vp9_decodframe.c

  for (mb_col = pc->cur_tile_mb_col_start;
       mb_col < pc->cur_tile_mb_col_end; mb_col += 4) {
    if (vp9_read(bc, pc->sb64_coded)) {
#ifdef DEC_DEBUG
      dec_debug = (pc->current_video_frame == 11 && pc->show_frame &&
                   mb_row == 8 && mb_col == 0);
      if (dec_debug)
        printf("Debug Decode SB64\n");
#endif
      set_offsets(pbi, 64, mb_row, mb_col);
      vp9_decode_mb_mode_mv(pbi, xd, mb_row, mb_col, bc);
      set_refs(pbi, 64, mb_row, mb_col);
      decode_superblock64(pbi, xd, mb_row, mb_col, bc);
      xd->corrupted |= bool_error(bc);
    } else {
      int j;

      for (j = 0; j < 4; j++) {
        const int x_idx_sb = (j & 1) << 1, y_idx_sb = j & 2;

        if (mb_row + y_idx_sb >= pc->mb_rows ||
            mb_col + x_idx_sb >= pc->mb_cols) {
          // MB lies outside frame, skip on to next
          continue;
        }

        xd->sb_index = j;

        if (vp9_read(bc, pc->sb32_coded)) {
#ifdef DEC_DEBUG
          dec_debug = (pc->current_video_frame == 11 && pc->show_frame &&
                       mb_row + y_idx_sb == 8 && mb_col + x_idx_sb == 0);
          if (dec_debug)
            printf("Debug Decode SB32\n");
#endif
          set_offsets(pbi, 32, mb_row + y_idx_sb, mb_col + x_idx_sb);
          vp9_decode_mb_mode_mv(pbi,
                                xd, mb_row + y_idx_sb, mb_col + x_idx_sb, bc);
          set_refs(pbi, 32, mb_row + y_idx_sb, mb_col + x_idx_sb);
          decode_superblock32(pbi,
                              xd, mb_row + y_idx_sb, mb_col + x_idx_sb, bc);
          xd->corrupted |= bool_error(bc);
        } else {
          int i;

          // Process the 4 MBs within the SB in the order:
          // top-left, top-right, bottom-left, bottom-right
          for (i = 0; i < 4; i++) {
            const int x_idx = x_idx_sb + (i & 1), y_idx = y_idx_sb + (i >> 1);

            if (mb_row + y_idx >= pc->mb_rows ||
                mb_col + x_idx >= pc->mb_cols) {
              // MB lies outside frame, skip on to next
              continue;
            }
#ifdef DEC_DEBUG
            dec_debug = (pc->current_video_frame == 11 && pc->show_frame &&
                         mb_row + y_idx == 8 && mb_col + x_idx == 0);
            if (dec_debug)
              printf("Debug Decode MB\n");
#endif

            set_offsets(pbi, 16, mb_row + y_idx, mb_col + x_idx);
            xd->mb_index = i;
            vp9_decode_mb_mode_mv(pbi, xd, mb_row + y_idx, mb_col + x_idx, bc);
            set_refs(pbi, 16, mb_row + y_idx, mb_col + x_idx);
            decode_macroblock(pbi, xd, mb_row + y_idx, mb_col + x_idx, bc);

            /* check if the boolean decoder has suffered an error */
            xd->corrupted |= bool_error(bc);
          }
        }
      }
    }
  }
}


static void setup_token_decoder(VP9D_COMP *pbi,
                                const unsigned char *cx_data,
                                BOOL_DECODER* const bool_decoder) {
  VP9_COMMON *pc = &pbi->common;
  const unsigned char *user_data_end = pbi->Source + pbi->source_sz;
  const unsigned char *partition = cx_data;
  ptrdiff_t bytes_left = user_data_end - partition;
  ptrdiff_t partition_size = bytes_left;

  // 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(partition, partition_size, user_data_end)) {
    vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
                       "Truncated packet or corrupt partition "
                       "%d length", 1);
  }

  if (vp9_start_decode(bool_decoder,
                       partition, (unsigned int)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);
  }

  if (pc->frame_type != KEY_FRAME) {
    pc->mcomp_filter_type = pc->use_bilinear_mc_filter ? BILINEAR : EIGHTTAP;

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

  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;
  xd->fullpixel_mask = pc->full_pixel ? 0xfffffff8 : 0xffffffff;
}

