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LibGfx/LibVideo: Check for overreads only at end of a VPX range decode

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Errors are now deferred until `finish_decode()` is finished, meaning
branches to return errors only need to occur at the end of a ranged
decode. If VPX_DEBUG is enabled, a debug message will be printed
immediately when an overread occurs.

Average decoding times for `Tests/LibGfx/test-inputs/4.webp` improve
by about 4.7% with this change, absolute decode times changing from
27.4ms±1.1ms down to 26.1ms±1.0ms.
This commit is contained in:
Zaggy1024 2023-06-01 19:16:57 -05:00 • committed by Andreas Kling
parent 873b0e9470
commit 24ae35086d
8 changed files with 353 additions and 366 deletions
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129
Userland/Libraries/LibGfx/ImageFormats/WebPLoaderLossy.cpp
View file

@ -107,11 +107,11 @@ ErrorOr<VP8Header> decode_webp_chunk_VP8_header(ReadonlyBytes vp8_data)
namespace {
// Reads n bits followed by a sign bit (0: positive, 1: negative).
ErrorOr<i8> read_signed_literal(BooleanDecoder& decoder, u8 n)
i8 read_signed_literal(BooleanDecoder& decoder, u8 n)
{
VERIFY(n <= 7);
i8 i = TRY(decoder.read_literal(n));
if (TRY(decoder.read_literal(1)))
i8 i = decoder.read_literal(n);
if (decoder.read_literal(1))
i = -i;
return i;
}
@ -139,7 +139,7 @@ struct Segmentation {
u8 macroblock_segment_tree_probabilities[3] = { 255, 255, 255 };
};
ErrorOr<Segmentation> decode_VP8_frame_header_segmentation(BooleanDecoder&);
Segmentation decode_VP8_frame_header_segmentation(BooleanDecoder&);
// Also https://datatracker.ietf.org/doc/html/rfc6386#section-9.6 "Dequantization Indices"
struct QuantizationIndices {
@ -152,14 +152,14 @@ struct QuantizationIndices {
i8 uv_dc_delta { 0 };
i8 uv_ac_delta { 0 };
};
ErrorOr<QuantizationIndices> decode_VP8_frame_header_quantization_indices(BooleanDecoder&);
QuantizationIndices decode_VP8_frame_header_quantization_indices(BooleanDecoder&);
struct LoopFilterAdjustment {
bool enable_loop_filter_adjustment { false };
i8 ref_frame_delta[4] {};
i8 mb_mode_delta[4] {};
};
ErrorOr<LoopFilterAdjustment> decode_VP8_frame_header_loop_filter_adjustment(BooleanDecoder&);
LoopFilterAdjustment decode_VP8_frame_header_loop_filter_adjustment(BooleanDecoder&);
using CoefficientProbabilities = Prob[4][8][3][num_dct_tokens - 1];
ErrorOr<void> decode_VP8_frame_header_coefficient_probabilities(BooleanDecoder&, CoefficientProbabilities);
@ -210,42 +210,42 @@ ErrorOr<FrameHeader> decode_VP8_frame_header(BooleanDecoder& decoder)
FrameHeader header;
// In the VP8 spec, this is in an `if (key_frames)`, but webp files only have key frames.
