Parse VP9 compressed header

media/filters/vp9_compressed_header_parser.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "media/filters/vp9_compressed_header_parser.h"
+
+#include "base/logging.h"

[Pawel Osciak, 2016/08/04 10:20:18]

Nit: header out of order.

[kcwu, 2016/08/05 11:38:47]

vp9_compressed_header_parser.h first because it's corresponding header of this
.cc.

+
+namespace media {
+
+namespace {
+
+// 6.3.6 Inv recenter noneg syntax
+int inv_recenter_nonneg(int v, int m) {

[Pawel Osciak, 2016/08/04 10:20:18]

I know this is to match the spec, but I think we should use CamelCase, and
perhaps just keep this name in the comment?

[kcwu, 2016/08/05 11:38:47]

Done.

+  DCHECK_LE(m, kVp9MaxProb / 2);
+  if (v > 2 * m)
+    return v;
+
+  if (v & 1)
+    return m - ((v + 1) >> 1);
+  return m + (v >> 1);
+}
+
+// 6.3.5 Inv remap prob syntax
+int inv_remap_prob(int delta_prob, int prob) {
+  static uint8_t inv_map_table[kVp9MaxProb] = {
+      7,   20,  33,  46,  59,  72,  85,  98,  111, 124, 137, 150, 163, 176,
+      189, 202, 215, 228, 241, 254, 1,   2,   3,   4,   5,   6,   8,   9,
+      10,  11,  12,  13,  14,  15,  16,  17,  18,  19,  21,  22,  23,  24,
+      25,  26,  27,  28,  29,  30,  31,  32,  34,  35,  36,  37,  38,  39,
+      40,  41,  42,  43,  44,  45,  47,  48,  49,  50,  51,  52,  53,  54,
+      55,  56,  57,  58,  60,  61,  62,  63,  64,  65,  66,  67,  68,  69,
+      70,  71,  73,  74,  75,  76,  77,  78,  79,  80,  81,  82,  83,  84,
+      86,  87,  88,  89,  90,  91,  92,  93,  94,  95,  96,  97,  99,  100,
+      101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 112, 113, 114, 115,
+      116, 117, 118, 119, 120, 121, 122, 123, 125, 126, 127, 128, 129, 130,
+      131, 132, 133, 134, 135, 136, 138, 139, 140, 141, 142, 143, 144, 145,
+      146, 147, 148, 149, 151, 152, 153, 154, 155, 156, 157, 158, 159, 160,
+      161, 162, 164, 165, 166, 167, 168, 169, 170, 171, 172, 173, 174, 175,
+      177, 178, 179, 180, 181, 182, 183, 184, 185, 186, 187, 188, 190, 191,
+      192, 193, 194, 195, 196, 197, 198, 199, 200, 201, 203, 204, 205, 206,
+      207, 208, 209, 210, 211, 212, 213, 214, 216, 217, 218, 219, 220, 221,
+      222, 223, 224, 225, 226, 227, 229, 230, 231, 232, 233, 234, 235, 236,
+      237, 238, 239, 240, 242, 243, 244, 245, 246, 247, 248, 249, 250, 251,
+      252, 253, 253};
+  int m = prob;
+  int v = delta_prob;
+  DCHECK_GE(m, 1);
+  DCHECK_LE(m, kVp9MaxProb);
+  DCHECK_LT(static_cast<size_t>(v), arraysize(inv_map_table));
+  v = inv_map_table[v];
+  m--;
+  if ((m << 1) <= kVp9MaxProb) {
+    return 1 + inv_recenter_nonneg(v, m);
+  } else {
+    return kVp9MaxProb - inv_recenter_nonneg(v, kVp9MaxProb - 1 - m);
+  }
+}
+
+}  // namespace
+
+Vp9CompressedHeaderParser::Vp9CompressedHeaderParser() {}
+
+// 6.3.1 Tx mode syntax
+void Vp9CompressedHeaderParser::ReadTxMode(Vp9FrameHeader* fhdr) {
+  int tx_mode;
+  if (fhdr->quant_params.IsLossless()) {
+    tx_mode = ONLY_4X4;
+  } else {
+    tx_mode = reader_.ReadLiteral(2);
+    if (tx_mode == ALLOW_32X32)
+      tx_mode += reader_.ReadLiteral(1);
+  }
+  fhdr->compressed_header.tx_mode = static_cast<Vp9TxMode>(tx_mode);
+}
+
+// 6.3.4 Decode term subexp syntax
+int Vp9CompressedHeaderParser::DecodeTermSubexp() {
+  if (reader_.ReadLiteral(1) == 0)
+    return reader_.ReadLiteral(4);
+  if (reader_.ReadLiteral(1) == 0)