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

  if (!vp9_read_bit(bc)) return;

  if (block_size == 32) {
    tokens = NZC32X32_TOKENS;
    nzc_probs = cm->fc.nzc_probs_32x32[0][0][0];
    upd = NZC_UPDATE_PROB_32X32;
  } else if (block_size == 16) {
    tokens = NZC16X16_TOKENS;
    nzc_probs = cm->fc.nzc_probs_16x16[0][0][0];
    upd = NZC_UPDATE_PROB_16X16;
  } else if (block_size == 8) {
    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 (!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, 4);
  if (cm->txfm_mode != ONLY_4X4)
    read_nzc_probs_common(cm, bc, 8);
  if (cm->txfm_mode > ALLOW_8X8)
    read_nzc_probs_common(cm, bc, 16);
  if (cm->txfm_mode > ALLOW_16X16)
    read_nzc_probs_common(cm, bc, 32);
#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,
                                   int block_types) {
#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 (l >= 3 && k == 0)
              continue;
            for (m = CONFIG_CODE_NONZEROCOUNT; 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, BLOCK_TYPES);

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

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

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

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

  /* our internal buffers are always multiples of 16 */
  const int width = (cm->width + 15) & ~15;
  const int height = (cm->height + 15) & ~15;

  cm->mb_rows = height >> 4;
  cm->mb_cols = width >> 4;
  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,
                               BOOL_DECODER *header_bc) {
  int i, j;

  // Is segmentation enabled
  xd->segmentation_enabled = vp9_read_bit(header_bc);

  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(header_bc);

    // If so what method will be used.
    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(header_bc) ?
              (vp9_prob)vp9_read_literal(header_bc, 8) : 255;
      }

      // Read the prediction probs needed to decode the segment id
      pc->temporal_update = vp9_read_bit(header_bc);
      for (i = 0; i < PREDICTION_PROBS; i++) {
        if (pc->temporal_update) {
          pc->segment_pred_probs[i] = vp9_read_bit(header_bc) ?
              (vp9_prob)vp9_read_literal(header_bc, 8) : 255;
        } else {
          pc->segment_pred_probs[i] = 255;
        }
      }

      if (pc->temporal_update) {
        int count[4];
        const vp9_prob *p = xd->mb_segment_tree_probs;
        vp9_prob *p_mod = xd->mb_segment_mispred_tree_probs;

        count[0] =        p[0]  *        p[1];
        count[1] =        p[0]  * (256 - p[1]);
        count[2] = (256 - p[0]) *        p[2];
        count[3] = (256 - p[0]) * (256 - p[2]);

        p_mod[0] = get_binary_prob(count[1], count[2] + count[3]);
        p_mod[1] = get_binary_prob(count[0], count[2] + count[3]);
        p_mod[2] = get_binary_prob(count[0] + count[1], count[3]);
        p_mod[3] = get_binary_prob(count[0] + count[1], count[2]);
      }
    }
    // Is the segment data being updated
    xd->update_mb_segmentation_data = vp9_read_bit(header_bc);

    if (xd->update_mb_segmentation_data) {
      int data;

      xd->mb_segment_abs_delta = vp9_read_bit(header_bc);

      vp9_clearall_segfeatures(xd);

      // For each segmentation...
      for (i = 0; i < MAX_MB_SEGMENTS; i++) {
        // For each of the segments features...
        for (j = 0; j < SEG_LVL_MAX; j++) {
          // Is the feature enabled
          if (vp9_read_bit(header_bc)) {
            // Update the feature data and mask
            vp9_enable_segfeature(xd, i, j);

            data = vp9_decode_unsigned_max(header_bc,
                                           vp9_seg_feature_data_max(j));

            // Is the segment data signed..
            if (vp9_is_segfeature_signed(j)) {
              if (vp9_read_bit(header_bc))
                data = -data;
            }
          } else {
            data = 0;
          }

          vp9_set_segdata(xd, i, j, data);
        }
      }
    }
  }
}

static void setup_loopfilter(VP9_COMMON *pc, MACROBLOCKD *xd,
                             BOOL_DECODER *header_bc) {
  int i;

  pc->filter_type = (LOOPFILTERTYPE) vp9_read_bit(header_bc);
  pc->filter_level = vp9_read_literal(header_bc, 6);
  pc->sharpness_level = vp9_read_literal(header_bc, 3);

#if CONFIG_LOOP_DERING
  if (vp9_read_bit(header_bc))
    pc->dering_enabled = 1 + vp9_read_literal(header_bc, 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(header_bc);

  if (xd->mode_ref_lf_delta_enabled) {
    // Do the deltas need to be updated
    xd->mode_ref_lf_delta_update = vp9_read_bit(header_bc);

    if (xd->mode_ref_lf_delta_update) {
      // Send update
      for (i = 0; i < MAX_REF_LF_DELTAS; i++) {
        if (vp9_read_bit(header_bc)) {
          // sign = vp9_read_bit( &header_bc );
          xd->ref_lf_deltas[i] = (signed char)vp9_read_literal(header_bc, 6);

          if (vp9_read_bit(header_bc))
            xd->ref_lf_deltas[i] = -xd->ref_lf_deltas[i];  // Apply sign
        }
      }