header.color_space = ColorSpaceAndPixelType { TRY(L(1)) };
header.clamping_type = ClampingSpecification { TRY(L(1)) };
header.color_space = ColorSpaceAndPixelType { L(1) };
header.clamping_type = ClampingSpecification { L(1) };
dbgln_if(WEBP_DEBUG, "color_space {} clamping_type {}", (int)header.color_space, (int)header.clamping_type);
// https://datatracker.ietf.org/doc/html/rfc6386#section-9.3 "Segment-Based Adjustments"
header.is_segmentation_enabled = TRY(L(1));
header.is_segmentation_enabled = L(1);
dbgln_if(WEBP_DEBUG, "segmentation_enabled {}", header.is_segmentation_enabled);
if (header.is_segmentation_enabled)
header.segmentation = TRY(decode_VP8_frame_header_segmentation(decoder));
header.segmentation = decode_VP8_frame_header_segmentation(decoder);
header.filter_type = FilterType { TRY(L(1)) };
header.loop_filter_level = TRY(L(6));
header.sharpness_level = TRY(L(3));
header.filter_type = FilterType { L(1) };
header.loop_filter_level = L(6);
header.sharpness_level = L(3);
dbgln_if(WEBP_DEBUG, "filter_type {} loop_filter_level {} sharpness_level {}", (int)header.filter_type, header.loop_filter_level, header.sharpness_level);
header.loop_filter_adjustment = TRY(decode_VP8_frame_header_loop_filter_adjustment(decoder));
header.loop_filter_adjustment = decode_VP8_frame_header_loop_filter_adjustment(decoder);
u8 log2_nbr_of_dct_partitions = TRY(L(2));
u8 log2_nbr_of_dct_partitions = L(2);
dbgln_if(WEBP_DEBUG, "log2_nbr_of_dct_partitions {}", log2_nbr_of_dct_partitions);
header.number_of_dct_partitions = 1 << log2_nbr_of_dct_partitions;
header.quantization_indices = TRY(decode_VP8_frame_header_quantization_indices(decoder));
header.quantization_indices = decode_VP8_frame_header_quantization_indices(decoder);
// In the VP8 spec, this is in an `if (key_frames)` followed by a lengthy `else`, but webp files only have key frames.
u8 refresh_entropy_probs = TRY(L(1)); // Has no effect in webp files.
u8 refresh_entropy_probs = L(1); // Has no effect in webp files.
dbgln_if(WEBP_DEBUG, "refresh_entropy_probs {}", refresh_entropy_probs);
memcpy(header.coefficient_probabilities, DEFAULT_COEFFICIENT_PROBABILITIES, sizeof(header.coefficient_probabilities));
TRY(decode_VP8_frame_header_coefficient_probabilities(decoder, header.coefficient_probabilities));
// https://datatracker.ietf.org/doc/html/rfc6386#section-9.11 "Remaining Frame Header Data (Key Frame)"
header.enable_skipping_of_macroblocks_containing_only_zero_coefficients = TRY(L(1));
header.enable_skipping_of_macroblocks_containing_only_zero_coefficients = L(1);
dbgln_if(WEBP_DEBUG, "mb_no_skip_coeff {}", header.enable_skipping_of_macroblocks_containing_only_zero_coefficients);
if (header.enable_skipping_of_macroblocks_containing_only_zero_coefficients) {
header.probability_skip_false = TRY(L(8));
header.probability_skip_false = L(8);
dbgln_if(WEBP_DEBUG, "prob_skip_false {}", header.probability_skip_false);
}
@ -254,35 +254,35 @@ ErrorOr<FrameHeader> decode_VP8_frame_header(BooleanDecoder& decoder)
return header;
}
ErrorOr<Segmentation> decode_VP8_frame_header_segmentation(BooleanDecoder& decoder)
Segmentation decode_VP8_frame_header_segmentation(BooleanDecoder& decoder)
{
// Corresponds to "update_segmentation()" in section 19.2 of the spec.
