predict.c

MPEG2视频编解码算法方面的源代码(包括编码和解码)

/* predict.c, motion compensated prediction                                 */

/* Copyright (C) 1996, MPEG Software Simulation Group. All Rights Reserved. */

/*
 * Disclaimer of Warranty
 *
 * These software programs are available to the user without any license fee or
 * royalty on an "as is" basis.  The MPEG Software Simulation Group disclaims
 * any and all warranties, whether express, implied, or statuary, including any
 * implied warranties or merchantability or of fitness for a particular
 * purpose.  In no event shall the copyright-holder be liable for any
 * incidental, punitive, or consequential damages of any kind whatsoever
 * arising from the use of these programs.
 *
 * This disclaimer of warranty extends to the user of these programs and user's
 * customers, employees, agents, transferees, successors, and assigns.
 *
 * The MPEG Software Simulation Group does not represent or warrant that the
 * programs furnished hereunder are free of infringement of any third-party
 * patents.
 *
 * Commercial implementations of MPEG-1 and MPEG-2 video, including shareware,
 * are subject to royalty fees to patent holders.  Many of these patents are
 * general enough such that they are unavoidable regardless of implementation
 * design.
 *
 */

#include <stdio.h>
#include "config.h"
#include "global.h"

/* private prototypes */
static void predict_mb _ANSI_ARGS_((
  unsigned char *oldref[], unsigned char *newref[], unsigned char *cur[],
  int lx, int bx, int by, int pict_type, int pict_struct, int mb_type,
  int motion_type, int secondfield,
  int PMV[2][2][2], int mv_field_sel[2][2], int dmvector[2]));

static void pred _ANSI_ARGS_((unsigned char *src[], int sfield,
  unsigned char *dst[], int dfield,
  int lx, int w, int h, int x, int y, int dx, int dy, int addflag));

static void pred_comp _ANSI_ARGS_((unsigned char *src, unsigned char *dst,
  int lx, int w, int h, int x, int y, int dx, int dy, int addflag));

static void calc_DMV _ANSI_ARGS_((int DMV[][2], int *dmvector, int mvx,
  int mvy));

static void clearblock _ANSI_ARGS_((unsigned char *cur[], int i0, int j0));


/* form prediction for a complete picture (frontend for predict_mb)
 *
 * reff: reference frame for forward prediction
 * refb: reference frame for backward prediction
 * cur:  destination (current) frame
 * secondfield: predict second field of a frame
 * mbi:  macroblock info
 *
 * Notes:
 * - cf. predict_mb
 */

void predict(reff,refb,cur,secondfield,mbi)
unsigned char *reff[],*refb[],*cur[3];
int secondfield;
struct mbinfo *mbi;
{
  int i, j, k;

  k = 0;

  /* loop through all macroblocks of the picture */
  for (j=0; j<height2; j+=16)
    for (i=0; i<width; i+=16)
    {
      predict_mb(reff,refb,cur,width,i,j,pict_type,pict_struct,
                 mbi[k].mb_type,mbi[k].motion_type,secondfield,
                 mbi[k].MV,mbi[k].mv_field_sel,mbi[k].dmvector);

      k++;
    }
}

/* form prediction for one macroblock
 *
 * oldref: reference frame for forward prediction
 * newref: reference frame for backward prediction
 * cur:    destination (current) frame
 * lx:     frame width (identical to global var `width')
 * bx,by:  picture (field or frame) coordinates of macroblock to be predicted
 * pict_type: I, P or B
 * pict_struct: FRAME_PICTURE, TOP_FIELD, BOTTOM_FIELD
 * mb_type:     MB_FORWARD, MB_BACKWARD, MB_INTRA
 * motion_type: MC_FRAME, MC_FIELD, MC_16X8, MC_DMV
 * secondfield: predict second field of a frame
 * PMV[2][2][2]: motion vectors (in half pel picture coordinates)
 * mv_field_sel[2][2]: motion vertical field selects (for field predictions)
 * dmvector: differential motion vectors (for dual prime)
 *
 * Notes:
 * - when predicting a P type picture which is the second field of
 *   a frame, the same parity reference field is in oldref, while the
 *   opposite parity reference field is assumed to be in newref!
 * - intra macroblocks are modelled to have a constant prediction of 128
 *   for all pels; this results in a DC DCT coefficient symmetric to 0
 * - vectors for field prediction in frame pictures are in half pel frame
 *   coordinates (vertical component is twice the field value and always
 *   even)
 *
 * already covers dual prime (not yet used)
 */

static void predict_mb(oldref,newref,cur,lx,bx,by,pict_type,pict_struct,
  mb_type,motion_type,secondfield,PMV,mv_field_sel,dmvector)
unsigned char *oldref[],*newref[],*cur[];
int lx;
int bx,by;
int pict_type;
int pict_struct;
int mb_type;
int motion_type;
int secondfield;
int PMV[2][2][2], mv_field_sel[2][2], dmvector[2];
{
  int addflag, currentfield;
  unsigned char **predframe;
  int DMV[2][2];

  if (mb_type&MB_INTRA)
  {
    clearblock(cur,bx,by);
    return;
  }

  addflag = 0; /* first prediction is stored, second is added and averaged */

  if ((mb_type & MB_FORWARD) || (pict_type==P_TYPE))
  {
    /* forward prediction, including zero MV in P pictures */

    if (pict_struct==FRAME_PICTURE)
    {
      /* frame picture */

      if ((motion_type==MC_FRAME) || !(mb_type & MB_FORWARD))
      {
        /* frame-based prediction in frame picture */
        pred(oldref,0,cur,0,
          lx,16,16,bx,by,PMV[0][0][0],PMV[0][0][1],0);
      }
      else if (motion_type==MC_FIELD)
      {
        /* field-based prediction in frame picture
         *
         * note scaling of the vertical coordinates (by, PMV[][0][1])
         * from frame to field!
         */

