src/common/lossy/residuals_aom.cc - codecs/libwebp2 - Git at Google

 // Copyright 2019 Google LLC
 //
 // 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
 //
 //     https://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.
 // -----------------------------------------------------------------------------
 //
 //   Common code for AOM residuals, branched from libgav1, with as little
 //   changes as possible.
 //
 // Author: Vincent Rabaud (vrabaud@google.com)

 #include "src/common/lossy/residuals_aom.h"

 #include <numeric>

 #include "src/common/lossy/aom/cdfs.inc"
 #include "src/utils/utils.h"

 namespace WP2 {
 namespace libgav1 {

 //------------------------------------------------------------------------------
 // From libgav1/src/symbol_decoder_context.cc

 #define CDF_COPY(source, destination) \
   memcpy(destination, source, sizeof(source))

 void SymbolDecoderContext::Initialize(int quantizer_context) {
   CDF_COPY(kDefaultAllZeroCdf[quantizer_context], all_zero_cdf);
   CDF_COPY(kDefaultEobPt16Cdf[quantizer_context], eob_pt_16_cdf);
   CDF_COPY(kDefaultEobPt32Cdf[quantizer_context], eob_pt_32_cdf);
   CDF_COPY(kDefaultEobPt64Cdf[quantizer_context], eob_pt_64_cdf);
   CDF_COPY(kDefaultEobPt128Cdf[quantizer_context], eob_pt_128_cdf);
   CDF_COPY(kDefaultEobPt256Cdf[quantizer_context], eob_pt_256_cdf);
   CDF_COPY(kDefaultEobPt512Cdf[quantizer_context], eob_pt_512_cdf);
   CDF_COPY(kDefaultEobPt1024Cdf[quantizer_context], eob_pt_1024_cdf);
   CDF_COPY(kDefaultEobExtraCdf[quantizer_context], eob_extra_cdf);
   CDF_COPY(kDefaultCoeffBaseEobCdf[quantizer_context], coeff_base_eob_cdf);
   CDF_COPY(kDefaultCoeffBaseCdf[quantizer_context], coeff_base_cdf);
   CDF_COPY(kDefaultCoeffBaseRangeCdf[quantizer_context], coeff_base_range_cdf);
   CDF_COPY(kDefaultDcSignCdf[quantizer_context], dc_sign_cdf);
 }

 #undef CDF_COPY

 //------------------------------------------------------------------------------
 // From libgav1/src/utils/constants.cc

 const uint8_t kBlockWidthPixels[kMaxBlockSizes] = {
     4,  4,  4,  8,  8,  8,  8,  16, 16, 16,  16,
     16, 32, 32, 32, 32, 64, 64, 64, 64, 128, 128};

 const uint8_t kBlockHeightPixels[kMaxBlockSizes] = {
     4,  8, 16, 4,  8,  16, 32, 4,  8,   16, 32,
     64, 8, 16, 32, 64, 16, 32, 64, 128, 64, 128};

 const uint8_t kTransformWidth[kNumTransformSizes] = {
     4, 4, 4, 8, 8, 8, 8, 16, 16, 16, 16, 16, 32, 32, 32, 32, 64, 64, 64};

 const uint8_t kTransformHeight[kNumTransformSizes] = {
     4, 8, 16, 4, 8, 16, 32, 4, 8, 16, 32, 64, 8, 16, 32, 64, 16, 32, 64};

 const uint8_t kTransformWidth4x4[kNumTransformSizes] = {
     1, 1, 1, 2, 2, 2, 2, 4, 4, 4, 4, 4, 8, 8, 8, 8, 16, 16, 16};

 const uint8_t kTransformHeight4x4[kNumTransformSizes] = {
     1, 2, 4, 1, 2, 4, 8, 1, 2, 4, 8, 16, 2, 4, 8, 16, 4, 8, 16};

 const uint8_t kTransformWidthLog2[kNumTransformSizes] = {
     2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6};

