av1/common/cfl.c - aom - Git at Google

 /*
  * Copyright (c) 2016, Alliance for Open Media. All rights reserved
  *
  * This source code is subject to the terms of the BSD 2 Clause License and
  * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
  * was not distributed with this source code in the LICENSE file, you can
  * obtain it at www.aomedia.org/license/software. If the Alliance for Open
  * Media Patent License 1.0 was not distributed with this source code in the
  * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
  */

 #include "av1/common/cfl.h"
 #include "av1/common/common_data.h"
 #include "av1/common/onyxc_int.h"

 void cfl_init(CFL_CTX *cfl, AV1_COMMON *cm) {
   if ((cm->subsampling_x != 0 && cm->subsampling_x != 1) ||
       (cm->subsampling_y != 0 && cm->subsampling_y != 1)) {
     aom_internal_error(&cm->error, AOM_CODEC_UNSUP_BITSTREAM,
                        "Only 4:4:4, 4:4:0, 4:2:2 and 4:2:0 are currently "
                        "supported by CfL, %d %d "
                        "subsampling is not supported.\n",
                        cm->subsampling_x, cm->subsampling_y);
   }
   memset(&cfl->pred_buf_q3, 0, sizeof(cfl->pred_buf_q3));
   cfl->subsampling_x = cm->subsampling_x;
   cfl->subsampling_y = cm->subsampling_y;
   cfl->are_parameters_computed = 0;
   cfl->store_y = 0;
 #if CONFIG_DEBUG
   cfl_clear_sub8x8_val(cfl);
   cfl->store_counter = 0;
   cfl->last_compute_counter = 0;
 #endif  // CONFIG_DEBUG
 }

 // Due to frame boundary issues, it is possible that the total area covered by
 // chroma exceeds that of luma. When this happens, we fill the missing pixels by
 // repeating the last columns and/or rows.
 static INLINE void cfl_pad(CFL_CTX *cfl, int width, int height) {
   const int diff_width = width - cfl->buf_width;
   const int diff_height = height - cfl->buf_height;

   if (diff_width > 0) {
     const int min_height = height - diff_height;
     int16_t *pred_buf_q3 = cfl->pred_buf_q3 + (width - diff_width);
     for (int j = 0; j < min_height; j++) {
       const int16_t last_pixel = pred_buf_q3[-1];
       for (int i = 0; i < diff_width; i++) {
         pred_buf_q3[i] = last_pixel;
       }
       pred_buf_q3 += MAX_SB_SIZE;
     }
     cfl->buf_width = width;
   }
   if (diff_height > 0) {
     int16_t *pred_buf_q3 =
         cfl->pred_buf_q3 + ((height - diff_height) * MAX_SB_SIZE);
     for (int j = 0; j < diff_height; j++) {
       const int16_t *last_row_q3 = pred_buf_q3 - MAX_SB_SIZE;
       for (int i = 0; i < width; i++) {
         pred_buf_q3[i] = last_row_q3[i];
       }
       pred_buf_q3 += MAX_SB_SIZE;
     }
     cfl->buf_height = height;
   }
 }

 static void cfl_subtract_averages(CFL_CTX *cfl, TX_SIZE tx_size) {
   const int width = cfl->uv_width;
   const int height = cfl->uv_height;
   const int tx_height = tx_size_high[tx_size];
   const int tx_width = tx_size_wide[tx_size];
   const int block_row_stride = MAX_SB_SIZE << tx_size_high_log2[tx_size];
   const int num_pel_log2 =
       (tx_size_high_log2[tx_size] + tx_size_wide_log2[tx_size]);
   int16_t *pred_buf_q3 = cfl->pred_buf_q3;

   cfl_pad(cfl, width, height);

   for (int b_j = 0; b_j < height; b_j += tx_height) {
     for (int b_i = 0; b_i < width; b_i += tx_width) {
       int sum_q3 = 0;
       int16_t *tx_pred_buf_q3 = pred_buf_q3;
       for (int t_j = 0; t_j < tx_height; t_j++) {
         for (int t_i = b_i; t_i < b_i + tx_width; t_i++) {
           sum_q3 += tx_pred_buf_q3[t_i];
         }
         tx_pred_buf_q3 += MAX_SB_SIZE;
       }
       int avg_q3 = (sum_q3 + (1 << (num_pel_log2 - 1))) >> num_pel_log2;
       // Loss is never more than 1/2 (in Q3)
       assert(abs((avg_q3 * (1 << num_pel_log2)) - sum_q3) <=
              1 << num_pel_log2 >> 1);

       tx_pred_buf_q3 = pred_buf_q3;
       for (int t_j = 0; t_j < tx_height; t_j++) {
         for (int t_i = b_i; t_i < b_i + tx_width; t_i++) {
           tx_pred_buf_q3[t_i] -= avg_q3;
         }

         tx_pred_buf_q3 += MAX_SB_SIZE;
       }
     }
     pred_buf_q3 += block_row_stride;
   }
 }

 static INLINE int cfl_idx_to_alpha(int alpha_idx, int joint_sign,
                                    CFL_PRED_TYPE pred_type) {
   const int alpha_sign = (pred_type == CFL_PRED_U) ? CFL_SIGN_U(joint_sign)
                                                    : CFL_SIGN_V(joint_sign);
   if (alpha_sign == CFL_SIGN_ZERO) return 0;
   const int abs_alpha_q3 =
       (pred_type == CFL_PRED_U) ? CFL_IDX_U(alpha_idx) : CFL_IDX_V(alpha_idx);
   return (alpha_sign == CFL_SIGN_POS) ? abs_alpha_q3 + 1 : -abs_alpha_q3 - 1;
 }

 static void cfl_build_prediction_lbd(const int16_t *pred_buf_q3, uint8_t *dst,
                                      int dst_stride, int width, int height,
                                      int alpha_q3) {
   for (int j = 0; j < height; j++) {
     for (int i = 0; i < width; i++) {
       dst[i] =
           clip_pixel(get_scaled_luma_q0(alpha_q3, pred_buf_q3[i]) + dst[i]);
     }
     dst += dst_stride;
     pred_buf_q3 += MAX_SB_SIZE;
   }
 }

