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

      mv.x-=range;
    }

    if (mv.y < low) {
      mv.y += range;
    } else if (mv.y > high) {
      mv.y -= range;
    }
    
    pMB->mvs[0]=pMB->mvs[1]=pMB->mvs[2]=pMB->mvs[3]=mv;
  }
  else
  {
    mvf1.x = get_mv(bs, fcode);
    mvf1.y = get_mv(bs, fcode);

    mvf1.x += pmv.x;
    mvf1.y = 2*(mvf1.y+pmv.y/2); /* It's multiple of 2 */

    if (mvf1.x < low) {
      mvf1.x += range;
    } else if (mvf1.x > high) {
      mvf1.x -= range;
    }

    if (mvf1.y < low) {
      mvf1.y += range;
    } else if (mvf1.y > high) {
      mvf1.y -= range;
    }

    mvf2.x = get_mv(bs, fcode);
    mvf2.y = get_mv(bs, fcode);

    mvf2.x += pmv.x;
    mvf2.y = 2*(mvf2.y+pmv.y/2); /* It's multiple of 2 */

    if (mvf2.x < low) {
      mvf2.x += range;
    } else if (mvf2.x > high) {
      mvf2.x -= range;
    }

    if (mvf2.y < low) {
      mvf2.y += range;
    } else if (mvf2.y > high) {
      mvf2.y -= range;
    }

    pMB->mvs[0]=mvf1;
    pMB->mvs[1]=mvf2;
    pMB->mvs[2].x=pMB->mvs[3].x=0;
    pMB->mvs[2].y=pMB->mvs[3].y=0;
  
    /* Calculate average for as it is field predicted */
    pMB->mvs_avg.x=DIV2ROUND(pMB->mvs[0].x+pMB->mvs[1].x);
    pMB->mvs_avg.y=DIV2ROUND(pMB->mvs[0].y+pMB->mvs[1].y);
  }
}

/* for P_VOP set gmc_warp to NULL */
static void
decoder_pframe(DECODER * dec,
        Bitstream * bs,
        int rounding,
        int quant,
        int fcode,
        int intra_dc_threshold,
        const WARPPOINTS *const gmc_warp)
{
  uint32_t x, y;
  uint32_t bound;
  int cp_mb, st_mb;
  const uint32_t mb_width = dec->mb_width;
  const uint32_t mb_height = dec->mb_height;

  if (!dec->is_edged[0]) {

    image_setedges(&dec->refn[0], dec->edged_width, dec->edged_height,
            dec->width, dec->height, dec->bs_version);
    dec->is_edged[0] = 1;
   
  }

  if (gmc_warp) {
    /* accuracy: 0==1/2, 1=1/4, 2=1/8, 3=1/16 */
    generate_GMCparameters( dec->sprite_warping_points,
        dec->sprite_warping_accuracy, gmc_warp,
        dec->width, dec->height, &dec->new_gmc_data);

    /* image warping is done block-based in decoder_mbgmc(), now */
  }

  bound = 0;

  for (y = 0; y < mb_height; y++) {
    cp_mb = st_mb = 0;
    for (x = 0; x < mb_width; x++) {
      MACROBLOCK *mb;

      /* skip stuffing */
      while (BitstreamShowBits(bs, 10) == 1)
        BitstreamSkip(bs, 10);

      if (check_resync_marker(bs, fcode - 1)) {
        bound = read_video_packet_header(bs, dec, fcode - 1,
          &quant, &fcode, 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));

      if (!(BitstreamGetBit(bs))) { /* block _is_ coded */
        uint32_t mcbpc, cbpc, cbpy, cbp;
        uint32_t intra, acpred_flag = 0;
        int mcsel = 0;    /* mcsel: '0'=local motion, '1'=GMC */

        cp_mb++;
        mcbpc = get_mcbpc_inter(bs);
        mb->mode = mcbpc & 7;
        cbpc = (mcbpc >> 4);

