libvpx: Pull from upstream

source/libvpx/vp9/decoder/vp9_decodeframe.c

+/*
+ *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include <assert.h>
+#include <stdlib.h>  // qsort()
+
+#include "./vp9_rtcd.h"
+#include "./vpx_scale_rtcd.h"
+
+#include "vpx_mem/vpx_mem.h"
+#include "vpx_scale/vpx_scale.h"
+
+#include "vp9/common/vp9_alloccommon.h"
+#include "vp9/common/vp9_common.h"
+#include "vp9/common/vp9_entropy.h"
+#include "vp9/common/vp9_entropymode.h"
+#include "vp9/common/vp9_idct.h"
+#include "vp9/common/vp9_pred_common.h"
+#include "vp9/common/vp9_quant_common.h"
+#include "vp9/common/vp9_reconintra.h"
+#include "vp9/common/vp9_reconinter.h"
+#include "vp9/common/vp9_seg_common.h"
+#include "vp9/common/vp9_tile_common.h"
+
+#include "vp9/decoder/vp9_dboolhuff.h"
+#include "vp9/decoder/vp9_decodeframe.h"
+#include "vp9/decoder/vp9_detokenize.h"
+#include "vp9/decoder/vp9_decodemv.h"
+#include "vp9/decoder/vp9_dsubexp.h"
+#include "vp9/decoder/vp9_onyxd_int.h"
+#include "vp9/decoder/vp9_read_bit_buffer.h"
+#include "vp9/decoder/vp9_thread.h"
+
+typedef struct TileWorkerData {
+  VP9_COMMON *cm;
+  vp9_reader bit_reader;
+  DECLARE_ALIGNED(16, MACROBLOCKD, xd);
+  DECLARE_ALIGNED(16, int16_t,  dqcoeff[MAX_MB_PLANE][64 * 64]);
+} TileWorkerData;
+
+static int read_be32(const uint8_t *p) {
+  return (p[0] << 24) | (p[1] << 16) | (p[2] << 8) | p[3];
+}
+
+static int is_compound_reference_allowed(const VP9_COMMON *cm) {
+  int i;
+  for (i = 1; i < REFS_PER_FRAME; ++i)
+    if  (cm->ref_frame_sign_bias[i + 1] != cm->ref_frame_sign_bias[1])
+      return 1;
+
+  return 0;
+}
+
+static void setup_compound_reference(VP9_COMMON *cm) {
+  if (cm->ref_frame_sign_bias[LAST_FRAME] ==
+          cm->ref_frame_sign_bias[GOLDEN_FRAME]) {
+    cm->comp_fixed_ref = ALTREF_FRAME;
+    cm->comp_var_ref[0] = LAST_FRAME;
+    cm->comp_var_ref[1] = GOLDEN_FRAME;
+  } else if (cm->ref_frame_sign_bias[LAST_FRAME] ==
+                 cm->ref_frame_sign_bias[ALTREF_FRAME]) {
+    cm->comp_fixed_ref = GOLDEN_FRAME;
+    cm->comp_var_ref[0] = LAST_FRAME;
+    cm->comp_var_ref[1] = ALTREF_FRAME;
+  } else {
+    cm->comp_fixed_ref = LAST_FRAME;
+    cm->comp_var_ref[0] = GOLDEN_FRAME;
+    cm->comp_var_ref[1] = ALTREF_FRAME;
+  }
+}
+
+// len == 0 is not allowed
+static int read_is_valid(const uint8_t *start, size_t len, const uint8_t *end) {
+  return start + len > start && start + len <= end;
+}
+
+static int decode_unsigned_max(struct vp9_read_bit_buffer *rb, int max) {
+  const int data = vp9_rb_read_literal(rb, get_unsigned_bits(max));
+  return data > max ? max : data;
+}
+
+static TX_MODE read_tx_mode(vp9_reader *r) {
+  TX_MODE tx_mode = vp9_read_literal(r, 2);
+  if (tx_mode == ALLOW_32X32)
+    tx_mode += vp9_read_bit(r);
+  return tx_mode;
+}
+
+static void read_tx_mode_probs(struct tx_probs *tx_probs, vp9_reader *r) {
+  int i, j;
+
+  for (i = 0; i < TX_SIZE_CONTEXTS; ++i)
+    for (j = 0; j < TX_SIZES - 3; ++j)
+      vp9_diff_update_prob(r, &tx_probs->p8x8[i][j]);
+
+  for (i = 0; i < TX_SIZE_CONTEXTS; ++i)
+    for (j = 0; j < TX_SIZES - 2; ++j)
+      vp9_diff_update_prob(r, &tx_probs->p16x16[i][j]);
+
+  for (i = 0; i < TX_SIZE_CONTEXTS; ++i)
+    for (j = 0; j < TX_SIZES - 1; ++j)
+      vp9_diff_update_prob(r, &tx_probs->p32x32[i][j]);
+}
+
+static void read_switchable_interp_probs(FRAME_CONTEXT *fc, vp9_reader *r) {
+  int i, j;
+  for (j = 0; j < SWITCHABLE_FILTER_CONTEXTS; ++j)
+    for (i = 0; i < SWITCHABLE_FILTERS - 1; ++i)
+      vp9_diff_update_prob(r, &fc->switchable_interp_prob[j][i]);
+}
+
+static void read_inter_mode_probs(FRAME_CONTEXT *fc, vp9_reader *r) {
+  int i, j;
+  for (i = 0; i < INTER_MODE_CONTEXTS; ++i)
+    for (j = 0; j < INTER_MODES - 1; ++j)
+      vp9_diff_update_prob(r, &fc->inter_mode_probs[i][j]);
+}
+
+static REFERENCE_MODE read_reference_mode(VP9_COMMON *cm, vp9_reader *r) {
+  if (is_compound_reference_allowed(cm)) {
+    REFERENCE_MODE mode = vp9_read_bit(r);
+    if (mode)
+      mode += vp9_read_bit(r);
+    setup_compound_reference(cm);
+    return mode;
+  } else {
+    return SINGLE_REFERENCE;
+  }
+}
+
+static void read_reference_mode_probs(VP9_COMMON *cm, vp9_reader *r) {
+  int i;
+  if (cm->reference_mode == REFERENCE_MODE_SELECT)
+    for (i = 0; i < COMP_INTER_CONTEXTS; i++)
+      vp9_diff_update_prob(r, &cm->fc.comp_inter_prob[i]);
+
+  if (cm->reference_mode != COMPOUND_REFERENCE)
+    for (i = 0; i < REF_CONTEXTS; i++) {
+      vp9_diff_update_prob(r, &cm->fc.single_ref_prob[i][0]);
+      vp9_diff_update_prob(r, &cm->fc.single_ref_prob[i][1]);
+    }
+
+  if (cm->reference_mode != SINGLE_REFERENCE)
+    for (i = 0; i < REF_CONTEXTS; i++)
+      vp9_diff_update_prob(r, &cm->fc.comp_ref_prob[i]);
+}
+
+static void update_mv_probs(vp9_prob *p, int n, vp9_reader *r) {
+  int i;
+  for (i = 0; i < n; ++i)
+    if (vp9_read(r, NMV_UPDATE_PROB))
+      p[i] = (vp9_read_literal(r, 7) << 1) | 1;
+}
+
+static void read_mv_probs(nmv_context *ctx, int allow_hp, vp9_reader *r) {
+  int i, j;
+
+  update_mv_probs(ctx->joints, MV_JOINTS - 1, r);
+
+  for (i = 0; i < 2; ++i) {
+    nmv_component *const comp_ctx = &ctx->comps[i];
+    update_mv_probs(&comp_ctx->sign, 1, r);
+    update_mv_probs(comp_ctx->classes, MV_CLASSES - 1, r);
+    update_mv_probs(comp_ctx->class0, CLASS0_SIZE - 1, r);
+    update_mv_probs(comp_ctx->bits, MV_OFFSET_BITS, r);
+  }
+
+  for (i = 0; i < 2; ++i) {
+    nmv_component *const comp_ctx = &ctx->comps[i];
+    for (j = 0; j < CLASS0_SIZE; ++j)
+      update_mv_probs(comp_ctx->class0_fp[j], MV_FP_SIZE - 1, r);
+    update_mv_probs(comp_ctx->fp, 3, r);
+  }
+
+  if (allow_hp) {
+    for (i = 0; i < 2; ++i) {
+      nmv_component *const comp_ctx = &ctx->comps[i];
+      update_mv_probs(&comp_ctx->class0_hp, 1, r);
+      update_mv_probs(&comp_ctx->hp, 1, r);
+    }
+  }
+}
+
+static void setup_plane_dequants(VP9_COMMON *cm, MACROBLOCKD *xd, int q_index) {
+  int i;
+  xd->plane[0].dequant = cm->y_dequant[q_index];
+
+  for (i = 1; i < MAX_MB_PLANE; i++)
+    xd->plane[i].dequant = cm->uv_dequant[q_index];
+}
+
+// Allocate storage for each tile column.