Segmentation segmentation;
segmentation.update_macroblock_segmentation_map = TRY(L(1));
u8 update_segment_feature_data = TRY(L(1));
segmentation.update_macroblock_segmentation_map = L(1);
u8 update_segment_feature_data = L(1);
dbgln_if(WEBP_DEBUG, "update_mb_segmentation_map {} update_segment_feature_data {}",
segmentation.update_macroblock_segmentation_map, update_segment_feature_data);
if (update_segment_feature_data) {
segmentation.segment_feature_mode = static_cast<SegmentFeatureMode>(TRY(L(1)));
segmentation.segment_feature_mode = static_cast<SegmentFeatureMode>(L(1));
dbgln_if(WEBP_DEBUG, "segment_feature_mode {}", (int)segmentation.segment_feature_mode);
for (int i = 0; i < 4; ++i) {
u8 quantizer_update = TRY(L(1));
u8 quantizer_update = L(1);
dbgln_if(WEBP_DEBUG, "quantizer_update {}", quantizer_update);
if (quantizer_update) {
i8 quantizer_update_value = TRY(L_signed(7));
i8 quantizer_update_value = L_signed(7);
dbgln_if(WEBP_DEBUG, "quantizer_update_value {}", quantizer_update_value);
segmentation.quantizer_update_value[i] = quantizer_update_value;
}
}
for (int i = 0; i < 4; ++i) {
u8 loop_filter_update = TRY(L(1));
u8 loop_filter_update = L(1);
dbgln_if(WEBP_DEBUG, "loop_filter_update {}", loop_filter_update);
if (loop_filter_update) {
i8 loop_filter_update_value = TRY(L_signed(6));
i8 loop_filter_update_value = L_signed(6);
dbgln_if(WEBP_DEBUG, "loop_filter_update_value {}", loop_filter_update_value);
segmentation.loop_filter_update_value[i] = loop_filter_update_value;
}
@ -292,10 +292,10 @@ ErrorOr<Segmentation> decode_VP8_frame_header_segmentation(BooleanDecoder& decod
if (segmentation.update_macroblock_segmentation_map) {
// This reads mb_segment_tree_probs for https://datatracker.ietf.org/doc/html/rfc6386#section-10.
for (int i = 0; i < 3; ++i) {
u8 segment_prob_update = TRY(L(1));
u8 segment_prob_update = L(1);
dbgln_if(WEBP_DEBUG, "segment_prob_update {}", segment_prob_update);
if (segment_prob_update) {
u8 segment_prob = TRY(L(8));
u8 segment_prob = L(8);
dbgln_if(WEBP_DEBUG, "segment_prob {}", segment_prob);
segmentation.macroblock_segment_tree_probabilities[i] = segment_prob;
}
@ -305,7 +305,7 @@ ErrorOr<Segmentation> decode_VP8_frame_header_segmentation(BooleanDecoder& decod
return segmentation;
}
ErrorOr<QuantizationIndices> decode_VP8_frame_header_quantization_indices(BooleanDecoder& decoder)
QuantizationIndices decode_VP8_frame_header_quantization_indices(BooleanDecoder& decoder)
{
// Corresponds to "quant_indices()" in section 19.2 of the spec.
QuantizationIndices quantization_indices;
@ -314,52 +314,51 @@ ErrorOr<QuantizationIndices> decode_VP8_frame_header_quantization_indices(Boolea
// Y-plane AC coefficients, called yac_qi. It is always coded and acts
// as a baseline for the other 5 quantization indices, each of which is
// represented by a delta from this baseline index."
quantization_indices.y_ac = TRY(L(7));
quantization_indices.y_ac = L(7);
dbgln_if(WEBP_DEBUG, "y_ac_qi {}", quantization_indices.y_ac);
auto read_delta = [&decoder](StringView name, i8* destination) -> ErrorOr<void> {
u8 is_present = TRY(L(1));
auto read_delta = [&decoder](StringView name, i8* destination) -> void {
u8 is_present = L(1);
dbgln_if(WEBP_DEBUG, "{}_present {}", name, is_present);
if (is_present) {
i8 delta = TRY(L_signed(4));
i8 delta = L_signed(4);
dbgln_if(WEBP_DEBUG, "{} {}", name, delta);
*destination = delta;
}
return {};
};
TRY(read_delta("y_dc_delta"sv, &quantization_indices.y_dc_delta));
TRY(read_delta("y2_dc_delta"sv, &quantization_indices.y2_dc_delta));
TRY(read_delta("y2_ac_delta"sv, &quantization_indices.y2_ac_delta));
TRY(read_delta("uv_dc_delta"sv, &quantization_indices.uv_dc_delta));
TRY(read_delta("uv_ac_delta"sv, &quantization_indices.uv_ac_delta));
read_delta("y_dc_delta"sv, &quantization_indices.y_dc_delta);
read_delta("y2_dc_delta"sv, &quantization_indices.y2_dc_delta);
read_delta("y2_ac_delta"sv, &quantization_indices.y2_ac_delta);
read_delta("uv_dc_delta"sv, &quantization_indices.uv_dc_delta);
read_delta("uv_ac_delta"sv, &quantization_indices.uv_ac_delta);
return quantization_indices;
}
ErrorOr<LoopFilterAdjustment> decode_VP8_frame_header_loop_filter_adjustment(BooleanDecoder& decoder)
LoopFilterAdjustment decode_VP8_frame_header_loop_filter_adjustment(BooleanDecoder& decoder)
{
// Corresponds to "mb_lf_adjustments()" in section 19.2 of the spec.
