getpic.c

linux下的一款mpeg播放器

/* getpic.c, picture decoding                                               */

/*
 * All modifications (mpeg2decode -> mpeg2play) are
 * Copyright (C) 1994, Stefan Eckart. All Rights Reserved.
 */

/* Copyright (C) 1994, 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 getMBs _ANSI_ARGS_((int framenum));
static void macroblock_modes _ANSI_ARGS_((int *pmb_type, int *pstwtype,
  int *pstwclass, int *pmotion_type, int *pmv_count, int *pmv_format, int *pdmv,
  int *pmvscale, int *pdct_type));
static void clearblock _ANSI_ARGS_((int comp));
static void sumblock _ANSI_ARGS_((int comp));
static void addblock _ANSI_ARGS_((int comp, int bx, int by,
  int dct_type, int addflag));

/* decode one frame or field picture */

void getpicture(framenum)
int framenum;
{
  int i;
  unsigned char *tmp;

  if (pict_struct==FRAME_PICTURE && secondfield)
  {
    /* recover from illegal number of field pictures */
    printf("odd number of field pictures\n");
    secondfield = 0;
  }

  for (i=0; i<3; i++)
  {
    if (pict_type==B_TYPE)
    {
      newframe[i] = auxframe[i];
    }
    else
    {
      if (!secondfield)
      {
        tmp = oldrefframe[i];
        oldrefframe[i] = refframe[i];
        refframe[i] = tmp;
      }

      newframe[i] = refframe[i];
    }

    if (pict_struct==BOTTOM_FIELD)
      newframe[i]+= (i==0) ? coded_picture_width : chrom_width;
  }

  if (base.pict_scal && !secondfield)
    getspatref();

  getMBs(framenum);

  if (framenum!=0)
  {
    if (pict_struct==FRAME_PICTURE || secondfield)
    {
      if (outtype==T_X11)
        if (pict_type==B_TYPE)
          dither(auxframe);
        else
          dither(oldrefframe);
    }
    else if (outtype==T_X11)
    {
      display_second_field();
    }
  }

  if (pict_struct!=FRAME_PICTURE)
    secondfield = !secondfield;
}


/* store last frame */

void putlast(framenum)
int framenum;
{
  if (secondfield)
    printf("last frame incomplete, not stored\n");
  else if (outtype==T_X11)
    dither(refframe);
}


/* decode all macroblocks of the current picture */

static void getMBs(framenum)
int framenum;
{
  int comp;
  int MBA, MBAmax, MBAinc, mb_type, cbp, motion_type, dct_type;
  int slice_vert_pos_ext;
  int bx, by;
  unsigned int code;
  int dc_dct_pred[3];
  int mv_count, mv_format, mvscale;
  int PMV[2][2][2], mv_field_sel[2][2];
  int dmv, dmvector[2];
  int qs;
  int stwtype, stwclass;
  int SNRMBA, SNRMBAinc, SNRmb_type, SNRcbp, SNRdct_type, dummy; /* SNR scal. */

  /* number of macroblocks per picture */
  MBAmax = mb_width*mb_height;

  if (pict_struct!=FRAME_PICTURE)
    MBAmax>>=1; /* field picture has half as mnay macroblocks as frame */

  MBA = 0; /* macroblock address */
  MBAinc = 0;

  if (twostreams && enhan.scalable_mode==SC_SNR)
  {
    SNRMBA=0;
    SNRMBAinc=0;
  }

  fault=0;

  for (;;)
  {
#ifdef TRACE
    if (trace)
      printf("frame %d, MB %d\n",framenum,MBA);
#endif

    if (!prog_seq && pict_struct==FRAME_PICTURE && MBA==(MBAmax>>1) &&
        framenum!=0 && outtype==T_X11)
      display_second_field();

    ld = &base;
    if (MBAinc==0)
    {
      if (base.scalable_mode==SC_DP && base.pri_brk==1)
          ld = &enhan;

      if (!showbits(23) || fault) /* startcode or fault */
      {
resync: /* if fault: resynchronize to next startcode */
        fault = 0;
        ld = &base;

        if (MBA>=MBAmax)
          return; /* all macroblocks decoded */

        startcode();
        code = showbits(32);

        if (code<SLICE_MIN_START || code>SLICE_MAX_START)
        {
          /* only slice headers are allowed in picture_data */
          if (!quiet)
            printf("Premature end of picture\n");
          return;
        }

        flushbits32();