+// TODO(jzern): when max_threads <= 1 the same storage could be used for each
+// tile.
+static void alloc_tile_storage(VP9D_COMP *pbi, int tile_rows, int tile_cols) {
+  VP9_COMMON *const cm = &pbi->common;
+  const int aligned_mi_cols = mi_cols_aligned_to_sb(cm->mi_cols);
+  int i, tile_row, tile_col;
+
+  CHECK_MEM_ERROR(cm, pbi->mi_streams,
+                  vpx_realloc(pbi->mi_streams, tile_rows * tile_cols *
+                              sizeof(*pbi->mi_streams)));
+  for (tile_row = 0; tile_row < tile_rows; ++tile_row) {
+    for (tile_col = 0; tile_col < tile_cols; ++tile_col) {
+      TileInfo tile;
+      vp9_tile_init(&tile, cm, tile_row, tile_col);
+      pbi->mi_streams[tile_row * tile_cols + tile_col] =
+          &cm->mi[tile.mi_row_start * cm->mode_info_stride
+                  + tile.mi_col_start];
+    }
+  }
+
+  // 2 contexts per 'mi unit', so that we have one context per 4x4 txfm
+  // block where mi unit size is 8x8.
+  CHECK_MEM_ERROR(cm, pbi->above_context[0],
+                  vpx_realloc(pbi->above_context[0],
+                              sizeof(*pbi->above_context[0]) * MAX_MB_PLANE *
+                              2 * aligned_mi_cols));
+  for (i = 1; i < MAX_MB_PLANE; ++i) {
+    pbi->above_context[i] = pbi->above_context[0] +
+                            i * sizeof(*pbi->above_context[0]) *
+                            2 * aligned_mi_cols;
+  }
+
+  // This is sized based on the entire frame. Each tile operates within its
+  // column bounds.
+  CHECK_MEM_ERROR(cm, pbi->above_seg_context,
+                  vpx_realloc(pbi->above_seg_context,
+                              sizeof(*pbi->above_seg_context) *
+                              aligned_mi_cols));
+}
+
+static void inverse_transform_block(MACROBLOCKD* xd, int plane, int block,
+                                    TX_SIZE tx_size, uint8_t *dst, int stride,
+                                    int eob) {
+  struct macroblockd_plane *const pd = &xd->plane[plane];
+  if (eob > 0) {
+    TX_TYPE tx_type;
+    const int plane_type = pd->plane_type;
+    int16_t *const dqcoeff = BLOCK_OFFSET(pd->dqcoeff, block);
+    switch (tx_size) {
+      case TX_4X4:
+        tx_type = get_tx_type_4x4(plane_type, xd, block);
+        if (tx_type == DCT_DCT)
+          xd->itxm_add(dqcoeff, dst, stride, eob);
+        else
+          vp9_iht4x4_16_add(dqcoeff, dst, stride, tx_type);
+        break;
+      case TX_8X8:
+        tx_type = get_tx_type_8x8(plane_type, xd);
+        vp9_iht8x8_add(tx_type, dqcoeff, dst, stride, eob);
+        break;
+      case TX_16X16:
+        tx_type = get_tx_type_16x16(plane_type, xd);
+        vp9_iht16x16_add(tx_type, dqcoeff, dst, stride, eob);
+        break;
+      case TX_32X32:
+        tx_type = DCT_DCT;
+        vp9_idct32x32_add(dqcoeff, dst, stride, eob);
+        break;
+      default:
+        assert(0 && "Invalid transform size");
+    }
+
+    if (eob == 1) {
+      vpx_memset(dqcoeff, 0, 2 * sizeof(dqcoeff[0]));
+    } else {
+      if (tx_type == DCT_DCT && tx_size <= TX_16X16 && eob <= 10)
+        vpx_memset(dqcoeff, 0, 4 * (4 << tx_size) * sizeof(dqcoeff[0]));
+      else if (tx_size == TX_32X32 && eob <= 34)
+        vpx_memset(dqcoeff, 0, 256 * sizeof(dqcoeff[0]));
+      else
+        vpx_memset(dqcoeff, 0, (16 << (tx_size << 1)) * sizeof(dqcoeff[0]));
+    }
+  }
+}
+
+struct intra_args {
+  VP9_COMMON *cm;
+  MACROBLOCKD *xd;
+  vp9_reader *r;
+};
+
+static void predict_and_reconstruct_intra_block(int plane, int block,
+                                                BLOCK_SIZE plane_bsize,
+                                                TX_SIZE tx_size, void *arg) {
+  struct intra_args *const args = arg;
+  VP9_COMMON *const cm = args->cm;
+  MACROBLOCKD *const xd = args->xd;
+  struct macroblockd_plane *const pd = &xd->plane[plane];
+  MODE_INFO *const mi = xd->mi_8x8[0];
+  const MB_PREDICTION_MODE mode = (plane == 0)
+          ? ((mi->mbmi.sb_type < BLOCK_8X8) ? mi->bmi[block].as_mode
+                                            : mi->mbmi.mode)
+          : mi->mbmi.uv_mode;
+  int x, y;
+  uint8_t *dst;
+  txfrm_block_to_raster_xy(plane_bsize, tx_size, block, &x, &y);
+  dst = &pd->dst.buf[4 * y * pd->dst.stride + 4 * x];
+
+  if (xd->mb_to_right_edge < 0 || xd->mb_to_bottom_edge < 0)
+    extend_for_intra(xd, plane_bsize, plane, x, y);
+
+  vp9_predict_intra_block(xd, block >> (tx_size << 1),
+                          b_width_log2(plane_bsize), tx_size, mode,
+                          dst, pd->dst.stride, dst, pd->dst.stride);
+
+  if (!mi->mbmi.skip_coeff) {
+    const int eob = vp9_decode_block_tokens(cm, xd, plane, block,
+                                            plane_bsize, x, y, tx_size,
+                                            args->r);
+    inverse_transform_block(xd, plane, block, tx_size, dst, pd->dst.stride,
+                            eob);
+  }
+}
+
+struct inter_args {
+  VP9_COMMON *cm;
+  MACROBLOCKD *xd;
+  vp9_reader *r;
+  int *eobtotal;
+};
+
+static void reconstruct_inter_block(int plane, int block,
+                                    BLOCK_SIZE plane_bsize,
+                                    TX_SIZE tx_size, void *arg) {
+  struct inter_args *args = arg;
+  VP9_COMMON *const cm = args->cm;
+  MACROBLOCKD *const xd = args->xd;
+  struct macroblockd_plane *const pd = &xd->plane[plane];
+  int x, y, eob;
+  txfrm_block_to_raster_xy(plane_bsize, tx_size, block, &x, &y);
+  eob = vp9_decode_block_tokens(cm, xd, plane, block, plane_bsize, x, y,
+                                tx_size, args->r);
+  inverse_transform_block(xd, plane, block, tx_size,
+                          &pd->dst.buf[4 * y * pd->dst.stride + 4 * x],
+                          pd->dst.stride, eob);
+  *args->eobtotal += eob;
+}
+
+static void set_offsets(VP9_COMMON *const cm, MACROBLOCKD *const xd,
+                        const TileInfo *const tile,
+                        BLOCK_SIZE bsize, int mi_row, int mi_col) {
+  const int bw = num_8x8_blocks_wide_lookup[bsize];
+  const int bh = num_8x8_blocks_high_lookup[bsize];
+  const int x_mis = MIN(bw, cm->mi_cols - mi_col);
+  const int y_mis = MIN(bh, cm->mi_rows - mi_row);
+  const int offset = mi_row * cm->mode_info_stride + mi_col;
+  const int tile_offset = tile->mi_row_start * cm->mode_info_stride +
+                          tile->mi_col_start;
+  int x, y;
+
+  xd->mi_8x8 = cm->mi_grid_visible + offset;
+  xd->prev_mi_8x8 = cm->prev_mi_grid_visible + offset;
+  // Special case: if prev_mi is NULL, the previous mode info context
+  // cannot be used.