LoopFilterAdjustment adjustment;
adjustment.enable_loop_filter_adjustment = TRY(L(1));
adjustment.enable_loop_filter_adjustment = L(1);
if (adjustment.enable_loop_filter_adjustment) {
u8 mode_ref_lf_delta_update = TRY(L(1));
u8 mode_ref_lf_delta_update = L(1);
dbgln_if(WEBP_DEBUG, "mode_ref_lf_delta_update {}", mode_ref_lf_delta_update);
if (mode_ref_lf_delta_update) {
for (int i = 0; i < 4; ++i) {
u8 ref_frame_delta_update_flag = TRY(L(1));
u8 ref_frame_delta_update_flag = L(1);
dbgln_if(WEBP_DEBUG, "ref_frame_delta_update_flag {}", ref_frame_delta_update_flag);
if (ref_frame_delta_update_flag) {
i8 delta = TRY(L_signed(6));
i8 delta = L_signed(6);
dbgln_if(WEBP_DEBUG, "delta {}", delta);
adjustment.ref_frame_delta[i] = delta;
}
}
for (int i = 0; i < 4; ++i) {
u8 mb_mode_delta_update_flag = TRY(L(1));
u8 mb_mode_delta_update_flag = L(1);
dbgln_if(WEBP_DEBUG, "mb_mode_delta_update_flag {}", mb_mode_delta_update_flag);
if (mb_mode_delta_update_flag) {
i8 delta = TRY(L_signed(6));
i8 delta = L_signed(6);
dbgln_if(WEBP_DEBUG, "delta {}", delta);
adjustment.mb_mode_delta[i] = delta;
}
@ -379,8 +378,8 @@ ErrorOr<void> decode_VP8_frame_header_coefficient_probabilities(BooleanDecoder&
for (int l = 0; l < 11; l++) {
// token_prob_update() says L(1) and L(8), but it's actually B(p) and L(8).
// https://datatracker.ietf.org/doc/html/rfc6386#section-13.4 "Token Probability Updates" describes it correctly.