 #if CONFIG_HIGHBITDEPTH
 static void cfl_build_prediction_hbd(const int16_t *pred_buf_q3, uint16_t *dst,
                                      int dst_stride, int width, int height,
                                      int alpha_q3, int bit_depth) {
   for (int j = 0; j < height; j++) {
     for (int i = 0; i < width; i++) {
       dst[i] = clip_pixel_highbd(
           get_scaled_luma_q0(alpha_q3, pred_buf_q3[i]) + dst[i], bit_depth);
     }
     dst += dst_stride;
     pred_buf_q3 += MAX_SB_SIZE;
   }
 }
 #endif  // CONFIG_HIGHBITDEPTH

 static void cfl_compute_parameters(MACROBLOCKD *const xd, TX_SIZE tx_size) {
   CFL_CTX *const cfl = &xd->cfl;
   MB_MODE_INFO *mbmi = &xd->mi[0]->mbmi;

   // Do not call cfl_compute_parameters multiple time on the same values.
   assert(cfl->are_parameters_computed == 0);

   const BLOCK_SIZE plane_bsize = AOMMAX(
       BLOCK_4X4, get_plane_block_size(mbmi->sb_type, &xd->plane[AOM_PLANE_U]));
 #if CONFIG_DEBUG
   BLOCK_SIZE bsize = mbmi->sb_type;
   if (block_size_high[bsize] == 4 || block_size_wide[bsize] == 4) {
     const uint16_t compute_counter = cfl->sub8x8_val[0];
     assert(compute_counter != cfl->last_compute_counter);
     bsize = scale_chroma_bsize(bsize, cfl->subsampling_x, cfl->subsampling_y);
     const int val_wide = mi_size_wide[bsize];
     const int val_high = mi_size_high[bsize];
     assert(val_wide <= CFL_SUB8X8_VAL_MI_SIZE);
     assert(val_high <= CFL_SUB8X8_VAL_MI_SIZE);
     for (int val_r = 0; val_r < val_high; val_r++) {
       for (int val_c = 0; val_c < val_wide; val_c++) {
         // If all counters in the validation buffer are equal then they are all
         // related to the same chroma reference block.
         assert(cfl->sub8x8_val[val_r * CFL_SUB8X8_VAL_MI_SIZE + val_c] ==
                compute_counter);
       }
     }
     cfl->last_compute_counter = compute_counter;
   }
 #endif  // CONFIG_DEBUG

   // AOM_PLANE_U is used, but both planes will have the same sizes.
   cfl->uv_width = max_intra_block_width(xd, plane_bsize, AOM_PLANE_U, tx_size);
   cfl->uv_height =
       max_intra_block_height(xd, plane_bsize, AOM_PLANE_U, tx_size);

   cfl_subtract_averages(cfl, tx_size);
   cfl->are_parameters_computed = 1;
 }

 void cfl_predict_block(MACROBLOCKD *const xd, uint8_t *dst, int dst_stride,
                        int row, int col, TX_SIZE tx_size, int plane) {
   CFL_CTX *const cfl = &xd->cfl;
   MB_MODE_INFO *mbmi = &xd->mi[0]->mbmi;

   if (!cfl->are_parameters_computed) cfl_compute_parameters(xd, tx_size);

   const int16_t *pred_buf_q3 =
       cfl->pred_buf_q3 + ((row * MAX_SB_SIZE + col) << tx_size_wide_log2[0]);
   const int alpha_q3 =
       cfl_idx_to_alpha(mbmi->cfl_alpha_idx, mbmi->cfl_alpha_signs, plane - 1);
 #if CONFIG_HIGHBITDEPTH
   if (get_bitdepth_data_path_index(xd)) {
     uint16_t *dst_16 = CONVERT_TO_SHORTPTR(dst);
     cfl_build_prediction_hbd(pred_buf_q3, dst_16, dst_stride,
                              tx_size_wide[tx_size], tx_size_high[tx_size],
                              alpha_q3, xd->bd);
     return;
   }
 #endif  // CONFIG_HIGHBITDEPTH
   cfl_build_prediction_lbd(pred_buf_q3, dst, dst_stride, tx_size_wide[tx_size],
                            tx_size_high[tx_size], alpha_q3);
 }

 static void cfl_luma_subsampling_420_lbd(const uint8_t *input, int input_stride,
                                          int16_t *output_q3, int width,
                                          int height) {
   for (int j = 0; j < height; j++) {
     for (int i = 0; i < width; i++) {
       int top = i << 1;
       int bot = top + input_stride;
       output_q3[i] = (input[top] + input[top + 1] + input[bot] + input[bot + 1])
                      << 1;
     }
     input += input_stride << 1;
     output_q3 += MAX_SB_SIZE;
   }
 }

 static void cfl_luma_subsampling_422_lbd(const uint8_t *input, int input_stride,
                                          int16_t *output_q3, int width,
                                          int height) {
   for (int j = 0; j < height; j++) {
     for (int i = 0; i < width; i++) {
       int left = i << 1;
       output_q3[i] = (input[left] + input[left + 1]) << 2;
     }
     input += input_stride;
     output_q3 += MAX_SB_SIZE;
   }
 }

 static void cfl_luma_subsampling_440_lbd(const uint8_t *input, int input_stride,
                                          int16_t *output_q3, int width,
                                          int height) {
   for (int j = 0; j < height; j++) {
     for (int i = 0; i < width; i++) {
       output_q3[i] = (input[i] + input[i + input_stride]) << 2;
     }
     input += input_stride << 1;
     output_q3 += MAX_SB_SIZE;
   }
 }