+  xd->last_mi = cm->prev_mi ? xd->prev_mi_8x8[0] : NULL;
+
+  xd->mi_8x8[0] = xd->mi_stream + offset - tile_offset;
+  xd->mi_8x8[0]->mbmi.sb_type = bsize;
+  for (y = 0; y < y_mis; ++y)
+    for (x = !y; x < x_mis; ++x)
+      xd->mi_8x8[y * cm->mode_info_stride + x] = xd->mi_8x8[0];
+
+  set_skip_context(xd, xd->above_context, xd->left_context, mi_row, mi_col);
+
+  // Distance of Mb to the various image edges. These are specified to 8th pel
+  // as they are always compared to values that are in 1/8th pel units
+  set_mi_row_col(xd, tile, mi_row, bh, mi_col, bw, cm->mi_rows, cm->mi_cols);
+
+  setup_dst_planes(xd, get_frame_new_buffer(cm), mi_row, mi_col);
+}
+
+static void set_ref(VP9_COMMON *const cm, MACROBLOCKD *const xd,
+                    int idx, int mi_row, int mi_col) {
+  MB_MODE_INFO *const mbmi = &xd->mi_8x8[0]->mbmi;
+  const int ref = mbmi->ref_frame[idx] - LAST_FRAME;
+  const YV12_BUFFER_CONFIG *cfg = get_frame_ref_buffer(cm, ref);
+  const struct scale_factors_common *sfc = &cm->active_ref_scale_comm[ref];
+
+  xd->ref_buf[idx] = cfg;
+  if (!vp9_is_valid_scale(sfc))
+    vpx_internal_error(&cm->error, VPX_CODEC_UNSUP_BITSTREAM,
+                       "Invalid scale factors");
+
+  xd->scale_factor[idx].sfc = sfc;
+  setup_pre_planes(xd, idx, cfg, mi_row, mi_col, &xd->scale_factor[idx]);
+  xd->corrupted |= cfg->corrupted;
+}
+
+static void decode_modes_b(VP9_COMMON *const cm, MACROBLOCKD *const xd,
+                           const TileInfo *const tile,
+                           int mi_row, int mi_col,
+                           vp9_reader *r, BLOCK_SIZE bsize) {
+  const int less8x8 = bsize < BLOCK_8X8;
+  MB_MODE_INFO *mbmi;
+
+  set_offsets(cm, xd, tile, bsize, mi_row, mi_col);
+  vp9_read_mode_info(cm, xd, tile, mi_row, mi_col, r);
+
+  if (less8x8)
+    bsize = BLOCK_8X8;
+
+  // Has to be called after set_offsets
+  mbmi = &xd->mi_8x8[0]->mbmi;
+
+  if (mbmi->skip_coeff) {
+    reset_skip_context(xd, bsize);
+  } else {
+    if (cm->seg.enabled)
+      setup_plane_dequants(cm, xd, vp9_get_qindex(&cm->seg, mbmi->segment_id,
+                                                  cm->base_qindex));
+  }
+
+  if (!is_inter_block(mbmi)) {
+    struct intra_args arg = { cm, xd, r };
+    foreach_transformed_block(xd, bsize, predict_and_reconstruct_intra_block,
+                              &arg);
+  } else {
+    // Setup
+    set_ref(cm, xd, 0, mi_row, mi_col);
+    if (has_second_ref(mbmi))
+      set_ref(cm, xd, 1, mi_row, mi_col);
+
+    xd->subpix.filter_x = xd->subpix.filter_y =
+        vp9_get_filter_kernel(mbmi->interp_filter);
+
+    // Prediction
+    vp9_dec_build_inter_predictors_sb(xd, mi_row, mi_col, bsize);
+
+    // Reconstruction
+    if (!mbmi->skip_coeff) {
+      int eobtotal = 0;
+      struct inter_args arg = { cm, xd, r, &eobtotal };
+      foreach_transformed_block(xd, bsize, reconstruct_inter_block, &arg);
+      if (!less8x8 && eobtotal == 0)
+        mbmi->skip_coeff = 1;  // skip loopfilter
+    }
+  }
+
+  xd->corrupted |= vp9_reader_has_error(r);
+}
+
+static PARTITION_TYPE read_partition(VP9_COMMON *cm, MACROBLOCKD *xd, int hbs,
+                                     int mi_row, int mi_col, BLOCK_SIZE bsize,
+                                     vp9_reader *r) {
+  const int ctx = partition_plane_context(xd->above_seg_context,
+                                          xd->left_seg_context,
+                                          mi_row, mi_col, bsize);
+  const vp9_prob *const probs = get_partition_probs(cm, ctx);
+  const int has_rows = (mi_row + hbs) < cm->mi_rows;
+  const int has_cols = (mi_col + hbs) < cm->mi_cols;
+  PARTITION_TYPE p;
+
+  if (has_rows && has_cols)
+    p = vp9_read_tree(r, vp9_partition_tree, probs);
+  else if (!has_rows && has_cols)
+    p = vp9_read(r, probs[1]) ? PARTITION_SPLIT : PARTITION_HORZ;
+  else if (has_rows && !has_cols)
+    p = vp9_read(r, probs[2]) ? PARTITION_SPLIT : PARTITION_VERT;
+  else
+    p = PARTITION_SPLIT;
+
+  if (!cm->frame_parallel_decoding_mode)
+    ++cm->counts.partition[ctx][p];
+
+  return p;
+}
+
+static void decode_modes_sb(VP9_COMMON *const cm, MACROBLOCKD *const xd,
+                            const TileInfo *const tile,
+                            int mi_row, int mi_col,
+                            vp9_reader* r, BLOCK_SIZE bsize) {
+  const int hbs = num_8x8_blocks_wide_lookup[bsize] / 2;
+  PARTITION_TYPE partition;
+  BLOCK_SIZE subsize;
+
+  if (mi_row >= cm->mi_rows || mi_col >= cm->mi_cols)
+    return;
+
+  partition = read_partition(cm, xd, hbs, mi_row, mi_col, bsize, r);
+  subsize = get_subsize(bsize, partition);
+  if (subsize < BLOCK_8X8) {
+    decode_modes_b(cm, xd, tile, mi_row, mi_col, r, subsize);
+  } else {
+    switch (partition) {
+      case PARTITION_NONE:
+        decode_modes_b(cm, xd, tile, mi_row, mi_col, r, subsize);
+        break;
+      case PARTITION_HORZ:
+        decode_modes_b(cm, xd, tile, mi_row, mi_col, r, subsize);
+        if (mi_row + hbs < cm->mi_rows)
+          decode_modes_b(cm, xd, tile, mi_row + hbs, mi_col, r, subsize);
+        break;
+      case PARTITION_VERT:
+        decode_modes_b(cm, xd, tile, mi_row, mi_col, r, subsize);
+        if (mi_col + hbs < cm->mi_cols)
+          decode_modes_b(cm, xd, tile, mi_row, mi_col + hbs, r, subsize);
+        break;
+      case PARTITION_SPLIT:
+        decode_modes_sb(cm, xd, tile, mi_row, mi_col, r, subsize);
+        decode_modes_sb(cm, xd, tile, mi_row, mi_col + hbs, r, subsize);
+        decode_modes_sb(cm, xd, tile, mi_row + hbs, mi_col, r, subsize);
+        decode_modes_sb(cm, xd, tile, mi_row + hbs, mi_col + hbs, r, subsize);
+        break;
+      default:
+        assert(0 && "Invalid partition type");
+    }
+  }
+
+  // update partition context
+  if (bsize >= BLOCK_8X8 &&
+      (bsize == BLOCK_8X8 || partition != PARTITION_SPLIT))
+    update_partition_context(xd->above_seg_context, xd->left_seg_context,
+                             mi_row, mi_col, subsize, bsize);
+}
+
+static void setup_token_decoder(const uint8_t *data,
+                                const uint8_t *data_end,