        DPRINTF(XVID_DEBUG_MB, "mode %i\n", mb->mode);
        DPRINTF(XVID_DEBUG_MB, "cbpc %i\n", cbpc);

        intra = (mb->mode == MODE_INTRA || mb->mode == MODE_INTRA_Q);

        if (gmc_warp && (mb->mode == MODE_INTER || mb->mode == MODE_INTER_Q))
          mcsel = BitstreamGetBit(bs);
        else if (intra)
          acpred_flag = BitstreamGetBit(bs);

        cbpy = get_cbpy(bs, intra);
        DPRINTF(XVID_DEBUG_MB, "cbpy %i mcsel %i \n", cbpy,mcsel);

        cbp = (cbpy << 2) | cbpc;

        if (mb->mode == MODE_INTER_Q || mb->mode == MODE_INTRA_Q) {
          int dquant = dquant_table[BitstreamGetBits(bs, 2)];
          DPRINTF(XVID_DEBUG_MB, "dquant %i\n", dquant);
          quant += dquant;
          if (quant > 31) {
            quant = 31;
          } else if (quant < 1) {
            quant = 1;
          }
          DPRINTF(XVID_DEBUG_MB, "quant %i\n", quant);
        }
        mb->quant = quant;

         mb->field_pred=0;
        if (dec->interlacing) {
          if (cbp || intra) {
            mb->field_dct = BitstreamGetBit(bs);
            DPRINTF(XVID_DEBUG_MB,"decp: field_dct: %i\n", mb->field_dct);
          }

          if ((mb->mode == MODE_INTER || mb->mode == MODE_INTER_Q) && !mcsel) {
            mb->field_pred = BitstreamGetBit(bs);
            DPRINTF(XVID_DEBUG_MB, "decp: field_pred: %i\n", mb->field_pred);

            if (mb->field_pred) {
              mb->field_for_top = BitstreamGetBit(bs);
              DPRINTF(XVID_DEBUG_MB,"decp: field_for_top: %i\n", mb->field_for_top);
              mb->field_for_bot = BitstreamGetBit(bs);
              DPRINTF(XVID_DEBUG_MB,"decp: field_for_bot: %i\n", mb->field_for_bot);
            }
          }
        }

        if (mcsel) {
          decoder_mbgmc(dec, mb, x, y, fcode, cbp, bs, rounding);
          continue;

        } else if (mb->mode == MODE_INTER || mb->mode == MODE_INTER_Q) {

          if(dec->interlacing) {
            /* Get motion vectors interlaced, field_pred is handled there */
            get_motion_vector_interlaced(dec, bs, x, y, 0, mb, fcode, bound);
          } else {
            get_motion_vector(dec, bs, x, y, 0, &mb->mvs[0], fcode, bound);
            mb->mvs[1] = mb->mvs[2] = mb->mvs[3] = mb->mvs[0];
          }
        } else if (mb->mode == MODE_INTER4V ) {
          /* interlaced missing here */
          get_motion_vector(dec, bs, x, y, 0, &mb->mvs[0], fcode, bound);
          get_motion_vector(dec, bs, x, y, 1, &mb->mvs[1], fcode, bound);
          get_motion_vector(dec, bs, x, y, 2, &mb->mvs[2], fcode, bound);
          get_motion_vector(dec, bs, x, y, 3, &mb->mvs[3], fcode, bound);
        } else { /* MODE_INTRA, MODE_INTRA_Q */
          mb->mvs[0].x = mb->mvs[1].x = mb->mvs[2].x = mb->mvs[3].x = 0;
          mb->mvs[0].y = mb->mvs[1].y = mb->mvs[2].y = mb->mvs[3].y = 0;
          decoder_mbintra(dec, mb, x, y, acpred_flag, cbp, bs, quant,
                  intra_dc_threshold, bound);
          continue;
        }

        /* See how to decode */
        if(!mb->field_pred)
         decoder_mbinter(dec, mb, x, y, cbp, bs, rounding, 0, 0);
        else 
         decoder_mbinter_field(dec, mb, x, y, cbp, bs, rounding, 0, 0);

