text: /*
   *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
   *
   *  Use of this source code is governed by a BSD-style license
   *  that can be found in the LICENSE file in the root of the source
   *  tree. An additional intellectual property rights grant can be found
   *  in the file PATENTS.  All contributing project authors may
   *  be found in the AUTHORS file in the root of the source tree.
   */
  
  #include "./vpx_config.h"
  #include "vp9/common/vp9_loopfilter.h"
  #include "vp9/common/vp9_onyxc_int.h"
  #include "vp9/common/vp9_reconinter.h"
  #include "vpx_mem/vpx_mem.h"
  
  #include "vp9/common/vp9_seg_common.h"
  
  // This structure holds bit masks for all 8x8 blocks in a 64x64 region.
  // Each 1 bit represents a position in which we want to apply the loop filter.
  // Left_ entries refer to whether we apply a filter on the border to the
  // left of the block.   Above_ entries refer to whether or not to apply a
  // filter on the above border.   Int_ entries refer to whether or not to
  // apply borders on the 4x4 edges within the 8x8 block that each bit
  // represents.
  // Since each transform is accompanied by a potentially different type of
  // loop filter there is a different entry in the array for each transform size.
  typedef struct {
    uint64_t left_y[TX_SIZES];
    uint64_t above_y[TX_SIZES];
    uint64_t int_4x4_y;
    uint16_t left_uv[TX_SIZES];
    uint16_t above_uv[TX_SIZES];
    uint16_t int_4x4_uv;
    uint8_t lfl_y[64];
    uint8_t lfl_uv[16];
  } LOOP_FILTER_MASK;
  
  // 64 bit masks for left transform size.  Each 1 represents a position where
  // we should apply a loop filter across the left border of an 8x8 block
  // boundary.
  //
  // In the case of TX_16X16->  ( in low order byte first we end up with
  // a mask that looks like this
  //
  //    10101010
  //    10101010
  //    10101010
  //    10101010
  //    10101010
  //    10101010
  //    10101010
  //    10101010
  //
  // A loopfilter should be applied to every other 8x8 horizontally.
  static const uint64_t left_64x64_txform_mask[TX_SIZES]= {
      0xffffffffffffffff,  // TX_4X4
      0xffffffffffffffff,  // TX_8x8
      0x5555555555555555,  // TX_16x16
      0x1111111111111111,  // TX_32x32
  };
  
  // 64 bit masks for above transform size.  Each 1 represents a position where
  // we should apply a loop filter across the top border of an 8x8 block
  // boundary.
  //
  // In the case of TX_32x32 ->  ( in low order byte first we end up with
  // a mask that looks like this
  //
  //    11111111
  //    00000000
  //    00000000
  //    00000000
  //    11111111
  //    00000000
  //    00000000
  //    00000000
  //
  // A loopfilter should be applied to every other 4 the row vertically.
  static const uint64_t above_64x64_txform_mask[TX_SIZES]= {
      0xffffffffffffffff,  // TX_4X4
      0xffffffffffffffff,  // TX_8x8
      0x00ff00ff00ff00ff,  // TX_16x16
      0x000000ff000000ff,  // TX_32x32
  };
  
  // 64 bit masks for prediction sizes (left).  Each 1 represents a position
  // where left border of an 8x8 block.  These are aligned to the right most
  // appropriate bit,  and then shifted into place.
  //
  // In the case of TX_16x32 ->  ( low order byte first ) we end up with
  // a mask that looks like this :
  //
  //  10000000
  //  10000000
  //  10000000
  //  10000000
  //  00000000
  //  00000000
  //  00000000
  //  00000000
  static const uint64_t left_prediction_mask[BLOCK_SIZES] = {
      0x0000000000000001,  // BLOCK_4X4,
      0x0000000000000001,  // BLOCK_4X8,
      0x0000000000000001,  // BLOCK_8X4,
      0x0000000000000001,  // BLOCK_8X8,
      0x0000000000000101,  // BLOCK_8X16,
      0x0000000000000001,  // BLOCK_16X8,
      0x0000000000000101,  // BLOCK_16X16,
      0x0000000001010101,  // BLOCK_16X32,
      0x0000000000000101,  // BLOCK_32X16,
      0x0000000001010101,  // BLOCK_32X32,
      0x0101010101010101,  // BLOCK_32X64,
      0x0000000001010101,  // BLOCK_64X32,
      0x0101010101010101,  // BLOCK_64X64
  };
  
  // 64 bit mask to shift and set for each prediction size.
  static const uint64_t above_prediction_mask[BLOCK_SIZES] = {
      0x0000000000000001,  // BLOCK_4X4
      0x0000000000000001,  // BLOCK_4X8
      0x0000000000000001,  // BLOCK_8X4
      0x0000000000000001,  // BLOCK_8X8
      0x0000000000000001,  // BLOCK_8X16,
      0x0000000000000003,  // BLOCK_16X8
      0x0000000000000003,  // BLOCK_16X16
      0x0000000000000003,  // BLOCK_16X32,
      0x000000000000000f,  // BLOCK_32X16,
      0x000000000000000f,  // BLOCK_32X32,
      0x000000000000000f,  // BLOCK_32X64,
      0x00000000000000ff,  // BLOCK_64X32,
      0x00000000000000ff,  // BLOCK_64X64
  };
  // 64 bit mask to shift and set for each prediction size.  A bit is set for
  // each 8x8 block that would be in the left most block of the given block
  // size in the 64x64 block.
  static const uint64_t size_mask[BLOCK_SIZES] = {
      0x0000000000000001,  // BLOCK_4X4
      0x0000000000000001,  // BLOCK_4X8
      0x0000000000000001,  // BLOCK_8X4
      0x0000000000000001,  // BLOCK_8X8
      0x0000000000000101,  // BLOCK_8X16,
      0x0000000000000003,  // BLOCK_16X8
      0x0000000000000303,  // BLOCK_16X16
      0x0000000003030303,  // BLOCK_16X32,
      0x0000000000000f0f,  // BLOCK_32X16,
      0x000000000f0f0f0f,  // BLOCK_32X32,
      0x0f0f0f0f0f0f0f0f,  // BLOCK_32X64,
      0x00000000ffffffff,  // BLOCK_64X32,
      0xffffffffffffffff,  // BLOCK_64X64
  };
  
  // These are used for masking the left and above borders.
  static const uint64_t left_border =  0x1111111111111111;
  static const uint64_t above_border = 0x000000ff000000ff;
  
  // 16 bit masks for uv transform sizes.
  static const uint16_t left_64x64_txform_mask_uv[TX_SIZES]= {
      0xffff,  // TX_4X4
      0xffff,  // TX_8x8
      0x5555,  // TX_16x16
      0x1111,  // TX_32x32
  };
  
  static const uint16_t above_64x64_txform_mask_uv[TX_SIZES]= {
      0xffff,  // TX_4X4
      0xffff,  // TX_8x8
      0x0f0f,  // TX_16x16
      0x000f,  // TX_32x32
  };
  