+                                size_t read_size,
+                                struct vpx_internal_error_info *error_info,
+                                vp9_reader *r) {
+  // 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, read_size, data_end))
+    vpx_internal_error(error_info, VPX_CODEC_CORRUPT_FRAME,
+                       "Truncated packet or corrupt tile length");
+
+  if (vp9_reader_init(r, data, read_size))
+    vpx_internal_error(error_info, VPX_CODEC_MEM_ERROR,
+                       "Failed to allocate bool decoder %d", 1);
+}
+
+static void read_coef_probs_common(vp9_coeff_probs_model *coef_probs,
+                                   vp9_reader *r) {
+  int i, j, k, l, m;
+
+  if (vp9_read_bit(r))
+    for (i = 0; i < PLANE_TYPES; ++i)
+      for (j = 0; j < REF_TYPES; ++j)
+        for (k = 0; k < COEF_BANDS; ++k)
+          for (l = 0; l < BAND_COEFF_CONTEXTS(k); ++l)
+            for (m = 0; m < UNCONSTRAINED_NODES; ++m)
+              vp9_diff_update_prob(r, &coef_probs[i][j][k][l][m]);
+}
+
+static void read_coef_probs(FRAME_CONTEXT *fc, TX_MODE tx_mode,
+                            vp9_reader *r) {
+    const TX_SIZE max_tx_size = tx_mode_to_biggest_tx_size[tx_mode];
+    TX_SIZE tx_size;
+    for (tx_size = TX_4X4; tx_size <= max_tx_size; ++tx_size)
+      read_coef_probs_common(fc->coef_probs[tx_size], r);
+}
+
+static void setup_segmentation(struct segmentation *seg,
+                               struct vp9_read_bit_buffer *rb) {
+  int i, j;
+
+  seg->update_map = 0;
+  seg->update_data = 0;
+
+  seg->enabled = vp9_rb_read_bit(rb);
+  if (!seg->enabled)
+    return;
+
+  // Segmentation map update
+  seg->update_map = vp9_rb_read_bit(rb);
+  if (seg->update_map) {
+    for (i = 0; i < SEG_TREE_PROBS; i++)
+      seg->tree_probs[i] = vp9_rb_read_bit(rb) ? vp9_rb_read_literal(rb, 8)
+                                               : MAX_PROB;
+
+    seg->temporal_update = vp9_rb_read_bit(rb);
+    if (seg->temporal_update) {
+      for (i = 0; i < PREDICTION_PROBS; i++)
+        seg->pred_probs[i] = vp9_rb_read_bit(rb) ? vp9_rb_read_literal(rb, 8)
+                                                 : MAX_PROB;
+    } else {
+      for (i = 0; i < PREDICTION_PROBS; i++)
+        seg->pred_probs[i] = MAX_PROB;
+    }
+  }
+
+  // Segmentation data update
+  seg->update_data = vp9_rb_read_bit(rb);
+  if (seg->update_data) {
+    seg->abs_delta = vp9_rb_read_bit(rb);
+
+    vp9_clearall_segfeatures(seg);
+
+    for (i = 0; i < MAX_SEGMENTS; i++) {
+      for (j = 0; j < SEG_LVL_MAX; j++) {
+        int data = 0;
+        const int feature_enabled = vp9_rb_read_bit(rb);
+        if (feature_enabled) {
+          vp9_enable_segfeature(seg, i, j);
+          data = decode_unsigned_max(rb, vp9_seg_feature_data_max(j));
+          if (vp9_is_segfeature_signed(j))
+            data = vp9_rb_read_bit(rb) ? -data : data;
+        }
+        vp9_set_segdata(seg, i, j, data);
+      }
+    }
+  }
+}
+
+static void setup_loopfilter(struct loopfilter *lf,
+                             struct vp9_read_bit_buffer *rb) {
+  lf->filter_level = vp9_rb_read_literal(rb, 6);
+  lf->sharpness_level = vp9_rb_read_literal(rb, 3);
+
+  // Read in loop filter deltas applied at the MB level based on mode or ref
+  // frame.
+  lf->mode_ref_delta_update = 0;
+
+  lf->mode_ref_delta_enabled = vp9_rb_read_bit(rb);
+  if (lf->mode_ref_delta_enabled) {
+    lf->mode_ref_delta_update = vp9_rb_read_bit(rb);
+    if (lf->mode_ref_delta_update) {
+      int i;
+
+      for (i = 0; i < MAX_REF_LF_DELTAS; i++)
+        if (vp9_rb_read_bit(rb))
+          lf->ref_deltas[i] = vp9_rb_read_signed_literal(rb, 6);
+
+      for (i = 0; i < MAX_MODE_LF_DELTAS; i++)
+        if (vp9_rb_read_bit(rb))
+          lf->mode_deltas[i] = vp9_rb_read_signed_literal(rb, 6);
+    }
+  }
+}
+
+static int read_delta_q(struct vp9_read_bit_buffer *rb, int *delta_q) {
+  const int old = *delta_q;
+  *delta_q = vp9_rb_read_bit(rb) ? vp9_rb_read_signed_literal(rb, 4) : 0;
+  return old != *delta_q;
+}
+
+static void setup_quantization(VP9_COMMON *const cm, MACROBLOCKD *const xd,
+                               struct vp9_read_bit_buffer *rb) {
+  int update = 0;
+
+  cm->base_qindex = vp9_rb_read_literal(rb, QINDEX_BITS);
+  update |= read_delta_q(rb, &cm->y_dc_delta_q);
+  update |= read_delta_q(rb, &cm->uv_dc_delta_q);
+  update |= read_delta_q(rb, &cm->uv_ac_delta_q);
+  if (update)
+    vp9_init_dequantizer(cm);
+
+  xd->lossless = cm->base_qindex == 0 &&
+                 cm->y_dc_delta_q == 0 &&
+                 cm->uv_dc_delta_q == 0 &&
+                 cm->uv_ac_delta_q == 0;
+
+  xd->itxm_add = xd->lossless ? vp9_iwht4x4_add : vp9_idct4x4_add;
+}
+
+static INTERPOLATION_TYPE read_interp_filter_type(
+                              struct vp9_read_bit_buffer *rb) {
+  const INTERPOLATION_TYPE literal_to_type[] = { EIGHTTAP_SMOOTH,
+                                                 EIGHTTAP,
+                                                 EIGHTTAP_SHARP,
+                                                 BILINEAR };
+  return vp9_rb_read_bit(rb) ? SWITCHABLE
+                             : literal_to_type[vp9_rb_read_literal(rb, 2)];
+}
+
+static void read_frame_size(struct vp9_read_bit_buffer *rb,
+                            int *width, int *height) {
+  const int w = vp9_rb_read_literal(rb, 16) + 1;
+  const int h = vp9_rb_read_literal(rb, 16) + 1;
+  *width = w;
+  *height = h;
+}
+
+static void setup_display_size(VP9_COMMON *cm, struct vp9_read_bit_buffer *rb) {
+  cm->display_width = cm->width;
+  cm->display_height = cm->height;
+  if (vp9_rb_read_bit(rb))
+    read_frame_size(rb, &cm->display_width, &cm->display_height);
+}
+
+static void apply_frame_size(VP9D_COMP *pbi, int width, int height) {
+  VP9_COMMON *cm = &pbi->common;
+
+  if (cm->width != width || cm->height != height) {
+    // Change in frame size.
+    // TODO(agrange) Don't test width/height, check overall size.
+    if (width > cm->width || height > cm->height) {
+      // Rescale frame buffers only if they're not big enough already.
