vp9_decodframe.c

                                vp9_reader *r) {
  VP9_COMMON *pc = &pbi->common;
  const uint8_t *data_end = pbi->source + pbi->source_sz;
  const size_t partition_size = data_end - data;

  // Validate the calculated partition length. If the buffer
  // described by the partition can't be fully read, then restrict
  // it to the portion that can be (for EC mode) or throw an error.
  if (!read_is_valid(data, partition_size, data_end))
    vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
                       "Truncated packet or corrupt partition "
                       "%d length", 1);

  if (vp9_start_decode(r, data, partition_size))
    vpx_internal_error(&pc->error, VPX_CODEC_MEM_ERROR,
                       "Failed to allocate bool decoder %d", 1);
}

static void init_frame(VP9D_COMP *pbi) {
  VP9_COMMON *const pc = &pbi->common;
  MACROBLOCKD *const xd = &pbi->mb;

  if (pc->frame_type == KEY_FRAME) {
    vp9_setup_past_independence(pc, xd);
    // All buffers are implicitly updated on key frames.
    pbi->refresh_frame_flags = (1 << NUM_REF_FRAMES) - 1;
  } else if (pc->error_resilient_mode) {
    vp9_setup_past_independence(pc, xd);
  }

  xd->mode_info_context = pc->mi;
  xd->prev_mode_info_context = pc->prev_mi;
  xd->frame_type = pc->frame_type;
  xd->mode_info_context->mbmi.mode = DC_PRED;
  xd->mode_info_stride = pc->mode_info_stride;
  xd->corrupted = 0;
}

#if CONFIG_CODE_NONZEROCOUNT
static void read_nzc_probs_common(VP9_COMMON *cm,
                                  BOOL_DECODER* const bc,
                                  TX_SIZE tx_size) {
  int c, r, b, t;
  int tokens, nodes;
  vp9_prob *nzc_probs;
  vp9_prob upd;

  if (!get_nzc_used(tx_size)) return;
  if (!vp9_read_bit(bc)) return;

  if (tx_size == TX_32X32) {
    tokens = NZC32X32_TOKENS;
    nzc_probs = cm->fc.nzc_probs_32x32[0][0][0];
    upd = NZC_UPDATE_PROB_32X32;
  } else if (tx_size == TX_16X16) {
    tokens = NZC16X16_TOKENS;
    nzc_probs = cm->fc.nzc_probs_16x16[0][0][0];
    upd = NZC_UPDATE_PROB_16X16;
  } else if (tx_size == TX_8X8) {
    tokens = NZC8X8_TOKENS;
    nzc_probs = cm->fc.nzc_probs_8x8[0][0][0];
    upd = NZC_UPDATE_PROB_8X8;
  } else {
    tokens = NZC4X4_TOKENS;
    nzc_probs = cm->fc.nzc_probs_4x4[0][0][0];
    upd = NZC_UPDATE_PROB_4X4;
  }
  nodes = tokens - 1;
  for (c = 0; c < MAX_NZC_CONTEXTS; ++c) {
    for (r = 0; r < REF_TYPES; ++r) {
      for (b = 0; b < BLOCK_TYPES; ++b) {
        int offset = c * REF_TYPES * BLOCK_TYPES + r * BLOCK_TYPES + b;
        int offset_nodes = offset * nodes;
        for (t = 0; t < nodes; ++t) {
          vp9_prob *p = &nzc_probs[offset_nodes + t];
          if (vp9_read(bc, upd)) {
            *p = read_prob_diff_update(bc, *p);
          }
        }
      }
    }
  }
}

static void read_nzc_pcat_probs(VP9_COMMON *cm, BOOL_DECODER* const bc) {
  int c, t, b;
  vp9_prob upd = NZC_UPDATE_PROB_PCAT;
  if (!(get_nzc_used(TX_4X4) || get_nzc_used(TX_8X8) ||
        get_nzc_used(TX_16X16) || get_nzc_used(TX_32X32)))
    return;
  if (!vp9_read_bit(bc)) {
    return;
  }
  for (c = 0; c < MAX_NZC_CONTEXTS; ++c) {
    for (t = 0; t < NZC_TOKENS_EXTRA; ++t) {
      int bits = vp9_extranzcbits[t + NZC_TOKENS_NOEXTRA];
      for (b = 0; b < bits; ++b) {
        vp9_prob *p = &cm->fc.nzc_pcat_probs[c][t][b];
        if (vp9_read(bc, upd)) {
          *p = read_prob_diff_update(bc, *p);
        }
      }
    }
  }
}

