decoder.c

xvid解码的精简版本.非常好的版本,节省了分离xvid源代码的过程

     prevents crashes if bitstream is broken
  */
  int shift = 5 + dec->quarterpel;
  int xborder_high = (int)(dec->mb_width - x_pos) << shift;
  int xborder_low = (-(int)x_pos-1) << shift;
  int yborder_high = (int)(dec->mb_height - y_pos) << shift;
  int yborder_low = (-(int)y_pos-1) << shift;

#define CHECK_MV(mv) \
  do { \
  if ((mv).x > xborder_high) { \
    DPRINTF(XVID_DEBUG_MV, "mv.x > max -- %d > %d, MB %d, %d", (mv).x, xborder_high, x_pos, y_pos); \
    (mv).x = xborder_high; \
  } else if ((mv).x < xborder_low) { \
    DPRINTF(XVID_DEBUG_MV, "mv.x < min -- %d < %d, MB %d, %d", (mv).x, xborder_low, x_pos, y_pos); \
    (mv).x = xborder_low; \
  } \
  if ((mv).y > yborder_high) { \
    DPRINTF(XVID_DEBUG_MV, "mv.y > max -- %d > %d, MB %d, %d", (mv).y, yborder_high, x_pos, y_pos); \
    (mv).y = yborder_high; \
  } else if ((mv).y < yborder_low) { \
    DPRINTF(XVID_DEBUG_MV, "mv.y < min -- %d < %d, MB %d, %d", (mv).y, yborder_low, x_pos, y_pos); \
    (mv).y = yborder_low; \
  } \
  } while (0)

  CHECK_MV(mv[0]);
  CHECK_MV(mv[1]);
  CHECK_MV(mv[2]);
  CHECK_MV(mv[3]);
}

/* Up to this version, chroma rounding was wrong with qpel. 
 * So we try to be backward compatible to avoid artifacts */
#define BS_VERSION_BUGGY_CHROMA_ROUNDING 1

/* decode an inter macroblock */
static void
decoder_mbinter(DECODER * dec,
        const MACROBLOCK * pMB,
        const uint32_t x_pos,
        const uint32_t y_pos,
        const uint32_t cbp,
        Bitstream * bs,
        const uint32_t rounding,
        const int ref,
		const int bvop)
{
  uint32_t stride = dec->edged_width;
  uint32_t stride2 = stride / 2;
  uint32_t i;

  uint8_t *pY_Cur, *pU_Cur, *pV_Cur;

  int uv_dx, uv_dy;
  VECTOR mv[4]; /* local copy of mvs */

  pY_Cur = dec->cur.y + (y_pos << 4) * stride + (x_pos << 4);
  pU_Cur = dec->cur.u + (y_pos << 3) * stride2 + (x_pos << 3);
  pV_Cur = dec->cur.v + (y_pos << 3) * stride2 + (x_pos << 3);
  for (i = 0; i < 4; i++)
    mv[i] = pMB->mvs[i];

  validate_vector(mv, x_pos, y_pos, dec);



  if ((pMB->mode != MODE_INTER4V) || (bvop)) { /* INTER, INTER_Q, NOT_CODED, FORWARD, BACKWARD */

    uv_dx = mv[0].x;
    uv_dy = mv[0].y;
    if (dec->quarterpel) {
			if (dec->bs_version <= BS_VERSION_BUGGY_CHROMA_ROUNDING) {
  				uv_dx = (uv_dx>>1) | (uv_dx&1);
				uv_dy = (uv_dy>>1) | (uv_dy&1);
			}
			else {
        uv_dx /= 2;
        uv_dy /= 2;
      }
    }
    uv_dx = (uv_dx >> 1) + roundtab_79[uv_dx & 0x3];
    uv_dy = (uv_dy >> 1) + roundtab_79[uv_dy & 0x3];

    if (dec->quarterpel)
      interpolate16x16_quarterpel(dec->cur.y, dec->refn[ref].y, dec->qtmp.y, dec->qtmp.y + 64,
                  dec->qtmp.y + 128, 16*x_pos, 16*y_pos,
                      mv[0].x, mv[0].y, stride, rounding);
    else
      interpolate16x16_switch(dec->cur.y, dec->refn[ref].y, 16*x_pos, 16*y_pos,
                  mv[0].x, mv[0].y, stride, rounding);