+      if (vp9_resize_frame_buffers(cm, width, height))
+        vpx_internal_error(&cm->error, VPX_CODEC_MEM_ERROR,
+                           "Failed to allocate frame buffers");
+    }
+
+    cm->width = width;
+    cm->height = height;
+
+    vp9_update_frame_size(cm);
+  }
+
+  if (cm->fb_list != NULL) {
+    vpx_codec_frame_buffer_t *const ext_fb = &cm->fb_list[cm->new_fb_idx];
+    if (vp9_realloc_frame_buffer(get_frame_new_buffer(cm),
+                                 cm->width, cm->height,
+                                 cm->subsampling_x, cm->subsampling_y,
+                                 VP9BORDERINPIXELS, ext_fb,
+                                 cm->realloc_fb_cb, cm->user_priv)) {
+      vpx_internal_error(&cm->error, VPX_CODEC_MEM_ERROR,
+                         "Failed to allocate external frame buffer");
+    }
+  } else {
+    vp9_realloc_frame_buffer(get_frame_new_buffer(cm), cm->width, cm->height,
+                             cm->subsampling_x, cm->subsampling_y,
+                             VP9BORDERINPIXELS, NULL, NULL, NULL);
+  }
+}
+
+static void setup_frame_size(VP9D_COMP *pbi,
+                             struct vp9_read_bit_buffer *rb) {
+  int width, height;
+  read_frame_size(rb, &width, &height);
+  apply_frame_size(pbi, width, height);
+  setup_display_size(&pbi->common, rb);
+}
+
+static void setup_frame_size_with_refs(VP9D_COMP *pbi,
+                                       struct vp9_read_bit_buffer *rb) {
+  VP9_COMMON *const cm = &pbi->common;
+
+  int width, height;
+  int found = 0, i;
+  for (i = 0; i < REFS_PER_FRAME; ++i) {
+    if (vp9_rb_read_bit(rb)) {
+      YV12_BUFFER_CONFIG *const cfg = get_frame_ref_buffer(cm, i);
+      width = cfg->y_crop_width;
+      height = cfg->y_crop_height;
+      found = 1;
+      break;
+    }
+  }
+
+  if (!found)
+    read_frame_size(rb, &width, &height);
+
+  if (!width || !height)
+    vpx_internal_error(&cm->error, VPX_CODEC_CORRUPT_FRAME,
+                       "Referenced frame with invalid size");
+
+  apply_frame_size(pbi, width, height);
+  setup_display_size(cm, rb);
+}
+
+static void setup_tile_context(VP9D_COMP *const pbi, MACROBLOCKD *const xd,
+                               int tile_row, int tile_col) {
+  int i;
+  const int tile_cols = 1 << pbi->common.log2_tile_cols;
+  xd->mi_stream = pbi->mi_streams[tile_row * tile_cols + tile_col];
+
+  for (i = 0; i < MAX_MB_PLANE; ++i) {
+    xd->above_context[i] = pbi->above_context[i];
+  }
+  // see note in alloc_tile_storage().
+  xd->above_seg_context = pbi->above_seg_context;
+}
+
+static void decode_tile(VP9D_COMP *pbi, const TileInfo *const tile,
+                        vp9_reader *r) {
+  const int num_threads = pbi->oxcf.max_threads;
+  VP9_COMMON *const cm = &pbi->common;
+  int mi_row, mi_col;
+  MACROBLOCKD *xd = &pbi->mb;
+
+  if (pbi->do_loopfilter_inline) {
+    LFWorkerData *const lf_data = (LFWorkerData*)pbi->lf_worker.data1;
+    lf_data->frame_buffer = get_frame_new_buffer(cm);
+    lf_data->cm = cm;
+    lf_data->xd = pbi->mb;
+    lf_data->stop = 0;
+    lf_data->y_only = 0;
+    vp9_loop_filter_frame_init(cm, cm->lf.filter_level);
+  }
+
+  for (mi_row = tile->mi_row_start; mi_row < tile->mi_row_end;
+       mi_row += MI_BLOCK_SIZE) {
+    // For a SB there are 2 left contexts, each pertaining to a MB row within
+    vp9_zero(xd->left_context);
+    vp9_zero(xd->left_seg_context);
+    for (mi_col = tile->mi_col_start; mi_col < tile->mi_col_end;
+         mi_col += MI_BLOCK_SIZE) {
+      decode_modes_sb(cm, xd, tile, mi_row, mi_col, r, BLOCK_64X64);
+    }
+
+    if (pbi->do_loopfilter_inline) {
+      const int lf_start = mi_row - MI_BLOCK_SIZE;
+      LFWorkerData *const lf_data = (LFWorkerData*)pbi->lf_worker.data1;
+
+      // delay the loopfilter by 1 macroblock row.
+      if (lf_start < 0) continue;
+
+      // decoding has completed: finish up the loop filter in this thread.
+      if (mi_row + MI_BLOCK_SIZE >= tile->mi_row_end) continue;
+
+      vp9_worker_sync(&pbi->lf_worker);
+      lf_data->start = lf_start;
+      lf_data->stop = mi_row;
+      if (num_threads > 1) {
+        vp9_worker_launch(&pbi->lf_worker);
+      } else {
+        vp9_worker_execute(&pbi->lf_worker);
+      }
+    }
+  }
+
+  if (pbi->do_loopfilter_inline) {
+    LFWorkerData *const lf_data = (LFWorkerData*)pbi->lf_worker.data1;
+
+    vp9_worker_sync(&pbi->lf_worker);
+    lf_data->start = lf_data->stop;
+    lf_data->stop = cm->mi_rows;
+    vp9_worker_execute(&pbi->lf_worker);
+  }
+}
+
+static void setup_tile_info(VP9_COMMON *cm, struct vp9_read_bit_buffer *rb) {
+  int min_log2_tile_cols, max_log2_tile_cols, max_ones;
+  vp9_get_tile_n_bits(cm->mi_cols, &min_log2_tile_cols, &max_log2_tile_cols);
+
+  // columns
+  max_ones = max_log2_tile_cols - min_log2_tile_cols;
+  cm->log2_tile_cols = min_log2_tile_cols;
+  while (max_ones-- && vp9_rb_read_bit(rb))
+    cm->log2_tile_cols++;
+
+  // rows
+  cm->log2_tile_rows = vp9_rb_read_bit(rb);
+  if (cm->log2_tile_rows)
+    cm->log2_tile_rows += vp9_rb_read_bit(rb);
+}
+
+// Reads the next tile returning its size and adjusting '*data' accordingly
+// based on 'is_last'.
+static size_t get_tile(const uint8_t *const data_end,
+                       int is_last,
+                       struct vpx_internal_error_info *error_info,
+                       const uint8_t **data) {
+  size_t size;
+
+  if (!is_last) {
+    if (!read_is_valid(*data, 4, data_end))
+      vpx_internal_error(error_info, VPX_CODEC_CORRUPT_FRAME,
+          "Truncated packet or corrupt tile length");
+
+    size = read_be32(*data);
+    *data += 4;
+  } else {
+    size = data_end - *data;
+  }
+  return size;
+}
+
+typedef struct TileBuffer {
+  const uint8_t *data;
+  size_t size;
+  int col;  // only used with multi-threaded decoding
+} TileBuffer;
+
+static const uint8_t *decode_tiles(VP9D_COMP *pbi, const uint8_t *data) {
+  VP9_COMMON *const cm = &pbi->common;
+  MACROBLOCKD *const xd = &pbi->mb;
+  const int aligned_cols = mi_cols_aligned_to_sb(cm->mi_cols);
+  const int tile_cols = 1 << cm->log2_tile_cols;
+  const int tile_rows = 1 << cm->log2_tile_rows;
+  TileBuffer tile_buffers[4][1 << 6];
+  int tile_row, tile_col;
+  const uint8_t *const data_end = pbi->source + pbi->source_sz;
+  const uint8_t *end = NULL;
+  vp9_reader r;
+
+  assert(tile_rows <= 4);
+  assert(tile_cols <= (1 << 6));
+
+  // Note: this memset assumes above_context[0], [1] and [2]
+  // are allocated as part of the same buffer.
