LibVideo/VP9: Use an enum to select segment features

This throws out some ugly `#define`s we had that were taking the role
of an enum anyway. We now have some nice getters in the contexts that
take the place of the combo of `seg_feature_active()` and then doing a
lookup in `FrameContext::m_segmentation_features` directly.

Userland/Libraries/LibVideo/VP9/Context.h

@@ -143,7 +143,11 @@ public:
     bool use_predicted_segment_id_tree { false };
     Array<u8, 3> predicted_segment_id_tree_probabilities;
     bool should_use_absolute_segment_base_quantizer { false };
-    Array<Array<SegmentFeature, SEG_LVL_MAX>, MAX_SEGMENTS> segmentation_features;
+    SegmentationFeatures segmentation_features;
+    SegmentFeatureStatus get_segment_feature(u8 segment_id, SegmentFeature feature) const
+    {
+        return segmentation_features[segment_id][to_underlying(feature)];
+    }
 
     u16 header_size_in_bytes { 0 };
 
@@ -334,6 +338,11 @@ struct BlockContext {
     SegmentationPredictionContextView above_segmentation_ids;
     NonZeroTokensView left_non_zero_tokens;
     SegmentationPredictionContextView left_segmentation_ids;
+
+    SegmentFeatureStatus get_segment_feature(SegmentFeature feature) const
+    {
+        return frame_context.get_segment_feature(segment_id, feature);
+    }
 };
 
 struct BlockMotionVectorCandidateSet {

Userland/Libraries/LibVideo/VP9/ContextStorage.h

@@ -243,11 +243,14 @@ struct PersistentBlockContext {
     u8 segment_id { 0 };
 };
 
-struct SegmentFeature {
+struct SegmentFeatureStatus {
     bool enabled { false };
     u8 value { 0 };
 };
 
+using SegmentFeatures = Array<SegmentFeatureStatus, to_underlying(SegmentFeature::Sentinel)>;
+using SegmentationFeatures = Array<SegmentFeatures, MAX_SEGMENTS>;
+
 struct ColorConfig {
     u8 bit_depth { 8 };
     ColorSpace color_space { ColorSpace::Bt601 };

Userland/Libraries/LibVideo/VP9/Decoder.cpp

@@ -1173,9 +1173,10 @@ u8 Decoder::get_base_quantizer_index(BlockContext const& block_context)
 {
     // The function get_qindex( ) returns the quantizer index for the current block and is specified by the following:
     // − If seg_feature_active( SEG_LVL_ALT_Q ) is equal to 1 the following ordered steps apply:
-    if (Parser::seg_feature_active(block_context, SEG_LVL_ALT_Q)) {
+    auto alternative_quantizer_feature = block_context.get_segment_feature(SegmentFeature::UseAlternativeQuantizerBase);
+    if (alternative_quantizer_feature.enabled) {
         // 1. Set the variable data equal to FeatureData[ segment_id ][ SEG_LVL_ALT_Q ].
-        auto data = block_context.frame_context.segmentation_features[block_context.segment_id][SEG_LVL_ALT_Q].value;
+        auto data = alternative_quantizer_feature.value;
 
         // 2. If segmentation_abs_or_delta_update is equal to 0, set data equal to base_q_idx + data
         if (!block_context.frame_context.should_use_absolute_segment_base_quantizer) {

Userland/Libraries/LibVideo/VP9/Enums.h

@@ -161,4 +161,17 @@ enum Token : u8 {
     DctValCat6 = 10,
 };
 
+enum class SegmentFeature : u8 {
+    // SEG_LVL_ALT_Q
+    UseAlternativeQuantizerBase,
+    // SEG_LVL_ALT_L
+    UseAlternativeLoopFilterBase,
+    // SEG_LVL_REF_FRAME
+    ReferenceFrameOverride,
+    // SEG_LVL_SKIP
+    SkipResidualsOverride,
+    // SEG_LVL_MAX
+    Sentinel,
+};
+
 }