  // 16 bit left mask to shift and set for each uv prediction size.
  static const uint16_t left_prediction_mask_uv[BLOCK_SIZES] = {
      0x0001,  // BLOCK_4X4,
      0x0001,  // BLOCK_4X8,
      0x0001,  // BLOCK_8X4,
      0x0001,  // BLOCK_8X8,
      0x0001,  // BLOCK_8X16,
      0x0001,  // BLOCK_16X8,
      0x0001,  // BLOCK_16X16,
      0x0011,  // BLOCK_16X32,
      0x0001,  // BLOCK_32X16,
      0x0011,  // BLOCK_32X32,
      0x1111,  // BLOCK_32X64
      0x0011,  // BLOCK_64X32,
      0x1111,  // BLOCK_64X64
  };
  // 16 bit above mask to shift and set for uv each prediction size.
  static const uint16_t above_prediction_mask_uv[BLOCK_SIZES] = {
      0x0001,  // BLOCK_4X4
      0x0001,  // BLOCK_4X8
      0x0001,  // BLOCK_8X4
      0x0001,  // BLOCK_8X8
      0x0001,  // BLOCK_8X16,
      0x0001,  // BLOCK_16X8
      0x0001,  // BLOCK_16X16
      0x0001,  // BLOCK_16X32,
      0x0003,  // BLOCK_32X16,
      0x0003,  // BLOCK_32X32,
      0x0003,  // BLOCK_32X64,
      0x000f,  // BLOCK_64X32,
      0x000f,  // BLOCK_64X64
  };
  
  // 64 bit mask to shift and set for each uv prediction size
  static const uint16_t size_mask_uv[BLOCK_SIZES] = {
      0x0001,  // BLOCK_4X4
      0x0001,  // BLOCK_4X8
      0x0001,  // BLOCK_8X4
      0x0001,  // BLOCK_8X8
      0x0001,  // BLOCK_8X16,
      0x0001,  // BLOCK_16X8
      0x0001,  // BLOCK_16X16
      0x0011,  // BLOCK_16X32,
      0x0003,  // BLOCK_32X16,
      0x0033,  // BLOCK_32X32,
      0x3333,  // BLOCK_32X64,
      0x00ff,  // BLOCK_64X32,
      0xffff,  // BLOCK_64X64
  };
  static const uint16_t left_border_uv =  0x1111;
  static const uint16_t above_border_uv = 0x000f;
  
  
  static void lf_init_lut(loop_filter_info_n *lfi) {
    lfi->mode_lf_lut[DC_PRED] = 0;
    lfi->mode_lf_lut[D45_PRED] = 0;
    lfi->mode_lf_lut[D135_PRED] = 0;
    lfi->mode_lf_lut[D117_PRED] = 0;
    lfi->mode_lf_lut[D153_PRED] = 0;
    lfi->mode_lf_lut[D207_PRED] = 0;
    lfi->mode_lf_lut[D63_PRED] = 0;
    lfi->mode_lf_lut[V_PRED] = 0;
    lfi->mode_lf_lut[H_PRED] = 0;
    lfi->mode_lf_lut[TM_PRED] = 0;
    lfi->mode_lf_lut[ZEROMV]  = 0;
    lfi->mode_lf_lut[NEARESTMV] = 1;
    lfi->mode_lf_lut[NEARMV] = 1;
    lfi->mode_lf_lut[NEWMV] = 1;
  }
  
  static void update_sharpness(loop_filter_info_n *lfi, int sharpness_lvl) {
    int lvl;
  
    // For each possible value for the loop filter fill out limits
    for (lvl = 0; lvl <= MAX_LOOP_FILTER; lvl++) {
      // Set loop filter paramaeters that control sharpness.
      int block_inside_limit = lvl >> ((sharpness_lvl > 0) + (sharpness_lvl > 4));
  
      if (sharpness_lvl > 0) {
        if (block_inside_limit > (9 - sharpness_lvl))
          block_inside_limit = (9 - sharpness_lvl);
      }
  
      if (block_inside_limit < 1)
        block_inside_limit = 1;
  
      vpx_memset(lfi->lfthr[lvl].lim, block_inside_limit, SIMD_WIDTH);
      vpx_memset(lfi->lfthr[lvl].mblim, (2 * (lvl + 2) + block_inside_limit),
                 SIMD_WIDTH);
    }
  }
  
  void vp9_loop_filter_init(VP9_COMMON *cm) {
    loop_filter_info_n *lfi = &cm->lf_info;
    struct loopfilter *lf = &cm->lf;
    int lvl;
  
    // init limits for given sharpness
    update_sharpness(lfi, lf->sharpness_level);
    lf->last_sharpness_level = lf->sharpness_level;
  
    // init LUT for lvl  and hev thr picking
    lf_init_lut(lfi);
  
    // init hev threshold const vectors
    for (lvl = 0; lvl <= MAX_LOOP_FILTER; lvl++)
      vpx_memset(lfi->lfthr[lvl].hev_thr, (lvl >> 4), SIMD_WIDTH);
  }
  
  void vp9_loop_filter_frame_init(VP9_COMMON *cm, int default_filt_lvl) {
    int seg_id;
    // n_shift is the a multiplier for lf_deltas
    // the multiplier is 1 for when filter_lvl is between 0 and 31;
    // 2 when filter_lvl is between 32 and 63
    const int scale = 1 << (default_filt_lvl >> 5);
    loop_filter_info_n *const lfi = &cm->lf_info;
    struct loopfilter *const lf = &cm->lf;
    const struct segmentation *const seg = &cm->seg;
  
    // update limits if sharpness has changed
    if (lf->last_sharpness_level != lf->sharpness_level) {
      update_sharpness(lfi, lf->sharpness_level);
      lf->last_sharpness_level = lf->sharpness_level;
    }
  
    for (seg_id = 0; seg_id < MAX_SEGMENTS; seg_id++) {
      int lvl_seg = default_filt_lvl;
      if (vp9_segfeature_active(seg, seg_id, SEG_LVL_ALT_LF)) {
        const int data = vp9_get_segdata(seg, seg_id, SEG_LVL_ALT_LF);
        lvl_seg = seg->abs_delta == SEGMENT_ABSDATA
                    ? data
                    : clamp(default_filt_lvl + data, 0, MAX_LOOP_FILTER);
      }
  
      if (!lf->mode_ref_delta_enabled) {
        // we could get rid of this if we assume that deltas are set to
        // zero when not in use; encoder always uses deltas
        vpx_memset(lfi->lvl[seg_id], lvl_seg, sizeof(lfi->lvl[seg_id]));
      } else {
        int ref, mode;
        const int intra_lvl = lvl_seg + lf->ref_deltas[INTRA_FRAME] * scale;
        lfi->lvl[seg_id][INTRA_FRAME][0] = clamp(intra_lvl, 0, MAX_LOOP_FILTER);
  
