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LibVideo/VP9: Index inter-frame references with named fields or an enum

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Previously, we were using size_t, often coerced from bool or u8, to
index reference pairs. Now, they must either be taken directly from
named fields or indexed using the `ReferenceIndex` enum with options
`primary` and `secondary`. With a more explicit method of indexing
these, the compiler can aid in using reference pairs correctly, and
fuzzers may be able to detect undefined behavior more easily.
This commit is contained in:
Zaggy1024 2022-11-25 03:03:22 -06:00 • committed by Andreas Kling
parent 3af4deba6d
commit f4761dab09
8 changed files with 174 additions and 157 deletions
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29
Userland/Libraries/LibVideo/VP9/Decoder.cpp
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@ -671,7 +671,7 @@ DecoderErrorOr<void> Decoder::predict_intra(u8 plane, BlockContext const& block_
return {};
}
MotionVector Decoder::select_motion_vector(u8 plane, BlockContext const& block_context, u8 ref_list, u32 block_index)
MotionVector Decoder::select_motion_vector(u8 plane, BlockContext const& block_context, ReferenceIndex reference_index, u32 block_index)
{
// The inputs to this process are:
// − a variable plane specifying which plane is being predicted,
@ -706,27 +706,27 @@ MotionVector Decoder::select_motion_vector(u8 plane, BlockContext const& block_c
// − If plane is equal to 0, or MiSize is greater than or equal to BLOCK_8X8, mv is set equal to
// BlockMvs[ refList ][ blockIdx ].
if (plane == 0 || block_context.size >= Block_8x8)
return vectors[block_index][ref_list];
return vectors[block_index][reference_index];
// − Otherwise, if subsampling_x is equal to 0 and subsampling_y is equal to 0, mv is set equal to
// BlockMvs[ refList ][ blockIdx ].
if (!block_context.frame_context.color_config.subsampling_x && !block_context.frame_context.color_config.subsampling_y)
return vectors[block_index][ref_list];
return vectors[block_index][reference_index];
// − Otherwise, if subsampling_x is equal to 0 and subsampling_y is equal to 1, mv[ comp ] is set equal to
// round_mv_comp_q2( BlockMvs[ refList ][ blockIdx ][ comp ] + BlockMvs[ refList ][ blockIdx + 2 ][ comp ] )
// for comp = 0..1.
if (!block_context.frame_context.color_config.subsampling_x && block_context.frame_context.color_config.subsampling_y)
return round_mv_comp_q2(vectors[block_index][ref_list] + vectors[block_index + 2][ref_list]);
return round_mv_comp_q2(vectors[block_index][reference_index] + vectors[block_index + 2][reference_index]);
// − Otherwise, if subsampling_x is equal to 1 and subsampling_y is equal to 0, mv[ comp ] is set equal to
// round_mv_comp_q2( BlockMvs[ refList ][ blockIdx ][ comp ] + BlockMvs[ refList ][ blockIdx + 1 ][ comp ] )
// for comp = 0..1.
if (block_context.frame_context.color_config.subsampling_x && !block_context.frame_context.color_config.subsampling_y)
return round_mv_comp_q2(vectors[block_index][ref_list] + vectors[block_index + 1][ref_list]);
return round_mv_comp_q2(vectors[block_index][reference_index] + vectors[block_index + 1][reference_index]);
// − Otherwise, (subsampling_x is equal to 1 and subsampling_y is equal to 1), mv[ comp ] is set equal to
// round_mv_comp_q4( BlockMvs[ refList ][ 0 ][ comp ] + BlockMvs[ refList ][ 1 ][ comp ] +
// BlockMvs[ refList ][ 2 ][ comp ] + BlockMvs[ refList ][ 3 ][ comp ] ) for comp = 0..1.
VERIFY(block_context.frame_context.color_config.subsampling_x && block_context.frame_context.color_config.subsampling_y);
return round_mv_comp_q4(vectors[0][ref_list] + vectors[1][ref_list]
+ vectors[2][ref_list] + vectors[3][ref_list]);
return round_mv_comp_q4(vectors[0][reference_index] + vectors[1][reference_index]
+ vectors[2][reference_index] + vectors[3][reference_index]);
}
MotionVector Decoder::clamp_motion_vector(u8 plane, BlockContext const& block_context, u32 block_row, u32 block_column, MotionVector vector)
@ -761,12 +761,12 @@ MotionVector Decoder::clamp_motion_vector(u8 plane, BlockContext const& block_co
};
}
DecoderErrorOr<void> Decoder::predict_inter_block(u8 plane, BlockContext const& block_context, u8 ref_list, u32 block_row, u32 block_column, u32 x, u32 y, u32 width, u32 height, u32 block_index, Span<u16> block_buffer)
DecoderErrorOr<void> Decoder::predict_inter_block(u8 plane, BlockContext const& block_context, ReferenceIndex reference_index, u32 block_row, u32 block_column, u32 x, u32 y, u32 width, u32 height, u32 block_index, Span<u16> block_buffer)
{
VERIFY(width <= maximum_block_dimensions && height <= maximum_block_dimensions);
// 2. The motion vector selection process in section 8.5.2.1 is invoked with plane, refList, blockIdx as inputs
// and the output being the motion vector mv.