 //------------------------------------------------------------------------------

 namespace {

 /* clang-format off */
 constexpr uint8_t kCoeffBaseContextOffset[kNumTransformSizes][5][5] = {
     {{0,  1,  6,  6, 0},
      {1,  6,  6, 21, 0},
      {6,  6, 21, 21, 0},
      {6, 21, 21, 21, 0},
      {0,  0,  0,  0, 0}},    // 4x4

     {{ 0, 11, 11, 11, 0},
      {11, 11, 11, 11, 0},
      { 6,  6, 21, 21, 0},
      { 6, 21, 21, 21, 0},
      {21, 21, 21, 21, 0}},   // 4x8

     {{ 0, 11, 11, 11, 0},
      {11, 11, 11, 11, 0},
      { 6,  6, 21, 21, 0},
      { 6, 21, 21, 21, 0},
      {21, 21, 21, 21, 0}},   // 4x16

     {{ 0, 16,  6,  6, 21},
      {16, 16,  6, 21, 21},
      {16, 16, 21, 21, 21},
      {16, 16, 21, 21, 21},
      { 0,  0,  0,  0,  0}},  // 8x4

     {{ 0,  1,  6,  6, 21},
      { 1,  6,  6, 21, 21},
      { 6,  6, 21, 21, 21},
      { 6, 21, 21, 21, 21},
      {21, 21, 21, 21, 21}},  // 8x8

     {{ 0, 11, 11, 11, 11},
      {11, 11, 11, 11, 11},
      { 6,  6, 21, 21, 21},
      { 6, 21, 21, 21, 21},
      {21, 21, 21, 21, 21}},  // 8x16

     {{ 0, 11, 11, 11, 11},
      {11, 11, 11, 11, 11},
      { 6,  6, 21, 21, 21},
      { 6, 21, 21, 21, 21},
      {21, 21, 21, 21, 21}},  // 8x32

     {{ 0, 16,  6,  6, 21},
      {16, 16,  6, 21, 21},
      {16, 16, 21, 21, 21},
      {16, 16, 21, 21, 21},
      { 0,  0,  0,  0,  0}},  // 16x4

     {{ 0, 16,  6,  6, 21},
      {16, 16,  6, 21, 21},
      {16, 16, 21, 21, 21},
      {16, 16, 21, 21, 21},
      {16, 16, 21, 21, 21}},  // 16x8

     {{ 0,  1,  6,  6, 21},
      { 1,  6,  6, 21, 21},
      { 6,  6, 21, 21, 21},
      { 6, 21, 21, 21, 21},
      {21, 21, 21, 21, 21}},  // 16x16

     {{ 0, 11, 11, 11, 11},
      {11, 11, 11, 11, 11},
      { 6,  6, 21, 21, 21},
      { 6, 21, 21, 21, 21},
      {21, 21, 21, 21, 21}},  // 16x32

     {{ 0, 11, 11, 11, 11},
      {11, 11, 11, 11, 11},
      { 6,  6, 21, 21, 21},
      { 6, 21, 21, 21, 21},
      {21, 21, 21, 21, 21}},  // 16x64

     {{ 0, 16,  6,  6, 21},
      {16, 16,  6, 21, 21},
      {16, 16, 21, 21, 21},
      {16, 16, 21, 21, 21},
      {16, 16, 21, 21, 21}},  // 32x8

     {{ 0, 16,  6,  6, 21},
      {16, 16,  6, 21, 21},
      {16, 16, 21, 21, 21},
      {16, 16, 21, 21, 21},
      {16, 16, 21, 21, 21}},  // 32x16

     {{ 0,  1,  6,  6, 21},
      { 1,  6,  6, 21, 21},
      { 6,  6, 21, 21, 21},
      { 6, 21, 21, 21, 21},
      {21, 21, 21, 21, 21}},  // 32x32

     {{ 0, 11, 11, 11, 11},
      {11, 11, 11, 11, 11},
      { 6,  6, 21, 21, 21},
      { 6, 21, 21, 21, 21},
      {21, 21, 21, 21, 21}},  // 32x64