+  vpx_memset(pbi->above_context[0], 0,
+             sizeof(*pbi->above_context[0]) * MAX_MB_PLANE * 2 * aligned_cols);
+
+  vpx_memset(pbi->above_seg_context, 0,
+             sizeof(*pbi->above_seg_context) * aligned_cols);
+
+  // Load tile data into tile_buffers
+  for (tile_row = 0; tile_row < tile_rows; ++tile_row) {
+    for (tile_col = 0; tile_col < tile_cols; ++tile_col) {
+      const int last_tile = tile_row == tile_rows - 1 &&
+                            tile_col == tile_cols - 1;
+      const size_t size = get_tile(data_end, last_tile, &cm->error, &data);
+      TileBuffer *const buf = &tile_buffers[tile_row][tile_col];
+      buf->data = data;
+      buf->size = size;
+      data += size;
+    }
+  }
+
+  // Decode tiles using data from tile_buffers
+  for (tile_row = 0; tile_row < tile_rows; ++tile_row) {
+    for (tile_col = 0; tile_col < tile_cols; ++tile_col) {
+      const int col = pbi->oxcf.inv_tile_order ? tile_cols - tile_col - 1
+                                               : tile_col;
+      const int last_tile = tile_row == tile_rows - 1 &&
+                                 col == tile_cols - 1;
+      const TileBuffer *const buf = &tile_buffers[tile_row][col];
+      TileInfo tile;
+
+      vp9_tile_init(&tile, cm, tile_row, col);
+      setup_token_decoder(buf->data, data_end, buf->size, &cm->error, &r);
+      setup_tile_context(pbi, xd, tile_row, col);
+      decode_tile(pbi, &tile, &r);
+
+      if (last_tile)
+        end = vp9_reader_find_end(&r);
+    }
+  }
+
+  return end;
+}
+
+static void setup_tile_macroblockd(TileWorkerData *const tile_data) {
+  MACROBLOCKD *xd = &tile_data->xd;
+  struct macroblockd_plane *const pd = xd->plane;
+  int i;
+
+  for (i = 0; i < MAX_MB_PLANE; ++i) {
+    pd[i].dqcoeff = tile_data->dqcoeff[i];
+    vpx_memset(xd->plane[i].dqcoeff, 0, 64 * 64 * sizeof(int16_t));
+  }
+}
+
+static int tile_worker_hook(void *arg1, void *arg2) {
+  TileWorkerData *const tile_data = (TileWorkerData*)arg1;
+  const TileInfo *const tile = (TileInfo*)arg2;
+  int mi_row, mi_col;
+
+  for (mi_row = tile->mi_row_start; mi_row < tile->mi_row_end;
+       mi_row += MI_BLOCK_SIZE) {
+    vp9_zero(tile_data->xd.left_context);
+    vp9_zero(tile_data->xd.left_seg_context);
+    for (mi_col = tile->mi_col_start; mi_col < tile->mi_col_end;
+         mi_col += MI_BLOCK_SIZE) {
+      decode_modes_sb(tile_data->cm, &tile_data->xd, tile,
+                      mi_row, mi_col, &tile_data->bit_reader, BLOCK_64X64);
+    }
+  }
+  return !tile_data->xd.corrupted;
+}
+
+// sorts in descending order
+static int compare_tile_buffers(const void *a, const void *b) {
+  const TileBuffer *const buf1 = (const TileBuffer*)a;
+  const TileBuffer *const buf2 = (const TileBuffer*)b;
+  if (buf1->size < buf2->size) {
+    return 1;
+  } else if (buf1->size == buf2->size) {
+    return 0;
+  } else {
+    return -1;
+  }
+}
+
+static const uint8_t *decode_tiles_mt(VP9D_COMP *pbi, const uint8_t *data) {
+  VP9_COMMON *const cm = &pbi->common;
+  const uint8_t *bit_reader_end = NULL;
+  const uint8_t *const data_end = pbi->source + pbi->source_sz;
+  const int aligned_mi_cols = mi_cols_aligned_to_sb(cm->mi_cols);
+  const int tile_cols = 1 << cm->log2_tile_cols;
+  const int tile_rows = 1 << cm->log2_tile_rows;
+  const int num_workers = MIN(pbi->oxcf.max_threads & ~1, tile_cols);
+  TileBuffer tile_buffers[1 << 6];
+  int n;
+  int final_worker = -1;
+
+  assert(tile_cols <= (1 << 6));
+  assert(tile_rows == 1);
+  (void)tile_rows;
+
+  if (num_workers > pbi->num_tile_workers) {
+    int i;
+    CHECK_MEM_ERROR(cm, pbi->tile_workers,
+                    vpx_realloc(pbi->tile_workers,
+                                num_workers * sizeof(*pbi->tile_workers)));
+    for (i = pbi->num_tile_workers; i < num_workers; ++i) {
+      VP9Worker *const worker = &pbi->tile_workers[i];
+      ++pbi->num_tile_workers;
+
+      vp9_worker_init(worker);
+      worker->hook = (VP9WorkerHook)tile_worker_hook;
+      CHECK_MEM_ERROR(cm, worker->data1,
+                      vpx_memalign(32, sizeof(TileWorkerData)));
+      CHECK_MEM_ERROR(cm, worker->data2, vpx_malloc(sizeof(TileInfo)));
+      if (i < num_workers - 1 && !vp9_worker_reset(worker)) {
+        vpx_internal_error(&cm->error, VPX_CODEC_ERROR,
+                           "Tile decoder thread creation failed");
+      }
+    }
+  }
+
+  // Note: this memset assumes above_context[0], [1] and [2]
+  // are allocated as part of the same buffer.
+  vpx_memset(pbi->above_context[0], 0,
+             sizeof(*pbi->above_context[0]) * MAX_MB_PLANE *
+             2 * aligned_mi_cols);
+  vpx_memset(pbi->above_seg_context, 0,
+             sizeof(*pbi->above_seg_context) * aligned_mi_cols);
+
+  // Load tile data into tile_buffers
+  for (n = 0; n < tile_cols; ++n) {
+    const size_t size =
+        get_tile(data_end, n == tile_cols - 1, &cm->error, &data);
+    TileBuffer *const buf = &tile_buffers[n];
+    buf->data = data;
+    buf->size = size;
+    buf->col = n;
+    data += size;
+  }
+
+  // Sort the buffers based on size in descending order.
+  qsort(tile_buffers, tile_cols, sizeof(tile_buffers[0]), compare_tile_buffers);
+
+  // Rearrange the tile buffers such that per-tile group the largest, and
+  // presumably the most difficult, tile will be decoded in the main thread.
+  // This should help minimize the number of instances where the main thread is
+  // waiting for a worker to complete.