if (TRY(B(COEFFICIENT_UPDATE_PROBABILITIES[i][j][k][l])))
coefficient_probabilities[i][j][k][l] = TRY(L(8));
if (B(COEFFICIENT_UPDATE_PROBABILITIES[i][j][k][l]))
coefficient_probabilities[i][j][k][l] = L(8);
}
}
}
@ -390,11 +389,11 @@ ErrorOr<void> decode_VP8_frame_header_coefficient_probabilities(BooleanDecoder&
}
// https://datatracker.ietf.org/doc/html/rfc6386#section-8.1 "Tree Coding Implementation"
ErrorOr<u8> tree_decode(BooleanDecoder& decoder, ReadonlySpan<TreeIndex> tree, ReadonlyBytes probabilities, TreeIndex initial_i = 0)
u8 tree_decode(BooleanDecoder& decoder, ReadonlySpan<TreeIndex> tree, ReadonlyBytes probabilities, TreeIndex initial_i = 0)
{
TreeIndex i = initial_i;
while (true) {
u8 b = TRY(B(probabilities[i >> 1]));
u8 b = B(probabilities[i >> 1]);
i = tree[i + b];
if (i <= 0)
return -i;
@ -454,12 +453,12 @@ ErrorOr<Vector<MacroblockMetadata>> decode_VP8_macroblock_metadata(BooleanDecode
MacroblockMetadata metadata;
if (header.segmentation.update_macroblock_segmentation_map)
metadata.segment_id = TRY(tree_decode(decoder, MACROBLOCK_SEGMENT_TREE, header.segmentation.macroblock_segment_tree_probabilities));
metadata.segment_id = tree_decode(decoder, MACROBLOCK_SEGMENT_TREE, header.segmentation.macroblock_segment_tree_probabilities);
if (header.enable_skipping_of_macroblocks_containing_only_zero_coefficients)
metadata.skip_coefficients = TRY(B(header.probability_skip_false));
metadata.skip_coefficients = B(header.probability_skip_false);
int intra_y_mode = TRY(tree_decode(decoder, KEYFRAME_YMODE_TREE, KEYFRAME_YMODE_PROBABILITIES));
int intra_y_mode = tree_decode(decoder, KEYFRAME_YMODE_TREE, KEYFRAME_YMODE_PROBABILITIES);
metadata.intra_y_mode = (IntraMacroblockMode)intra_y_mode;
// "If the Ymode is B_PRED, it is followed by a (tree-coded) mode for each of the 16 Y subblocks."
@ -472,7 +471,7 @@ ErrorOr<Vector<MacroblockMetadata>> decode_VP8_macroblock_metadata(BooleanDecode
int A = above[mb_x * 4 + x];
int L = left[y];
auto intra_b_mode = static_cast<IntraBlockMode>(TRY(tree_decode(decoder, BLOCK_MODE_TREE, KEYFRAME_BLOCK_MODE_PROBABILITIES[A][L])));
auto intra_b_mode = static_cast<IntraBlockMode>(tree_decode(decoder, BLOCK_MODE_TREE, KEYFRAME_BLOCK_MODE_PROBABILITIES[A][L]));
metadata.intra_b_modes[y * 4 + x] = intra_b_mode;
above[mb_x * 4 + x] = intra_b_mode;
@ -489,7 +488,7 @@ ErrorOr<Vector<MacroblockMetadata>> decode_VP8_macroblock_metadata(BooleanDecode
}
}
metadata.uv_mode = (IntraMacroblockMode)TRY(tree_decode(decoder, UV_MODE_TREE, KEYFRAME_UV_MODE_PROBABILITIES));
metadata.uv_mode = (IntraMacroblockMode)tree_decode(decoder, UV_MODE_TREE, KEYFRAME_UV_MODE_PROBABILITIES);
TRY(macroblock_metadata.try_append(metadata));
}
@ -557,7 +556,7 @@ int plane_index(CoefficientBlockIndex index, bool have_y2)
return 3;
}
ErrorOr<i16> coefficient_value_for_token(BooleanDecoder& decoder, u8 token)
i16 coefficient_value_for_token(BooleanDecoder& decoder, u8 token)
{
// Implements the second half of https://datatracker.ietf.org/doc/html/rfc6386#section-13.2 "Coding of Individual Coefficient Values"
i16 v = static_cast<i16>(token); // For DCT_0 to DCT4
@ -578,13 +577,13 @@ ErrorOr<i16> coefficient_value_for_token(BooleanDecoder& decoder, u8 token)
// This loop corresponds to `DCTextra` in the spec in section 13.2.
for (int i = 0; i < bits[token - dct_cat1]; ++i)
v = (v << 1) | TRY(decoder.read_bool(Pcats[token - dct_cat1][i]));
v = (v << 1) | decoder.read_bool(Pcats[token - dct_cat1][i]);
v += starts[token - dct_cat1];
}
if (v) {
if (TRY(decoder.read_bool(128)))
if (decoder.read_bool(128))
v = -v;
}
@ -720,7 +719,7 @@ struct CoefficientReadingContext {
using Coefficients = i16[16];
// Returns if any non-zero coefficients were read.