     {{ 0, 16,  6,  6, 21},
      {16, 16,  6, 21, 21},
      {16, 16, 21, 21, 21},
      {16, 16, 21, 21, 21},
      {16, 16, 21, 21, 21}},  // 64x16

     {{ 0, 16,  6,  6, 21},
      {16, 16,  6, 21, 21},
      {16, 16, 21, 21, 21},
      {16, 16, 21, 21, 21},
      {16, 16, 21, 21, 21}},  // 64x32

     {{ 0,  1,  6,  6, 21},
      { 1,  6,  6, 21, 21},
      { 6,  6, 21, 21, 21},
      { 6, 21, 21, 21, 21},
      {21, 21, 21, 21, 21}}   // 64x64
 };
 /* clang-format on */

 constexpr uint8_t kCoeffBasePositionContextOffset[3] = {26, 31, 36};

 }  // namespace

 // Section 8.3.2 in the spec, under coeff_base_eob.
 int AOMResidualIO::GetCoeffBaseContextEob(TransformSize tx_size, int index) {
   if (index == 0) return 0;
   const TransformSize adjusted_tx_size = kAdjustedTransformSize[tx_size];
   const int tx_width_log2 = kTransformWidthLog2[adjusted_tx_size];
   const int tx_height = kTransformHeight[adjusted_tx_size];
   if (index <= DivideBy8(tx_height << tx_width_log2)) return 1;
   if (index <= DivideBy4(tx_height << tx_width_log2)) return 2;
   return 3;
 }

 // Section 8.3.2 in the spec, under coeff_base.
 static int GetCoeffBaseContext2D(const uint8_t qlevels[],
                                  TransformSize tx_size,
                                  int adjusted_tx_width_log2,
                                  uint16_t pos) {
   if (pos == 0) return 0;
   const int tx_width = 1 << adjusted_tx_width_log2;
   const int padded_tx_width = tx_width + kQuantizedCoefficientBufferPadding;
   const uint8_t* const levels =
       &qlevels[PaddedIndex(pos, adjusted_tx_width_log2)];
   const int context = std::min(
       4, DivideBy2(1 + levels[1] + levels[2] +
                        levels[padded_tx_width] +
                        levels[padded_tx_width + 1] +
                        levels[2 * padded_tx_width]));
   const int row = pos >> adjusted_tx_width_log2;
   const int column = pos & (tx_width - 1);
   return context + kCoeffBaseContextOffset[tx_size][std::min(row, 4)]
                                           [std::min(column, 4)];
 }

 // Section 8.3.2 in the spec, under coeff_base.
 static int GetCoeffBaseContextHorizontal(
     const uint8_t qlevels[], TransformSize /*tx_size*/,
     int adjusted_tx_width_log2, uint16_t pos) {
   const int tx_width = 1 << adjusted_tx_width_log2;
   const int padded_tx_width = tx_width + kQuantizedCoefficientBufferPadding;
   const uint8_t* const levels =
       &qlevels[PaddedIndex(pos, adjusted_tx_width_log2)];
   const int context = std::min(
       4, DivideBy2(1 + levels[1] + levels[2] + levels[3] + levels[4] +
                        levels[padded_tx_width]));
   const int index = pos & (tx_width - 1);
   return context + kCoeffBasePositionContextOffset[std::min(index, 2)];
 }

 // Section 8.3.2 in the spec, under coeff_base.
 static int GetCoeffBaseContextVertical(
     const uint8_t qlevels[], TransformSize /*tx_size*/,
     int adjusted_tx_width_log2, uint16_t pos) {
   const int tx_width = 1 << adjusted_tx_width_log2;
   const int padded_tx_width = tx_width + kQuantizedCoefficientBufferPadding;
   const uint8_t* const levels =
       &qlevels[PaddedIndex(pos, adjusted_tx_width_log2)];
   const int context = std::min(
       4, DivideBy2(1 + levels[1] +
                        levels[1 * padded_tx_width] +
                        levels[2 * padded_tx_width] +
                        levels[3 * padded_tx_width] +
                        levels[4 * padded_tx_width]));
   const int index = pos >> adjusted_tx_width_log2;
   return context + kCoeffBasePositionContextOffset[std::min(index, 2)];
 }

 static constexpr CoeffBaseContextFunc kCoeffBaseContextFuncs[] = {
   GetCoeffBaseContext2D,
   GetCoeffBaseContextHorizontal,
   GetCoeffBaseContextVertical
 };