Userland/Libraries/LibVideo/VP9/LookupTables.h

@@ -15,8 +15,8 @@ namespace Video::VP9 {
 
 static constexpr InterpolationFilter literal_to_type[4] = { EightTapSmooth, EightTap, EightTapSharp, Bilinear };
 static constexpr TransformSize tx_mode_to_biggest_tx_size[TX_MODES] = { Transform_4x4, Transform_8x8, Transform_16x16, Transform_32x32, Transform_32x32 };
-static constexpr u8 segmentation_feature_bits[SEG_LVL_MAX] = { 8, 6, 2, 0 };
+static constexpr u8 segmentation_feature_bits[to_underlying(SegmentFeature::Sentinel)] = { 8, 6, 2, 0 };
-static constexpr bool segmentation_feature_signed[SEG_LVL_MAX] = { true, true, false, false };
+static constexpr bool segmentation_feature_signed[to_underlying(SegmentFeature::Sentinel)] = { true, true, false, false };
 static constexpr u8 inv_map_table[MAX_PROB] = {
     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,

Userland/Libraries/LibVideo/VP9/Parser.cpp

@@ -476,14 +476,14 @@ DecoderErrorOr<void> Parser::segmentation_params(FrameContext& frame_context)
         return {};
 
     frame_context.should_use_absolute_segment_base_quantizer = TRY_READ(frame_context.bit_stream.read_bit());
-    for (auto i = 0; i < MAX_SEGMENTS; i++) {
+    for (auto segment_id = 0; segment_id < MAX_SEGMENTS; segment_id++) {
-        for (auto j = 0; j < SEG_LVL_MAX; j++) {
+        for (auto feature_id = 0; feature_id < to_underlying(SegmentFeature::Sentinel); feature_id++) {
-            auto& feature = frame_context.segmentation_features[i][j];
+            auto& feature = frame_context.segmentation_features[segment_id][feature_id];
             feature.enabled = TRY_READ(frame_context.bit_stream.read_bit());
             if (feature.enabled) {
-                auto bits_to_read = segmentation_feature_bits[j];
+                auto bits_to_read = segmentation_feature_bits[feature_id];
                 feature.value = TRY_READ(frame_context.bit_stream.read_bits(bits_to_read));
-                if (segmentation_feature_signed[j]) {
+                if (segmentation_feature_signed[feature_id]) {
                     if (TRY_READ(frame_context.bit_stream.read_bit()))
                         feature.value = -feature.value;
                 }
@@ -1094,16 +1094,11 @@ DecoderErrorOr<void> Parser::set_intra_segment_id(BlockContext& block_context)
 
 DecoderErrorOr<bool> Parser::read_should_skip_residuals(BlockContext& block_context, FrameBlockContext above_context, FrameBlockContext left_context)
 {
-    if (seg_feature_active(block_context, SEG_LVL_SKIP))
+    if (block_context.get_segment_feature(SegmentFeature::SkipResidualsOverride).enabled)
         return true;
     return TRY_READ(TreeParser::parse_skip(block_context.decoder, *m_probability_tables, block_context.counter, above_context, left_context));
 }
 
-bool Parser::seg_feature_active(BlockContext const& block_context, u8 feature)
-{
-    return block_context.frame_context.segmentation_features[block_context.segment_id][feature].enabled;
-}
-
 DecoderErrorOr<TransformSize> Parser::read_tx_size(BlockContext& block_context, FrameBlockContext above_context, FrameBlockContext left_context, bool allow_select)
 {
     auto max_tx_size = max_txsize_lookup[block_context.size];
@@ -1176,8 +1171,9 @@ u8 Parser::get_segment_id(BlockContext const& block_context)
 
 DecoderErrorOr<bool> Parser::read_is_inter(BlockContext& block_context, FrameBlockContext above_context, FrameBlockContext left_context)
 {
-    if (seg_feature_active(block_context, SEG_LVL_REF_FRAME))
+    auto reference_frame_override_feature = block_context.get_segment_feature(SegmentFeature::ReferenceFrameOverride);
-        return block_context.frame_context.segmentation_features[block_context.segment_id][SEG_LVL_REF_FRAME].value != ReferenceFrameType::None;
+    if (reference_frame_override_feature.enabled)
+        return reference_frame_override_feature.value != ReferenceFrameType::None;
     return TRY_READ(TreeParser::parse_block_is_inter_predicted(block_context.decoder, *m_probability_tables, block_context.counter, above_context, left_context));
 }
 