static void read_nzc_probs(VP9_COMMON *cm,
                           BOOL_DECODER* const bc) {
  read_nzc_probs_common(cm, bc, TX_4X4);
  if (cm->txfm_mode != ONLY_4X4)
    read_nzc_probs_common(cm, bc, TX_8X8);
  if (cm->txfm_mode > ALLOW_8X8)
    read_nzc_probs_common(cm, bc, TX_16X16);
  if (cm->txfm_mode > ALLOW_16X16)
    read_nzc_probs_common(cm, bc, TX_32X32);
#ifdef NZC_PCAT_UPDATE
  read_nzc_pcat_probs(cm, bc);
#endif
}
#endif  // CONFIG_CODE_NONZEROCOUNT

static void read_coef_probs_common(BOOL_DECODER* const bc,
                                   vp9_coeff_probs *coef_probs,
                                   TX_SIZE tx_size) {
#if CONFIG_MODELCOEFPROB && MODEL_BASED_UPDATE
  const int entropy_nodes_update = UNCONSTRAINED_UPDATE_NODES;
#else
  const int entropy_nodes_update = ENTROPY_NODES;
#endif

  int i, j, k, l, m;

  if (vp9_read_bit(bc)) {
    for (i = 0; i < BLOCK_TYPES; i++) {
      for (j = 0; j < REF_TYPES; j++) {
        for (k = 0; k < COEF_BANDS; k++) {
          for (l = 0; l < PREV_COEF_CONTEXTS; l++) {
#if CONFIG_CODE_NONZEROCOUNT
            const int mstart = get_nzc_used(tx_size);
#else
            const int mstart = 0;
#endif
            if (l >= 3 && k == 0)
              continue;

            for (m = mstart; m < entropy_nodes_update; m++) {
              vp9_prob *const p = coef_probs[i][j][k][l] + m;

              if (vp9_read(bc, vp9_coef_update_prob[m])) {
                *p = read_prob_diff_update(bc, *p);
#if CONFIG_MODELCOEFPROB && MODEL_BASED_UPDATE
                if (m == UNCONSTRAINED_NODES - 1)
                  vp9_get_model_distribution(*p, coef_probs[i][j][k][l], i, j);
#endif
              }
            }
          }
        }
      }
    }
  }
}

static void read_coef_probs(VP9D_COMP *pbi, BOOL_DECODER* const bc) {
  VP9_COMMON *const pc = &pbi->common;

  read_coef_probs_common(bc, pc->fc.coef_probs_4x4, TX_4X4);

  if (pbi->common.txfm_mode != ONLY_4X4)
    read_coef_probs_common(bc, pc->fc.coef_probs_8x8, TX_8X8);

  if (pbi->common.txfm_mode > ALLOW_8X8)
    read_coef_probs_common(bc, pc->fc.coef_probs_16x16, TX_16X16);

  if (pbi->common.txfm_mode > ALLOW_16X16)
    read_coef_probs_common(bc, pc->fc.coef_probs_32x32, TX_32X32);
}

static void update_frame_size(VP9D_COMP *pbi) {
  VP9_COMMON *cm = &pbi->common;

  const int width = multiple16(cm->width);
  const int height = multiple16(cm->height);

  cm->mb_rows = height / 16;
  cm->mb_cols = width / 16;
  cm->MBs = cm->mb_rows * cm->mb_cols;
  cm->mode_info_stride = cm->mb_cols + 1;
  memset(cm->mip, 0,
        (cm->mb_cols + 1) * (cm->mb_rows + 1) * sizeof(MODE_INFO));
  vp9_update_mode_info_border(cm, cm->mip);

  cm->mi = cm->mip + cm->mode_info_stride + 1;
  cm->prev_mi = cm->prev_mip + cm->mode_info_stride + 1;
  vp9_update_mode_info_in_image(cm, cm->mi);
}

static void setup_segmentation(VP9_COMMON *pc, MACROBLOCKD *xd, vp9_reader *r) {
  int i, j;

  xd->segmentation_enabled = vp9_read_bit(r);
  if (xd->segmentation_enabled) {
    // Read whether or not the segmentation map is being explicitly updated
    // this frame.
    xd->update_mb_segmentation_map = vp9_read_bit(r);

    if (xd->update_mb_segmentation_map) {
      // Which macro block level features are enabled. Read the probs used to
      // decode the segment id for each macro block.
      for (i = 0; i < MB_FEATURE_TREE_PROBS; i++)
        xd->mb_segment_tree_probs[i] = vp9_read_bit(r) ? vp9_read_prob(r) : 255;