+  {
+    int group_start = 0;
+    while (group_start < tile_cols) {
+      const TileBuffer largest = tile_buffers[group_start];
+      const int group_end = MIN(group_start + num_workers, tile_cols) - 1;
+      memmove(tile_buffers + group_start, tile_buffers + group_start + 1,
+              (group_end - group_start) * sizeof(tile_buffers[0]));
+      tile_buffers[group_end] = largest;
+      group_start = group_end + 1;
+    }
+  }
+
+  n = 0;
+  while (n < tile_cols) {
+    int i;
+    for (i = 0; i < num_workers && n < tile_cols; ++i) {
+      VP9Worker *const worker = &pbi->tile_workers[i];
+      TileWorkerData *const tile_data = (TileWorkerData*)worker->data1;
+      TileInfo *const tile = (TileInfo*)worker->data2;
+      TileBuffer *const buf = &tile_buffers[n];
+
+      tile_data->cm = cm;
+      tile_data->xd = pbi->mb;
+      tile_data->xd.corrupted = 0;
+      vp9_tile_init(tile, tile_data->cm, 0, buf->col);
+
+      setup_token_decoder(buf->data, data_end, buf->size, &cm->error,
+                          &tile_data->bit_reader);
+      setup_tile_context(pbi, &tile_data->xd, 0, buf->col);
+      setup_tile_macroblockd(tile_data);
+
+      worker->had_error = 0;
+      if (i == num_workers - 1 || n == tile_cols - 1) {
+        vp9_worker_execute(worker);
+      } else {
+        vp9_worker_launch(worker);
+      }
+
+      if (buf->col == tile_cols - 1) {
+        final_worker = i;
+      }
+
+      ++n;
+    }
+
+    for (; i > 0; --i) {
+      VP9Worker *const worker = &pbi->tile_workers[i - 1];
+      pbi->mb.corrupted |= !vp9_worker_sync(worker);
+    }
+    if (final_worker > -1) {
+      TileWorkerData *const tile_data =
+          (TileWorkerData*)pbi->tile_workers[final_worker].data1;
+      bit_reader_end = vp9_reader_find_end(&tile_data->bit_reader);
+      final_worker = -1;
+    }
+  }
+
+  return bit_reader_end;
+}
+
+static void check_sync_code(VP9_COMMON *cm, struct vp9_read_bit_buffer *rb) {
+  if (vp9_rb_read_literal(rb, 8) != VP9_SYNC_CODE_0 ||
+      vp9_rb_read_literal(rb, 8) != VP9_SYNC_CODE_1 ||
+      vp9_rb_read_literal(rb, 8) != VP9_SYNC_CODE_2) {
+    vpx_internal_error(&cm->error, VPX_CODEC_UNSUP_BITSTREAM,
+                       "Invalid frame sync code");
+  }
+}
+
+static void error_handler(void *data, size_t bit_offset) {
+  VP9_COMMON *const cm = (VP9_COMMON *)data;
+  vpx_internal_error(&cm->error, VPX_CODEC_CORRUPT_FRAME, "Truncated packet");
+}
+
+#define RESERVED \
+  if (vp9_rb_read_bit(rb)) \
+      vpx_internal_error(&cm->error, VPX_CODEC_UNSUP_BITSTREAM, \
+                         "Reserved bit must be unset")
+
+static size_t read_uncompressed_header(VP9D_COMP *pbi,
+                                       struct vp9_read_bit_buffer *rb) {
+  VP9_COMMON *const cm = &pbi->common;
+  size_t sz;
+  int i;
+
+  cm->last_frame_type = cm->frame_type;
+
+  if (vp9_rb_read_literal(rb, 2) != VP9_FRAME_MARKER)
+      vpx_internal_error(&cm->error, VPX_CODEC_UNSUP_BITSTREAM,
+                         "Invalid frame marker");
+
+  cm->version = vp9_rb_read_bit(rb);
+  RESERVED;
+
+  if (vp9_rb_read_bit(rb)) {
+    // show an existing frame directly
+    int frame_to_show = cm->ref_frame_map[vp9_rb_read_literal(rb, 3)];
+    ref_cnt_fb(cm->fb_idx_ref_cnt, &cm->new_fb_idx, frame_to_show);
+    pbi->refresh_frame_flags = 0;
+    cm->lf.filter_level = 0;
+    return 0;
+  }
+
+  cm->frame_type = (FRAME_TYPE) vp9_rb_read_bit(rb);
+  cm->show_frame = vp9_rb_read_bit(rb);
+  cm->error_resilient_mode = vp9_rb_read_bit(rb);
+
+  if (cm->frame_type == KEY_FRAME) {
+    check_sync_code(cm, rb);
+
+    cm->color_space = vp9_rb_read_literal(rb, 3);  // colorspace
+    if (cm->color_space != SRGB) {
+      vp9_rb_read_bit(rb);  // [16,235] (including xvycc) vs [0,255] range
+      if (cm->version == 1) {
+        cm->subsampling_x = vp9_rb_read_bit(rb);
+        cm->subsampling_y = vp9_rb_read_bit(rb);
+        vp9_rb_read_bit(rb);  // has extra plane
+      } else {
+        cm->subsampling_y = cm->subsampling_x = 1;
+      }
+    } else {
+      if (cm->version == 1) {
+        cm->subsampling_y = cm->subsampling_x = 0;
+        vp9_rb_read_bit(rb);  // has extra plane
+      } else {
+        vpx_internal_error(&cm->error, VPX_CODEC_UNSUP_BITSTREAM,
+                           "RGB not supported in profile 0");
+      }
+    }
+
+    pbi->refresh_frame_flags = (1 << REF_FRAMES) - 1;
+
+    for (i = 0; i < REFS_PER_FRAME; ++i)
+      cm->active_ref_idx[i] = cm->new_fb_idx;
+
+    setup_frame_size(pbi, rb);
+  } else {
+    cm->intra_only = cm->show_frame ? 0 : vp9_rb_read_bit(rb);
+
+    cm->reset_frame_context = cm->error_resilient_mode ?
+        0 : vp9_rb_read_literal(rb, 2);
+
+    if (cm->intra_only) {
+      check_sync_code(cm, rb);
+
+      pbi->refresh_frame_flags = vp9_rb_read_literal(rb, REF_FRAMES);
+      setup_frame_size(pbi, rb);
+    } else {
+      pbi->refresh_frame_flags = vp9_rb_read_literal(rb, REF_FRAMES);
+
+      for (i = 0; i < REFS_PER_FRAME; ++i) {
+        const int ref = vp9_rb_read_literal(rb, REF_FRAMES_LOG2);
+        cm->active_ref_idx[i] = cm->ref_frame_map[ref];
+        cm->ref_frame_sign_bias[LAST_FRAME + i] = vp9_rb_read_bit(rb);
+      }
+
+      setup_frame_size_with_refs(pbi, rb);
+
+      cm->allow_high_precision_mv = vp9_rb_read_bit(rb);
+      cm->mcomp_filter_type = read_interp_filter_type(rb);
+
+      for (i = 0; i < REFS_PER_FRAME; ++i) {
+        vp9_setup_scale_factors(cm, i);
+        if (vp9_is_scaled(&cm->active_ref_scale_comm[i]))
+          vp9_extend_frame_borders(&cm->yv12_fb[cm->active_ref_idx[i]],
+                                   cm->subsampling_x, cm->subsampling_y);
+      }
+    }
+  }
+
+  if (!cm->error_resilient_mode) {
+    cm->refresh_frame_context = vp9_rb_read_bit(rb);
+    cm->frame_parallel_decoding_mode = vp9_rb_read_bit(rb);
+  } else {
+    cm->refresh_frame_context = 0;
+    cm->frame_parallel_decoding_mode = 1;
+  }
+
+  // This flag will be overridden by the call to vp9_setup_past_independence
+  // below, forcing the use of context 0 for those frame types.
+  cm->frame_context_idx = vp9_rb_read_literal(rb, FRAME_CONTEXTS_LOG2);
+
+  if (frame_is_intra_only(cm) || cm->error_resilient_mode)
+    vp9_setup_past_independence(cm);
+
+  setup_loopfilter(&cm->lf, rb);
+  setup_quantization(cm, &pbi->mb, rb);
+  setup_segmentation(&cm->seg, rb);
+
+  setup_tile_info(cm, rb);
+  sz = vp9_rb_read_literal(rb, 16);
+
+  if (sz == 0)
+    vpx_internal_error(&cm->error, VPX_CODEC_CORRUPT_FRAME,
+                       "Invalid header size");
+
+  return sz;
+}
+
+static int read_compressed_header(VP9D_COMP *pbi, const uint8_t *data,
+                                  size_t partition_size) {
+  VP9_COMMON *const cm = &pbi->common;
+  MACROBLOCKD *const xd = &pbi->mb;
+  FRAME_CONTEXT *const fc = &cm->fc;
+  vp9_reader r;
+  int k;
+
+  if (vp9_reader_init(&r, data, partition_size))
+    vpx_internal_error(&cm->error, VPX_CODEC_MEM_ERROR,
+                       "Failed to allocate bool decoder 0");
+
+  cm->tx_mode = xd->lossless ? ONLY_4X4 : read_tx_mode(&r);
+  if (cm->tx_mode == TX_MODE_SELECT)
+    read_tx_mode_probs(&fc->tx_probs, &r);
+  read_coef_probs(fc, cm->tx_mode, &r);
+
+  for (k = 0; k < MBSKIP_CONTEXTS; ++k)
+    vp9_diff_update_prob(&r, &fc->mbskip_probs[k]);
+
+  if (!frame_is_intra_only(cm)) {
+    nmv_context *const nmvc = &fc->nmvc;
+    int i, j;
+
+    read_inter_mode_probs(fc, &r);
+
+    if (cm->mcomp_filter_type == SWITCHABLE)
+      read_switchable_interp_probs(fc, &r);
+
+    for (i = 0; i < INTRA_INTER_CONTEXTS; i++)
+      vp9_diff_update_prob(&r, &fc->intra_inter_prob[i]);
+
+    cm->reference_mode = read_reference_mode(cm, &r);
+    read_reference_mode_probs(cm, &r);
+
+    for (j = 0; j < BLOCK_SIZE_GROUPS; j++)
+      for (i = 0; i < INTRA_MODES - 1; ++i)
+        vp9_diff_update_prob(&r, &fc->y_mode_prob[j][i]);
+
+    for (j = 0; j < PARTITION_CONTEXTS; ++j)
+      for (i = 0; i < PARTITION_TYPES - 1; ++i)
+        vp9_diff_update_prob(&r, &fc->partition_prob[j][i]);
+
+    read_mv_probs(nmvc, cm->allow_high_precision_mv, &r);
+  }
+
+  return vp9_reader_has_error(&r);
+}
+
+void vp9_init_dequantizer(VP9_COMMON *cm) {
+  int q;
+
+  for (q = 0; q < QINDEX_RANGE; q++) {
+    cm->y_dequant[q][0] = vp9_dc_quant(q, cm->y_dc_delta_q);
+    cm->y_dequant[q][1] = vp9_ac_quant(q, 0);
+
+    cm->uv_dequant[q][0] = vp9_dc_quant(q, cm->uv_dc_delta_q);
+    cm->uv_dequant[q][1] = vp9_ac_quant(q, cm->uv_ac_delta_q);
+  }
+}
+
+#ifdef NDEBUG
+#define debug_check_frame_counts(cm) (void)0
+#else  // !NDEBUG
+// Counts should only be incremented when frame_parallel_decoding_mode and
+// error_resilient_mode are disabled.