        for (ref = LAST_FRAME; ref < MAX_REF_FRAMES; ++ref) {
          for (mode = 0; mode < MAX_MODE_LF_DELTAS; ++mode) {
            const int inter_lvl = lvl_seg + lf->ref_deltas[ref] * scale
                                          + lf->mode_deltas[mode] * scale;
            lfi->lvl[seg_id][ref][mode] = clamp(inter_lvl, 0, MAX_LOOP_FILTER);
          }
        }
      }
    }
  }
  
  static void filter_selectively_vert(uint8_t *s, int pitch,
                                      unsigned int mask_16x16,
                                      unsigned int mask_8x8,
                                      unsigned int mask_4x4,
                                      unsigned int mask_4x4_int,
                                      const loop_filter_info_n *lfi_n,
                                      const uint8_t *lfl) {
    unsigned int mask;
  
    for (mask = mask_16x16 | mask_8x8 | mask_4x4 | mask_4x4_int;
         mask; mask >>= 1) {
      const loop_filter_thresh *lfi = lfi_n->lfthr + *lfl;
  
      if (mask & 1) {
        if (mask_16x16 & 1) {
          vp9_mb_lpf_vertical_edge_w(s, pitch, lfi->mblim, lfi->lim,
                                     lfi->hev_thr);
        } else if (mask_8x8 & 1) {
          vp9_mbloop_filter_vertical_edge(s, pitch, lfi->mblim, lfi->lim,
                                          lfi->hev_thr, 1);
        } else if (mask_4x4 & 1) {
          vp9_loop_filter_vertical_edge(s, pitch, lfi->mblim, lfi->lim,
                                        lfi->hev_thr, 1);
        }
      }
      if (mask_4x4_int & 1)
        vp9_loop_filter_vertical_edge(s + 4, pitch, lfi->mblim, lfi->lim,
                                      lfi->hev_thr, 1);
      s += 8;
      lfl += 1;
      mask_16x16 >>= 1;
      mask_8x8 >>= 1;
      mask_4x4 >>= 1;
      mask_4x4_int >>= 1;
    }
  }
  
  static void filter_selectively_horiz(uint8_t *s, int pitch,
                                       unsigned int mask_16x16,
                                       unsigned int mask_8x8,
                                       unsigned int mask_4x4,
                                       unsigned int mask_4x4_int,
                                       const loop_filter_info_n *lfi_n,
                                       const uint8_t *lfl) {
    unsigned int mask;
    int count;
  
    for (mask = mask_16x16 | mask_8x8 | mask_4x4 | mask_4x4_int;
         mask; mask >>= count) {
      const loop_filter_thresh *lfi = lfi_n->lfthr + *lfl;
  
      count = 1;
      if (mask & 1) {
        if (mask_16x16 & 1) {
          if ((mask_16x16 & 3) == 3) {
            vp9_mb_lpf_horizontal_edge_w(s, pitch, lfi->mblim, lfi->lim,
                                         lfi->hev_thr, 2);
            count = 2;
          } else {
            vp9_mb_lpf_horizontal_edge_w(s, pitch, lfi->mblim, lfi->lim,
                                         lfi->hev_thr, 1);
          }
        } else if (mask_8x8 & 1) {
          if ((mask_8x8 & 3) == 3) {
            // Next block's thresholds
            const loop_filter_thresh *lfin = lfi_n->lfthr + *(lfl + 1);
  
            // TODO(yunqingwang): Combine next 2 calls as 1 wide filtering.
            vp9_mbloop_filter_horizontal_edge(s, pitch, lfi->mblim, lfi->lim,
                                              lfi->hev_thr, 1);
            vp9_mbloop_filter_horizontal_edge(s + 8, pitch, lfin->mblim,
                                              lfin->lim, lfin->hev_thr, 1);
  
            if ((mask_4x4_int & 3) == 3) {
              // TODO(yunqingwang): Combine next 2 calls as 1 wide filtering.
              vp9_loop_filter_horizontal_edge(s + 4 * pitch, pitch, lfi->mblim,
                                              lfi->lim, lfi->hev_thr, 1);
              vp9_loop_filter_horizontal_edge(s + 8 + 4 * pitch, pitch,
                                              lfin->mblim, lfin->lim,
                                              lfin->hev_thr, 1);
            } else {
              if (mask_4x4_int & 1)
                vp9_loop_filter_horizontal_edge(s + 4 * pitch, pitch, lfi->mblim,
                                                lfi->lim, lfi->hev_thr, 1);
              else if (mask_4x4_int & 2)
                vp9_loop_filter_horizontal_edge(s + 8 + 4 * pitch, pitch,
                                                lfin->mblim, lfin->lim,
                                                lfin->hev_thr, 1);
            }
            count = 2;
          } else {
            vp9_mbloop_filter_horizontal_edge(s, pitch, lfi->mblim, lfi->lim,
                                              lfi->hev_thr, 1);
  
            if (mask_4x4_int & 1)
              vp9_loop_filter_horizontal_edge(s + 4 * pitch, pitch, lfi->mblim,
                                              lfi->lim, lfi->hev_thr, 1);
          }
        } else if (mask_4x4 & 1) {
          if ((mask_4x4 & 3) == 3) {
            // Next block's thresholds
            const loop_filter_thresh *lfin = lfi_n->lfthr + *(lfl + 1);
  
            // TODO(yunqingwang): Combine next 2 calls as 1 wide filtering.
            vp9_loop_filter_horizontal_edge(s, pitch, lfi->mblim, lfi->lim,
                                              lfi->hev_thr, 1);
            vp9_loop_filter_horizontal_edge(s + 8, pitch, lfin->mblim, lfin->lim,
                                              lfin->hev_thr, 1);
  
            if ((mask_4x4_int & 3) == 3) {
              // TODO(yunqingwang): Combine next 2 calls as 1 wide filtering.
              vp9_loop_filter_horizontal_edge(s + 4 * pitch, pitch, lfi->mblim,
                                              lfi->lim, lfi->hev_thr, 1);
              vp9_loop_filter_horizontal_edge(s + 8 + 4 * pitch, pitch,
                                              lfin->mblim, lfin->lim,
                                              lfin->hev_thr, 1);
            } else {
              if (mask_4x4_int & 1)
                vp9_loop_filter_horizontal_edge(s + 4 * pitch, pitch, lfi->mblim,
                                                lfi->lim, lfi->hev_thr, 1);
              else if (mask_4x4_int & 2)
                vp9_loop_filter_horizontal_edge(s + 8 + 4 * pitch, pitch,
                                                lfin->mblim, lfin->lim,
                                                lfin->hev_thr, 1);
            }
            count = 2;
          } else {
          vp9_loop_filter_horizontal_edge(s, pitch, lfi->mblim, lfi->lim,
                                          lfi->hev_thr, 1);
  
          if (mask_4x4_int & 1)
            vp9_loop_filter_horizontal_edge(s + 4 * pitch, pitch, lfi->mblim,
                                            lfi->lim, lfi->hev_thr, 1);
          }
        } else if (mask_4x4_int & 1) {
          vp9_loop_filter_horizontal_edge(s + 4 * pitch, pitch, lfi->mblim,
                                          lfi->lim, lfi->hev_thr, 1);
        }
      }
      s += 8 * count;
      lfl += count;
      mask_16x16 >>= count;
      mask_8x8 >>= count;
      mask_4x4 >>= count;
      mask_4x4_int >>= count;
    }
  }
  