 CoeffBaseContextFunc
   AOMResidualIO::GetCoeffsBaseContextFunc(uint32_t tx_class) {
   return kCoeffBaseContextFuncs[tx_class];
 }

 // Section 8.3.2 in the spec, under coeff_br.
 static int GetCoeffBaseRangeContext2D(
     const uint8_t qlevels[], int adjusted_tx_width_log2,
     int pos) {
   const uint8_t tx_width = 1 << adjusted_tx_width_log2;
   const int padded_tx_width = tx_width + kQuantizedCoefficientBufferPadding;
   const uint8_t* const levels =
       &qlevels[PaddedIndex(pos, adjusted_tx_width_log2)];
   const int context = std::min(
       6, DivideBy2(1 + levels[1] +
                        levels[padded_tx_width] +
                        levels[padded_tx_width + 1]));
   if (pos == 0) return context;
   const int row = pos >> adjusted_tx_width_log2;
   const int column = pos & (tx_width - 1);
   return context + (((row | column) < 2) ? 7 : 14);
 }

 // Section 8.3.2 in the spec, under coeff_br.
 static int GetCoeffBaseRangeContextHorizontal(
     const uint8_t qlevels[], int adjusted_tx_width_log2, int pos) {
   const uint8_t tx_width = 1 << adjusted_tx_width_log2;
   const int padded_tx_width = tx_width + kQuantizedCoefficientBufferPadding;
   const uint8_t* const levels =
       &qlevels[PaddedIndex(pos, adjusted_tx_width_log2)];
   const int context = std::min(
       6, DivideBy2(1 + levels[1] + levels[2] + levels[padded_tx_width]));
   if (pos == 0) return context;
   const int column = pos & (tx_width - 1);
   return context + ((column == 0) ? 7 : 14);
 }

 // Section 8.3.2 in the spec, under coeff_br.
 static int GetCoeffBaseRangeContextVertical(
     const uint8_t qlevels[], int adjusted_tx_width_log2, int pos) {
   const uint8_t tx_width = 1 << adjusted_tx_width_log2;
   const int padded_tx_width = tx_width + kQuantizedCoefficientBufferPadding;
   const uint8_t* const levels =
       &qlevels[PaddedIndex(pos, adjusted_tx_width_log2)];
   const int context = std::min(
       6, DivideBy2(1 + levels[1] +
                        levels[padded_tx_width] + levels[2 * padded_tx_width]));
   if (pos == 0) return context;
   const int row = pos >> adjusted_tx_width_log2;
   return context + ((row == 0) ? 7 : 14);
 }

 static constexpr CoeffBaseRangeContextFunc kCoeffBaseRangeContextFuncs[] = {
   GetCoeffBaseRangeContext2D,
   GetCoeffBaseRangeContextHorizontal,
   GetCoeffBaseRangeContextVertical
 };

 CoeffBaseRangeContextFunc
   AOMResidualIO::GetCoeffBaseRangeContextFunc(uint32_t tx_class) {
   return kCoeffBaseRangeContextFuncs[tx_class];
 }

 // Section 8.3.2 in the spec, under coeff_br. Optimized for end of block based
 // on the fact that {0, 1}, {1, 0}, {1, 1}, {0, 2} and {2, 0} will all be 0 in
 // the end of block case.
 int AOMResidualIO::GetCoeffBaseRangeContextEob(int adjusted_tx_width_log2,
                                                int pos) {
   if (pos == 0) return 0;
   const uint8_t tx_width = 1 << adjusted_tx_width_log2;
   const int row = pos >> adjusted_tx_width_log2;
   const int column = pos & (tx_width - 1);
   return ((row | column) < 2) ? 7 : 14;
 }