+    return reader_.ReadLiteral(4) + 16;
+  if (reader_.ReadLiteral(1) == 0)
+    return reader_.ReadLiteral(5) + 32;
+  int v = reader_.ReadLiteral(7);
+  if (v < 65)
+    return v + 64;
+  return (v << 1) - 1 + reader_.ReadLiteral(1);
+}
+
+// 6.3.3 Diff update prob syntax
+void Vp9CompressedHeaderParser::DiffUpdateProb(Vp9Prob* prob) {
+  const Vp9Prob kUpdateProb = 252;
+  if (reader_.ReadBool(kUpdateProb)) {
+    int delta_prob = DecodeTermSubexp();
+    *prob = inv_remap_prob(delta_prob, *prob);
+  }
+}
+
+// Helper function to DiffUpdateProb an array of probs.
+template <int N>
+void Vp9CompressedHeaderParser::DiffUpdateProbArray(Vp9Prob (&prob_array)[N]) {
+  for (auto& x : prob_array) {
+    DiffUpdateProb(&x);
+  }
+}
+
+// 6.3.2 Tx mode probs syntax
+void Vp9CompressedHeaderParser::ReadTxModeProbs(
+    Vp9FrameContext* frame_context) {
+  for (auto& a : frame_context->tx_probs_8x8) {
+    DiffUpdateProbArray(a);
+  }
+  for (auto& a : frame_context->tx_probs_16x16) {
+    DiffUpdateProbArray(a);
+  }
+  for (auto& a : frame_context->tx_probs_32x32) {
+    DiffUpdateProbArray(a);
+  }
+}
+
+// 6.3.7 Coef probs syntax
+void Vp9CompressedHeaderParser::ReadCoefProbs(Vp9FrameHeader* fhdr) {
+  const Vp9TxSize tx_mode_to_biggest_tx_size[TX_MODES] = {
+      TX_4X4, TX_8X8, TX_16X16, TX_32X32, TX_32X32,
+  };
+
+  const Vp9TxSize max_tx_size =
+      tx_mode_to_biggest_tx_size[fhdr->compressed_header.tx_mode];
+  for (int tx_size = TX_4X4; tx_size <= max_tx_size; tx_size++) {
+    if (reader_.ReadLiteral(1) == 0)
+      continue;
+
+    for (auto& ai : fhdr->frame_context.coef_probs[tx_size]) {
+      for (auto& aj : ai) {
+        for (auto& ak : aj) {
+          int max_l = (ak == aj[0]) ? 3 : 6;
+          for (int l = 0; l < max_l; l++) {
+            DiffUpdateProbArray(ak[l]);
+          }
+        }
+      }
+    }
+  }
+}
+
+// 6.3.8 Skip probs syntax
+void Vp9CompressedHeaderParser::ReadSkipProb(Vp9FrameContext* frame_context) {
+  DiffUpdateProbArray(frame_context->skip_prob);
+}
+
+// 6.3.9 Inter mode probs syntax
+void Vp9CompressedHeaderParser::ReadInterModeProbs(
+    Vp9FrameContext* frame_context) {
+  for (auto& a : frame_context->inter_mode_probs)
+    DiffUpdateProbArray(a);
+}
+
+// 6.3.10 Interp filter probs syntax
+void Vp9CompressedHeaderParser::ReadInterpFilterProbs(
+    Vp9FrameContext* frame_context) {
+  for (auto& a : frame_context->interp_filter_probs)
+    DiffUpdateProbArray(a);
+}
+
+// 6.3.11 Intra inter probs syntax
+void Vp9CompressedHeaderParser::ReadIsInterProbs(
+    Vp9FrameContext* frame_context) {
+  DiffUpdateProbArray(frame_context->is_inter_prob);
+}
+
+// 6.3.12 Frame reference mode syntax
+void Vp9CompressedHeaderParser::ReadFrameReferenceMode(Vp9FrameHeader* fhdr) {
+  bool compound_reference_allowed = false;
+  for (int i = VP9_FRAME_LAST + 1; i < VP9_FRAME_MAX; i++)
+    if (fhdr->ref_frame_sign_bias[i] != fhdr->ref_frame_sign_bias[1])
+      compound_reference_allowed = true;
+
+  if (compound_reference_allowed && reader_.ReadLiteral(1)) {
+    fhdr->compressed_header.reference_mode =
+        reader_.ReadLiteral(1) ? REFERENCE_MODE_SELECT : COMPOUND_REFERENCE;
+  } else {
+    fhdr->compressed_header.reference_mode = SINGLE_REFERENCE;
+  }
+}
+
+// 6.3.13 Frame reference mode probs syntax
+void Vp9CompressedHeaderParser::ReadFrameReferenceModeProbs(
+    Vp9FrameHeader* fhdr) {