  } else {  /* MODE_INTER4V */

    if(dec->quarterpel) {
			if (dec->bs_version <= BS_VERSION_BUGGY_CHROMA_ROUNDING) {
				int z;
				uv_dx = 0; uv_dy = 0;
				for (z = 0; z < 4; z++) {
				  uv_dx += ((mv[z].x>>1) | (mv[z].x&1));
				  uv_dy += ((mv[z].y>>1) | (mv[z].y&1));
				}
			}
			else {
        uv_dx = (mv[0].x / 2) + (mv[1].x / 2) + (mv[2].x / 2) + (mv[3].x / 2);
        uv_dy = (mv[0].y / 2) + (mv[1].y / 2) + (mv[2].y / 2) + (mv[3].y / 2);
      }
    } else {
      uv_dx = mv[0].x + mv[1].x + mv[2].x + mv[3].x;
      uv_dy = mv[0].y + mv[1].y + mv[2].y + mv[3].y;
    }

    uv_dx = (uv_dx >> 3) + roundtab_76[uv_dx & 0xf];
    uv_dy = (uv_dy >> 3) + roundtab_76[uv_dy & 0xf];

    if (dec->quarterpel) {
      interpolate8x8_quarterpel(dec->cur.y, dec->refn[0].y , dec->qtmp.y, dec->qtmp.y + 64,
                  dec->qtmp.y + 128, 16*x_pos, 16*y_pos,
                  mv[0].x, mv[0].y, stride, rounding);
      interpolate8x8_quarterpel(dec->cur.y, dec->refn[0].y , dec->qtmp.y, dec->qtmp.y + 64,
                  dec->qtmp.y + 128, 16*x_pos + 8, 16*y_pos,
                  mv[1].x, mv[1].y, stride, rounding);
      interpolate8x8_quarterpel(dec->cur.y, dec->refn[0].y , dec->qtmp.y, dec->qtmp.y + 64,
                  dec->qtmp.y + 128, 16*x_pos, 16*y_pos + 8,
                  mv[2].x, mv[2].y, stride, rounding);
      interpolate8x8_quarterpel(dec->cur.y, dec->refn[0].y , dec->qtmp.y, dec->qtmp.y + 64,
                  dec->qtmp.y + 128, 16*x_pos + 8, 16*y_pos + 8,
                  mv[3].x, mv[3].y, stride, rounding);
    } else {
      interpolate8x8_switch(dec->cur.y, dec->refn[0].y , 16*x_pos, 16*y_pos,
                mv[0].x, mv[0].y, stride, rounding);
      interpolate8x8_switch(dec->cur.y, dec->refn[0].y , 16*x_pos + 8, 16*y_pos,
                mv[1].x, mv[1].y, stride, rounding);
      interpolate8x8_switch(dec->cur.y, dec->refn[0].y , 16*x_pos, 16*y_pos + 8,
                mv[2].x, mv[2].y, stride, rounding);
      interpolate8x8_switch(dec->cur.y, dec->refn[0].y , 16*x_pos + 8, 16*y_pos + 8,
                mv[3].x, mv[3].y, stride, rounding);
    }
  }

  /* chroma */
  interpolate8x8_switch(dec->cur.u, dec->refn[ref].u, 8 * x_pos, 8 * y_pos,
              uv_dx, uv_dy, stride2, rounding);
  interpolate8x8_switch(dec->cur.v, dec->refn[ref].v, 8 * x_pos, 8 * y_pos,
              uv_dx, uv_dy, stride2, rounding);



  if (cbp)
    decoder_mb_decode(dec, cbp, bs, pY_Cur, pU_Cur, pV_Cur, pMB);
}

/* decode an inter macroblock in field mode */
static void
decoder_mbinter_field(DECODER * dec,
        const MACROBLOCK * pMB,
        const uint32_t x_pos,
        const uint32_t y_pos,
        const uint32_t cbp,
        Bitstream * bs,
        const uint32_t rounding,
        const int ref,
		const int bvop)
{
  uint32_t stride = dec->edged_width;
  uint32_t stride2 = stride / 2;

  uint8_t *pY_Cur, *pU_Cur, *pV_Cur;

  int uvtop_dx, uvtop_dy;
  int uvbot_dx, uvbot_dy;
  VECTOR mv[4]; /* local copy of mvs */

  /* Get pointer to memory areas */
  pY_Cur = dec->cur.y + (y_pos << 4) * stride + (x_pos << 4);
  pU_Cur = dec->cur.u + (y_pos << 3) * stride2 + (x_pos << 3);
  pV_Cur = dec->cur.v + (y_pos << 3) * stride2 + (x_pos << 3);
  
  mv[0] = pMB->mvs[0];
  mv[1] = pMB->mvs[1];
  memset(&mv[2],0,2*sizeof(VECTOR));

  validate_vector(mv, x_pos, y_pos, dec);



  if((pMB->mode!=MODE_INTER4V) || (bvop))   /* INTER, INTER_Q, NOT_CODED, FORWARD, BACKWARD */
  { 
    /* Prepare top field vector */
    uvtop_dx = DIV2ROUND(mv[0].x);
    uvtop_dy = DIV2ROUND(mv[0].y);