 }  // namespace libgav1
 }  // namespace WP2
	// Copyright 2019 Google LLC
	//
	// 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
	//
	// https://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.
	// -----------------------------------------------------------------------------
	//
	// Common code for AOM residuals, branched from libgav1, with as little
	// changes as possible.
	//
	// Author: Vincent Rabaud (vrabaud@google.com)

	#include "src/common/lossy/residuals_aom.h"

	#include <numeric>

	#include "src/common/lossy/aom/cdfs.inc"
	#include "src/utils/utils.h"

	namespace WP2 {
	namespace libgav1 {

	//------------------------------------------------------------------------------
	// From libgav1/src/symbol_decoder_context.cc

	#define CDF_COPY(source, destination) \
	memcpy(destination, source, sizeof(source))

	void SymbolDecoderContext::Initialize(int quantizer_context) {
	CDF_COPY(kDefaultAllZeroCdf[quantizer_context], all_zero_cdf);
	CDF_COPY(kDefaultEobPt16Cdf[quantizer_context], eob_pt_16_cdf);
	CDF_COPY(kDefaultEobPt32Cdf[quantizer_context], eob_pt_32_cdf);
	CDF_COPY(kDefaultEobPt64Cdf[quantizer_context], eob_pt_64_cdf);
	CDF_COPY(kDefaultEobPt128Cdf[quantizer_context], eob_pt_128_cdf);
	CDF_COPY(kDefaultEobPt256Cdf[quantizer_context], eob_pt_256_cdf);
	CDF_COPY(kDefaultEobPt512Cdf[quantizer_context], eob_pt_512_cdf);
	CDF_COPY(kDefaultEobPt1024Cdf[quantizer_context], eob_pt_1024_cdf);
	CDF_COPY(kDefaultEobExtraCdf[quantizer_context], eob_extra_cdf);
	CDF_COPY(kDefaultCoeffBaseEobCdf[quantizer_context], coeff_base_eob_cdf);
	CDF_COPY(kDefaultCoeffBaseCdf[quantizer_context], coeff_base_cdf);
	CDF_COPY(kDefaultCoeffBaseRangeCdf[quantizer_context], coeff_base_range_cdf);
	CDF_COPY(kDefaultDcSignCdf[quantizer_context], dc_sign_cdf);
	}

	#undef CDF_COPY

	//------------------------------------------------------------------------------
	// From libgav1/src/utils/constants.cc

	const uint8_t kBlockWidthPixels[kMaxBlockSizes] = {
	4, 4, 4, 8, 8, 8, 8, 16, 16, 16, 16,
	16, 32, 32, 32, 32, 64, 64, 64, 64, 128, 128};

	const uint8_t kBlockHeightPixels[kMaxBlockSizes] = {
	4, 8, 16, 4, 8, 16, 32, 4, 8, 16, 32,
	64, 8, 16, 32, 64, 16, 32, 64, 128, 64, 128};

	const uint8_t kTransformWidth[kNumTransformSizes] = {
	4, 4, 4, 8, 8, 8, 8, 16, 16, 16, 16, 16, 32, 32, 32, 32, 64, 64, 64};

	const uint8_t kTransformHeight[kNumTransformSizes] = {
	4, 8, 16, 4, 8, 16, 32, 4, 8, 16, 32, 64, 8, 16, 32, 64, 16, 32, 64};

	const uint8_t kTransformWidth4x4[kNumTransformSizes] = {
	1, 1, 1, 2, 2, 2, 2, 4, 4, 4, 4, 4, 8, 8, 8, 8, 16, 16, 16};

	const uint8_t kTransformHeight4x4[kNumTransformSizes] = {
	1, 2, 4, 1, 2, 4, 8, 1, 2, 4, 8, 16, 2, 4, 8, 16, 4, 8, 16};

	const uint8_t kTransformWidthLog2[kNumTransformSizes] = {
	2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6};