 static void cfl_luma_subsampling_444_lbd(const uint8_t *input, int input_stride,
                                          int16_t *output_q3, int width,
                                          int height) {
   for (int j = 0; j < height; j++) {
     for (int i = 0; i < width; i++) {
       output_q3[i] = input[i] << 3;
     }
     input += input_stride;
     output_q3 += MAX_SB_SIZE;
   }
 }

 typedef void (*cfl_subsample_lbd_fn)(const uint8_t *input, int input_stride,
                                      int16_t *output_q3, int width, int height);

 static const cfl_subsample_lbd_fn subsample_lbd[2][2] = {
   //  (sub_y == 0, sub_x == 0)       (sub_y == 0, sub_x == 1)
   //  (sub_y == 1, sub_x == 0)       (sub_y == 1, sub_x == 1)
   { cfl_luma_subsampling_444_lbd, cfl_luma_subsampling_422_lbd },
   { cfl_luma_subsampling_440_lbd, cfl_luma_subsampling_420_lbd },
 };

 #if CONFIG_HIGHBITDEPTH
 static void cfl_luma_subsampling_420_hbd(const uint16_t *input,
                                          int input_stride, int16_t *output_q3,
                                          int width, int height) {
   for (int j = 0; j < height; j++) {
     for (int i = 0; i < width; i++) {
       int top = i << 1;
       int bot = top + input_stride;
       output_q3[i] = (input[top] + input[top + 1] + input[bot] + input[bot + 1])
                      << 1;
     }
     input += input_stride << 1;
     output_q3 += MAX_SB_SIZE;
   }
 }

 static void cfl_luma_subsampling_422_hbd(const uint16_t *input,
                                          int input_stride, int16_t *output_q3,
                                          int width, int height) {
   for (int j = 0; j < height; j++) {
     for (int i = 0; i < width; i++) {
       int left = i << 1;
       output_q3[i] = (input[left] + input[left + 1]) << 2;
     }
     input += input_stride;
     output_q3 += MAX_SB_SIZE;
   }
 }

 static void cfl_luma_subsampling_440_hbd(const uint16_t *input,
                                          int input_stride, int16_t *output_q3,
                                          int width, int height) {
   for (int j = 0; j < height; j++) {
     for (int i = 0; i < width; i++) {
       output_q3[i] = (input[i] + input[i + input_stride]) << 2;
     }
     input += input_stride << 1;
     output_q3 += MAX_SB_SIZE;
   }
 }

 static void cfl_luma_subsampling_444_hbd(const uint16_t *input,
                                          int input_stride, int16_t *output_q3,
                                          int width, int height) {
   for (int j = 0; j < height; j++) {
     for (int i = 0; i < width; i++) {
       output_q3[i] = input[i] << 3;
     }
     input += input_stride;
     output_q3 += MAX_SB_SIZE;
   }
 }

 typedef void (*cfl_subsample_hbd_fn)(const uint16_t *input, int input_stride,
                                      int16_t *output_q3, int width, int height);

 static const cfl_subsample_hbd_fn subsample_hbd[2][2] = {
   //  (sub_y == 0, sub_x == 0)       (sub_y == 0, sub_x == 1)
   //  (sub_y == 1, sub_x == 0)       (sub_y == 1, sub_x == 1)
   { cfl_luma_subsampling_444_hbd, cfl_luma_subsampling_422_hbd },
   { cfl_luma_subsampling_440_hbd, cfl_luma_subsampling_420_hbd },
 };
 #endif  // CONFIG_HIGHBITDEPTH

 static void cfl_store(CFL_CTX *cfl, const uint8_t *input, int input_stride,
                       int row, int col, int width, int height, int use_hbd) {
   const int tx_off_log2 = tx_size_wide_log2[0];
   const int sub_x = cfl->subsampling_x;
   const int sub_y = cfl->subsampling_y;
   const int store_row = row << (tx_off_log2 - sub_y);
   const int store_col = col << (tx_off_log2 - sub_x);
   const int store_height = height >> sub_y;
   const int store_width = width >> sub_x;

   // Invalidate current parameters
   cfl->are_parameters_computed = 0;

   // Store the surface of the pixel buffer that was written to, this way we
   // can manage chroma overrun (e.g. when the chroma surfaces goes beyond the
   // frame boundary)
   if (col == 0 && row == 0) {
     cfl->buf_width = store_width;
     cfl->buf_height = store_height;
   } else {
     cfl->buf_width = OD_MAXI(store_col + store_width, cfl->buf_width);
     cfl->buf_height = OD_MAXI(store_row + store_height, cfl->buf_height);
   }

   // Check that we will remain inside the pixel buffer.
   assert(store_row + store_height <= MAX_SB_SIZE);
   assert(store_col + store_width <= MAX_SB_SIZE);

   // Store the input into the CfL pixel buffer
   int16_t *pred_buf_q3 =
       cfl->pred_buf_q3 + (store_row * MAX_SB_SIZE + store_col);

 #if CONFIG_HIGHBITDEPTH
   if (use_hbd) {
     const uint16_t *input_16 = CONVERT_TO_SHORTPTR(input);
     // AND sub_x and sub_y with 1 to ensures that an attacker won't be able to
     // index the function pointer array out of bounds.
     subsample_hbd[sub_y & 1][sub_x & 1](input_16, input_stride, pred_buf_q3,
                                         store_width, store_height);
     return;
   }
 #endif  // CONFIG_HIGHBITDEPTH
   (void)use_hbd;
   // AND sub_x and sub_y with 1 to ensures that an attacker won't be able to
   // index the function pointer array out of bounds.
   subsample_lbd[sub_y & 1][sub_x & 1](input, input_stride, pred_buf_q3,
                                       store_width, store_height);
 }

