LibVideo: Parameterize parsing of the default VP9 intra mode tree

Userland/Libraries/LibVideo/VP9/Parser.cpp

@@ -1017,8 +1017,19 @@ DecoderErrorOr<void> Parser::intra_frame_mode_info()
     m_ref_frame[0] = IntraFrame;
     m_ref_frame[1] = None;
     m_is_inter = false;
+    // FIXME: This if statement is also present in parse_default_intra_mode. The selection of parameters for
+    //        the probability table lookup should be inlined here.
     if (m_mi_size >= Block_8x8) {
-        m_default_intra_mode = TRY_READ(m_tree_parser->parse_tree<PredictionMode>(SyntaxElementType::DefaultIntraMode));
+        // FIXME: This context should be available in the block setup. Make a struct to store the context
+        //        that is needed to call the tree parses and set it in decode_block().
+        auto above_context = Optional<Array<PredictionMode, 4> const&>();
+        auto left_context = Optional<Array<PredictionMode, 4> const&>();
+        if (m_available_u)
+            above_context = m_sub_modes[get_image_index(m_mi_row - 1, m_mi_col)];
+        if (m_available_l)
+            left_context = m_sub_modes[get_image_index(m_mi_row, m_mi_col - 1)];
+        m_default_intra_mode = TRY_READ(TreeParser::parse_default_intra_mode(*m_bit_stream, *m_probability_tables, m_mi_size, above_context, left_context, m_block_sub_modes, 0, 0));
+
         m_y_mode = m_default_intra_mode;
         for (auto& block_sub_mode : m_block_sub_modes)
             block_sub_mode = m_y_mode;
@@ -1027,8 +1038,15 @@ DecoderErrorOr<void> Parser::intra_frame_mode_info()
         m_num_4x4_h = num_4x4_blocks_high_lookup[m_mi_size];
         for (auto idy = 0; idy < 2; idy += m_num_4x4_h) {
             for (auto idx = 0; idx < 2; idx += m_num_4x4_w) {
-                m_tree_parser->set_default_intra_mode_variables(idx, idy);
+                // FIXME: See the FIXME above.
-                m_default_intra_mode = TRY_READ(m_tree_parser->parse_tree<PredictionMode>(SyntaxElementType::DefaultIntraMode));
+                auto above_context = Optional<Array<PredictionMode, 4> const&>();
+                auto left_context = Optional<Array<PredictionMode, 4> const&>();
+                if (m_available_u)
+                    above_context = m_sub_modes[get_image_index(m_mi_row - 1, m_mi_col)];
+                if (m_available_l)
+                    left_context = m_sub_modes[get_image_index(m_mi_row, m_mi_col - 1)];
+                m_default_intra_mode = TRY_READ(TreeParser::parse_default_intra_mode(*m_bit_stream, *m_probability_tables, m_mi_size, above_context, left_context, m_block_sub_modes, idx, idy));
+
                 for (auto y = 0; y < m_num_4x4_h; y++) {
                     for (auto x = 0; x < m_num_4x4_w; x++) {
                         auto index = (idy + y) * 2 + idx + x;

Userland/Libraries/LibVideo/VP9/Parser.h

@@ -243,6 +243,9 @@ private:
     u8 m_num_4x4_w { 0 };
     u8 m_num_4x4_h { 0 };
     PredictionMode m_uv_mode { 0 }; // FIXME: Is u8 the right size?
+    // FIXME: From spec: NOTE – We are using a 2D array to store the SubModes for clarity. It is possible to reduce memory
+    // consumption by only storing one intra mode for each 8x8 horizontal and vertical position, i.e. to use two 1D
+    // arrays instead.
     Vector<Array<PredictionMode, 4>> m_sub_modes;
     ReferenceFramePair m_left_ref_frame;
     ReferenceFramePair m_above_ref_frame;

Userland/Libraries/LibVideo/VP9/TreeParser.cpp

@@ -7,10 +7,10 @@
 
 #include <AK/Function.h>
 
-#include "TreeParser.h"
 #include "Enums.h"
 #include "LookupTables.h"
 #include "Parser.h"
+#include "TreeParser.h"
 
 namespace Video::VP9 {
 
@@ -104,13 +104,42 @@ ErrorOr<Partition> TreeParser::parse_partition(BitStream& bit_stream, Probabilit
     return value;
 }
 