+static void debug_check_frame_counts(const VP9_COMMON *const cm) {
+  FRAME_COUNTS zero_counts;
+  vp9_zero(zero_counts);
+  assert(cm->frame_parallel_decoding_mode || cm->error_resilient_mode);
+  assert(!memcmp(cm->counts.y_mode, zero_counts.y_mode,
+                 sizeof(cm->counts.y_mode)));
+  assert(!memcmp(cm->counts.uv_mode, zero_counts.uv_mode,
+                 sizeof(cm->counts.uv_mode)));
+  assert(!memcmp(cm->counts.partition, zero_counts.partition,
+                 sizeof(cm->counts.partition)));
+  assert(!memcmp(cm->counts.coef, zero_counts.coef,
+                 sizeof(cm->counts.coef)));
+  assert(!memcmp(cm->counts.eob_branch, zero_counts.eob_branch,
+                 sizeof(cm->counts.eob_branch)));
+  assert(!memcmp(cm->counts.switchable_interp, zero_counts.switchable_interp,
+                 sizeof(cm->counts.switchable_interp)));
+  assert(!memcmp(cm->counts.inter_mode, zero_counts.inter_mode,
+                 sizeof(cm->counts.inter_mode)));
+  assert(!memcmp(cm->counts.intra_inter, zero_counts.intra_inter,
+                 sizeof(cm->counts.intra_inter)));
+  assert(!memcmp(cm->counts.comp_inter, zero_counts.comp_inter,
+                 sizeof(cm->counts.comp_inter)));
+  assert(!memcmp(cm->counts.single_ref, zero_counts.single_ref,
+                 sizeof(cm->counts.single_ref)));
+  assert(!memcmp(cm->counts.comp_ref, zero_counts.comp_ref,
+                 sizeof(cm->counts.comp_ref)));
+  assert(!memcmp(&cm->counts.tx, &zero_counts.tx, sizeof(cm->counts.tx)));
+  assert(!memcmp(cm->counts.mbskip, zero_counts.mbskip,
+                 sizeof(cm->counts.mbskip)));
+  assert(!memcmp(&cm->counts.mv, &zero_counts.mv, sizeof(cm->counts.mv)));
+}
+#endif  // NDEBUG
+
+int vp9_decode_frame(VP9D_COMP *pbi, const uint8_t **p_data_end) {
+  int i;
+  VP9_COMMON *const cm = &pbi->common;
+  MACROBLOCKD *const xd = &pbi->mb;
+
+  const uint8_t *data = pbi->source;
+  const uint8_t *const data_end = pbi->source + pbi->source_sz;
+
+  struct vp9_read_bit_buffer rb = { data, data_end, 0, cm, error_handler };
+  const size_t first_partition_size = read_uncompressed_header(pbi, &rb);
+  const int keyframe = cm->frame_type == KEY_FRAME;
+  const int tile_rows = 1 << cm->log2_tile_rows;
+  const int tile_cols = 1 << cm->log2_tile_cols;
+  YV12_BUFFER_CONFIG *const new_fb = get_frame_new_buffer(cm);
+
+  if (!first_partition_size) {
+      // showing a frame directly
+      *p_data_end = data + 1;
+      return 0;
+  }
+
+  if (!pbi->decoded_key_frame && !keyframe)
+    return -1;
+
+  data += vp9_rb_bytes_read(&rb);
+  if (!read_is_valid(data, first_partition_size, data_end))
+    vpx_internal_error(&cm->error, VPX_CODEC_CORRUPT_FRAME,
+                       "Truncated packet or corrupt header length");
+
+  pbi->do_loopfilter_inline =
+      (cm->log2_tile_rows | cm->log2_tile_cols) == 0 && cm->lf.filter_level;
+  if (pbi->do_loopfilter_inline && pbi->lf_worker.data1 == NULL) {
+    CHECK_MEM_ERROR(cm, pbi->lf_worker.data1, vpx_malloc(sizeof(LFWorkerData)));
+    pbi->lf_worker.hook = (VP9WorkerHook)vp9_loop_filter_worker;
+    if (pbi->oxcf.max_threads > 1 && !vp9_worker_reset(&pbi->lf_worker)) {
+      vpx_internal_error(&cm->error, VPX_CODEC_ERROR,
+                         "Loop filter thread creation failed");
+    }
+  }
+
+  alloc_tile_storage(pbi, tile_rows, tile_cols);
+
+  xd->mode_info_stride = cm->mode_info_stride;
+  set_prev_mi(cm);
+
+  setup_plane_dequants(cm, xd, cm->base_qindex);
+  setup_block_dptrs(xd, cm->subsampling_x, cm->subsampling_y);
+
+  cm->fc = cm->frame_contexts[cm->frame_context_idx];
+  vp9_zero(cm->counts);
+  for (i = 0; i < MAX_MB_PLANE; ++i)
+    vpx_memset(xd->plane[i].dqcoeff, 0, 64 * 64 * sizeof(int16_t));
+
+  xd->corrupted = 0;
+  new_fb->corrupted = read_compressed_header(pbi, data, first_partition_size);
+
+  // TODO(jzern): remove frame_parallel_decoding_mode restriction for
+  // single-frame tile decoding.
+  if (pbi->oxcf.max_threads > 1 && tile_rows == 1 && tile_cols > 1 &&
+      cm->frame_parallel_decoding_mode) {
+    *p_data_end = decode_tiles_mt(pbi, data + first_partition_size);
+  } else {
+    *p_data_end = decode_tiles(pbi, data + first_partition_size);
+  }
+
+  cm->last_width = cm->width;
+  cm->last_height = cm->height;
+
+  new_fb->corrupted |= xd->corrupted;
+
+  if (!pbi->decoded_key_frame) {
+    if (keyframe && !new_fb->corrupted)
+      pbi->decoded_key_frame = 1;
+    else
+      vpx_internal_error(&cm->error, VPX_CODEC_CORRUPT_FRAME,
+                         "A stream must start with a complete key frame");
+  }
+
+  if (!cm->error_resilient_mode && !cm->frame_parallel_decoding_mode) {
+    vp9_adapt_coef_probs(cm);
+
+    if (!frame_is_intra_only(cm)) {
+      vp9_adapt_mode_probs(cm);
+      vp9_adapt_mv_probs(cm, cm->allow_high_precision_mv);
+    }
+  } else {
+    debug_check_frame_counts(cm);
+  }
+
+  if (cm->refresh_frame_context)
+    cm->frame_contexts[cm->frame_context_idx] = cm->fc;
+
+  return 0;
+}