	//------------------------------------------------------------------------------

	namespace {

	/* clang-format off */
	constexpr uint8_t kCoeffBaseContextOffset[kNumTransformSizes][5][5] = {
	{{0, 1, 6, 6, 0},
	{1, 6, 6, 21, 0},
	{6, 6, 21, 21, 0},
	{6, 21, 21, 21, 0},
	{0, 0, 0, 0, 0}}, // 4x4

	{{ 0, 11, 11, 11, 0},
	{11, 11, 11, 11, 0},
	{ 6, 6, 21, 21, 0},
	{ 6, 21, 21, 21, 0},
	{21, 21, 21, 21, 0}}, // 4x8

	{{ 0, 11, 11, 11, 0},
	{11, 11, 11, 11, 0},
	{ 6, 6, 21, 21, 0},
	{ 6, 21, 21, 21, 0},
	{21, 21, 21, 21, 0}}, // 4x16

	{{ 0, 16, 6, 6, 21},
	{16, 16, 6, 21, 21},
	{16, 16, 21, 21, 21},
	{16, 16, 21, 21, 21},
	{ 0, 0, 0, 0, 0}}, // 8x4

	{{ 0, 1, 6, 6, 21},
	{ 1, 6, 6, 21, 21},
	{ 6, 6, 21, 21, 21},
	{ 6, 21, 21, 21, 21},
	{21, 21, 21, 21, 21}}, // 8x8

	{{ 0, 11, 11, 11, 11},
	{11, 11, 11, 11, 11},
	{ 6, 6, 21, 21, 21},
	{ 6, 21, 21, 21, 21},
	{21, 21, 21, 21, 21}}, // 8x16

	{{ 0, 11, 11, 11, 11},
	{11, 11, 11, 11, 11},
	{ 6, 6, 21, 21, 21},
	{ 6, 21, 21, 21, 21},
	{21, 21, 21, 21, 21}}, // 8x32

	{{ 0, 16, 6, 6, 21},
	{16, 16, 6, 21, 21},
	{16, 16, 21, 21, 21},
	{16, 16, 21, 21, 21},
	{ 0, 0, 0, 0, 0}}, // 16x4

	{{ 0, 16, 6, 6, 21},
	{16, 16, 6, 21, 21},
	{16, 16, 21, 21, 21},
	{16, 16, 21, 21, 21},
	{16, 16, 21, 21, 21}}, // 16x8

	{{ 0, 1, 6, 6, 21},
	{ 1, 6, 6, 21, 21},
	{ 6, 6, 21, 21, 21},
	{ 6, 21, 21, 21, 21},
	{21, 21, 21, 21, 21}}, // 16x16

	{{ 0, 11, 11, 11, 11},
	{11, 11, 11, 11, 11},
	{ 6, 6, 21, 21, 21},
	{ 6, 21, 21, 21, 21},
	{21, 21, 21, 21, 21}}, // 16x32

	{{ 0, 11, 11, 11, 11},
	{11, 11, 11, 11, 11},
	{ 6, 6, 21, 21, 21},
	{ 6, 21, 21, 21, 21},
	{21, 21, 21, 21, 21}}, // 16x64

	{{ 0, 16, 6, 6, 21},
	{16, 16, 6, 21, 21},
	{16, 16, 21, 21, 21},
	{16, 16, 21, 21, 21},
	{16, 16, 21, 21, 21}}, // 32x8

	{{ 0, 16, 6, 6, 21},
	{16, 16, 6, 21, 21},
	{16, 16, 21, 21, 21},
	{16, 16, 21, 21, 21},
	{16, 16, 21, 21, 21}}, // 32x16

	{{ 0, 1, 6, 6, 21},
	{ 1, 6, 6, 21, 21},
	{ 6, 6, 21, 21, 21},
	{ 6, 21, 21, 21, 21},
	{21, 21, 21, 21, 21}}, // 32x32

	{{ 0, 11, 11, 11, 11},
	{11, 11, 11, 11, 11},
	{ 6, 6, 21, 21, 21},
	{ 6, 21, 21, 21, 21},
	{21, 21, 21, 21, 21}}, // 32x64