+ErrorOr<PredictionMode> TreeParser::parse_default_intra_mode(BitStream& bit_stream, ProbabilityTables const& probability_table, BlockSubsize mi_size, Optional<Array<PredictionMode, 4> const&> above_context, Optional<Array<PredictionMode, 4> const&> left_context, PredictionMode block_sub_modes[4], u8 index_x, u8 index_y)
+{
+    // FIXME: This should use a struct for the above and left contexts.
+
+    // Tree
+    TreeParser::TreeSelection tree = { intra_mode_tree };
+
+    // Probabilities
+    PredictionMode above_mode, left_mode;
+    if (mi_size >= Block_8x8) {
+        above_mode = above_context.has_value() ? above_context.value()[2] : PredictionMode::DcPred;
+        left_mode = left_context.has_value() ? left_context.value()[1] : PredictionMode::DcPred;
+    } else {
+        if (index_y > 0)
+            above_mode = block_sub_modes[index_x];
+        else
+            above_mode = above_context.has_value() ? above_context.value()[2 + index_x] : PredictionMode::DcPred;
+
+        if (index_x > 0)
+            left_mode = block_sub_modes[index_y << 1];
+        else
+            left_mode = left_context.has_value() ? left_context.value()[1 + (index_y << 1)] : PredictionMode::DcPred;
+    }
+    u8 const* probabilities = probability_table.kf_y_mode_probs()[to_underlying(above_mode)][to_underlying(left_mode)];
+
+    auto value = TRY(parse_tree_new<PredictionMode>(bit_stream, tree, [&](u8 node) { return probabilities[node]; }));
+    // Default intra mode is not counted.
+    return value;
+}
+
 /*
  * Select a tree value based on the type of syntax element being parsed, as well as some parser state, as specified in section 9.3.1
  */
 TreeParser::TreeSelection TreeParser::select_tree(SyntaxElementType type)
 {
     switch (type) {
-    case SyntaxElementType::DefaultIntraMode:
     case SyntaxElementType::DefaultUVMode:
     case SyntaxElementType::IntraMode:
     case SyntaxElementType::SubIntraMode:
@@ -166,8 +195,6 @@ TreeParser::TreeSelection TreeParser::select_tree(SyntaxElementType type)
 u8 TreeParser::select_tree_probability(SyntaxElementType type, u8 node)
 {
     switch (type) {
-    case SyntaxElementType::DefaultIntraMode:
-        return calculate_default_intra_mode_probability(node);
     case SyntaxElementType::DefaultUVMode:
         return calculate_default_uv_mode_probability(node);
     case SyntaxElementType::IntraMode:
@@ -241,36 +268,6 @@ u8 TreeParser::select_tree_probability(SyntaxElementType type, u8 node)
 #define ABOVE_SINGLE m_decoder.m_above_single
 #define LEFT_SINGLE m_decoder.m_left_single
 
-u8 TreeParser::calculate_default_intra_mode_probability(u8 node)
-{
-    PredictionMode above_mode, left_mode;
-    if (m_decoder.m_mi_size >= Block_8x8) {
-        above_mode = AVAIL_U
-            ? m_decoder.m_sub_modes[m_decoder.get_image_index(m_decoder.m_mi_row - 1, m_decoder.m_mi_col)][2]
-            : PredictionMode::DcPred;
-        left_mode = AVAIL_L
-            ? m_decoder.m_sub_modes[m_decoder.get_image_index(m_decoder.m_mi_row, m_decoder.m_mi_col - 1)][1]
-            : PredictionMode::DcPred;
-    } else {
-        if (m_idy) {
-            above_mode = m_decoder.m_block_sub_modes[m_idx];
-        } else {
-            above_mode = AVAIL_U
-                ? m_decoder.m_sub_modes[m_decoder.get_image_index(m_decoder.m_mi_row - 1, m_decoder.m_mi_col)][2 + m_idx]
-                : PredictionMode::DcPred;
-        }
-
-        if (m_idx) {
-            left_mode = m_decoder.m_block_sub_modes[m_idy * 2];
-        } else {
-            left_mode = AVAIL_L
-                ? m_decoder.m_sub_modes[m_decoder.get_image_index(m_decoder.m_mi_row, m_decoder.m_mi_col - 1)][1 + m_idy * 2]
-                : PredictionMode::DcPred;
-        }
-    }
-    return m_decoder.m_probability_tables->kf_y_mode_probs()[to_underlying(above_mode)][to_underlying(left_mode)][node];
-}
-
 u8 TreeParser::calculate_default_uv_mode_probability(u8 node)
 {
     return m_decoder.m_probability_tables->kf_uv_mode_prob()[to_underlying(m_decoder.m_y_mode)][node];
@@ -772,7 +769,6 @@ void TreeParser::count_syntax_element(SyntaxElementType type, int value)
     case SyntaxElementType::MoreCoefs:
         increment(m_decoder.m_syntax_element_counter->m_counts_more_coefs[m_tx_size][m_plane > 0][m_decoder.m_is_inter][m_band][m_ctx][value]);
         return;
-    case SyntaxElementType::DefaultIntraMode:
     case SyntaxElementType::DefaultUVMode:
     case SyntaxElementType::SegmentID:
     case SyntaxElementType::SegIDPredicted:

Userland/Libraries/LibVideo/VP9/TreeParser.h

@@ -63,6 +63,7 @@ public:
     void count_syntax_element(SyntaxElementType type, int value);
 
     static ErrorOr<Partition> parse_partition(BitStream&, ProbabilityTables const&, SyntaxElementCounter&, bool has_rows, bool has_columns, BlockSubsize block_subsize, u8 num_8x8, Vector<u8> const& above_partition_context, Vector<u8> const& left_partition_context, u32 row, u32 column, bool frame_is_intra);
+    static ErrorOr<PredictionMode> parse_default_intra_mode(BitStream&, ProbabilityTables const&, BlockSubsize mi_size, Optional<Array<PredictionMode, 4> const&> above_context, Optional<Array<PredictionMode, 4> const&> left_context, PredictionMode block_sub_modes[4], u8 index_x, u8 index_y);
 
     void set_default_intra_mode_variables(u8 idx, u8 idy)
     {
@@ -96,7 +97,6 @@ public:
     }
 
 private:
-    u8 calculate_default_intra_mode_probability(u8 node);
     u8 calculate_default_uv_mode_probability(u8 node);
     u8 calculate_intra_mode_probability(u8 node);
     u8 calculate_sub_intra_mode_probability(u8 node);