@@ -1221,7 +1217,7 @@ DecoderErrorOr<void> Parser::inter_block_mode_info(BlockContext& block_context,
         select_best_reference_motion_vectors(block_context, reference_motion_vectors, motion_vector_candidates, ReferenceIndex::Secondary);
     }
 
-    if (seg_feature_active(block_context, SEG_LVL_SKIP)) {
+    if (block_context.get_segment_feature(SegmentFeature::SkipResidualsOverride).enabled) {
         block_context.y_prediction_mode() = PredictionMode::ZeroMv;
     } else if (block_context.size >= Block_8x8) {
         block_context.y_prediction_mode() = TRY_READ(TreeParser::parse_inter_mode(block_context.decoder, *m_probability_tables, block_context.counter, block_context.mode_context[block_context.reference_frame_types.primary]));
@@ -1259,8 +1255,9 @@ DecoderErrorOr<void> Parser::inter_block_mode_info(BlockContext& block_context,
 
 DecoderErrorOr<void> Parser::read_ref_frames(BlockContext& block_context, FrameBlockContext above_context, FrameBlockContext left_context)
 {
-    if (seg_feature_active(block_context, SEG_LVL_REF_FRAME)) {
+    auto reference_frame_override_feature = block_context.get_segment_feature(SegmentFeature::ReferenceFrameOverride);
-        block_context.reference_frame_types = { static_cast<ReferenceFrameType>(block_context.frame_context.segmentation_features[block_context.segment_id][SEG_LVL_REF_FRAME].value), ReferenceFrameType::None };
+    if (reference_frame_override_feature.enabled) {
+        block_context.reference_frame_types = { static_cast<ReferenceFrameType>(reference_frame_override_feature.value), ReferenceFrameType::None };
         return {};
     }
 

Userland/Libraries/LibVideo/VP9/Parser.h

@@ -98,7 +98,6 @@ private:
     DecoderErrorOr<void> intra_frame_mode_info(BlockContext&, FrameBlockContext above_context, FrameBlockContext left_context);
     DecoderErrorOr<void> set_intra_segment_id(BlockContext&);
     DecoderErrorOr<bool> read_should_skip_residuals(BlockContext&, FrameBlockContext above_context, FrameBlockContext left_context);
-    static bool seg_feature_active(BlockContext const&, u8 feature);
     DecoderErrorOr<TransformSize> read_tx_size(BlockContext&, FrameBlockContext above_context, FrameBlockContext left_context, bool allow_select);
     DecoderErrorOr<void> inter_frame_mode_info(BlockContext&, FrameBlockContext above_context, FrameBlockContext left_context);
     DecoderErrorOr<void> set_inter_segment_id(BlockContext&);
@@ -130,7 +129,7 @@ private:
     Array<i8, MAX_REF_FRAMES> m_previous_loop_filter_ref_deltas;
     Array<i8, 2> m_previous_loop_filter_mode_deltas;
     bool m_previous_should_use_absolute_segment_base_quantizer;
-    Array<Array<SegmentFeature, SEG_LVL_MAX>, MAX_SEGMENTS> m_previous_segmentation_features;
+    SegmentationFeatures m_previous_segmentation_features;
 
     ReferenceFrame m_reference_frames[NUM_REF_FRAMES];
 

Userland/Libraries/LibVideo/VP9/Symbols.h

@@ -33,11 +33,6 @@ namespace Video::VP9 {
 #define COMP_MODE_CONTEXTS 5
 #define REF_CONTEXTS 5
 #define MAX_SEGMENTS 8
-#define SEG_LVL_ALT_Q 0
-#define SEG_LVL_ALT_L 1
-#define SEG_LVL_REF_FRAME 2
-#define SEG_LVL_SKIP 3
-#define SEG_LVL_MAX 4
 #define BLOCK_TYPES 2
 #define REF_TYPES 2
 #define COEF_BANDS 6