      } else if (gmc_warp) {  /* a not coded S(GMC)-VOP macroblock */
        mb->mode = MODE_NOT_CODED_GMC;
        mb->quant = quant;
        decoder_mbgmc(dec, mb, x, y, fcode, 0x00, bs, rounding);

        if(dec->out_frm && cp_mb > 0) {
          output_slice(&dec->cur, dec->edged_width,dec->width,dec->out_frm,st_mb,y,cp_mb);
          cp_mb = 0;
        }
        st_mb = x+1;
      } else { /* not coded P_VOP macroblock */
        mb->mode = MODE_NOT_CODED;
        mb->quant = quant;

        mb->mvs[0].x = mb->mvs[1].x = mb->mvs[2].x = mb->mvs[3].x = 0;
        mb->mvs[0].y = mb->mvs[1].y = mb->mvs[2].y = mb->mvs[3].y = 0;
        mb->field_pred=0; /* (!) */

        decoder_mbinter(dec, mb, x, y, 0, bs, 
                                rounding, 0, 0);

        if(dec->out_frm && cp_mb > 0) {
          output_slice(&dec->cur, dec->edged_width,dec->width,dec->out_frm,st_mb,y,cp_mb);
          cp_mb = 0;
        }
        st_mb = x+1;
      }
    }

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


/* decode B-frame motion vector */
static void
get_b_motion_vector(Bitstream * bs,
          VECTOR * mv,
          int fcode,
          const VECTOR pmv,
          const DECODER * const dec,
          const int x, const int y)
{
  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);

  int mv_x = get_mv(bs, fcode);
  int 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)
    mv_x -= range;

  if (mv_y < low)
    mv_y += range;
  else if (mv_y > high)
    mv_y -= range;

  mv->x = mv_x;
  mv->y = mv_y;
}

/* decode an B-frame direct & interpolate macroblock */
static void
decoder_bf_interpolate_mbinter(DECODER * dec,
                IMAGE forward,
                IMAGE backward,
                MACROBLOCK * pMB,
                const uint32_t x_pos,
                const uint32_t y_pos,
                Bitstream * bs,
                const int direct)
{
  uint32_t stride = dec->edged_width;
  uint32_t stride2 = stride / 2;
  int uv_dx, uv_dy;
  int b_uv_dx, b_uv_dy;
  uint8_t *pY_Cur, *pU_Cur, *pV_Cur;
  const uint32_t cbp = pMB->cbp;

  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);

  validate_vector(pMB->mvs, x_pos, y_pos, dec);
  validate_vector(pMB->b_mvs, x_pos, y_pos, dec);

  if (!direct) {
    uv_dx = pMB->mvs[0].x;
    uv_dy = pMB->mvs[0].y;
    b_uv_dx = pMB->b_mvs[0].x;
    b_uv_dy = pMB->b_mvs[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);
				b_uv_dx = (b_uv_dx>>1) | (b_uv_dx&1);
				b_uv_dy = (b_uv_dy>>1) | (b_uv_dy&1);
			}
			else {
        uv_dx /= 2;
        uv_dy /= 2;
        b_uv_dx /= 2;
        b_uv_dy /= 2;
      }
    }

    uv_dx = (uv_dx >> 1) + roundtab_79[uv_dx & 0x3];
    uv_dy = (uv_dy >> 1) + roundtab_79[uv_dy & 0x3];
    b_uv_dx = (b_uv_dx >> 1) + roundtab_79[b_uv_dx & 0x3];
    b_uv_dy = (b_uv_dy >> 1) + roundtab_79[b_uv_dy & 0x3];