	{{ 0, 16, 6, 6, 21},
	{16, 16, 6, 21, 21},
	{16, 16, 21, 21, 21},
	{16, 16, 21, 21, 21},
	{16, 16, 21, 21, 21}}, // 64x16

	{{ 0, 16, 6, 6, 21},
	{16, 16, 6, 21, 21},
	{16, 16, 21, 21, 21},
	{16, 16, 21, 21, 21},
	{16, 16, 21, 21, 21}}, // 64x32

	{{ 0, 1, 6, 6, 21},
	{ 1, 6, 6, 21, 21},
	{ 6, 6, 21, 21, 21},
	{ 6, 21, 21, 21, 21},
	{21, 21, 21, 21, 21}} // 64x64
	};
	/* clang-format on */

	constexpr uint8_t kCoeffBasePositionContextOffset[3] = {26, 31, 36};

	} // namespace

	// Section 8.3.2 in the spec, under coeff_base_eob.
	int AOMResidualIO::GetCoeffBaseContextEob(TransformSize tx_size, int index) {
	if (index == 0) return 0;
	const TransformSize adjusted_tx_size = kAdjustedTransformSize[tx_size];
	const int tx_width_log2 = kTransformWidthLog2[adjusted_tx_size];
	const int tx_height = kTransformHeight[adjusted_tx_size];
	if (index <= DivideBy8(tx_height << tx_width_log2)) return 1;
	if (index <= DivideBy4(tx_height << tx_width_log2)) return 2;
	return 3;
	}

	// Section 8.3.2 in the spec, under coeff_base.
	static int GetCoeffBaseContext2D(const uint8_t qlevels[],
	TransformSize tx_size,
	int adjusted_tx_width_log2,
	uint16_t pos) {
	if (pos == 0) return 0;
	const int tx_width = 1 << adjusted_tx_width_log2;
	const int padded_tx_width = tx_width + kQuantizedCoefficientBufferPadding;
	const uint8_t* const levels =
	&qlevels[PaddedIndex(pos, adjusted_tx_width_log2)];
	const int context = std::min(
	4, DivideBy2(1 + levels[1] + levels[2] +
	levels[padded_tx_width] +
	levels[padded_tx_width + 1] +
	levels[2 * padded_tx_width]));
	const int row = pos >> adjusted_tx_width_log2;
	const int column = pos & (tx_width - 1);
	return context + kCoeffBaseContextOffset[tx_size][std::min(row, 4)]
	[std::min(column, 4)];
	}

	// Section 8.3.2 in the spec, under coeff_base.
	static int GetCoeffBaseContextHorizontal(
	const uint8_t qlevels[], TransformSize /tx_size/,
	int adjusted_tx_width_log2, uint16_t pos) {
	const int tx_width = 1 << adjusted_tx_width_log2;
	const int padded_tx_width = tx_width + kQuantizedCoefficientBufferPadding;
	const uint8_t* const levels =
	&qlevels[PaddedIndex(pos, adjusted_tx_width_log2)];
	const int context = std::min(
	4, DivideBy2(1 + levels[1] + levels[2] + levels[3] + levels[4] +
	levels[padded_tx_width]));
	const int index = pos & (tx_width - 1);
	return context + kCoeffBasePositionContextOffset[std::min(index, 2)];
	}

	// Section 8.3.2 in the spec, under coeff_base.
	static int GetCoeffBaseContextVertical(
	const uint8_t qlevels[], TransformSize /tx_size/,
	int adjusted_tx_width_log2, uint16_t pos) {
	const int tx_width = 1 << adjusted_tx_width_log2;
	const int padded_tx_width = tx_width + kQuantizedCoefficientBufferPadding;
	const uint8_t* const levels =
	&qlevels[PaddedIndex(pos, adjusted_tx_width_log2)];
	const int context = std::min(
	4, DivideBy2(1 + levels[1] +
	levels[1 * padded_tx_width] +
	levels[2 * padded_tx_width] +
	levels[3 * padded_tx_width] +
	levels[4 * padded_tx_width]));
	const int index = pos >> adjusted_tx_width_log2;
	return context + kCoeffBasePositionContextOffset[std::min(index, 2)];
	}

	static constexpr CoeffBaseContextFunc kCoeffBaseContextFuncs[] = {
	GetCoeffBaseContext2D,
	GetCoeffBaseContextHorizontal,
	GetCoeffBaseContextVertical
	};

