========================================================================*
 *
 * ComputeBDiffDCTs
 *
 *	compute the DCT of the error term
 *
 * RETURNS:	appropriate blocks of current will contain the DCTs
 *
 * SIDE EFFECTS:    none
 *
 * PRECONDITION:	the motion vectors must be valid!
 *
 *===========================================================================*/
static void
ComputeBDiffDCTs(current, prev, next, by, bx, mode, fmy, fmx, bmy, bmx, pattern)
    MpegFrame *current;
    MpegFrame *prev;
    MpegFrame *next;
    int by;
    int bx;
    int mode;
    int fmy;
    int fmx;
    int bmy;
    int bmx;
    int *pattern;
{
    Block   motionBlock;

    if ( *pattern & 0x20 ) {
	ComputeBMotionBlock(prev, next, by, bx, mode, fmy, fmx,
			    bmy, bmx, motionBlock, LUM_BLOCK);
	if (! ComputeDiffDCTBlock(current->y_blocks[by][bx], dct[by][bx], motionBlock)) {
	  *pattern ^=  0x20;
	}
    }

    if ( *pattern & 0x10 ) {
	ComputeBMotionBlock(prev, next, by, bx+1, mode, fmy, fmx,
			    bmy, bmx, motionBlock, LUM_BLOCK);
	if (! ComputeDiffDCTBlock(current->y_blocks[by][bx+1], dct[by][bx+1], motionBlock)) {
	  *pattern ^=  0x10;
	}
    }

    if ( *pattern & 0x8 ) {
	ComputeBMotionBlock(prev, next, by+1, bx, mode, fmy, fmx,
			    bmy, bmx, motionBlock, LUM_BLOCK);
	if (! ComputeDiffDCTBlock(current->y_blocks[by+1][bx], dct[by+1][bx], motionBlock)) {
	  *pattern ^= 0x8;
	}
    }

    if ( *pattern & 0x4 ) {
	ComputeBMotionBlock(prev, next, by+1, bx+1, mode, fmy, fmx,
			    bmy, bmx, motionBlock, LUM_BLOCK);
	if (! ComputeDiffDCTBlock(current->y_blocks[by+1][bx+1], dct[by+1][bx+1], motionBlock)) {
	  *pattern ^= 0x4;
	}
    }

    if ( *pattern & 0x2 ) {
	ComputeBMotionBlock(prev, next, by>>1, bx>>1, mode, fmy/2, fmx/2,
			    bmy/2, bmx/2, motionBlock, CB_BLOCK);
	if (! ComputeDiffDCTBlock(current->cb_blocks[by >> 1][bx >> 1], dctb[by >> 1][bx >> 1], motionBlock)) {
	  *pattern ^= 0x2;
	}
    }

    if ( *pattern & 0x1 ) {
	ComputeBMotionBlock(prev, next, by>>1, bx>>1, mode, fmy/2, fmx/2,
			    bmy/2, bmx/2, motionBlock, CR_BLOCK);
	if (! ComputeDiffDCTBlock(current->cr_blocks[by >> 1][bx >> 1], dctr[by >> 1][bx >> 1], motionBlock)) {
	  *pattern ^= 0x1;
	}
    }
}


/*===========================================================================*
 *
 *			    USER-MODIFIABLE
 *
 * DoBIntraCode
 *
 *	decides if this block should be coded as intra-block
 *
 * RETURNS:	TRUE if intra-coding should be used; FALSE otherwise
 *
 * SIDE EFFECTS:    none
 *
 * PRECONDITION:	the motion vectors must be valid!
 *
 *===========================================================================*/
static boolean
DoBIntraCode(current, prev, next, by, bx, mode, fmy, fmx, bmy, bmx)
    MpegFrame *current;
    MpegFrame *prev;
    MpegFrame *next;
    int by;
    int bx;
    int mode;
    int fmy;
    int fmx;
    int bmy;
    int bmx;
{
    int	    x, y;
    int32 sum = 0, vard = 0, varc = 0, dif;
    int32 currPixel, prevPixel;
    LumBlock	motionBlock;
    int	    fy, fx;