        /* decode slice header (may change quant_scale) */
        slice_vert_pos_ext = getslicehdr();

        if (base.scalable_mode==SC_DP)
        {
          ld = &enhan;
          startcode();
          code = showbits(32);

          if (code<SLICE_MIN_START || code>SLICE_MAX_START)
          {
            /* only slice headers are allowed in picture_data */
            if (!quiet)
              printf("Premature end of picture\n");
            return;
          }

          flushbits32();

          /* decode slice header (may change quant_scale) */
          slice_vert_pos_ext = getslicehdr();

          if (base.pri_brk!=1)
            ld = &base;
        }

        /* decode macroblock address increment */
        MBAinc = getMBA();

        if (fault) goto resync;

        /* set current location */
        MBA = ((slice_vert_pos_ext<<7) + (code&255) - 1)*mb_width + MBAinc - 1;
        MBAinc = 1; /* first macroblock in slice: not skipped */

        /* reset all DC coefficient and motion vector predictors */
        dc_dct_pred[0]=dc_dct_pred[1]=dc_dct_pred[2]=0;
        PMV[0][0][0]=PMV[0][0][1]=PMV[1][0][0]=PMV[1][0][1]=0;
        PMV[0][1][0]=PMV[0][1][1]=PMV[1][1][0]=PMV[1][1][1]=0;
      }
      else /* neither startcode nor fault */
      {
        if (MBA>=MBAmax)
        {
          if (!quiet)
            printf("Too many macroblocks in picture\n");
          return;
        }

        if (base.scalable_mode==SC_DP && base.pri_brk==1)
          ld = &enhan;

        /* decode macroblock address increment */
        MBAinc = getMBA();

        if (fault) goto resync;
      }
    }

    if (MBA>=MBAmax)
    {
      /* MBAinc points beyond picture dimensions */
      if (!quiet)
        printf("Too many macroblocks in picture\n");
      return;
    }

    if (MBAinc==1) /* not skipped */
    {
      if (base.scalable_mode==SC_DP)
      {
        if (base.pri_brk<=2)
          ld = &enhan;
        else
          ld = &base;
      }

      macroblock_modes(&mb_type, &stwtype, &stwclass,
        &motion_type, &mv_count, &mv_format, &dmv, &mvscale,
        &dct_type);

      if (fault) goto resync;

      if (mb_type & MB_QUANT)
      {
        qs = getbits(5);

#ifdef TRACE
        if (trace)
        {
          printf("quantiser_scale_code (");
          printbits(qs,5,5);
          printf("): %d\n",qs);
        }
#endif

        if (ld->mpeg2)
          ld->quant_scale =
            ld->qscale_type ? non_linear_mquant_table[qs] : (qs << 1);
        else
          ld->quant_scale = qs;

        if (base.scalable_mode==SC_DP)
          /* make sure base.quant_scale is valid */
          base.quant_scale = ld->quant_scale;
      }

      /* motion vectors */

      /* decode forward motion vectors */
      if ((mb_type & MB_FORWARD) || ((mb_type & MB_INTRA) && conceal_mv))
      {
        if (ld->mpeg2)
          motion_vectors(PMV,dmvector,mv_field_sel,
            0,mv_count,mv_format,h_forw_r_size,v_forw_r_size,dmv,mvscale);
        else
          motion_vector(PMV[0][0],dmvector,
            forw_r_size,forw_r_size,0,0,full_forw);
      }

      if (fault) goto resync;