ErrorOr<bool> read_coefficent_block(BooleanDecoder& decoder, Coefficients out_coefficients, CoefficientBlockIndex block_index, CoefficientReadingContext& coefficient_reading_context, int mb_x, bool have_y2, int segment_id, FrameHeader const& header)
bool read_coefficent_block(BooleanDecoder& decoder, Coefficients out_coefficients, CoefficientBlockIndex block_index, CoefficientReadingContext& coefficient_reading_context, int mb_x, bool have_y2, int segment_id, FrameHeader const& header)
{
// Corresponds to `residual_block()` in https://datatracker.ietf.org/doc/html/rfc6386#section-19.3,
// but also does dequantization of the stored values.
@ -788,11 +787,11 @@ ErrorOr<bool> read_coefficent_block(BooleanDecoder& decoder, Coefficients out_co
// However, if the preceding coefficient is a DCT_0, decoding will skip
// the first branch, since it is not possible for dct_eob to follow a
// DCT_0."
u8 token = TRY(tree_decode(decoder, COEFFICIENT_TREE, header.coefficient_probabilities[plane][band][tricky], last_decoded_value == DCT_0 ? 2 : 0));
u8 token = tree_decode(decoder, COEFFICIENT_TREE, header.coefficient_probabilities[plane][band][tricky], last_decoded_value == DCT_0 ? 2 : 0);
if (token == dct_eob)
break;
i16 v = TRY(coefficient_value_for_token(decoder, token));
i16 v = coefficient_value_for_token(decoder, token);
if (v) {
// Subblock has non-0 coefficients. Store that, so that `tricky` on the next subblock is initialized correctly.
@ -817,7 +816,7 @@ struct MacroblockCoefficients {
Coefficients v_coeffs[4] {};
};
ErrorOr<MacroblockCoefficients> read_macroblock_coefficients(BooleanDecoder& decoder, FrameHeader const& header, CoefficientReadingContext& coefficient_reading_context, MacroblockMetadata const& metadata, int mb_x)
MacroblockCoefficients read_macroblock_coefficients(BooleanDecoder& decoder, FrameHeader const& header, CoefficientReadingContext& coefficient_reading_context, MacroblockMetadata const& metadata, int mb_x)
{
// Corresponds to `residual_data()` in https://datatracker.ietf.org/doc/html/rfc6386#section-19.3,
// but also does the inverse walsh-hadamard transform if a Y2 block is present.
@ -865,7 +864,7 @@ ErrorOr<MacroblockCoefficients> read_macroblock_coefficients(BooleanDecoder& dec
to_read = coefficients.v_coeffs[i - 21];
else // Y
to_read = coefficients.y_coeffs[i - 1];
subblock_has_nonzero_coefficients = TRY(read_coefficent_block(decoder, to_read, block_index, coefficient_reading_context, mb_x, have_y2, metadata.segment_id, header));
subblock_has_nonzero_coefficients = read_coefficent_block(decoder, to_read, block_index, coefficient_reading_context, mb_x, have_y2, metadata.segment_id, header);
}
coefficient_reading_context.update(block_index, mb_x, subblock_has_nonzero_coefficients);
@ -1181,7 +1180,7 @@ ErrorOr<void> decode_VP8_image_data(Gfx::Bitmap& bitmap, FrameHeader const& head
for (int mb_x = 0; mb_x < macroblock_width; ++mb_x, ++macroblock_index) {
auto const& metadata = macroblock_metadata[macroblock_index];
auto coefficients = TRY(read_macroblock_coefficients(decoder, header, coefficient_reading_context, metadata, mb_x));
auto coefficients = read_macroblock_coefficients(decoder, header, coefficient_reading_context, metadata, mb_x);
u8 y_data[16 * 16] {};
if (metadata.intra_y_mode == B_PRED)