  // This function ors into the current lfm structure, where to do loop
  // filters for the specific mi we are looking at.   It uses information
  // including the block_size_type (32x16, 32x32, etc),  the transform size,
  // whether there were any coefficients encoded, and the loop filter strength
  // block we are currently looking at. Shift is used to position the
  // 1's we produce.
  // TODO(JBB) Need another function for different resolution color..
  static void build_masks(const loop_filter_info_n *const lfi_n,
                          const MODE_INFO *mi, const int shift_y,
                          const int shift_uv,
                          LOOP_FILTER_MASK *lfm) {
    const BLOCK_SIZE block_size = mi->mbmi.sb_type;
    const TX_SIZE tx_size_y = mi->mbmi.tx_size;
    const TX_SIZE tx_size_uv = get_uv_tx_size(&mi->mbmi);
    const int skip = mi->mbmi.skip_coeff;
    const int seg = mi->mbmi.segment_id;
    const int ref = mi->mbmi.ref_frame[0];
    const int mode = lfi_n->mode_lf_lut[mi->mbmi.mode];
    const int filter_level = lfi_n->lvl[seg][ref][mode];
    uint64_t *left_y = &lfm->left_y[tx_size_y];
    uint64_t *above_y = &lfm->above_y[tx_size_y];
    uint64_t *int_4x4_y = &lfm->int_4x4_y;
    uint16_t *left_uv = &lfm->left_uv[tx_size_uv];
    uint16_t *above_uv = &lfm->above_uv[tx_size_uv];
    uint16_t *int_4x4_uv = &lfm->int_4x4_uv;
    int i;
    int w = num_8x8_blocks_wide_lookup[block_size];
    int h = num_8x8_blocks_high_lookup[block_size];
  
    // If filter level is 0 we don't loop filter.
    if (!filter_level) {
      return;
    } else {
      int index = shift_y;
      for (i = 0; i < h; i++) {
        vpx_memset(&lfm->lfl_y[index], filter_level, w);
        index += 8;
      }
    }
  
    // These set 1 in the current block size for the block size edges.
    // For instance if the block size is 32x16,   we'll set :
    //    above =   1111
    //              0000
    //    and
    //    left  =   1000
    //          =   1000
    // NOTE : In this example the low bit is left most ( 1000 ) is stored as
    //        1,  not 8...
    //
    // U and v set things on a 16 bit scale.
    //
    *above_y |= above_prediction_mask[block_size] << shift_y;
    *above_uv |= above_prediction_mask_uv[block_size] << shift_uv;
    *left_y |= left_prediction_mask[block_size] << shift_y;
    *left_uv |= left_prediction_mask_uv[block_size] << shift_uv;
  
    // If the block has no coefficients and is not intra we skip applying
    // the loop filter on block edges.
    if (skip && ref > INTRA_FRAME)
      return;
  
    // Here we are adding a mask for the transform size.  The transform
    // size mask is set to be correct for a 64x64 prediction block size. We
    // mask to match the size of the block we are working on and then shift it
    // into place..
    *above_y |= (size_mask[block_size] &
                 above_64x64_txform_mask[tx_size_y]) << shift_y;
    *above_uv |= (size_mask_uv[block_size] &
                  above_64x64_txform_mask_uv[tx_size_uv]) << shift_uv;
  
    *left_y |= (size_mask[block_size] &
                left_64x64_txform_mask[tx_size_y]) << shift_y;
    *left_uv |= (size_mask_uv[block_size] &
                 left_64x64_txform_mask_uv[tx_size_uv]) << shift_uv;
  
    // Here we are trying to determine what to do with the internal 4x4 block
    // boundaries.  These differ from the 4x4 boundaries on the outside edge of
    // an 8x8 in that the internal ones can be skipped and don't depend on
    // the prediction block size.
    if (tx_size_y == TX_4X4) {
      *int_4x4_y |= (size_mask[block_size] & 0xffffffffffffffff) << shift_y;
    }
    if (tx_size_uv == TX_4X4) {
      *int_4x4_uv |= (size_mask_uv[block_size] & 0xffff) << shift_uv;
    }
  }
  
  // This function does the same thing as the one above with the exception that
  // it only affects the y masks.   It exists because for blocks < 16x16 in size,
  // we only update u and v masks on the first block.
  static void build_y_mask(const loop_filter_info_n *const lfi_n,
                           const MODE_INFO *mi, const int shift_y,
                           LOOP_FILTER_MASK *lfm) {
    const BLOCK_SIZE block_size = mi->mbmi.sb_type;
    const TX_SIZE tx_size_y = mi->mbmi.tx_size;
    const int skip = mi->mbmi.skip_coeff;
    const int seg = mi->mbmi.segment_id;
    const int ref = mi->mbmi.ref_frame[0];
    const int mode = lfi_n->mode_lf_lut[mi->mbmi.mode];
    const int filter_level = lfi_n->lvl[seg][ref][mode];
    uint64_t *left_y = &lfm->left_y[tx_size_y];
    uint64_t *above_y = &lfm->above_y[tx_size_y];
    uint64_t *int_4x4_y = &lfm->int_4x4_y;
    int i;
    int w = num_8x8_blocks_wide_lookup[block_size];
    int h = num_8x8_blocks_high_lookup[block_size];
  
    if (!filter_level) {
      return;
    } else {
      int index = shift_y;
      for (i = 0; i < h; i++) {
        vpx_memset(&lfm->lfl_y[index], filter_level, w);
        index += 8;
      }
    }
  
    *above_y |= above_prediction_mask[block_size] << shift_y;
    *left_y |= left_prediction_mask[block_size] << shift_y;
  
    if (skip && ref > INTRA_FRAME)
      return;
  
    *above_y |= (size_mask[block_size] &
                 above_64x64_txform_mask[tx_size_y]) << shift_y;
  
    *left_y |= (size_mask[block_size] &
                left_64x64_txform_mask[tx_size_y]) << shift_y;
  
    if (tx_size_y == TX_4X4) {
      *int_4x4_y |= (size_mask[block_size] & 0xffffffffffffffff) << shift_y;
    }
  }
  
