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// Copyright 2019 The libgav1 Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include <cassert>
#include <cstdint>
#include "src/symbol_decoder_context.h"
#include "src/tile.h"
#include "src/utils/block_parameters_holder.h"
#include "src/utils/common.h"
#include "src/utils/constants.h"
#include "src/utils/entropy_decoder.h"
#include "src/utils/types.h"
namespace libgav1 {
namespace {
uint16_t PartitionCdfGatherHorizontalAlike(const uint16_t* const partition_cdf,
BlockSize block_size) {
// The spec computes the cdf value using the following formula (not writing
// partition_cdf[] and using short forms for partition names for clarity):
// cdf = None - H + V - S + S - HTS + HTS - HBS + HBS - VLS;
// if (block_size != 128x128) {
// cdf += VRS - H4;
// }
// After canceling out the repeated terms with opposite signs, we have:
// cdf = None - H + V - VLS;
// if (block_size != 128x128) {
// cdf += VRS - H4;
// }
uint16_t cdf = partition_cdf[kPartitionNone] -
partition_cdf[kPartitionHorizontal] +
partition_cdf[kPartitionVertical] -
partition_cdf[kPartitionVerticalWithLeftSplit];
if (block_size != kBlock128x128) {
cdf += partition_cdf[kPartitionVerticalWithRightSplit] -
partition_cdf[kPartitionHorizontal4];
}
return cdf;
}
uint16_t PartitionCdfGatherVerticalAlike(const uint16_t* const partition_cdf,
BlockSize block_size) {
// The spec computes the cdf value using the following formula (not writing
// partition_cdf[] and using short forms for partition names for clarity):
// cdf = H - V + V - S + HBS - VLS + VLS - VRS + S - HTS;
// if (block_size != 128x128) {
// cdf += H4 - V4;
// }
// V4 is always zero. So, after canceling out the repeated terms with opposite
// signs, we have:
// cdf = H + HBS - VRS - HTS;
// if (block_size != 128x128) {
// cdf += H4;
// }
// VRS is zero for 128x128 blocks. So, further simplifying we have:
// cdf = H + HBS - HTS;
// if (block_size != 128x128) {
// cdf += H4 - VRS;
// }
uint16_t cdf = partition_cdf[kPartitionHorizontal] +
partition_cdf[kPartitionHorizontalWithBottomSplit] -
partition_cdf[kPartitionHorizontalWithTopSplit];
if (block_size != kBlock128x128) {
cdf += partition_cdf[kPartitionHorizontal4] -
partition_cdf[kPartitionVerticalWithRightSplit];
}
return cdf;
}
} // namespace
uint16_t* Tile::GetPartitionCdf(int row4x4, int column4x4,
BlockSize block_size) {
const int block_size_log2 = k4x4WidthLog2[block_size];
int top = 0;
if (IsTopInside(row4x4)) {
top = static_cast<int>(
k4x4WidthLog2[block_parameters_holder_.Find(row4x4 - 1, column4x4)
->size] < block_size_log2);
}
int left = 0;
if (IsLeftInside(column4x4)) {
left = static_cast<int>(
k4x4HeightLog2[block_parameters_holder_.Find(row4x4, column4x4 - 1)
->size] < block_size_log2);
}
const int context = left * 2 + top;
return symbol_decoder_context_.partition_cdf[block_size_log2 - 1][context];
}
bool Tile::ReadPartition(int row4x4, int column4x4, BlockSize block_size,
bool has_rows, bool has_columns,
Partition* const partition) {
if (IsBlockSmallerThan8x8(block_size)) {
*partition = kPartitionNone;
return true;
}
if (!has_rows && !has_columns) {
*partition = kPartitionSplit;
return true;
}
uint16_t* const partition_cdf =
GetPartitionCdf(row4x4, column4x4, block_size);
if (partition_cdf == nullptr) {
return false;
}
if (has_rows && has_columns) {
const int bsize_log2 = k4x4WidthLog2[block_size];
// The partition block size should be 8x8 or above.
assert(bsize_log2 > 0);
if (bsize_log2 == 1) {
*partition = static_cast<Partition>(
reader_.ReadSymbol<kPartitionSplit + 1>(partition_cdf));
} else if (bsize_log2 == 5) {
*partition = static_cast<Partition>(
reader_.ReadSymbol<kPartitionVerticalWithRightSplit + 1>(
partition_cdf));
} else {
*partition = static_cast<Partition>(
reader_.ReadSymbol<kMaxPartitionTypes>(partition_cdf));
}
} else if (has_columns) {
const uint16_t cdf =
PartitionCdfGatherVerticalAlike(partition_cdf, block_size);
*partition = reader_.ReadSymbolWithoutCdfUpdate(cdf) ? kPartitionSplit
: kPartitionHorizontal;
} else {
const uint16_t cdf =
PartitionCdfGatherHorizontalAlike(partition_cdf, block_size);
*partition = reader_.ReadSymbolWithoutCdfUpdate(cdf) ? kPartitionSplit
: kPartitionVertical;
}
return true;
}
} // namespace libgav1
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