      /* decode backward motion vectors */
      if (mb_type & MB_BACKWARD)
      {
        if (ld->mpeg2)
          motion_vectors(PMV,dmvector,mv_field_sel,
            1,mv_count,mv_format,h_back_r_size,v_back_r_size,0,mvscale);
        else
          motion_vector(PMV[0][1],dmvector,
            back_r_size,back_r_size,0,0,full_back);
      }

      if (fault) goto resync;

      if ((mb_type & MB_INTRA) && conceal_mv)
        flushbits(1); /* remove marker_bit */

      if (base.scalable_mode==SC_DP && base.pri_brk==3)
        ld = &enhan;

      /* macroblock_pattern */
      if (mb_type & MB_PATTERN)
      {
        cbp = getCBP();
        if (chroma_format==CHROMA422)
        {
          cbp = (cbp<<2) | getbits(2); /* coded_block_pattern_1 */

#ifdef TRACE
          if (trace)
          {
            printf("coded_block_pattern_1: ");
            printbits(cbp,2,2);
            printf(" (%d)\n",cbp&3);
          }
#endif
        }
        else if (chroma_format==CHROMA444)
        {
          cbp = (cbp<<6) | getbits(6); /* coded_block_pattern_2 */

#ifdef TRACE
          if (trace)
          {
            printf("coded_block_pattern_2: ");
            printbits(cbp,6,6);
            printf(" (%d)\n",cbp&63);
          }
#endif
        }
      }
      else
        cbp = (mb_type & MB_INTRA) ? (1<<blk_cnt)-1 : 0;

      if (fault) goto resync;

      /* decode blocks */
      for (comp=0; comp<blk_cnt; comp++)
      {
        if (base.scalable_mode==SC_DP)
          ld = &base;

        clearblock(comp);

        if (cbp & (1<<(blk_cnt-1-comp)))
        {
          if (mb_type & MB_INTRA)
          {
            if (ld->mpeg2)
              getmpg2intrablock(comp,dc_dct_pred);
            else
              getintrablock(comp,dc_dct_pred);
          }
          else
          {
            if (ld->mpeg2)
              getmpg2interblock(comp);
            else
              getinterblock(comp);
          }

          if (fault) goto resync;
        }
      }

      /* reset intra_dc predictors */
      if (!(mb_type & MB_INTRA))
        dc_dct_pred[0]=dc_dct_pred[1]=dc_dct_pred[2]=0;

      /* reset motion vector predictors */
      if ((mb_type & MB_INTRA) && !conceal_mv)
      {
        /* intra mb without concealment motion vectors */
        PMV[0][0][0]=PMV[0][0][1]=PMV[1][0][0]=PMV[1][0][1]=0;
        PMV[0][1][0]=PMV[0][1][1]=PMV[1][1][0]=PMV[1][1][1]=0;
      }

      if ((pict_type==P_TYPE) && !(mb_type & (MB_FORWARD|MB_INTRA)))
      {
        /* non-intra mb without forward mv in a P picture */
        PMV[0][0][0]=PMV[0][0][1]=PMV[1][0][0]=PMV[1][0][1]=0;

        /* derive motion_type */
        if (pict_struct==FRAME_PICTURE)
          motion_type = MC_FRAME;
        else
        {
          motion_type = MC_FIELD;
          /* predict from field of same parity */
          mv_field_sel[0][0] = (pict_struct==BOTTOM_FIELD);
        }
      }

      if (stwclass==4)
      {
        /* purely spatially predicted macroblock */
        PMV[0][0][0]=PMV[0][0][1]=PMV[1][0][0]=PMV[1][0][1]=0;
        PMV[0][1][0]=PMV[0][1][1]=PMV[1][1][0]=PMV[1][1][1]=0;
      }
    }
    else /* MBAinc!=1: skipped macroblock */
    {
      if (base.scalable_mode==SC_DP)