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LibVideo/VP9: Split/clean up the token tree-parsing context function

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Since the context information for parsing residual tokens changes based
on whether we're parsing the first coefficient or subsequent ones, the
TreeParser::get_tokens_context function was split into two new ones to
allow them to read more cleanly. All variables now have meaningful
names to aid in readability as well.

The math used in the function for the first token was changed to
be more friendly to tile- or block-specific coordinates to facilitate
range-restricted Spans of the above and left context arrays.
This commit is contained in:
Zaggy1024 2022-11-28 00:15:53 -06:00 • committed by Andreas Kling
parent 3667f9bf2c
commit 06082d310f
3 changed files with 68 additions and 52 deletions
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20
Userland/Libraries/LibVideo/VP9/Parser.cpp
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@ -1391,7 +1391,7 @@ DecoderErrorOr<bool> Parser::residual(BlockContext& block_context, bool has_bloc
TRY(m_decoder.predict_intra(plane, block_context, transform_x_in_px, transform_y_in_px, has_block_left || x > 0, has_block_above || y > 0, (x + transform_size_in_sub_blocks) < block_size_in_sub_blocks.width(), transform_size, sub_block_index));
if (!block_context.should_skip_residuals) {
auto transform_set = select_transform_type(block_context, plane, transform_size, sub_block_index);
sub_block_had_non_zero_tokens = TRY(tokens(block_context, plane, transform_x_in_px, transform_y_in_px, transform_size, transform_set, token_cache));
sub_block_had_non_zero_tokens = TRY(tokens(block_context, plane, x, y, transform_size, transform_set, token_cache));
block_had_non_zero_tokens = block_had_non_zero_tokens || sub_block_had_non_zero_tokens;
TRY(m_decoder.reconstruct(plane, block_context, transform_x_in_px, transform_y_in_px, transform_size, transform_set));
}
@ -1445,7 +1445,7 @@ static u16 const* get_scan(TransformSize transform_size, TransformSet transform_
return default_scan_32x32;
}
DecoderErrorOr<bool> Parser::tokens(BlockContext& block_context, size_t plane, u32 start_x, u32 start_y, TransformSize transform_size, TransformSet transform_set, Array<u8, 1024> token_cache)
DecoderErrorOr<bool> Parser::tokens(BlockContext& block_context, size_t plane, u32 sub_block_column, u32 sub_block_row, TransformSize transform_size, TransformSet transform_set, Array<u8, 1024> token_cache)
{
block_context.residual_tokens.fill(0);
@ -1453,17 +1453,21 @@ DecoderErrorOr<bool> Parser::tokens(BlockContext& block_context, size_t plane, u
auto check_for_more_coefficients = true;
u16 coef_index = 0;
u16 segment_eob = 16 << (transform_size << 1);
for (; coef_index < segment_eob; coef_index++) {
auto pos = scan[coef_index];
u16 transform_pixel_count = 16 << (transform_size << 1);
for (; coef_index < transform_pixel_count; coef_index++) {
auto band = (transform_size == Transform_4x4) ? coefband_4x4[coef_index] : coefband_8x8plus[coef_index];
auto tokens_context = TreeParser::get_tokens_context(block_context.frame_context.color_config.subsampling_x, block_context.frame_context.color_config.subsampling_y, block_context.frame_context.rows(), block_context.frame_context.columns(), m_above_nonzero_context, m_left_nonzero_context, token_cache, transform_size, transform_set, plane, start_x, start_y, pos, block_context.is_inter_predicted(), band, coef_index);
auto token_position = scan[coef_index];
TokensContext tokens_context;
if (coef_index == 0)
tokens_context = TreeParser::get_context_for_first_token(block_context, m_above_nonzero_context, m_left_nonzero_context, transform_size, plane, sub_block_column, sub_block_row, block_context.is_inter_predicted(), band);
else
tokens_context = TreeParser::get_context_for_other_tokens(token_cache, transform_size, transform_set, plane, token_position, block_context.is_inter_predicted(), band);
if (check_for_more_coefficients && !TRY_READ(TreeParser::parse_more_coefficients(*m_bit_stream, *m_probability_tables, *m_syntax_element_counter, tokens_context)))
break;
auto token = TRY_READ(TreeParser::parse_token(*m_bit_stream, *m_probability_tables, *m_syntax_element_counter, tokens_context));
token_cache[pos] = energy_class[token];
token_cache[token_position] = energy_class[token];
i32 coef;
if (token == ZeroToken) {
@ -1473,7 +1477,7 @@ DecoderErrorOr<bool> Parser::tokens(BlockContext& block_context, size_t plane, u
coef = TRY(read_coef(block_context.frame_context.color_config.bit_depth, token));
check_for_more_coefficients = true;
}
block_context.residual_tokens[pos] = coef;
block_context.residual_tokens[token_position] = coef;
}
return coef_index > 0;