      // Read the prediction probs needed to decode the segment id
      pc->temporal_update = vp9_read_bit(r);
      if (pc->temporal_update) {
        const vp9_prob *p = xd->mb_segment_tree_probs;
        vp9_prob *p_mod = xd->mb_segment_mispred_tree_probs;

        const int c0 =        p[0]  *        p[1];
        const int c1 =        p[0]  * (256 - p[1]);
        const int c2 = (256 - p[0]) *        p[2];
        const int c3 = (256 - p[0]) * (256 - p[2]);

        p_mod[0] = get_binary_prob(c1, c2 + c3);
        p_mod[1] = get_binary_prob(c0, c2 + c3);
        p_mod[2] = get_binary_prob(c0 + c1, c3);
        p_mod[3] = get_binary_prob(c0 + c1, c2);

        for (i = 0; i < PREDICTION_PROBS; i++)
          pc->segment_pred_probs[i] = vp9_read_bit(r) ? vp9_read_prob(r) : 255;
      } else {
        for (i = 0; i < PREDICTION_PROBS; i++)
          pc->segment_pred_probs[i] = 255;
      }
    }

    xd->update_mb_segmentation_data = vp9_read_bit(r);
    if (xd->update_mb_segmentation_data) {
      xd->mb_segment_abs_delta = vp9_read_bit(r);

      vp9_clearall_segfeatures(xd);

      for (i = 0; i < MAX_MB_SEGMENTS; i++) {
        for (j = 0; j < SEG_LVL_MAX; j++) {
          int data = 0;
          const int feature_enabled = vp9_read_bit(r);
          if (feature_enabled) {
            vp9_enable_segfeature(xd, i, j);
            data = vp9_decode_unsigned_max(r, vp9_seg_feature_data_max(j));
            if (vp9_is_segfeature_signed(j) && vp9_read_bit(r)) {
              data = -data;
            }
          }
          vp9_set_segdata(xd, i, j, data);
        }
      }
    }
  }
}

static void setup_pred_probs(VP9_COMMON *pc, vp9_reader *r) {
  // Read common prediction model status flag probability updates for the
  // reference frame
  if (pc->frame_type == KEY_FRAME) {
    // Set the prediction probabilities to defaults
    pc->ref_pred_probs[0] = 120;
    pc->ref_pred_probs[1] = 80;
    pc->ref_pred_probs[2] = 40;
  } else {
    int i;
    for (i = 0; i < PREDICTION_PROBS; ++i)
      if (vp9_read_bit(r))
        pc->ref_pred_probs[i] = vp9_read_prob(r);
  }
}

static void setup_loopfilter(VP9_COMMON *pc, MACROBLOCKD *xd, vp9_reader *r) {
  pc->filter_type = (LOOPFILTER_TYPE) vp9_read_bit(r);
  pc->filter_level = vp9_read_literal(r, 6);
  pc->sharpness_level = vp9_read_literal(r, 3);

#if CONFIG_LOOP_DERING
  if (vp9_read_bit(r))
    pc->dering_enabled = 1 + vp9_read_literal(r, 4);
  else
    pc->dering_enabled = 0;
#endif

  // Read in loop filter deltas applied at the MB level based on mode or ref
  // frame.
  xd->mode_ref_lf_delta_update = 0;
  xd->mode_ref_lf_delta_enabled = vp9_read_bit(r);

  if (xd->mode_ref_lf_delta_enabled) {
    xd->mode_ref_lf_delta_update = vp9_read_bit(r);
    if (xd->mode_ref_lf_delta_update) {
      int i;

      for (i = 0; i < MAX_REF_LF_DELTAS; i++) {
        if (vp9_read_bit(r)) {
          int value = vp9_read_literal(r, 6);
          if (vp9_read_bit(r))
            value = -value;
          xd->ref_lf_deltas[i] = value;
        }
      }