    /* Prepare bottom field vector */
    uvbot_dx = DIV2ROUND(mv[1].x);
    uvbot_dy = DIV2ROUND(mv[1].y);

    if(dec->quarterpel)
    {
      /* NOT supported */
    }
    else
    {
      /* Interpolate top field left part(we use double stride for every 2nd line) */
      interpolate8x8_switch(dec->cur.y,dec->refn[ref].y+pMB->field_for_top*stride,
                            16*x_pos,8*y_pos,mv[0].x, mv[0].y>>1,2*stride, rounding);
      /* top field right part */
      interpolate8x8_switch(dec->cur.y,dec->refn[ref].y+pMB->field_for_top*stride,
                            16*x_pos+8,8*y_pos,mv[0].x, mv[0].y>>1,2*stride, rounding);

      /* Interpolate bottom field left part(we use double stride for every 2nd line) */
      interpolate8x8_switch(dec->cur.y+stride,dec->refn[ref].y+pMB->field_for_bot*stride,
                            16*x_pos,8*y_pos,mv[1].x, mv[1].y>>1,2*stride, rounding);
      /* Bottom field right part */
      interpolate8x8_switch(dec->cur.y+stride,dec->refn[ref].y+pMB->field_for_bot*stride,
                            16*x_pos+8,8*y_pos,mv[1].x, mv[1].y>>1,2*stride, rounding);

      /* Interpolate field1 U */
      interpolate8x4_switch(dec->cur.u,dec->refn[ref].u+pMB->field_for_top*stride2,
                            8*x_pos,4*y_pos,uvtop_dx,DIV2ROUND(uvtop_dy),stride,rounding);
      
      /* Interpolate field1 V */
      interpolate8x4_switch(dec->cur.v,dec->refn[ref].v+pMB->field_for_top*stride2,
                            8*x_pos,4*y_pos,uvtop_dx,DIV2ROUND(uvtop_dy),stride,rounding);
    
      /* Interpolate field2 U */
      interpolate8x4_switch(dec->cur.u+stride2,dec->refn[ref].u+pMB->field_for_bot*stride2,
                            8*x_pos,4*y_pos,uvbot_dx,DIV2ROUND(uvbot_dy),stride,rounding);
    
      /* Interpolate field2 V */
      interpolate8x4_switch(dec->cur.v+stride2,dec->refn[ref].v+pMB->field_for_bot*stride2,
                            8*x_pos,4*y_pos,uvbot_dx,DIV2ROUND(uvbot_dy),stride,rounding);
    }
  } 
  else 
  {
    /* We don't expect 4 motion vectors in interlaced mode */
  }



  /* Must add error correction? */
  if(cbp)
   decoder_mb_decode(dec, cbp, bs, pY_Cur, pU_Cur, pV_Cur, pMB);
}

static void
decoder_mbgmc(DECODER * dec,
        MACROBLOCK * const pMB,
        const uint32_t x_pos,
        const uint32_t y_pos,
        const uint32_t fcode,
        const uint32_t cbp,
        Bitstream * bs,
        const uint32_t rounding)
{
  const uint32_t stride = dec->edged_width;
  const uint32_t stride2 = stride / 2;

  uint8_t *const pY_Cur=dec->cur.y + (y_pos << 4) * stride + (x_pos << 4);
  uint8_t *const pU_Cur=dec->cur.u + (y_pos << 3) * stride2 + (x_pos << 3);
  uint8_t *const pV_Cur=dec->cur.v + (y_pos << 3) * stride2 + (x_pos << 3);

  NEW_GMC_DATA * gmc_data = &dec->new_gmc_data;

  pMB->mvs[0] = pMB->mvs[1] = pMB->mvs[2] = pMB->mvs[3] = pMB->amv;



/* this is where the calculations are done */

  gmc_data->predict_16x16(gmc_data,
      dec->cur.y + y_pos*16*stride + x_pos*16, dec->refn[0].y,
      stride, stride, x_pos, y_pos, rounding);

  gmc_data->predict_8x8(gmc_data,
      dec->cur.u + y_pos*8*stride2 + x_pos*8, dec->refn[0].u,
      dec->cur.v + y_pos*8*stride2 + x_pos*8, dec->refn[0].v,
      stride2, stride2, x_pos, y_pos, rounding);

  gmc_data->get_average_mv(gmc_data, &pMB->amv, x_pos, y_pos, dec->quarterpel);

  pMB->amv.x = gmc_sanitize(pMB->amv.x, dec->quarterpel, fcode);
  pMB->amv.y = gmc_sanitize(pMB->amv.y, dec->quarterpel, fcode);

  pMB->mvs[0] = pMB->mvs[1] = pMB->mvs[2] = pMB->mvs[3] = pMB->amv;



  if (cbp)
    decoder_mb_decode(dec, cbp, bs, pY_Cur, pU_Cur, pV_Cur, pMB);