    ComputeBMotionLumBlock(prev, next, by, bx, mode, fmy, fmx,
			   bmy, bmx, motionBlock);

    MOTION_TO_FRAME_COORD(by, bx, 0, 0, fy, fx);

    for ( y = 0; y < 16; y++ ) {
	for ( x = 0; x < 16; x++ ) {
	    currPixel = current->orig_y[fy+y][fx+x];
	    prevPixel = motionBlock[y][x];

	    sum += currPixel;
	    varc += currPixel*currPixel;

	    dif = currPixel - prevPixel;
	    vard += dif*dif;
	}
    }

    vard >>= 8;		/* divide by 256; assumes mean is close to zero */
    varc = (varc>>8) - (sum>>8)*(sum>>8);

    if ( vard <= 64 ) {
	return FALSE;
    } else if ( vard < varc ) {
	return FALSE;
    } else {
	return TRUE;
    }
}

static int
ComputeBlockColorDiff(current, motionBlock)
    Block current, motionBlock;
{
  register int x, y, diff_total = 0, diff_tmp;
  
  for ( y = 0; y < 8; y++ ) {
    for ( x = 0; x < 8; x++ ) {
      diff_tmp = current[y][x] - motionBlock[y][x];
      diff_total += ABS(diff_tmp);
    }
  }
  return diff_total;
}

/*===========================================================================*
 *
 *			    USER-MODIFIABLE
 *
 * MotionSufficient
 *
 *	decides if this motion vector is sufficient without DCT coding
 *
 * RETURNS:	TRUE if no DCT is needed; FALSE otherwise
 *
 * SIDE EFFECTS:    none
 *
 * PRECONDITION:	the motion vectors must be valid!
 *
 *===========================================================================*/
static boolean
MotionSufficient(curr, currBlock, prev, next, by, bx, mode, fmy, fmx, bmy, bmx)
    MpegFrame *curr;
    LumBlock currBlock;
    MpegFrame *prev;
    MpegFrame *next;
    int by, bx;
    int mode;
    int fmy, fmx;
    int bmy, bmx;
{
    LumBlock   mLumBlock;
    Block mColorBlock;
    int lumErr, colorErr;

    /* check bounds */
    if ( mode != MOTION_BACKWARD ) {
	if ( (by*DCTSIZE+(fmy-1)/2 < 0) || ((by+2)*DCTSIZE+(fmy+1)/2-1 >= Fsize_y) ) {
	    return FALSE;
	}
	if ( (bx*DCTSIZE+(fmx-1)/2 < 0) || ((bx+2)*DCTSIZE+(fmx+1)/2-1 >= Fsize_x) ) {
	    return FALSE;
	}
    }

    if ( mode != MOTION_FORWARD ) {
	if ( (by*DCTSIZE+(bmy-1)/2 < 0) || ((by+2)*DCTSIZE+(bmy+1)/2-1 >= Fsize_y) ) {
	    return FALSE;
	}
	if ( (bx*DCTSIZE+(bmx-1)/2 < 0) || ((bx+2)*DCTSIZE+(bmx+1)/2-1 >= Fsize_x) ) {
	    return FALSE;
	}
    }

    /* check Lum */
    ComputeBMotionLumBlock(prev, next, by, bx, mode, fmy, fmx,
			   bmy, bmx, mLumBlock);
    lumErr =  LumBlockMAD(currBlock, mLumBlock, 0x7fffffff);
    if (lumErr > 512) {
      return FALSE;
    }

    /* check color */
    ComputeBMotionBlock(prev, next, by>>1, bx>>1, mode, fmy/2, fmx/2, 
			bmy/2, bmx/2, mColorBlock, CR_BLOCK);
    colorErr = ComputeBlockColorDiff(curr->cr_blocks[by >> 1][bx >> 1], mColorBlock);
    ComputeBMotionBlock(prev, next, by>>1, bx>>1, mode, fmy/2, fmx/2, 
			bmy/2, bmx/2, mColorBlock, CB_BLOCK);
    colorErr += ComputeBlockColorDiff(curr->cr_blocks[by >> 1][bx >> 1], mColorBlock);
    
    return (colorErr < 256); /* lumErr checked above */
}