      for (i = 0; i < MAX_MODE_LF_DELTAS; i++) {
        if (vp9_read_bit(r)) {
          int value = vp9_read_literal(r, 6);
          if (vp9_read_bit(r))
            value = -value;
          xd->mode_lf_deltas[i] = value;
        }
      }
    }
  }
}

static const uint8_t *read_frame_size(VP9_COMMON *const pc, const uint8_t *data,
                                      const uint8_t *data_end,
                                      int *width, int *height) {
  if (data + 4 < data_end) {
    *width = read_le16(data);
    *height = read_le16(data + 2);
    data += 4;
  } else {
    vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
                       "Failed to read frame size");
  }
  return data;
}

static const uint8_t *setup_frame_size(VP9D_COMP *pbi, int scaling_active,
                                      const uint8_t *data,
                                      const uint8_t *data_end) {
  // If error concealment is enabled we should only parse the new size
  // if we have enough data. Otherwise we will end up with the wrong size.
  VP9_COMMON *const pc = &pbi->common;
  int display_width = pc->display_width;
  int display_height = pc->display_height;
  int width = pc->width;
  int height = pc->height;

  if (scaling_active)
    data = read_frame_size(pc, data, data_end, &display_width, &display_height);

  data = read_frame_size(pc, data, data_end, &width, &height);

  if (pc->width != width || pc->height != height) {
    if (width <= 0)
      vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
                         "Invalid frame width");

    if (height <= 0)
      vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
                         "Invalid frame height");

    if (!pbi->initial_width || !pbi->initial_height) {
      if (vp9_alloc_frame_buffers(pc, width, height))
        vpx_internal_error(&pc->error, VPX_CODEC_MEM_ERROR,
                           "Failed to allocate frame buffers");
        pbi->initial_width = width;
        pbi->initial_height = height;
    } else {
      if (width > pbi->initial_width)
        vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
                           "Frame width too large");

      if (height > pbi->initial_height)
        vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
                           "Frame height too large");
    }

    pc->width = width;
    pc->height = height;
    pc->display_width = scaling_active ? display_width : width;
    pc->display_height = scaling_active ? display_height : height;

    update_frame_size(pbi);
  }

  return data;
}

static void update_frame_context(VP9D_COMP *pbi, vp9_reader *r) {
  FRAME_CONTEXT *const fc = &pbi->common.fc;

  vp9_copy(fc->pre_coef_probs_4x4, fc->coef_probs_4x4);
  vp9_copy(fc->pre_coef_probs_8x8, fc->coef_probs_8x8);
  vp9_copy(fc->pre_coef_probs_16x16, fc->coef_probs_16x16);
  vp9_copy(fc->pre_coef_probs_32x32, fc->coef_probs_32x32);
  vp9_copy(fc->pre_ymode_prob, fc->ymode_prob);
  vp9_copy(fc->pre_sb_ymode_prob, fc->sb_ymode_prob);
  vp9_copy(fc->pre_uv_mode_prob, fc->uv_mode_prob);
  vp9_copy(fc->pre_bmode_prob, fc->bmode_prob);
  vp9_copy(fc->pre_i8x8_mode_prob, fc->i8x8_mode_prob);
  vp9_copy(fc->pre_sub_mv_ref_prob, fc->sub_mv_ref_prob);
  vp9_copy(fc->pre_mbsplit_prob, fc->mbsplit_prob);
  fc->pre_nmvc = fc->nmvc;

  vp9_zero(fc->coef_counts_4x4);
  vp9_zero(fc->coef_counts_8x8);
  vp9_zero(fc->coef_counts_16x16);
  vp9_zero(fc->coef_counts_32x32);
  vp9_zero(fc->eob_branch_counts);
  vp9_zero(fc->ymode_counts);
  vp9_zero(fc->sb_ymode_counts);
  vp9_zero(fc->uv_mode_counts);
  vp9_zero(fc->bmode_counts);
  vp9_zero(fc->i8x8_mode_counts);
  vp9_zero(fc->sub_mv_ref_counts);
  vp9_zero(fc->mbsplit_counts);
  vp9_zero(fc->NMVcount);
  vp9_zero(fc->mv_ref_ct);

#if CONFIG_COMP_INTERINTRA_PRED
  fc->pre_interintra_prob = fc->interintra_prob;
  vp9_zero(fc->interintra_counts);
#endif