 // Adjust the row and column of blocks smaller than 8X8, as chroma-referenced
 // and non-chroma-referenced blocks are stored together in the CfL buffer.
 static INLINE void sub8x8_adjust_offset(const CFL_CTX *cfl, int *row_out,
                                         int *col_out) {
   // Increment row index for bottom: 8x4, 16x4 or both bottom 4x4s.
   if ((cfl->mi_row & 0x01) && cfl->subsampling_y) {
     assert(*row_out == 0);
     (*row_out)++;
   }

   // Increment col index for right: 4x8, 4x16 or both right 4x4s.
   if ((cfl->mi_col & 0x01) && cfl->subsampling_x) {
     assert(*col_out == 0);
     (*col_out)++;
   }
 }
 #if CONFIG_DEBUG
 // Since the chroma surface of sub8x8 block span across multiple luma blocks,
 // this function validates that the reconstructed luma area required to predict
 // the chroma block using CfL has been stored during the previous luma encode.
 //
 //   Issue 1: Chroma intra prediction is not always performed after luma. One
 //   such example is when luma RD cost is really high and the mode decision
 //   algorithm decides to terminate instead of evaluating chroma.
 //
 //   Issue 2: When multiple CfL predictions are computed for a given sub8x8
 //   block. The reconstructed luma that belongs to the non-reference sub8x8
 //   blocks must remain in the buffer (we cannot clear the buffer when we
 //   compute the CfL prediction
 //
 // To resolve these issues, we increment the store_counter on each store. if
 // other sub8x8 blocks have already been coded and the counter corresponds to
 // the previous value they are also set to the current value. If a sub8x8 block
 // is not stored the store_counter won't match which will be detected when the
 // CfL parements are computed.
 static void sub8x8_set_val(CFL_CTX *cfl, int row, int col, TX_SIZE y_tx_size) {
   const int y_tx_wide_unit = tx_size_wide_unit[y_tx_size];
   const int y_tx_high_unit = tx_size_high_unit[y_tx_size];

   // How many 4x4 are in tx_size
   const int y_tx_unit_len = y_tx_wide_unit * y_tx_high_unit;
   assert(y_tx_unit_len == 1 || y_tx_unit_len == 2 || y_tx_unit_len == 4);

   // Invalidate other counters if (0,0)
   const int is_first = row + col == 0;
   cfl->store_counter += is_first ? 2 : 1;

   const int inc =
       (y_tx_wide_unit >= y_tx_high_unit) ? 1 : CFL_SUB8X8_VAL_MI_SIZE;
   uint16_t *sub8x8_val = cfl->sub8x8_val + (row * CFL_SUB8X8_VAL_MI_SIZE + col);
   for (int i = 0; i < y_tx_unit_len; i++) {
     *sub8x8_val = cfl->store_counter;
     sub8x8_val += inc;
   }

   if (!is_first) {
     const uint16_t prev_store_counter = cfl->store_counter - 1;
     int found = 0;
     (void)found;
     sub8x8_val = cfl->sub8x8_val;
     for (int y = 0; y < CFL_SUB8X8_VAL_MI_SIZE; y++) {
       for (int x = 0; x < CFL_SUB8X8_VAL_MI_SIZE; x++) {
         if (sub8x8_val[x] == prev_store_counter) {
           sub8x8_val[x] = cfl->store_counter;
           found = 1;
         }
       }
       sub8x8_val += CFL_SUB8X8_VAL_MI_SIZE;
     }
     // Something is wrong if (0,0) is missing
     assert(found);
   }
 }
 #endif  // CONFIG_DEBUG

 void cfl_store_tx(MACROBLOCKD *const xd, int row, int col, TX_SIZE tx_size,
                   BLOCK_SIZE bsize) {
   CFL_CTX *const cfl = &xd->cfl;
   struct macroblockd_plane *const pd = &xd->plane[AOM_PLANE_Y];
   uint8_t *dst =
       &pd->dst.buf[(row * pd->dst.stride + col) << tx_size_wide_log2[0]];

   assert(is_cfl_allowed(&xd->mi[0]->mbmi));
   if (block_size_high[bsize] == 4 || block_size_wide[bsize] == 4) {
     // Only dimensions of size 4 can have an odd offset.
     assert(!((col & 1) && tx_size_wide[tx_size] != 4));
     assert(!((row & 1) && tx_size_high[tx_size] != 4));
     sub8x8_adjust_offset(cfl, &row, &col);
 #if CONFIG_DEBUG
     sub8x8_set_val(cfl, row, col, tx_size);
 #endif  // CONFIG_DEBUG
   }
   cfl_store(cfl, dst, pd->dst.stride, row, col, tx_size_wide[tx_size],
             tx_size_high[tx_size], get_bitdepth_data_path_index(xd));
 }

 void cfl_store_block(MACROBLOCKD *const xd, BLOCK_SIZE bsize, TX_SIZE tx_size) {
   CFL_CTX *const cfl = &xd->cfl;
   struct macroblockd_plane *const pd = &xd->plane[AOM_PLANE_Y];
   int row = 0;
   int col = 0;
   bsize = AOMMAX(BLOCK_4X4, bsize);

   assert(is_cfl_allowed(&xd->mi[0]->mbmi));
   if (block_size_high[bsize] == 4 || block_size_wide[bsize] == 4) {
     sub8x8_adjust_offset(cfl, &row, &col);
 #if CONFIG_DEBUG
     // Point to the last transform block inside the partition.
     const int off_row =
         row + (mi_size_high[bsize] - tx_size_high_unit[tx_size]);
     const int off_col =
         col + (mi_size_wide[bsize] - tx_size_wide_unit[tx_size]);
     sub8x8_set_val(cfl, off_row, off_col, tx_size);
 #endif  // CONFIG_DEBUG
   }
   const int width = max_intra_block_width(xd, bsize, AOM_PLANE_Y, tx_size);
   const int height = max_intra_block_height(xd, bsize, AOM_PLANE_Y, tx_size);
   cfl_store(cfl, pd->dst.buf, pd->dst.stride, row, col, width, height,
             get_bitdepth_data_path_index(xd));
 }
	/*
	* Copyright (c) 2016, Alliance for Open Media. All rights reserved
	*
	* This source code is subject to the terms of the BSD 2 Clause License and
	* the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
	* was not distributed with this source code in the LICENSE file, you can
	* obtain it at www.aomedia.org/license/software. If the Alliance for Open
	* Media Patent License 1.0 was not distributed with this source code in the
	* PATENTS file, you can obtain it at www.aomedia.org/license/patent.
	*/