      // Send update
      for (i = 0; i < MAX_MODE_LF_DELTAS; i++) {
        if (vp9_read_bit(header_bc)) {
          // sign = vp9_read_bit( &header_bc );
          xd->mode_lf_deltas[i] = (signed char)vp9_read_literal(header_bc, 6);

          if (vp9_read_bit(header_bc))
            xd->mode_lf_deltas[i] = -xd->mode_lf_deltas[i];  // Apply sign
        }
      }
    }
  }
}


int vp9_decode_frame(VP9D_COMP *pbi, const unsigned char **p_data_end) {
  BOOL_DECODER header_bc, residual_bc;
  VP9_COMMON *const pc = &pbi->common;
  MACROBLOCKD *const xd  = &pbi->mb;
  const uint8_t *data = (const uint8_t *)pbi->Source;
  const uint8_t *data_end = data + pbi->source_sz;
  ptrdiff_t first_partition_length_in_bytes = 0;
  int mb_row, i, corrupt_tokens = 0;

  // printf("Decoding frame %d\n", pc->current_video_frame);
  /* start with no corruption of current frame */
  xd->corrupted = 0;
  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_length_in_bytes = read_le16(data + 1);

    if (!read_is_valid(data, first_partition_length_in_bytes, 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) {
      /* vet via sync code */
      /* 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;
    }
    {
      const int width = pc->width;
      const int height = pc->height;

      /* 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.
       */
      if (scaling_active && data + 4 < data_end) {
        pc->display_width = read_le16(data + 0);
        pc->display_height = read_le16(data + 2);
        data += 4;
      }
      if (data + 4 < data_end) {
        pc->width = read_le16(data + 0);
        pc->height = read_le16(data + 2);
        data += 4;
      }
      if (!scaling_active) {
        pc->display_width = pc->width;
        pc->display_height = pc->height;
      }

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

        if (pc->height <= 0) {
          pc->height = height;
          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, pc->width, pc->height))
            vpx_internal_error(&pc->error, VPX_CODEC_MEM_ERROR,
                               "Failed to allocate frame buffers");
          pbi->initial_width = pc->width;
          pbi->initial_height = pc->height;
        }

        if (pc->width > pbi->initial_width) {
          vpx_internal_error(&pc->error, VPX_CODEC_CORRUPT_FRAME,
                             "Frame width too large");
        }

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

        update_frame_size(pbi);
      }
    }
  }

  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,
                       (unsigned int)first_partition_length_in_bytes))
    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);

  // 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 {
    for (i = 0; i < PREDICTION_PROBS; i++) {
      if (vp9_read_bit(&header_bc))
        pc->ref_pred_probs[i] = (vp9_prob)vp9_read_literal(&header_bc, 8);
    }
  }

  pc->sb64_coded = vp9_read_literal(&header_bc, 8);
  pc->sb32_coded = vp9_read_literal(&header_bc, 8);
  xd->lossless = vp9_read_bit(&header_bc);
  if (xd->lossless) {
    pc->txfm_mode = ONLY_4X4;
  } else {
    // Read the loop filter level and type
    pc->txfm_mode = vp9_read_literal(&header_bc, 2);
    if (pc->txfm_mode == 3)
      pc->txfm_mode += vp9_read_bit(&header_bc);

    if (pc->txfm_mode == TX_MODE_SELECT) {
      pc->prob_tx[0] = vp9_read_literal(&header_bc, 8);
      pc->prob_tx[1] = vp9_read_literal(&header_bc, 8);
      pc->prob_tx[2] = vp9_read_literal(&header_bc, 8);
    }
  }

  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 */
    pc->y1dc_delta_q = get_delta_q(&header_bc, pc->y1dc_delta_q, &q_update);
    pc->uvdc_delta_q = get_delta_q(&header_bc, pc->uvdc_delta_q, &q_update);
    pc->uvac_delta_q = get_delta_q(&header_bc, pc->uvac_delta_q, &q_update);