  } else {
	  if (dec->quarterpel) { /* for qpel the /2 shall be done before summation. We've done it right in the encoder in the past. */
							 /* TODO: figure out if we ever did it wrong on the encoder side. If yes, add some workaround */
		if (dec->bs_version <= BS_VERSION_BUGGY_CHROMA_ROUNDING) {
			int z;
			uv_dx = 0; uv_dy = 0;
			b_uv_dx = 0; b_uv_dy = 0;
			for (z = 0; z < 4; z++) {
			  uv_dx += ((pMB->mvs[z].x>>1) | (pMB->mvs[z].x&1));
			  uv_dy += ((pMB->mvs[z].y>>1) | (pMB->mvs[z].y&1));
			  b_uv_dx += ((pMB->b_mvs[z].x>>1) | (pMB->b_mvs[z].x&1));
			  b_uv_dy += ((pMB->b_mvs[z].y>>1) | (pMB->b_mvs[z].y&1));
			}
		}
		else {
			uv_dx = (pMB->mvs[0].x / 2) + (pMB->mvs[1].x / 2) + (pMB->mvs[2].x / 2) + (pMB->mvs[3].x / 2);
			uv_dy = (pMB->mvs[0].y / 2) + (pMB->mvs[1].y / 2) + (pMB->mvs[2].y / 2) + (pMB->mvs[3].y / 2);
			b_uv_dx = (pMB->b_mvs[0].x / 2) + (pMB->b_mvs[1].x / 2) + (pMB->b_mvs[2].x / 2) + (pMB->b_mvs[3].x / 2);
			b_uv_dy = (pMB->b_mvs[0].y / 2) + (pMB->b_mvs[1].y / 2) + (pMB->b_mvs[2].y / 2) + (pMB->b_mvs[3].y / 2);
		} 
	} else {
      uv_dx = pMB->mvs[0].x + pMB->mvs[1].x + pMB->mvs[2].x + pMB->mvs[3].x;
      uv_dy = pMB->mvs[0].y + pMB->mvs[1].y + pMB->mvs[2].y + pMB->mvs[3].y;
      b_uv_dx = pMB->b_mvs[0].x + pMB->b_mvs[1].x + pMB->b_mvs[2].x + pMB->b_mvs[3].x;
      b_uv_dy = pMB->b_mvs[0].y + pMB->b_mvs[1].y + pMB->b_mvs[2].y + pMB->b_mvs[3].y;
    }

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


  if(dec->quarterpel) {
    if(!direct) {
      interpolate16x16_quarterpel(dec->cur.y, forward.y, dec->qtmp.y, dec->qtmp.y + 64,
                    dec->qtmp.y + 128, 16*x_pos, 16*y_pos,
                    pMB->mvs[0].x, pMB->mvs[0].y, stride, 0);
    } else {
      interpolate8x8_quarterpel(dec->cur.y, forward.y, dec->qtmp.y, dec->qtmp.y + 64,
                    dec->qtmp.y + 128, 16*x_pos, 16*y_pos,
                    pMB->mvs[0].x, pMB->mvs[0].y, stride, 0);
      interpolate8x8_quarterpel(dec->cur.y, forward.y, dec->qtmp.y, dec->qtmp.y + 64,
                    dec->qtmp.y + 128, 16*x_pos + 8, 16*y_pos,
                    pMB->mvs[1].x, pMB->mvs[1].y, stride, 0);
      interpolate8x8_quarterpel(dec->cur.y, forward.y, dec->qtmp.y, dec->qtmp.y + 64,
                    dec->qtmp.y + 128, 16*x_pos, 16*y_pos + 8,
                    pMB->mvs[2].x, pMB->mvs[2].y, stride, 0);
      interpolate8x8_quarterpel(dec->cur.y, forward.y, dec->qtmp.y, dec->qtmp.y + 64,
                    dec->qtmp.y + 128, 16*x_pos + 8, 16*y_pos + 8,
                    pMB->mvs[3].x, pMB->mvs[3].y, stride, 0);
    }
  } else {
    interpolate8x8_switch(dec->cur.y, forward.y, 16 * x_pos, 16 * y_pos,
              pMB->mvs[0].x, pMB->mvs[0].y, stride, 0);
    interpolate8x8_switch(dec->cur.y, forward.y, 16 * x_pos + 8, 16 * y_pos,
              pMB->mvs[1].x, pMB->mvs[1].y, stride, 0);
    interpolate8x8_switch(dec->cur.y, forward.y, 16 * x_pos, 16 * y_pos + 8,
              pMB->mvs[2].x, pMB->mvs[2].y, stride, 0);
    interpolate8x8_switch(dec->cur.y, forward.y, 16 * x_pos + 8, 16 * y_pos + 8,
              pMB->mvs[3].x, pMB->mvs[3].y, stride, 0);
  }