	#include "av1/common/cfl.h"
	#include "av1/common/common_data.h"
	#include "av1/common/onyxc_int.h"

	void cfl_init(CFL_CTX cfl, AV1_COMMON cm) {
	if ((cm->subsampling_x != 0 && cm->subsampling_x != 1) \|\|
	(cm->subsampling_y != 0 && cm->subsampling_y != 1)) {
	aom_internal_error(&cm->error, AOM_CODEC_UNSUP_BITSTREAM,
	"Only 4:4:4, 4:4:0, 4:2:2 and 4:2:0 are currently "
	"supported by CfL, %d %d "
	"subsampling is not supported.\n",
	cm->subsampling_x, cm->subsampling_y);
	}
	memset(&cfl->pred_buf_q3, 0, sizeof(cfl->pred_buf_q3));
	cfl->subsampling_x = cm->subsampling_x;
	cfl->subsampling_y = cm->subsampling_y;
	cfl->are_parameters_computed = 0;
	cfl->store_y = 0;
	#if CONFIG_DEBUG
	cfl_clear_sub8x8_val(cfl);
	cfl->store_counter = 0;
	cfl->last_compute_counter = 0;
	#endif // CONFIG_DEBUG
	}

	// Due to frame boundary issues, it is possible that the total area covered by
	// chroma exceeds that of luma. When this happens, we fill the missing pixels by
	// repeating the last columns and/or rows.
	static INLINE void cfl_pad(CFL_CTX *cfl, int width, int height) {
	const int diff_width = width - cfl->buf_width;
	const int diff_height = height - cfl->buf_height;

	if (diff_width > 0) {
	const int min_height = height - diff_height;
	int16_t *pred_buf_q3 = cfl->pred_buf_q3 + (width - diff_width);
	for (int j = 0; j < min_height; j++) {
	const int16_t last_pixel = pred_buf_q3[-1];
	for (int i = 0; i < diff_width; i++) {
	pred_buf_q3[i] = last_pixel;
	}
	pred_buf_q3 += MAX_SB_SIZE;
	}
	cfl->buf_width = width;
	}
	if (diff_height > 0) {
	int16_t *pred_buf_q3 =
	cfl->pred_buf_q3 + ((height - diff_height) * MAX_SB_SIZE);
	for (int j = 0; j < diff_height; j++) {
	const int16_t *last_row_q3 = pred_buf_q3 - MAX_SB_SIZE;
	for (int i = 0; i < width; i++) {
	pred_buf_q3[i] = last_row_q3[i];
	}
	pred_buf_q3 += MAX_SB_SIZE;
	}
	cfl->buf_height = height;
	}
	}

	static void cfl_subtract_averages(CFL_CTX *cfl, TX_SIZE tx_size) {
	const int width = cfl->uv_width;
	const int height = cfl->uv_height;
	const int tx_height = tx_size_high[tx_size];
	const int tx_width = tx_size_wide[tx_size];
	const int block_row_stride = MAX_SB_SIZE << tx_size_high_log2[tx_size];
	const int num_pel_log2 =
	(tx_size_high_log2[tx_size] + tx_size_wide_log2[tx_size]);
	int16_t *pred_buf_q3 = cfl->pred_buf_q3;

	cfl_pad(cfl, width, height);

	for (int b_j = 0; b_j < height; b_j += tx_height) {
	for (int b_i = 0; b_i < width; b_i += tx_width) {
	int sum_q3 = 0;
	int16_t *tx_pred_buf_q3 = pred_buf_q3;
	for (int t_j = 0; t_j < tx_height; t_j++) {
	for (int t_i = b_i; t_i < b_i + tx_width; t_i++) {
	sum_q3 += tx_pred_buf_q3[t_i];
	}
	tx_pred_buf_q3 += MAX_SB_SIZE;
	}
	int avg_q3 = (sum_q3 + (1 << (num_pel_log2 - 1))) >> num_pel_log2;
	// Loss is never more than 1/2 (in Q3)
	assert(abs((avg_q3 * (1 << num_pel_log2)) - sum_q3) <=
	1 << num_pel_log2 >> 1);

	tx_pred_buf_q3 = pred_buf_q3;
	for (int t_j = 0; t_j < tx_height; t_j++) {
	for (int t_i = b_i; t_i < b_i + tx_width; t_i++) {
	tx_pred_buf_q3[t_i] -= avg_q3;
	}

	tx_pred_buf_q3 += MAX_SB_SIZE;
	}
	}
	pred_buf_q3 += block_row_stride;
	}
	}

	static INLINE int cfl_idx_to_alpha(int alpha_idx, int joint_sign,
	CFL_PRED_TYPE pred_type) {
	const int alpha_sign = (pred_type == CFL_PRED_U) ? CFL_SIGN_U(joint_sign)
	: CFL_SIGN_V(joint_sign);
	if (alpha_sign == CFL_SIGN_ZERO) return 0;
	const int abs_alpha_q3 =
	(pred_type == CFL_PRED_U) ? CFL_IDX_U(alpha_idx) : CFL_IDX_V(alpha_idx);
	return (alpha_sign == CFL_SIGN_POS) ? abs_alpha_q3 + 1 : -abs_alpha_q3 - 1;
	}

	static void cfl_build_prediction_lbd(const int16_t pred_buf_q3, uint8_t dst,
	int dst_stride, int width, int height,
	int alpha_q3) {
	for (int j = 0; j < height; j++) {
	for (int i = 0; i < width; i++) {
	dst[i] =
	clip_pixel(get_scaled_luma_q0(alpha_q3, pred_buf_q3[i]) + dst[i]);
	}
	dst += dst_stride;
	pred_buf_q3 += MAX_SB_SIZE;
	}
	}