auto motion_vector = select_motion_vector(plane, block_context, ref_list, block_index);
auto motion_vector = select_motion_vector(plane, block_context, reference_index, block_index);
// 3. The motion vector clamping process in section 8.5.2.2 is invoked with plane, mv as inputs and the output
// being the clamped motion vector clampedMv
@ -789,7 +789,7 @@ DecoderErrorOr<void> Decoder::predict_inter_block(u8 plane, BlockContext const&
// A variable refIdx specifying which reference frame is being used is set equal to
// ref_frame_idx[ ref_frame[ refList ] - LAST_FRAME ].
auto reference_frame_index = block_context.frame_context.reference_frame_indices[block_context.reference_frame_types[ref_list] - LastFrame];
auto reference_frame_index = block_context.frame_context.reference_frame_indices[block_context.reference_frame_types[reference_index] - LastFrame];
// It is a requirement of bitstream conformance that all the following conditions are satisfied:
// − 2 * FrameWidth >= RefFrameWidth[ refIdx ]
@ -943,14 +943,12 @@ DecoderErrorOr<void> Decoder::predict_inter(u8 plane, BlockContext const& block_
// − a variable blockIdx, specifying how much of the block has already been predicted in units of 4x4 samples.
// The outputs of this process are inter predicted samples in the current frame CurrFrame.
// The variable isCompound is set equal to ref_frame[ 1 ] > NONE.
auto is_compound = block_context.reference_frame_types[1] > None;
// The prediction arrays are formed by the following ordered steps:
// 1. The variable refList is set equal to 0.
// 2. through 5.
Array<u16, maximum_block_size> predicted_buffer;
auto predicted_span = predicted_buffer.span().trim(width * height);
TRY(predict_inter_block(plane, block_context, 0, block_context.row, block_context.column, x, y, width, height, block_index, predicted_span));
TRY(predict_inter_block(plane, block_context, ReferenceIndex::Primary, block_context.row, block_context.column, x, y, width, height, block_index, predicted_span));
auto predicted_buffer_at = [&](Span<u16> buffer, u32 row, u32 column) -> u16& {
return buffer[row * width + column];
};
@ -969,9 +967,10 @@ DecoderErrorOr<void> Decoder::predict_inter(u8 plane, BlockContext const& block_
auto width_in_frame_buffer = min(width, frame_width - x);
auto height_in_frame_buffer = min(height, frame_height - y);
// The variable isCompound is set equal to ref_frame[ 1 ] > NONE.
// − If isCompound is equal to 0, CurrFrame[ plane ][ y + i ][ x + j ] is set equal to preds[ 0 ][ i ][ j ] for i = 0..h-1
// and j = 0..w-1.
if (!is_compound) {
if (!block_context.is_compound()) {
for (auto i = 0u; i < height_in_frame_buffer; i++) {
for (auto j = 0u; j < width_in_frame_buffer; j++)
frame_buffer_at(y + i, x + j) = predicted_buffer_at(predicted_span, i, j);
@ -984,7 +983,7 @@ DecoderErrorOr<void> Decoder::predict_inter(u8 plane, BlockContext const& block_
// for i = 0..h-1 and j = 0..w-1.
Array<u16, maximum_block_size> second_predicted_buffer;
auto second_predicted_span = second_predicted_buffer.span().trim(width * height);
TRY(predict_inter_block(plane, block_context, 1, block_context.row, block_context.column, x, y, width, height, block_index, second_predicted_span));
TRY(predict_inter_block(plane, block_context, ReferenceIndex::Secondary, block_context.row, block_context.column, x, y, width, height, block_index, second_predicted_span));
for (auto i = 0u; i < height_in_frame_buffer; i++) {
for (auto j = 0u; j < width_in_frame_buffer; j++)