#if CONFIG_CODE_NONZEROCOUNT
  vp9_copy(fc->pre_nzc_probs_4x4, fc->nzc_probs_4x4);
  vp9_copy(fc->pre_nzc_probs_8x8, fc->nzc_probs_8x8);
  vp9_copy(fc->pre_nzc_probs_16x16, fc->nzc_probs_16x16);
  vp9_copy(fc->pre_nzc_probs_32x32, fc->nzc_probs_32x32);
  vp9_copy(fc->pre_nzc_pcat_probs, fc->nzc_pcat_probs);

  vp9_zero(fc->nzc_counts_4x4);
  vp9_zero(fc->nzc_counts_8x8);
  vp9_zero(fc->nzc_counts_16x16);
  vp9_zero(fc->nzc_counts_32x32);
  vp9_zero(fc->nzc_pcat_counts);
#endif

  read_coef_probs(pbi, r);
#if CONFIG_CODE_NONZEROCOUNT
  read_nzc_probs(&pbi->common, r);
#endif
}

static void decode_tiles(VP9D_COMP *pbi,
                         const uint8_t *data, int first_partition_size,
                         BOOL_DECODER *header_bc, BOOL_DECODER *residual_bc) {
  VP9_COMMON *const pc = &pbi->common;

  const uint8_t *data_ptr = data + first_partition_size;
  int tile_row, tile_col, delta_log2_tiles;
  int mb_row;

  vp9_get_tile_n_bits(pc, &pc->log2_tile_columns, &delta_log2_tiles);
  while (delta_log2_tiles--) {
    if (vp9_read_bit(header_bc)) {
      pc->log2_tile_columns++;
    } else {
      break;
    }
  }
  pc->log2_tile_rows = vp9_read_bit(header_bc);
  if (pc->log2_tile_rows)
    pc->log2_tile_rows += vp9_read_bit(header_bc);
  pc->tile_columns = 1 << pc->log2_tile_columns;
  pc->tile_rows    = 1 << pc->log2_tile_rows;

  vpx_memset(pc->above_context, 0,
             sizeof(ENTROPY_CONTEXT_PLANES) * pc->mb_cols);

  if (pbi->oxcf.inv_tile_order) {
    const int n_cols = pc->tile_columns;
    const uint8_t *data_ptr2[4][1 << 6];
    BOOL_DECODER UNINITIALIZED_IS_SAFE(bc_bak);

    // pre-initialize the offsets, we're going to read in inverse order
    data_ptr2[0][0] = data_ptr;
    for (tile_row = 0; tile_row < pc->tile_rows; tile_row++) {
      if (tile_row) {
        const int size = read_le32(data_ptr2[tile_row - 1][n_cols - 1]);
        data_ptr2[tile_row - 1][n_cols - 1] += 4;
        data_ptr2[tile_row][0] = data_ptr2[tile_row - 1][n_cols - 1] + size;
      }

      for (tile_col = 1; tile_col < n_cols; tile_col++) {
        const int size = read_le32(data_ptr2[tile_row][tile_col - 1]);
        data_ptr2[tile_row][tile_col - 1] += 4;
        data_ptr2[tile_row][tile_col] =
            data_ptr2[tile_row][tile_col - 1] + size;
      }
    }

    for (tile_row = 0; tile_row < pc->tile_rows; tile_row++) {
      vp9_get_tile_row_offsets(pc, tile_row);
      for (tile_col = n_cols - 1; tile_col >= 0; tile_col--) {
        vp9_get_tile_col_offsets(pc, tile_col);
        setup_token_decoder(pbi, data_ptr2[tile_row][tile_col], residual_bc);

        // Decode a row of superblocks
        for (mb_row = pc->cur_tile_mb_row_start;
             mb_row < pc->cur_tile_mb_row_end; mb_row += 4) {
          decode_sb_row(pbi, mb_row, residual_bc);
        }

        if (tile_row == pc->tile_rows - 1 && tile_col == n_cols - 1)
          bc_bak = *residual_bc;
      }
    }
    *residual_bc = bc_bak;
  } else {
    int has_more;

    for (tile_row = 0; tile_row < pc->tile_rows; tile_row++) {
      vp9_get_tile_row_offsets(pc, tile_row);
      for (tile_col = 0; tile_col < pc->tile_columns; tile_col++) {
        vp9_get_tile_col_offsets(pc, tile_col);

        has_more = tile_col < pc->tile_columns - 1 ||
                   tile_row < pc->tile_rows - 1;