	#if CONFIG_HIGHBITDEPTH
	static void cfl_build_prediction_hbd(const int16_t pred_buf_q3, uint16_t dst,
	int dst_stride, int width, int height,
	int alpha_q3, int bit_depth) {
	for (int j = 0; j < height; j++) {
	for (int i = 0; i < width; i++) {
	dst[i] = clip_pixel_highbd(
	get_scaled_luma_q0(alpha_q3, pred_buf_q3[i]) + dst[i], bit_depth);
	}
	dst += dst_stride;
	pred_buf_q3 += MAX_SB_SIZE;
	}
	}
	#endif // CONFIG_HIGHBITDEPTH

	static void cfl_compute_parameters(MACROBLOCKD *const xd, TX_SIZE tx_size) {
	CFL_CTX *const cfl = &xd->cfl;
	MB_MODE_INFO *mbmi = &xd->mi[0]->mbmi;

	// Do not call cfl_compute_parameters multiple time on the same values.
	assert(cfl->are_parameters_computed == 0);

	const BLOCK_SIZE plane_bsize = AOMMAX(
	BLOCK_4X4, get_plane_block_size(mbmi->sb_type, &xd->plane[AOM_PLANE_U]));
	#if CONFIG_DEBUG
	BLOCK_SIZE bsize = mbmi->sb_type;
	if (block_size_high[bsize] == 4 \|\| block_size_wide[bsize] == 4) {
	const uint16_t compute_counter = cfl->sub8x8_val[0];
	assert(compute_counter != cfl->last_compute_counter);
	bsize = scale_chroma_bsize(bsize, cfl->subsampling_x, cfl->subsampling_y);
	const int val_wide = mi_size_wide[bsize];
	const int val_high = mi_size_high[bsize];
	assert(val_wide <= CFL_SUB8X8_VAL_MI_SIZE);
	assert(val_high <= CFL_SUB8X8_VAL_MI_SIZE);
	for (int val_r = 0; val_r < val_high; val_r++) {
	for (int val_c = 0; val_c < val_wide; val_c++) {
	// If all counters in the validation buffer are equal then they are all
	// related to the same chroma reference block.
	assert(cfl->sub8x8_val[val_r * CFL_SUB8X8_VAL_MI_SIZE + val_c] ==
	compute_counter);
	}
	}
	cfl->last_compute_counter = compute_counter;
	}
	#endif // CONFIG_DEBUG

	// AOM_PLANE_U is used, but both planes will have the same sizes.
	cfl->uv_width = max_intra_block_width(xd, plane_bsize, AOM_PLANE_U, tx_size);
	cfl->uv_height =
	max_intra_block_height(xd, plane_bsize, AOM_PLANE_U, tx_size);

	cfl_subtract_averages(cfl, tx_size);
	cfl->are_parameters_computed = 1;
	}

	void cfl_predict_block(MACROBLOCKD const xd, uint8_t dst, int dst_stride,
	int row, int col, TX_SIZE tx_size, int plane) {
	CFL_CTX *const cfl = &xd->cfl;
	MB_MODE_INFO *mbmi = &xd->mi[0]->mbmi;

	if (!cfl->are_parameters_computed) cfl_compute_parameters(xd, tx_size);

	const int16_t *pred_buf_q3 =
	cfl->pred_buf_q3 + ((row * MAX_SB_SIZE + col) << tx_size_wide_log2[0]);
	const int alpha_q3 =
	cfl_idx_to_alpha(mbmi->cfl_alpha_idx, mbmi->cfl_alpha_signs, plane - 1);
	#if CONFIG_HIGHBITDEPTH
	if (get_bitdepth_data_path_index(xd)) {
	uint16_t *dst_16 = CONVERT_TO_SHORTPTR(dst);
	cfl_build_prediction_hbd(pred_buf_q3, dst_16, dst_stride,
	tx_size_wide[tx_size], tx_size_high[tx_size],
	alpha_q3, xd->bd);
	return;
	}
	#endif // CONFIG_HIGHBITDEPTH
	cfl_build_prediction_lbd(pred_buf_q3, dst, dst_stride, tx_size_wide[tx_size],
	tx_size_high[tx_size], alpha_q3);
	}

	static void cfl_luma_subsampling_420_lbd(const uint8_t *input, int input_stride,
	int16_t *output_q3, int width,
	int height) {
	for (int j = 0; j < height; j++) {
	for (int i = 0; i < width; i++) {
	int top = i << 1;
	int bot = top + input_stride;
	output_q3[i] = (input[top] + input[top + 1] + input[bot] + input[bot + 1])
	<< 1;
	}
	input += input_stride << 1;
	output_q3 += MAX_SB_SIZE;
	}
	}

	static void cfl_luma_subsampling_422_lbd(const uint8_t *input, int input_stride,
	int16_t *output_q3, int width,
	int height) {
	for (int j = 0; j < height; j++) {
	for (int i = 0; i < width; i++) {
	int left = i << 1;
	output_q3[i] = (input[left] + input[left + 1]) << 2;
	}
	input += input_stride;
	output_q3 += MAX_SB_SIZE;
	}
	}

	static void cfl_luma_subsampling_440_lbd(const uint8_t *input, int input_stride,
	int16_t *output_q3, int width,
	int height) {
	for (int j = 0; j < height; j++) {
	for (int i = 0; i < width; i++) {
	output_q3[i] = (input[i] + input[i + input_stride]) << 2;
	}
	input += input_stride << 1;
	output_q3 += MAX_SB_SIZE;
	}
	}