  // This function sets up the bit masks for the entire 64x64 region represented
  // by mi_row, mi_col.
  // TODO(JBB): This function only works for yv12.
  static void setup_mask(VP9_COMMON *const cm, const int mi_row, const int mi_col,
                         MODE_INFO **mi_8x8, const int mode_info_stride,
                         LOOP_FILTER_MASK *lfm) {
    int idx_32, idx_16, idx_8;
    const loop_filter_info_n *const lfi_n = &cm->lf_info;
    MODE_INFO **mip = mi_8x8;
    MODE_INFO **mip2 = mi_8x8;
  
    // These are offsets to the next mi in the 64x64 block. It is what gets
    // added to the mi ptr as we go through each loop.  It helps us to avoids
    // setting up special row and column counters for each index.  The last step
    // brings us out back to the starting position.
    const int offset_32[] = {4, (mode_info_stride << 2) - 4, 4,
                             -(mode_info_stride << 2) - 4};
    const int offset_16[] = {2, (mode_info_stride << 1) - 2, 2,
                             -(mode_info_stride << 1) - 2};
    const int offset[] = {1, mode_info_stride - 1, 1, -mode_info_stride - 1};
  
    // Following variables represent shifts to position the current block
    // mask over the appropriate block.   A shift of 36 to the left will move
    // the bits for the final 32 by 32 block in the 64x64 up 4 rows and left
    // 4 rows to the appropriate spot.
    const int shift_32_y[] = {0, 4, 32, 36};
    const int shift_16_y[] = {0, 2, 16, 18};
    const int shift_8_y[] = {0, 1, 8, 9};
    const int shift_32_uv[] = {0, 2, 8, 10};
    const int shift_16_uv[] = {0, 1, 4, 5};
    int i;
    const int max_rows = (mi_row + MI_BLOCK_SIZE > cm->mi_rows ?
                          cm->mi_rows - mi_row : MI_BLOCK_SIZE);
    const int max_cols = (mi_col + MI_BLOCK_SIZE > cm->mi_cols ?
                          cm->mi_cols - mi_col : MI_BLOCK_SIZE);
  
    vp9_zero(*lfm);
  
    // TODO(jimbankoski): Try moving most of the following code into decode
    // loop and storing lfm in the mbmi structure so that we don't have to go
    // through the recursive loop structure multiple times.
    switch (mip[0]->mbmi.sb_type) {
      case BLOCK_64X64:
        build_masks(lfi_n, mip[0] , 0, 0, lfm);
        break;
      case BLOCK_64X32:
        build_masks(lfi_n, mip[0], 0, 0, lfm);
        mip2 = mip + mode_info_stride * 4;
        if (4 >= max_rows)
          break;
        build_masks(lfi_n, mip2[0], 32, 8, lfm);
        break;
      case BLOCK_32X64:
        build_masks(lfi_n, mip[0], 0, 0, lfm);
        mip2 = mip + 4;
        if (4 >= max_cols)
          break;
        build_masks(lfi_n, mip2[0], 4, 2, lfm);
        break;
      default:
        for (idx_32 = 0; idx_32 < 4; mip += offset_32[idx_32], ++idx_32) {
          const int shift_y = shift_32_y[idx_32];
          const int shift_uv = shift_32_uv[idx_32];
          const int mi_32_col_offset = ((idx_32 & 1) << 2);
          const int mi_32_row_offset = ((idx_32 >> 1) << 2);
          if (mi_32_col_offset >= max_cols || mi_32_row_offset >= max_rows)
            continue;
          switch (mip[0]->mbmi.sb_type) {
            case BLOCK_32X32:
              build_masks(lfi_n, mip[0], shift_y, shift_uv, lfm);
              break;
            case BLOCK_32X16:
              build_masks(lfi_n, mip[0], shift_y, shift_uv, lfm);
              if (mi_32_row_offset + 2 >= max_rows)
                continue;
              mip2 = mip + mode_info_stride * 2;
              build_masks(lfi_n, mip2[0], shift_y + 16, shift_uv + 4, lfm);
              break;
            case BLOCK_16X32:
              build_masks(lfi_n, mip[0], shift_y, shift_uv, lfm);
              if (mi_32_col_offset + 2 >= max_cols)
                continue;
              mip2 = mip + 2;
              build_masks(lfi_n, mip2[0], shift_y + 2, shift_uv + 1, lfm);
              break;
            default:
              for (idx_16 = 0; idx_16 < 4; mip += offset_16[idx_16], ++idx_16) {
                const int shift_y = shift_32_y[idx_32] + shift_16_y[idx_16];
                const int shift_uv = shift_32_uv[idx_32] + shift_16_uv[idx_16];
                const int mi_16_col_offset = mi_32_col_offset +
                    ((idx_16 & 1) << 1);
                const int mi_16_row_offset = mi_32_row_offset +
                    ((idx_16 >> 1) << 1);
  
                if (mi_16_col_offset >= max_cols || mi_16_row_offset >= max_rows)
                  continue;
  
                switch (mip[0]->mbmi.sb_type) {
                  case BLOCK_16X16:
                    build_masks(lfi_n, mip[0], shift_y, shift_uv, lfm);
                    break;
                  case BLOCK_16X8:
                    build_masks(lfi_n, mip[0], shift_y, shift_uv, lfm);
                    if (mi_16_row_offset + 1 >= max_rows)
                      continue;
                    mip2 = mip + mode_info_stride;
                    build_y_mask(lfi_n, mip2[0], shift_y+8, lfm);
                    break;
                  case BLOCK_8X16:
                    build_masks(lfi_n, mip[0], shift_y, shift_uv, lfm);
                    if (mi_16_col_offset +1 >= max_cols)
                      continue;
                    mip2 = mip + 1;
                    build_y_mask(lfi_n, mip2[0], shift_y+1, lfm);
                    break;
                  default: {
                    const int shift_y = shift_32_y[idx_32] +
                                        shift_16_y[idx_16] +
                                        shift_8_y[0];
                    build_masks(lfi_n, mip[0], shift_y, shift_uv, lfm);
                    mip += offset[0];
                    for (idx_8 = 1; idx_8 < 4; mip += offset[idx_8], ++idx_8) {
                      const int shift_y = shift_32_y[idx_32] +
                                          shift_16_y[idx_16] +
                                          shift_8_y[idx_8];
                      const int mi_8_col_offset = mi_16_col_offset +
                          ((idx_8 & 1));
                      const int mi_8_row_offset = mi_16_row_offset +
                          ((idx_8 >> 1));
  
                      if (mi_8_col_offset >= max_cols ||
                          mi_8_row_offset >= max_rows)
                        continue;
                      build_y_mask(lfi_n, mip[0], shift_y, lfm);
                    }
                    break;
                  }
                }
              }
              break;
          }
        }
        break;
    }
    // The largest loopfilter we have is 16x16 so we use the 16x16 mask
    // for 32x32 transforms also also.
    lfm->left_y[TX_16X16] |= lfm->left_y[TX_32X32];
    lfm->above_y[TX_16X16] |= lfm->above_y[TX_32X32];
    lfm->left_uv[TX_16X16] |= lfm->left_uv[TX_32X32];
    lfm->above_uv[TX_16X16] |= lfm->above_uv[TX_32X32];
  