        /* top field prediction */
        pred(oldref,mv_field_sel[0][0],cur,0,
          lx<<1,16,8,bx,by>>1,PMV[0][0][0],PMV[0][0][1]>>1,0);

        /* bottom field prediction */
        pred(oldref,mv_field_sel[1][0],cur,1,
          lx<<1,16,8,bx,by>>1,PMV[1][0][0],PMV[1][0][1]>>1,0);
      }
      else if (motion_type==MC_DMV)
      {
        /* dual prime prediction */

        /* calculate derived motion vectors */
        calc_DMV(DMV,dmvector,PMV[0][0][0],PMV[0][0][1]>>1);

        /* predict top field from top field */
        pred(oldref,0,cur,0,
          lx<<1,16,8,bx,by>>1,PMV[0][0][0],PMV[0][0][1]>>1,0);

        /* predict bottom field from bottom field */
        pred(oldref,1,cur,1,
          lx<<1,16,8,bx,by>>1,PMV[0][0][0],PMV[0][0][1]>>1,0);

        /* predict and add to top field from bottom field */
        pred(oldref,1,cur,0,
          lx<<1,16,8,bx,by>>1,DMV[0][0],DMV[0][1],1);

        /* predict and add to bottom field from top field */
        pred(oldref,0,cur,1,
          lx<<1,16,8,bx,by>>1,DMV[1][0],DMV[1][1],1);
      }
      else
      {
        /* invalid motion_type in frame picture */
        if (!quiet)
          fprintf(stderr,"invalid motion_type\n");
      }
    }
    else /* TOP_FIELD or BOTTOM_FIELD */
    {
      /* field picture */

      currentfield = (pict_struct==BOTTOM_FIELD);

      /* determine which frame to use for prediction */
      if ((pict_type==P_TYPE) && secondfield
          && (currentfield!=mv_field_sel[0][0]))
        predframe = newref; /* same frame */
      else
        predframe = oldref; /* previous frame */

      if ((motion_type==MC_FIELD) || !(mb_type & MB_FORWARD))
      {
        /* field-based prediction in field picture */
        pred(predframe,mv_field_sel[0][0],cur,currentfield,
          lx<<1,16,16,bx,by,PMV[0][0][0],PMV[0][0][1],0);
      }
      else if (motion_type==MC_16X8)
      {
        /* 16 x 8 motion compensation in field picture */

        /* upper half */
        pred(predframe,mv_field_sel[0][0],cur,currentfield,
          lx<<1,16,8,bx,by,PMV[0][0][0],PMV[0][0][1],0);

        /* determine which frame to use for lower half prediction */
        if ((pict_type==P_TYPE) && secondfield
            && (currentfield!=mv_field_sel[1][0]))
          predframe = newref; /* same frame */
        else
          predframe = oldref; /* previous frame */

        /* lower half */
        pred(predframe,mv_field_sel[1][0],cur,currentfield,
          lx<<1,16,8,bx,by+8,PMV[1][0][0],PMV[1][0][1],0);
      }
      else if (motion_type==MC_DMV)
      {
        /* dual prime prediction */

        /* determine which frame to use for prediction */
        if (secondfield)
          predframe = newref; /* same frame */
        else
          predframe = oldref; /* previous frame */

        /* calculate derived motion vectors */
        calc_DMV(DMV,dmvector,PMV[0][0][0],PMV[0][0][1]);

        /* predict from field of same parity */
        pred(oldref,currentfield,cur,currentfield,
          lx<<1,16,16,bx,by,PMV[0][0][0],PMV[0][0][1],0);

        /* predict from field of opposite parity */
        pred(predframe,!currentfield,cur,currentfield,
          lx<<1,16,16,bx,by,DMV[0][0],DMV[0][1],1);
      }
      else
      {
        /* invalid motion_type in field picture */
        if (!quiet)
          fprintf(stderr,"invalid motion_type\n");
      }
    }
    addflag = 1; /* next prediction (if any) will be averaged with this one */
  }

  if (mb_type & MB_BACKWARD)
  {
    /* backward prediction */

    if (pict_struct==FRAME_PICTURE)
    {
      /* frame picture */

      if (motion_type==MC_FRAME)
      {
        /* frame-based prediction in frame picture */
        pred(newref,0,cur,0,
          lx,16,16,bx,by,PMV[0][1][0],PMV[0][1][1],addflag);
      }
      else
      {
        /* field-based prediction in frame picture
         *
         * note scaling of the vertical coordinates (by, PMV[][1][1])
         * from frame to field!
         */

        /* top field prediction */
        pred(newref,mv_field_sel[0][1],cur,0,
          lx<<1,16,8,bx,by>>1,PMV[0][1][0],PMV[0][1][1]>>1,addflag);

        /* bottom field prediction */