	static void cfl_luma_subsampling_444_lbd(const uint8_t *input, int input_stride,
	int16_t *output_q3, int width,
	int height) {
	for (int j = 0; j < height; j++) {
	for (int i = 0; i < width; i++) {
	output_q3[i] = input[i] << 3;
	}
	input += input_stride;
	output_q3 += MAX_SB_SIZE;
	}
	}

	typedef void (cfl_subsample_lbd_fn)(const uint8_t input, int input_stride,
	int16_t *output_q3, int width, int height);

	static const cfl_subsample_lbd_fn subsample_lbd[2][2] = {
	// (sub_y == 0, sub_x == 0) (sub_y == 0, sub_x == 1)
	// (sub_y == 1, sub_x == 0) (sub_y == 1, sub_x == 1)
	{ cfl_luma_subsampling_444_lbd, cfl_luma_subsampling_422_lbd },
	{ cfl_luma_subsampling_440_lbd, cfl_luma_subsampling_420_lbd },
	};

	#if CONFIG_HIGHBITDEPTH
	static void cfl_luma_subsampling_420_hbd(const uint16_t *input,
	int input_stride, int16_t *output_q3,
	int width, int height) {
	for (int j = 0; j < height; j++) {
	for (int i = 0; i < width; i++) {
	int top = i << 1;
	int bot = top + input_stride;
	output_q3[i] = (input[top] + input[top + 1] + input[bot] + input[bot + 1])
	<< 1;
	}
	input += input_stride << 1;
	output_q3 += MAX_SB_SIZE;
	}
	}

	static void cfl_luma_subsampling_422_hbd(const uint16_t *input,
	int input_stride, int16_t *output_q3,
	int width, int height) {
	for (int j = 0; j < height; j++) {
	for (int i = 0; i < width; i++) {
	int left = i << 1;
	output_q3[i] = (input[left] + input[left + 1]) << 2;
	}
	input += input_stride;
	output_q3 += MAX_SB_SIZE;
	}
	}

	static void cfl_luma_subsampling_440_hbd(const uint16_t *input,
	int input_stride, int16_t *output_q3,
	int width, int height) {
	for (int j = 0; j < height; j++) {
	for (int i = 0; i < width; i++) {
	output_q3[i] = (input[i] + input[i + input_stride]) << 2;
	}
	input += input_stride << 1;
	output_q3 += MAX_SB_SIZE;
	}
	}

	static void cfl_luma_subsampling_444_hbd(const uint16_t *input,
	int input_stride, int16_t *output_q3,
	int width, int height) {
	for (int j = 0; j < height; j++) {
	for (int i = 0; i < width; i++) {
	output_q3[i] = input[i] << 3;
	}
	input += input_stride;
	output_q3 += MAX_SB_SIZE;
	}
	}

	typedef void (cfl_subsample_hbd_fn)(const uint16_t input, int input_stride,
	int16_t *output_q3, int width, int height);

	static const cfl_subsample_hbd_fn subsample_hbd[2][2] = {
	// (sub_y == 0, sub_x == 0) (sub_y == 0, sub_x == 1)
	// (sub_y == 1, sub_x == 0) (sub_y == 1, sub_x == 1)
	{ cfl_luma_subsampling_444_hbd, cfl_luma_subsampling_422_hbd },
	{ cfl_luma_subsampling_440_hbd, cfl_luma_subsampling_420_hbd },
	};
	#endif // CONFIG_HIGHBITDEPTH

	static void cfl_store(CFL_CTX cfl, const uint8_t input, int input_stride,
	int row, int col, int width, int height, int use_hbd) {
	const int tx_off_log2 = tx_size_wide_log2[0];
	const int sub_x = cfl->subsampling_x;
	const int sub_y = cfl->subsampling_y;
	const int store_row = row << (tx_off_log2 - sub_y);
	const int store_col = col << (tx_off_log2 - sub_x);
	const int store_height = height >> sub_y;
	const int store_width = width >> sub_x;

	// Invalidate current parameters
	cfl->are_parameters_computed = 0;

	// Store the surface of the pixel buffer that was written to, this way we
	// can manage chroma overrun (e.g. when the chroma surfaces goes beyond the
	// frame boundary)
	if (col == 0 && row == 0) {
	cfl->buf_width = store_width;
	cfl->buf_height = store_height;
	} else {
	cfl->buf_width = OD_MAXI(store_col + store_width, cfl->buf_width);
	cfl->buf_height = OD_MAXI(store_row + store_height, cfl->buf_height);
	}

	// Check that we will remain inside the pixel buffer.
	assert(store_row + store_height <= MAX_SB_SIZE);
	assert(store_col + store_width <= MAX_SB_SIZE);

	// Store the input into the CfL pixel buffer
	int16_t *pred_buf_q3 =
	cfl->pred_buf_q3 + (store_row * MAX_SB_SIZE + store_col);

	#if CONFIG_HIGHBITDEPTH
	if (use_hbd) {
	const uint16_t *input_16 = CONVERT_TO_SHORTPTR(input);
	// AND sub_x and sub_y with 1 to ensures that an attacker won't be able to
	// index the function pointer array out of bounds.
	subsample_hbd[sub_y & 1][sub_x & 1](input_16, input_stride, pred_buf_q3,
	store_width, store_height);
	return;
	}
	#endif // CONFIG_HIGHBITDEPTH
	(void)use_hbd;
	// AND sub_x and sub_y with 1 to ensures that an attacker won't be able to
	// index the function pointer array out of bounds.
	subsample_lbd[sub_y & 1][sub_x & 1](input, input_stride, pred_buf_q3,
	store_width, store_height);
	}