    // We do at least 8 tap filter on every 32x32 even if the transform size
    // is 4x4.  So if the 4x4 is set on a border pixel add it to the 8x8 and
    // remove it from the 4x4.
    lfm->left_y[TX_8X8] |= lfm->left_y[TX_4X4] & left_border;
    lfm->left_y[TX_4X4] &= ~left_border;
    lfm->above_y[TX_8X8] |= lfm->above_y[TX_4X4] & above_border;
    lfm->above_y[TX_4X4] &= ~above_border;
    lfm->left_uv[TX_8X8] |= lfm->left_uv[TX_4X4] & left_border_uv;
    lfm->left_uv[TX_4X4] &= ~left_border_uv;
    lfm->above_uv[TX_8X8] |= lfm->above_uv[TX_4X4] & above_border_uv;
    lfm->above_uv[TX_4X4] &= ~above_border_uv;
  
    // We do some special edge handling.
    if (mi_row + MI_BLOCK_SIZE > cm->mi_rows) {
      const uint64_t rows = cm->mi_rows - mi_row;
  
      // Each pixel inside the border gets a 1,
      const uint64_t mask_y = (((uint64_t) 1 << (rows << 3)) - 1);
      const uint16_t mask_uv = (((uint16_t) 1 << (((rows + 1) >> 1) << 2)) - 1);
  
      // Remove values completely outside our border.
      for (i = 0; i < TX_32X32; i++) {
        lfm->left_y[i] &= mask_y;
        lfm->above_y[i] &= mask_y;
        lfm->left_uv[i] &= mask_uv;
        lfm->above_uv[i] &= mask_uv;
      }
      lfm->int_4x4_y &= mask_y;
      lfm->int_4x4_uv &= mask_uv;
  
      // We don't apply a wide loop filter on the last uv block row.  If set
      // apply the shorter one instead.
      if (rows == 1) {
        lfm->above_uv[TX_8X8] |= lfm->above_uv[TX_16X16];
        lfm->above_uv[TX_16X16] = 0;
      }
      if (rows == 5) {
        lfm->above_uv[TX_8X8] |= lfm->above_uv[TX_16X16] & 0xff00;
        lfm->above_uv[TX_16X16] &= ~(lfm->above_uv[TX_16X16] & 0xff00);
      }
    }
  
    if (mi_col + MI_BLOCK_SIZE > cm->mi_cols) {
      const uint64_t columns = cm->mi_cols - mi_col;
  
      // Each pixel inside the border gets a 1, the multiply copies the border
      // to where we need it.
      const uint64_t mask_y  = (((1 << columns) - 1)) * 0x0101010101010101;
      const uint16_t mask_uv = ((1 << ((columns + 1) >> 1)) - 1) * 0x1111;
  
      // Internal edges are not applied on the last column of the image so
      // we mask 1 more for the internal edges
      const uint16_t mask_uv_int = ((1 << (columns >> 1)) - 1) * 0x1111;
  
      // Remove the bits outside the image edge.
      for (i = 0; i < TX_32X32; i++) {
        lfm->left_y[i] &= mask_y;
        lfm->above_y[i] &= mask_y;
        lfm->left_uv[i] &= mask_uv;
        lfm->above_uv[i] &= mask_uv;
      }
      lfm->int_4x4_y &= mask_y;
      lfm->int_4x4_uv &= mask_uv_int;
  
      // We don't apply a wide loop filter on the last uv column.  If set
      // apply the shorter one instead.
      if (columns == 1) {
        lfm->left_uv[TX_8X8] |= lfm->left_uv[TX_16X16];
        lfm->left_uv[TX_16X16] = 0;
      }
      if (columns == 5) {
        lfm->left_uv[TX_8X8] |= (lfm->left_uv[TX_16X16] & 0xcccc);
        lfm->left_uv[TX_16X16] &= ~(lfm->left_uv[TX_16X16] & 0xcccc);
      }
    }
    // We don't a loop filter on the first column in the image.  Mask that out.
    if (mi_col == 0) {
      for (i = 0; i < TX_32X32; i++) {
        lfm->left_y[i] &= 0xfefefefefefefefe;
        lfm->left_uv[i] &= 0xeeee;
      }
    }
  
    // Assert if we try to apply 2 different loop filters at the same position.
    assert(!(lfm->left_y[TX_16X16] & lfm->left_y[TX_8X8]));
    assert(!(lfm->left_y[TX_16X16] & lfm->left_y[TX_4X4]));
    assert(!(lfm->left_y[TX_8X8] & lfm->left_y[TX_4X4]));
    assert(!(lfm->int_4x4_y & lfm->left_y[TX_16X16]));
    assert(!(lfm->left_uv[TX_16X16]&lfm->left_uv[TX_8X8]));
    assert(!(lfm->left_uv[TX_16X16] & lfm->left_uv[TX_4X4]));
    assert(!(lfm->left_uv[TX_8X8] & lfm->left_uv[TX_4X4]));
    assert(!(lfm->int_4x4_uv & lfm->left_uv[TX_16X16]));
    assert(!(lfm->above_y[TX_16X16] & lfm->above_y[TX_8X8]));
    assert(!(lfm->above_y[TX_16X16] & lfm->above_y[TX_4X4]));
    assert(!(lfm->above_y[TX_8X8] & lfm->above_y[TX_4X4]));
    assert(!(lfm->int_4x4_y & lfm->above_y[TX_16X16]));
    assert(!(lfm->above_uv[TX_16X16] & lfm->above_uv[TX_8X8]));
    assert(!(lfm->above_uv[TX_16X16] & lfm->above_uv[TX_4X4]));
    assert(!(lfm->above_uv[TX_8X8] & lfm->above_uv[TX_4X4]));
    assert(!(lfm->int_4x4_uv & lfm->above_uv[TX_16X16]));
  }
  
  #if CONFIG_NON420
  static uint8_t build_lfi(const loop_filter_info_n *lfi_n,
                       const MB_MODE_INFO *mbmi) {
    const int seg = mbmi->segment_id;
    const int ref = mbmi->ref_frame[0];
    const int mode = lfi_n->mode_lf_lut[mbmi->mode];
    const int filter_level = lfi_n->lvl[seg][ref][mode];
  
    return filter_level;
  }
  
  static void filter_block_plane_non420(VP9_COMMON *cm,
                                        struct macroblockd_plane *plane,
                                        MODE_INFO **mi_8x8,
                                        int mi_row, int mi_col) {
    const int ss_x = plane->subsampling_x;
    const int ss_y = plane->subsampling_y;
    const int row_step = 1 << ss_x;
    const int col_step = 1 << ss_y;
    const int row_step_stride = cm->mode_info_stride * row_step;
    struct buf_2d *const dst = &plane->dst;
    uint8_t* const dst0 = dst->buf;
    unsigned int mask_16x16[MI_BLOCK_SIZE] = {0};
    unsigned int mask_8x8[MI_BLOCK_SIZE] = {0};
    unsigned int mask_4x4[MI_BLOCK_SIZE] = {0};
    unsigned int mask_4x4_int[MI_BLOCK_SIZE] = {0};
    uint8_t lfl[MI_BLOCK_SIZE * MI_BLOCK_SIZE];
    int r, c;
  
    for (r = 0; r < MI_BLOCK_SIZE && mi_row + r < cm->mi_rows; r += row_step) {
      unsigned int mask_16x16_c = 0;
      unsigned int mask_8x8_c = 0;
      unsigned int mask_4x4_c = 0;
      unsigned int border_mask;
  