        // Setup decoder
        setup_token_decoder(pbi, data_ptr + (has_more ? 4 : 0), residual_bc);

        // Decode a row of superblocks
        for (mb_row = pc->cur_tile_mb_row_start;
             mb_row < pc->cur_tile_mb_row_end; mb_row += 4) {
          decode_sb_row(pbi, mb_row, residual_bc);
        }

        if (has_more) {
          const int size = read_le32(data_ptr);
          data_ptr += 4 + size;
        }
      }
    }
  }
}

int vp9_decode_frame(VP9D_COMP *pbi, const uint8_t **p_data_end) {
  BOOL_DECODER header_bc, residual_bc;
  VP9_COMMON *const pc = &pbi->common;
  MACROBLOCKD *const xd  = &pbi->mb;
  const uint8_t *data = pbi->source;
  const uint8_t *data_end = data + pbi->source_sz;
  size_t first_partition_size = 0;
  int i, corrupt_tokens = 0;

  // printf("Decoding frame %d\n", pc->current_video_frame);

  xd->corrupted = 0;  // start with no corruption of current frame
  pc->yv12_fb[pc->new_fb_idx].corrupted = 0;

  if (data_end - data < 3) {
    vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME, "Truncated packet");
  } else {
    int scaling_active;
    pc->last_frame_type = pc->frame_type;
    pc->frame_type = (FRAME_TYPE)(data[0] & 1);
    pc->version = (data[0] >> 1) & 7;
    pc->show_frame = (data[0] >> 4) & 1;
    scaling_active = (data[0] >> 5) & 1;
    first_partition_size = read_le16(data + 1);

    if (!read_is_valid(data, first_partition_size, data_end))
      vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
                         "Truncated packet or corrupt partition 0 length");

    data += 3;

    vp9_setup_version(pc);

    if (pc->frame_type == KEY_FRAME) {
      // When error concealment is enabled we should only check the sync
      // code if we have enough bits available
      if (data + 3 < data_end) {
        if (data[0] != 0x9d || data[1] != 0x01 || data[2] != 0x2a)
          vpx_internal_error(&pc->error, VPX_CODEC_UNSUP_BITSTREAM,
                             "Invalid frame sync code");
      }
      data += 3;
    }

    data = setup_frame_size(pbi, scaling_active, data, data_end);
  }

  if ((!pbi->decoded_key_frame && pc->frame_type != KEY_FRAME) ||
      pc->width == 0 || pc->height == 0) {
    return -1;
  }

  init_frame(pbi);

  // Reset the frame pointers to the current frame size
  vp8_yv12_realloc_frame_buffer(&pc->yv12_fb[pc->new_fb_idx],
                                pc->width, pc->height,
                                VP9BORDERINPIXELS);

  if (vp9_start_decode(&header_bc, data, first_partition_size))
    vpx_internal_error(&pc->error, VPX_CODEC_MEM_ERROR,
                       "Failed to allocate bool decoder 0");

  pc->clr_type = (YUV_TYPE)vp9_read_bit(&header_bc);
  pc->clamp_type = (CLAMP_TYPE)vp9_read_bit(&header_bc);
  pc->error_resilient_mode = vp9_read_bit(&header_bc);

  setup_segmentation(pc, xd, &header_bc);

  setup_pred_probs(pc, &header_bc);

  pc->prob_sb64_coded = vp9_read_prob(&header_bc);
  pc->prob_sb32_coded = vp9_read_prob(&header_bc);
  xd->lossless = vp9_read_bit(&header_bc);
  pc->txfm_mode = xd->lossless ? ONLY_4X4 : read_txfm_mode(&header_bc);
  if (pc->txfm_mode == TX_MODE_SELECT) {
    pc->prob_tx[0] = vp9_read_prob(&header_bc);
    pc->prob_tx[1] = vp9_read_prob(&header_bc);
    pc->prob_tx[2] = vp9_read_prob(&header_bc);
  }

  setup_loopfilter(pc, xd, &header_bc);

  // Dummy read for now
  vp9_read_literal(&header_bc, 2);

  // Read the default quantizers.
  {
    int q_update = 0;
    pc->base_qindex = vp9_read_literal(&header_bc, QINDEX_BITS);