	// Adjust the row and column of blocks smaller than 8X8, as chroma-referenced
	// and non-chroma-referenced blocks are stored together in the CfL buffer.
	static INLINE void sub8x8_adjust_offset(const CFL_CTX cfl, int row_out,
	int *col_out) {
	// Increment row index for bottom: 8x4, 16x4 or both bottom 4x4s.
	if ((cfl->mi_row & 0x01) && cfl->subsampling_y) {
	assert(*row_out == 0);
	(*row_out)++;
	}

	// Increment col index for right: 4x8, 4x16 or both right 4x4s.
	if ((cfl->mi_col & 0x01) && cfl->subsampling_x) {
	assert(*col_out == 0);
	(*col_out)++;
	}
	}
	#if CONFIG_DEBUG
	// Since the chroma surface of sub8x8 block span across multiple luma blocks,
	// this function validates that the reconstructed luma area required to predict
	// the chroma block using CfL has been stored during the previous luma encode.
	//
	// Issue 1: Chroma intra prediction is not always performed after luma. One
	// such example is when luma RD cost is really high and the mode decision
	// algorithm decides to terminate instead of evaluating chroma.
	//
	// Issue 2: When multiple CfL predictions are computed for a given sub8x8
	// block. The reconstructed luma that belongs to the non-reference sub8x8
	// blocks must remain in the buffer (we cannot clear the buffer when we
	// compute the CfL prediction
	//
	// To resolve these issues, we increment the store_counter on each store. if
	// other sub8x8 blocks have already been coded and the counter corresponds to
	// the previous value they are also set to the current value. If a sub8x8 block
	// is not stored the store_counter won't match which will be detected when the
	// CfL parements are computed.
	static void sub8x8_set_val(CFL_CTX *cfl, int row, int col, TX_SIZE y_tx_size) {
	const int y_tx_wide_unit = tx_size_wide_unit[y_tx_size];
	const int y_tx_high_unit = tx_size_high_unit[y_tx_size];

	// How many 4x4 are in tx_size
	const int y_tx_unit_len = y_tx_wide_unit * y_tx_high_unit;
	assert(y_tx_unit_len == 1 \|\| y_tx_unit_len == 2 \|\| y_tx_unit_len == 4);

	// Invalidate other counters if (0,0)
	const int is_first = row + col == 0;
	cfl->store_counter += is_first ? 2 : 1;

	const int inc =
	(y_tx_wide_unit >= y_tx_high_unit) ? 1 : CFL_SUB8X8_VAL_MI_SIZE;
	uint16_t sub8x8_val = cfl->sub8x8_val + (row CFL_SUB8X8_VAL_MI_SIZE + col);
	for (int i = 0; i < y_tx_unit_len; i++) {
	*sub8x8_val = cfl->store_counter;
	sub8x8_val += inc;
	}

	if (!is_first) {
	const uint16_t prev_store_counter = cfl->store_counter - 1;
	int found = 0;
	(void)found;
	sub8x8_val = cfl->sub8x8_val;
	for (int y = 0; y < CFL_SUB8X8_VAL_MI_SIZE; y++) {
	for (int x = 0; x < CFL_SUB8X8_VAL_MI_SIZE; x++) {
	if (sub8x8_val[x] == prev_store_counter) {
	sub8x8_val[x] = cfl->store_counter;
	found = 1;
	}
	}
	sub8x8_val += CFL_SUB8X8_VAL_MI_SIZE;
	}
	// Something is wrong if (0,0) is missing
	assert(found);
	}
	}
	#endif // CONFIG_DEBUG

	void cfl_store_tx(MACROBLOCKD *const xd, int row, int col, TX_SIZE tx_size,
	BLOCK_SIZE bsize) {
	CFL_CTX *const cfl = &xd->cfl;
	struct macroblockd_plane *const pd = &xd->plane[AOM_PLANE_Y];
	uint8_t *dst =
	&pd->dst.buf[(row * pd->dst.stride + col) << tx_size_wide_log2[0]];

	assert(is_cfl_allowed(&xd->mi[0]->mbmi));
	if (block_size_high[bsize] == 4 \|\| block_size_wide[bsize] == 4) {
	// Only dimensions of size 4 can have an odd offset.
	assert(!((col & 1) && tx_size_wide[tx_size] != 4));
	assert(!((row & 1) && tx_size_high[tx_size] != 4));
	sub8x8_adjust_offset(cfl, &row, &col);
	#if CONFIG_DEBUG
	sub8x8_set_val(cfl, row, col, tx_size);
	#endif // CONFIG_DEBUG
	}
	cfl_store(cfl, dst, pd->dst.stride, row, col, tx_size_wide[tx_size],
	tx_size_high[tx_size], get_bitdepth_data_path_index(xd));
	}

	void cfl_store_block(MACROBLOCKD *const xd, BLOCK_SIZE bsize, TX_SIZE tx_size) {
	CFL_CTX *const cfl = &xd->cfl;
	struct macroblockd_plane *const pd = &xd->plane[AOM_PLANE_Y];
	int row = 0;
	int col = 0;
	bsize = AOMMAX(BLOCK_4X4, bsize);

	assert(is_cfl_allowed(&xd->mi[0]->mbmi));
	if (block_size_high[bsize] == 4 \|\| block_size_wide[bsize] == 4) {
	sub8x8_adjust_offset(cfl, &row, &col);
	#if CONFIG_DEBUG
	// Point to the last transform block inside the partition.
	const int off_row =
	row + (mi_size_high[bsize] - tx_size_high_unit[tx_size]);
	const int off_col =
	col + (mi_size_wide[bsize] - tx_size_wide_unit[tx_size]);
	sub8x8_set_val(cfl, off_row, off_col, tx_size);
	#endif // CONFIG_DEBUG
	}
	const int width = max_intra_block_width(xd, bsize, AOM_PLANE_Y, tx_size);
	const int height = max_intra_block_height(xd, bsize, AOM_PLANE_Y, tx_size);
	cfl_store(cfl, pd->dst.buf, pd->dst.stride, row, col, width, height,
	get_bitdepth_data_path_index(xd));
	}