+  Vp9FrameContext* frame_context = &fhdr->frame_context;
+  if (fhdr->compressed_header.reference_mode == REFERENCE_MODE_SELECT)
+    DiffUpdateProbArray(frame_context->comp_mode_prob);
+
+  if (fhdr->compressed_header.reference_mode != COMPOUND_REFERENCE)
+    for (auto& a : frame_context->single_ref_prob)
+      DiffUpdateProbArray(a);
+
+  if (fhdr->compressed_header.reference_mode != SINGLE_REFERENCE)
+    DiffUpdateProbArray(frame_context->comp_ref_prob);
+}
+
+// 6.3.14 Y mode probs syntax
+void Vp9CompressedHeaderParser::ReadYModeProbs(Vp9FrameContext* frame_context) {
+  for (auto& a : frame_context->y_mode_probs)
+    DiffUpdateProbArray(a);
+}
+
+// 6.3.15 Partition probs syntax
+void Vp9CompressedHeaderParser::ReadPartitionProbs(
+    Vp9FrameContext* frame_context) {
+  for (auto& a : frame_context->partition_probs)
+    DiffUpdateProbArray(a);
+}
+
+// 6.3.16 MV probs syntax
+void Vp9CompressedHeaderParser::ReadMvProbs(bool allow_high_precision_mv,
+                                            Vp9FrameContext* frame_context) {
+  UpdateMvProbArray(frame_context->mv_joint_probs);
+
+  for (int i = 0; i < 2; i++) {
+    UpdateMvProb(&frame_context->mv_sign_prob[i]);
+    UpdateMvProbArray(frame_context->mv_class_probs[i]);
+    UpdateMvProb(&frame_context->mv_class0_bit_prob[i]);
+    UpdateMvProbArray(frame_context->mv_bits_prob[i]);
+  }
+
+  for (int i = 0; i < 2; i++) {
+    for (auto& a : frame_context->mv_class0_fr_probs[i])
+      UpdateMvProbArray(a);
+    UpdateMvProbArray(frame_context->mv_fr_probs[i]);
+  }
+
+  if (allow_high_precision_mv) {
+    for (int i = 0; i < 2; i++) {
+      UpdateMvProb(&frame_context->mv_class0_hp_prob[i]);
+      UpdateMvProb(&frame_context->mv_hp_prob[i]);
+    }
+  }
+}
+
+// 6.3.17 Update mv prob syntax
+void Vp9CompressedHeaderParser::UpdateMvProb(Vp9Prob* prob) {
+  if (reader_.ReadBool(252))
+    *prob = reader_.ReadLiteral(7) << 1 | 1;
+}
+
+// Helper function to UpdateMvProb an array of probs.
+template <int N>
+void Vp9CompressedHeaderParser::UpdateMvProbArray(Vp9Prob (&prob_array)[N]) {
+  for (auto& x : prob_array) {
+    UpdateMvProb(&x);
+  }
+}
+
+// 6.3 Compressed header syntax
+bool Vp9CompressedHeaderParser::Parse(const uint8_t* stream,
+                                      off_t frame_size,
+                                      Vp9FrameHeader* fhdr) {
+  DVLOG(2) << "CompressedHeaderParser::Parse";
+  if (!reader_.Initialize(stream, frame_size))
+    return false;
+
+  ReadTxMode(fhdr);
+  if (fhdr->compressed_header.tx_mode == TX_MODE_SELECT)
+    ReadTxModeProbs(&fhdr->frame_context);
+
+  ReadCoefProbs(fhdr);
+  ReadSkipProb(&fhdr->frame_context);
+
+  if (!fhdr->IsIntra()) {
+    ReadInterModeProbs(&fhdr->frame_context);
+    if (fhdr->interpolation_filter == SWITCHABLE)
+      ReadInterpFilterProbs(&fhdr->frame_context);
+    ReadIsInterProbs(&fhdr->frame_context);
+    ReadFrameReferenceMode(fhdr);
+    ReadFrameReferenceModeProbs(fhdr);
+    ReadYModeProbs(&fhdr->frame_context);
+    ReadPartitionProbs(&fhdr->frame_context);
+    ReadMvProbs(fhdr->allow_high_precision_mv, &fhdr->frame_context);
+  }
+
+  if (!reader_.IsValid()) {
+    DVLOG(1) << "parser reads beyond the end of buffer";
+    return false;
+  }
+  if (!reader_.ConsumePaddingBits()) {
+    DVLOG(1) << "padding bits are not zero";
+    return false;
+  }
+  return true;
+}
+
+}  // namespace media