    // AC 1st order Q = default
    q_update = get_delta_q(&header_bc, &pc->y1dc_delta_q) |
               get_delta_q(&header_bc, &pc->uvdc_delta_q) |
               get_delta_q(&header_bc, &pc->uvac_delta_q);

    if (q_update)
      vp9_init_de_quantizer(pbi);

    // MB level dequantizer setup
    mb_init_dequantizer(pbi, &pbi->mb);
  }

  // Determine if the golden frame or ARF buffer should be updated and how.
  // For all non key frames the GF and ARF refresh flags and sign bias
  // flags must be set explicitly.
  if (pc->frame_type == KEY_FRAME) {
    pc->active_ref_idx[0] = pc->new_fb_idx;
    pc->active_ref_idx[1] = pc->new_fb_idx;
    pc->active_ref_idx[2] = pc->new_fb_idx;
  } else {
    // Should the GF or ARF be updated from the current frame
    pbi->refresh_frame_flags = vp9_read_literal(&header_bc, NUM_REF_FRAMES);

    // Select active reference frames
    for (i = 0; i < 3; i++) {
      int ref_frame_num = vp9_read_literal(&header_bc, NUM_REF_FRAMES_LG2);
      pc->active_ref_idx[i] = pc->ref_frame_map[ref_frame_num];
    }

    pc->ref_frame_sign_bias[GOLDEN_FRAME] = vp9_read_bit(&header_bc);
    pc->ref_frame_sign_bias[ALTREF_FRAME] = vp9_read_bit(&header_bc);

    // Is high precision mv allowed
    xd->allow_high_precision_mv = vp9_read_bit(&header_bc);

    // Read the type of subpel filter to use
    pc->mcomp_filter_type = vp9_read_bit(&header_bc)
                                ? SWITCHABLE
                                : vp9_read_literal(&header_bc, 2);

#if CONFIG_COMP_INTERINTRA_PRED
    pc->use_interintra = vp9_read_bit(&header_bc);
#endif

    /* Calculate scaling factors for each of the 3 available references */
    for (i = 0; i < 3; ++i) {
      if (pc->active_ref_idx[i] >= NUM_YV12_BUFFERS) {
        memset(&pc->active_ref_scale[i], 0, sizeof(pc->active_ref_scale[i]));
        continue;
      }

      vp9_setup_scale_factors_for_frame(&pc->active_ref_scale[i],
                                        &pc->yv12_fb[pc->active_ref_idx[i]],
                                        pc->width, pc->height);
    }

    // To enable choice of different interploation filters
    vp9_setup_interp_filters(xd, pc->mcomp_filter_type, pc);
  }

  if (!pc->error_resilient_mode) {
    pc->refresh_entropy_probs = vp9_read_bit(&header_bc);
    pc->frame_parallel_decoding_mode = vp9_read_bit(&header_bc);
  } else {
    pc->refresh_entropy_probs = 0;
    pc->frame_parallel_decoding_mode = 1;
  }
  pc->frame_context_idx = vp9_read_literal(&header_bc, NUM_FRAME_CONTEXTS_LG2);
  vpx_memcpy(&pc->fc, &pc->frame_contexts[pc->frame_context_idx],
             sizeof(pc->fc));

  // Read inter mode probability context updates
  if (pc->frame_type != KEY_FRAME) {
    int i, j;
    for (i = 0; i < INTER_MODE_CONTEXTS; ++i)
      for (j = 0; j < 4; ++j)
        if (vp9_read(&header_bc, 252))
          pc->fc.vp9_mode_contexts[i][j] = vp9_read_prob(&header_bc);
  }
#if CONFIG_MODELCOEFPROB && ADJUST_KF_COEF_PROBS
  if (pc->frame_type == KEY_FRAME)
    vp9_adjust_default_coef_probs(pc);
#endif

#if CONFIG_NEW_MVREF
  // If Key frame reset mv ref id probabilities to defaults
  if (pc->frame_type != KEY_FRAME) {
    // Read any mv_ref index probability updates
    int i, j;

    for (i = 0; i < MAX_REF_FRAMES; ++i) {
      // Skip the dummy entry for intra ref frame.
      if (i == INTRA_FRAME)
        continue;