}


static void
decoder_iframe(DECODER * dec,
        Bitstream * bs,
        int quant,
        int intra_dc_threshold)
{
  uint32_t bound;
  uint32_t x, y;
  const uint32_t mb_width = dec->mb_width;
  const uint32_t mb_height = dec->mb_height;

  bound = 0;

  for (y = 0; y < mb_height; y++) {
    for (x = 0; x < mb_width; x++) {
      MACROBLOCK *mb;
      uint32_t mcbpc;
      uint32_t cbpc;
      uint32_t acpred_flag;
      uint32_t cbpy;
      uint32_t cbp;

      while (BitstreamShowBits(bs, 9) == 1)
        BitstreamSkip(bs, 9);

      if (check_resync_marker(bs, 0))
      {
        bound = read_video_packet_header(bs, dec, 0,
              &quant, NULL, NULL, &intra_dc_threshold);
        x = bound % mb_width;
        y = bound / mb_width;
      }
      mb = &dec->mbs[y * dec->mb_width + x];

      DPRINTF(XVID_DEBUG_MB, "macroblock (%i,%i) %08x\n", x, y, BitstreamShowBits(bs, 32));

      mcbpc = get_mcbpc_intra(bs);
      mb->mode = mcbpc & 7;
      cbpc = (mcbpc >> 4);

      acpred_flag = BitstreamGetBit(bs);

      cbpy = get_cbpy(bs, 1);
      cbp = (cbpy << 2) | cbpc;

      if (mb->mode == MODE_INTRA_Q) {
        quant += dquant_table[BitstreamGetBits(bs, 2)];
        if (quant > 31) {
          quant = 31;
        } else if (quant < 1) {
          quant = 1;
        }
      }
      mb->quant = quant;
      mb->mvs[0].x = mb->mvs[0].y =
      mb->mvs[1].x = mb->mvs[1].y =
      mb->mvs[2].x = mb->mvs[2].y =
      mb->mvs[3].x = mb->mvs[3].y =0;

      if (dec->interlacing) {
        mb->field_dct = BitstreamGetBit(bs);
        DPRINTF(XVID_DEBUG_MB,"deci: field_dct: %i\n", mb->field_dct);
      }

      decoder_mbintra(dec, mb, x, y, acpred_flag, cbp, bs, quant,
              intra_dc_threshold, bound);

    }
    if(dec->out_frm)
      output_slice(&dec->cur, dec->edged_width,dec->width,dec->out_frm,0,y,mb_width);
  }

}


static void
get_motion_vector(DECODER * dec,
        Bitstream * bs,
        int x,
        int y,
        int k,
        VECTOR * ret_mv,
        int fcode,
        const int bound)
{

  const int scale_fac = 1 << (fcode - 1);
  const int high = (32 * scale_fac) - 1;
  const int low = ((-32) * scale_fac);
  const int range = (64 * scale_fac);

  const VECTOR pmv = get_pmv2(dec->mbs, dec->mb_width, bound, x, y, k);
  VECTOR mv;

  mv.x = get_mv(bs, fcode);
  mv.y = get_mv(bs, fcode);

  DPRINTF(XVID_DEBUG_MV,"mv_diff (%i,%i) pred (%i,%i) result (%i,%i)\n", mv.x, mv.y, pmv.x, pmv.y, mv.x+pmv.x, mv.y+pmv.y);

  mv.x += pmv.x;
  mv.y += pmv.y;

  if (mv.x < low) {
    mv.x += range;
  } else if (mv.x > high) {
    mv.x -= range;
  }

  if (mv.y < low) {
    mv.y += range;
  } else if (mv.y > high) {
    mv.y -= range;
  }

  ret_mv->x = mv.x;
  ret_mv->y = mv.y;
}

/* We use this when decoder runs interlaced -> different prediction */

static void get_motion_vector_interlaced(DECODER * dec,
        Bitstream * bs,
        int x,
        int y,
        int k,
        MACROBLOCK *pMB,
        int fcode,
        const int bound)
{
  const int scale_fac = 1 << (fcode - 1);
  const int high = (32 * scale_fac) - 1;
  const int low = ((-32) * scale_fac);
  const int range = (64 * scale_fac);
  
  /* Get interlaced prediction */
  const VECTOR pmv=get_pmv2_interlaced(dec->mbs,dec->mb_width,bound,x,y,k);
  VECTOR mv,mvf1,mvf2;

  if(!pMB->field_pred)
  {
    mv.x = get_mv(bs,fcode);
    mv.y = get_mv(bs,fcode);
    
    mv.x += pmv.x;
    mv.y += pmv.y;

    if(mv.x<low) {
      mv.x += range;
    } else if (mv.x>high) {