  interpolate8x8_switch(dec->cur.u, forward.u, 8 * x_pos, 8 * y_pos, uv_dx,
            uv_dy, stride2, 0);
  interpolate8x8_switch(dec->cur.v, forward.v, 8 * x_pos, 8 * y_pos, uv_dx,
            uv_dy, stride2, 0);


  if(dec->quarterpel) {
    if(!direct) {
      interpolate16x16_add_quarterpel(dec->cur.y, backward.y, dec->qtmp.y, dec->qtmp.y + 64,
          dec->qtmp.y + 128, 16*x_pos, 16*y_pos,
          pMB->b_mvs[0].x, pMB->b_mvs[0].y, stride, 0);
    } else {
      interpolate8x8_add_quarterpel(dec->cur.y, backward.y, dec->qtmp.y, dec->qtmp.y + 64,
          dec->qtmp.y + 128, 16*x_pos, 16*y_pos,
          pMB->b_mvs[0].x, pMB->b_mvs[0].y, stride, 0);
      interpolate8x8_add_quarterpel(dec->cur.y, backward.y, dec->qtmp.y, dec->qtmp.y + 64,
          dec->qtmp.y + 128, 16*x_pos + 8, 16*y_pos,
          pMB->b_mvs[1].x, pMB->b_mvs[1].y, stride, 0);
      interpolate8x8_add_quarterpel(dec->cur.y, backward.y, dec->qtmp.y, dec->qtmp.y + 64,
          dec->qtmp.y + 128, 16*x_pos, 16*y_pos + 8,
          pMB->b_mvs[2].x, pMB->b_mvs[2].y, stride, 0);
      interpolate8x8_add_quarterpel(dec->cur.y, backward.y, dec->qtmp.y, dec->qtmp.y + 64,
          dec->qtmp.y + 128, 16*x_pos + 8, 16*y_pos + 8,
          pMB->b_mvs[3].x, pMB->b_mvs[3].y, stride, 0);
    }
  } else {
    interpolate8x8_add_switch(dec->cur.y, backward.y, 16 * x_pos, 16 * y_pos,
        pMB->b_mvs[0].x, pMB->b_mvs[0].y, stride, 0);
    interpolate8x8_add_switch(dec->cur.y, backward.y, 16 * x_pos + 8,
        16 * y_pos, pMB->b_mvs[1].x, pMB->b_mvs[1].y, stride, 0);
    interpolate8x8_add_switch(dec->cur.y, backward.y, 16 * x_pos,
        16 * y_pos + 8, pMB->b_mvs[2].x, pMB->b_mvs[2].y, stride, 0);
    interpolate8x8_add_switch(dec->cur.y, backward.y, 16 * x_pos + 8,
        16 * y_pos + 8, pMB->b_mvs[3].x, pMB->b_mvs[3].y, stride, 0);
  }

  interpolate8x8_add_switch(dec->cur.u, backward.u, 8 * x_pos, 8 * y_pos,
      b_uv_dx, b_uv_dy, stride2, 0);
  interpolate8x8_add_switch(dec->cur.v, backward.v, 8 * x_pos, 8 * y_pos,
      b_uv_dx, b_uv_dy, stride2, 0);



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

/* for decode B-frame dbquant */
static __inline int32_t
get_dbquant(Bitstream * bs)
{
  if (!BitstreamGetBit(bs))   /*  '0' */
    return (0);
  else if (!BitstreamGetBit(bs))  /* '10' */