      // Read any updates to probabilities
      for (j = 0; j < MAX_MV_REF_CANDIDATES - 1; ++j)
        if (vp9_read(&header_bc, VP9_MVREF_UPDATE_PROB))
          xd->mb_mv_ref_probs[i][j] = vp9_read_prob(&header_bc);
    }
  }
#endif

  if (0) {
    FILE *z = fopen("decodestats.stt", "a");
    fprintf(z, "%6d F:%d,R:%d,Q:%d\n",
            pc->current_video_frame,
            pc->frame_type,
            pbi->refresh_frame_flags,
            pc->base_qindex);
    fclose(z);
  }

  update_frame_context(pbi, &header_bc);

  // Initialize xd pointers. Any reference should do for xd->pre, so use 0.
  vpx_memcpy(&xd->pre, &pc->yv12_fb[pc->active_ref_idx[0]],
             sizeof(YV12_BUFFER_CONFIG));
  vpx_memcpy(&xd->dst, &pc->yv12_fb[pc->new_fb_idx],
             sizeof(YV12_BUFFER_CONFIG));

  // Create the segmentation map structure and set to 0
  if (!pc->last_frame_seg_map)
    CHECK_MEM_ERROR(pc->last_frame_seg_map,
                    vpx_calloc((pc->mb_rows * pc->mb_cols), 1));

  // set up frame new frame for intra coded blocks
  vp9_setup_intra_recon(&pc->yv12_fb[pc->new_fb_idx]);

  vp9_setup_block_dptrs(xd);
  vp9_build_block_doffsets(xd);

  // clear out the coeff buffer
  vpx_memset(xd->plane[0].qcoeff, 0, sizeof(xd->plane[0].qcoeff));
  vpx_memset(xd->plane[1].qcoeff, 0, sizeof(xd->plane[1].qcoeff));
  vpx_memset(xd->plane[2].qcoeff, 0, sizeof(xd->plane[2].qcoeff));

  // Read the mb_no_coeff_skip flag
  pc->mb_no_coeff_skip = vp9_read_bit(&header_bc);

  vp9_decode_mode_mvs_init(pbi, &header_bc);

  decode_tiles(pbi, data, first_partition_size, &header_bc, &residual_bc);
  corrupt_tokens |= xd->corrupted;

  // keep track of the last coded dimensions
  pc->last_width = pc->width;
  pc->last_height = pc->height;

  // Collect information about decoder corruption.
  // 1. Check first boolean decoder for errors.
  // 2. Check the macroblock information
  pc->yv12_fb[pc->new_fb_idx].corrupted = bool_error(&header_bc) |
                                          corrupt_tokens;

  if (!pbi->decoded_key_frame) {
    if (pc->frame_type == KEY_FRAME && !pc->yv12_fb[pc->new_fb_idx].corrupted)
      pbi->decoded_key_frame = 1;
    else
      vpx_internal_error(&pbi->common.error, VPX_CODEC_CORRUPT_FRAME,
                         "A stream must start with a complete key frame");
  }

  if (!pc->error_resilient_mode && !pc->frame_parallel_decoding_mode) {
    vp9_adapt_coef_probs(pc);
#if CONFIG_CODE_NONZEROCOUNT
    vp9_adapt_nzc_probs(pc);
#endif
  }

  if (pc->frame_type != KEY_FRAME) {
    if (!pc->error_resilient_mode && !pc->frame_parallel_decoding_mode) {
      vp9_adapt_mode_probs(pc);
      vp9_adapt_nmv_probs(pc, xd->allow_high_precision_mv);
      vp9_adapt_mode_context(&pbi->common);
    }
  }

  if (pc->refresh_entropy_probs) {
    vpx_memcpy(&pc->frame_contexts[pc->frame_context_idx], &pc->fc,
               sizeof(pc->fc));
  }

#ifdef PACKET_TESTING
  {
    FILE *f = fopen("decompressor.VP8", "ab");
    unsigned int size = residual_bc.pos + header_bc.pos + 8;
    fwrite((void *) &size, 4, 1, f);
    fwrite((void *) pbi->Source, size, 1, f);
    fclose(f);
  }
#endif

  // Find the end of the coded buffer
  while (residual_bc.count > CHAR_BIT &&
         residual_bc.count < VP9_BD_VALUE_SIZE) {
    residual_bc.count -= CHAR_BIT;
    residual_bc.user_buffer--;
  }
  *p_data_end = residual_bc.user_buffer;
  return 0;
}