      // Determine the vertical edges that need filtering
      for (c = 0; c < MI_BLOCK_SIZE && mi_col + c < cm->mi_cols; c += col_step) {
        const MODE_INFO *mi = mi_8x8[c];
        const int skip_this = mi[0].mbmi.skip_coeff
                              && is_inter_block(&mi[0].mbmi);
        // left edge of current unit is block/partition edge -> no skip
        const int block_edge_left = b_width_log2(mi[0].mbmi.sb_type) ?
            !(c & ((1 << (b_width_log2(mi[0].mbmi.sb_type)-1)) - 1)) : 1;
        const int skip_this_c = skip_this && !block_edge_left;
        // top edge of current unit is block/partition edge -> no skip
        const int block_edge_above = b_height_log2(mi[0].mbmi.sb_type) ?
            !(r & ((1 << (b_height_log2(mi[0].mbmi.sb_type)-1)) - 1)) : 1;
        const int skip_this_r = skip_this && !block_edge_above;
        const TX_SIZE tx_size = (plane->plane_type == PLANE_TYPE_UV)
                              ? get_uv_tx_size(&mi[0].mbmi)
                              : mi[0].mbmi.tx_size;
        const int skip_border_4x4_c = ss_x && mi_col + c == cm->mi_cols - 1;
        const int skip_border_4x4_r = ss_y && mi_row + r == cm->mi_rows - 1;
  
        // Filter level can vary per MI
        if (!(lfl[(r << 3) + (c >> ss_x)] =
            build_lfi(&cm->lf_info, &mi[0].mbmi)))
          continue;
  
        // Build masks based on the transform size of each block
        if (tx_size == TX_32X32) {
          if (!skip_this_c && ((c >> ss_x) & 3) == 0) {
            if (!skip_border_4x4_c)
              mask_16x16_c |= 1 << (c >> ss_x);
            else
              mask_8x8_c |= 1 << (c >> ss_x);
          }
          if (!skip_this_r && ((r >> ss_y) & 3) == 0) {
            if (!skip_border_4x4_r)
              mask_16x16[r] |= 1 << (c >> ss_x);
            else
              mask_8x8[r] |= 1 << (c >> ss_x);
          }
        } else if (tx_size == TX_16X16) {
          if (!skip_this_c && ((c >> ss_x) & 1) == 0) {
            if (!skip_border_4x4_c)
              mask_16x16_c |= 1 << (c >> ss_x);
            else
              mask_8x8_c |= 1 << (c >> ss_x);
          }
          if (!skip_this_r && ((r >> ss_y) & 1) == 0) {
            if (!skip_border_4x4_r)
              mask_16x16[r] |= 1 << (c >> ss_x);
            else
              mask_8x8[r] |= 1 << (c >> ss_x);
          }
        } else {
          // force 8x8 filtering on 32x32 boundaries
          if (!skip_this_c) {
            if (tx_size == TX_8X8 || ((c >> ss_x) & 3) == 0)
              mask_8x8_c |= 1 << (c >> ss_x);
            else
              mask_4x4_c |= 1 << (c >> ss_x);
          }
  
          if (!skip_this_r) {
            if (tx_size == TX_8X8 || ((r >> ss_y) & 3) == 0)
              mask_8x8[r] |= 1 << (c >> ss_x);
            else
              mask_4x4[r] |= 1 << (c >> ss_x);
          }
  
          if (!skip_this && tx_size < TX_8X8 && !skip_border_4x4_c)
            mask_4x4_int[r] |= 1 << (c >> ss_x);
        }
      }
  
      // Disable filtering on the leftmost column
      border_mask = ~(mi_col == 0);
      filter_selectively_vert(dst->buf, dst->stride,
                              mask_16x16_c & border_mask,
                              mask_8x8_c & border_mask,
                              mask_4x4_c & border_mask,
                              mask_4x4_int[r],
                              &cm->lf_info, &lfl[r << 3]);
      dst->buf += 8 * dst->stride;
      mi_8x8 += row_step_stride;
    }
  
    // Now do horizontal pass
    dst->buf = dst0;
    for (r = 0; r < MI_BLOCK_SIZE && mi_row + r < cm->mi_rows; r += row_step) {
      const int skip_border_4x4_r = ss_y && mi_row + r == cm->mi_rows - 1;
      const unsigned int mask_4x4_int_r = skip_border_4x4_r ? 0 : mask_4x4_int[r];
  
      unsigned int mask_16x16_r;
      unsigned int mask_8x8_r;
      unsigned int mask_4x4_r;
  
      if (mi_row + r == 0) {
        mask_16x16_r = 0;
        mask_8x8_r = 0;
        mask_4x4_r = 0;
      } else {
        mask_16x16_r = mask_16x16[r];
        mask_8x8_r = mask_8x8[r];
        mask_4x4_r = mask_4x4[r];
      }
  
      filter_selectively_horiz(dst->buf, dst->stride,
                               mask_16x16_r,
                               mask_8x8_r,
                               mask_4x4_r,
                               mask_4x4_int_r,
                               &cm->lf_info, &lfl[r << 3]);
      dst->buf += 8 * dst->stride;
    }
  }
  #endif
  
  static void filter_block_plane(VP9_COMMON *const cm,
                                 struct macroblockd_plane *const plane,
                                 int mi_row,
                                 LOOP_FILTER_MASK *lfm) {
    struct buf_2d *const dst = &plane->dst;
    uint8_t* const dst0 = dst->buf;
    unsigned int mask_4x4_int_row[MI_BLOCK_SIZE] = {0};
    int r, c;
  
    if (!plane->plane_type) {
      uint64_t mask_16x16 = lfm->left_y[TX_16X16];
      uint64_t mask_8x8 = lfm->left_y[TX_8X8];
      uint64_t mask_4x4 = lfm->left_y[TX_4X4];
      uint64_t mask_4x4_int = lfm->int_4x4_y;
  
      // Vertical pass
      for (r = 0; r < MI_BLOCK_SIZE && mi_row + r < cm->mi_rows; r++) {
        mask_4x4_int_row[r] = mask_4x4_int & 0xff;
  