	CoeffBaseContextFunc
	AOMResidualIO::GetCoeffsBaseContextFunc(uint32_t tx_class) {
	return kCoeffBaseContextFuncs[tx_class];
	}

	// Section 8.3.2 in the spec, under coeff_br.
	static int GetCoeffBaseRangeContext2D(
	const uint8_t qlevels[], int adjusted_tx_width_log2,
	int pos) {
	const uint8_t tx_width = 1 << adjusted_tx_width_log2;
	const int padded_tx_width = tx_width + kQuantizedCoefficientBufferPadding;
	const uint8_t* const levels =
	&qlevels[PaddedIndex(pos, adjusted_tx_width_log2)];
	const int context = std::min(
	6, DivideBy2(1 + levels[1] +
	levels[padded_tx_width] +
	levels[padded_tx_width + 1]));
	if (pos == 0) return context;
	const int row = pos >> adjusted_tx_width_log2;
	const int column = pos & (tx_width - 1);
	return context + (((row \| column) < 2) ? 7 : 14);
	}

	// Section 8.3.2 in the spec, under coeff_br.
	static int GetCoeffBaseRangeContextHorizontal(
	const uint8_t qlevels[], int adjusted_tx_width_log2, int pos) {
	const uint8_t tx_width = 1 << adjusted_tx_width_log2;
	const int padded_tx_width = tx_width + kQuantizedCoefficientBufferPadding;
	const uint8_t* const levels =
	&qlevels[PaddedIndex(pos, adjusted_tx_width_log2)];
	const int context = std::min(
	6, DivideBy2(1 + levels[1] + levels[2] + levels[padded_tx_width]));
	if (pos == 0) return context;
	const int column = pos & (tx_width - 1);
	return context + ((column == 0) ? 7 : 14);
	}

	// Section 8.3.2 in the spec, under coeff_br.
	static int GetCoeffBaseRangeContextVertical(
	const uint8_t qlevels[], int adjusted_tx_width_log2, int pos) {
	const uint8_t tx_width = 1 << adjusted_tx_width_log2;
	const int padded_tx_width = tx_width + kQuantizedCoefficientBufferPadding;
	const uint8_t* const levels =
	&qlevels[PaddedIndex(pos, adjusted_tx_width_log2)];
	const int context = std::min(
	6, DivideBy2(1 + levels[1] +
	levels[padded_tx_width] + levels[2 * padded_tx_width]));
	if (pos == 0) return context;
	const int row = pos >> adjusted_tx_width_log2;
	return context + ((row == 0) ? 7 : 14);
	}

	static constexpr CoeffBaseRangeContextFunc kCoeffBaseRangeContextFuncs[] = {
	GetCoeffBaseRangeContext2D,
	GetCoeffBaseRangeContextHorizontal,
	GetCoeffBaseRangeContextVertical
	};

	CoeffBaseRangeContextFunc
	AOMResidualIO::GetCoeffBaseRangeContextFunc(uint32_t tx_class) {
	return kCoeffBaseRangeContextFuncs[tx_class];
	}

	// Section 8.3.2 in the spec, under coeff_br. Optimized for end of block based
	// on the fact that {0, 1}, {1, 0}, {1, 1}, {0, 2} and {2, 0} will all be 0 in
	// the end of block case.
	int AOMResidualIO::GetCoeffBaseRangeContextEob(int adjusted_tx_width_log2,
	int pos) {
	if (pos == 0) return 0;
	const uint8_t tx_width = 1 << adjusted_tx_width_log2;
	const int row = pos >> adjusted_tx_width_log2;
	const int column = pos & (tx_width - 1);
	return ((row \| column) < 2) ? 7 : 14;
	}

	} // namespace libgav1
	} // namespace WP2