    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 = (unsigned char)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
    /* 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_prob)vp9_read_literal(&header_bc, 8);
        }
      }
    }
  }
#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_prob)vp9_read_literal(&header_bc, 8);
        }
      }
    }
  }
#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);
  }

  vp9_copy(pbi->common.fc.pre_coef_probs_4x4,
           pbi->common.fc.coef_probs_4x4);
  vp9_copy(pbi->common.fc.pre_coef_probs_8x8,
           pbi->common.fc.coef_probs_8x8);
  vp9_copy(pbi->common.fc.pre_coef_probs_16x16,
           pbi->common.fc.coef_probs_16x16);
  vp9_copy(pbi->common.fc.pre_coef_probs_32x32,
           pbi->common.fc.coef_probs_32x32);
  vp9_copy(pbi->common.fc.pre_ymode_prob, pbi->common.fc.ymode_prob);
  vp9_copy(pbi->common.fc.pre_sb_ymode_prob, pbi->common.fc.sb_ymode_prob);
  vp9_copy(pbi->common.fc.pre_uv_mode_prob, pbi->common.fc.uv_mode_prob);
  vp9_copy(pbi->common.fc.pre_bmode_prob, pbi->common.fc.bmode_prob);
  vp9_copy(pbi->common.fc.pre_i8x8_mode_prob, pbi->common.fc.i8x8_mode_prob);
  vp9_copy(pbi->common.fc.pre_sub_mv_ref_prob, pbi->common.fc.sub_mv_ref_prob);
  vp9_copy(pbi->common.fc.pre_mbsplit_prob, pbi->common.fc.mbsplit_prob);
#if CONFIG_COMP_INTERINTRA_PRED
  pbi->common.fc.pre_interintra_prob = pbi->common.fc.interintra_prob;
#endif
  pbi->common.fc.pre_nmvc = pbi->common.fc.nmvc;
#if CONFIG_CODE_NONZEROCOUNT
  vp9_copy(pbi->common.fc.pre_nzc_probs_4x4,
           pbi->common.fc.nzc_probs_4x4);
  vp9_copy(pbi->common.fc.pre_nzc_probs_8x8,
           pbi->common.fc.nzc_probs_8x8);
  vp9_copy(pbi->common.fc.pre_nzc_probs_16x16,
           pbi->common.fc.nzc_probs_16x16);
  vp9_copy(pbi->common.fc.pre_nzc_probs_32x32,
           pbi->common.fc.nzc_probs_32x32);
  vp9_copy(pbi->common.fc.pre_nzc_pcat_probs,
           pbi->common.fc.nzc_pcat_probs);
#endif

  vp9_zero(pbi->common.fc.coef_counts_4x4);
  vp9_zero(pbi->common.fc.coef_counts_8x8);
  vp9_zero(pbi->common.fc.coef_counts_16x16);
  vp9_zero(pbi->common.fc.coef_counts_32x32);
  vp9_zero(pbi->common.fc.eob_branch_counts);
  vp9_zero(pbi->common.fc.ymode_counts);
  vp9_zero(pbi->common.fc.sb_ymode_counts);
  vp9_zero(pbi->common.fc.uv_mode_counts);
  vp9_zero(pbi->common.fc.bmode_counts);
  vp9_zero(pbi->common.fc.i8x8_mode_counts);
  vp9_zero(pbi->common.fc.sub_mv_ref_counts);
  vp9_zero(pbi->common.fc.mbsplit_counts);
  vp9_zero(pbi->common.fc.NMVcount);
  vp9_zero(pbi->common.fc.mv_ref_ct);
#if CONFIG_COMP_INTERINTRA_PRED
  vp9_zero(pbi->common.fc.interintra_counts);
#endif
#if CONFIG_CODE_NONZEROCOUNT
  vp9_zero(pbi->common.fc.nzc_counts_4x4);
  vp9_zero(pbi->common.fc.nzc_counts_8x8);
  vp9_zero(pbi->common.fc.nzc_counts_16x16);
  vp9_zero(pbi->common.fc.nzc_counts_32x32);
  vp9_zero(pbi->common.fc.nzc_pcat_counts);
#endif

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

  /* 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->qcoeff, 0, sizeof(xd->qcoeff));

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

  vp9_decode_mode_mvs_init(pbi, &header_bc);

  /* tile info */
  {
    const uint8_t *data_ptr = data + first_partition_length_in_bytes;
    int tile_row, tile_col, delta_log2_tiles;

    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, pc, mb_row, xd, &residual_bc);
          }
          if (tile_row == pc->tile_rows - 1 && tile_col == n_cols - 1)
            bc_bak = residual_bc;
        }
      }
      residual_bc = bc_bak;
    } else {
      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);

          if (tile_col < pc->tile_columns - 1 || tile_row < pc->tile_rows - 1)
            setup_token_decoder(pbi, data_ptr + 4, &residual_bc);
          else
            setup_token_decoder(pbi, data_ptr, &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, pc, mb_row, xd, &residual_bc);
          }

          if (tile_col < pc->tile_columns - 1 || tile_row < pc->tile_rows - 1) {
            int size = read_le32(data_ptr);
            data_ptr += 4 + size;
          }
        }
      }
    }
  }
  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;
}