        // Disable filtering on the leftmost column
        filter_selectively_vert(dst->buf, dst->stride,
                                mask_16x16 & 0xff,
                                mask_8x8 & 0xff,
                                mask_4x4 & 0xff,
                                mask_4x4_int_row[r],
                                &cm->lf_info, &lfm->lfl_y[r << 3]);
  
        dst->buf += 8 * dst->stride;
        mask_16x16 >>= 8;
        mask_8x8 >>= 8;
        mask_4x4 >>= 8;
        mask_4x4_int >>= 8;
      }
  
      // Horizontal pass
      dst->buf = dst0;
      mask_16x16 = lfm->above_y[TX_16X16];
      mask_8x8 = lfm->above_y[TX_8X8];
      mask_4x4 = lfm->above_y[TX_4X4];
  
      for (r = 0; r < MI_BLOCK_SIZE && mi_row + r < cm->mi_rows; r++) {
        unsigned int mask_16x16_r;
        unsigned int mask_8x8_r;
        unsigned int mask_4x4_r;
  
        if (mi_row + r == 0) {
          mask_16x16_r = 0;
          mask_8x8_r = 0;
          mask_4x4_r = 0;
        } else {
          mask_16x16_r = mask_16x16 & 0xff;
          mask_8x8_r = mask_8x8 & 0xff;
          mask_4x4_r = mask_4x4 & 0xff;
        }
  
        filter_selectively_horiz(dst->buf, dst->stride,
                                 mask_16x16_r,
                                 mask_8x8_r,
                                 mask_4x4_r,
                                 mask_4x4_int_row[r],
                                 &cm->lf_info, &lfm->lfl_y[r << 3]);
  
        dst->buf += 8 * dst->stride;
        mask_16x16 >>= 8;
        mask_8x8 >>= 8;
        mask_4x4 >>= 8;
      }
    } else {
      uint16_t mask_16x16 = lfm->left_uv[TX_16X16];
      uint16_t mask_8x8 = lfm->left_uv[TX_8X8];
      uint16_t mask_4x4 = lfm->left_uv[TX_4X4];
      uint16_t mask_4x4_int = lfm->int_4x4_uv;
  
      // Vertical pass
      for (r = 0; r < MI_BLOCK_SIZE && mi_row + r < cm->mi_rows; r += 2) {
        if (plane->plane_type == 1) {
          for (c = 0; c < (MI_BLOCK_SIZE >> 1); c++)
            lfm->lfl_uv[(r << 1) + c] = lfm->lfl_y[(r << 3) + (c << 1)];
        }
  
        mask_4x4_int_row[r] = mask_4x4_int & 0xf;
        // Disable filtering on the leftmost column
        filter_selectively_vert(dst->buf, dst->stride,
                                mask_16x16 & 0xf,
                                mask_8x8 & 0xf,
                                mask_4x4 & 0xf,
                                mask_4x4_int_row[r],
                                &cm->lf_info, &lfm->lfl_uv[r << 1]);
  
        dst->buf += 8 * dst->stride;
        mask_16x16 >>= 4;
        mask_8x8 >>= 4;
        mask_4x4 >>= 4;
        mask_4x4_int >>= 4;
      }
  
      // Horizontal pass
      dst->buf = dst0;
      mask_16x16 = lfm->above_uv[TX_16X16];
      mask_8x8 = lfm->above_uv[TX_8X8];
      mask_4x4 = lfm->above_uv[TX_4X4];
  
      for (r = 0; r < MI_BLOCK_SIZE && mi_row + r < cm->mi_rows; r += 2) {
        const int skip_border_4x4_r = mi_row + r == cm->mi_rows - 1;
        const unsigned int mask_4x4_int_r = skip_border_4x4_r ?
            0 : (mask_4x4_int_row[r]);
        unsigned int mask_16x16_r;
        unsigned int mask_8x8_r;
        unsigned int mask_4x4_r;
  
        if (mi_row + r == 0) {
          mask_16x16_r = 0;
          mask_8x8_r = 0;
          mask_4x4_r = 0;
        } else {
          mask_16x16_r = mask_16x16 & 0xf;
          mask_8x8_r = mask_8x8 & 0xf;
          mask_4x4_r = mask_4x4 & 0xf;
        }
  
        filter_selectively_horiz(dst->buf, dst->stride,
                                 mask_16x16_r,
                                 mask_8x8_r,
                                 mask_4x4_r,
                                 mask_4x4_int_r,
                                 &cm->lf_info, &lfm->lfl_uv[r << 1]);
  
        dst->buf += 8 * dst->stride;
        mask_16x16 >>= 4;
        mask_8x8 >>= 4;
        mask_4x4 >>= 4;
      }
    }
  }
  
  void vp9_loop_filter_rows(const YV12_BUFFER_CONFIG *frame_buffer,
                            VP9_COMMON *cm, MACROBLOCKD *xd,
                            int start, int stop, int y_only) {
    const int num_planes = y_only ? 1 : MAX_MB_PLANE;
    int mi_row, mi_col;
    LOOP_FILTER_MASK lfm;
  #if CONFIG_NON420
    int use_420 = y_only || (xd->plane[1].subsampling_y == 1 &&
        xd->plane[1].subsampling_x == 1);
  #endif
  
    for (mi_row = start; mi_row < stop; mi_row += MI_BLOCK_SIZE) {
      MODE_INFO **mi_8x8 = cm->mi_grid_visible + mi_row * cm->mode_info_stride;
  
      for (mi_col = 0; mi_col < cm->mi_cols; mi_col += MI_BLOCK_SIZE) {
        int plane;
  
        setup_dst_planes(xd, frame_buffer, mi_row, mi_col);
  
        // TODO(JBB): Make setup_mask work for non 420.
  #if CONFIG_NON420
        if (use_420)
  #endif
          setup_mask(cm, mi_row, mi_col, mi_8x8 + mi_col, cm->mode_info_stride,
                     &lfm);
  
        for (plane = 0; plane < num_planes; ++plane) {
  #if CONFIG_NON420
          if (use_420)
  #endif
            filter_block_plane(cm, &xd->plane[plane], mi_row, &lfm);
  #if CONFIG_NON420
          else
            filter_block_plane_non420(cm, &xd->plane[plane], mi_8x8 + mi_col,
                                      mi_row, mi_col);
  #endif
        }
      }
    }
  }
  
  void vp9_loop_filter_frame(VP9_COMMON *cm, MACROBLOCKD *xd,
                             int frame_filter_level,
                             int y_only, int partial) {
    int start_mi_row, end_mi_row, mi_rows_to_filter;
    if (!frame_filter_level) return;
    start_mi_row = 0;
    mi_rows_to_filter = cm->mi_rows;
    if (partial && cm->mi_rows > 8) {
      start_mi_row = cm->mi_rows >> 1;
      start_mi_row &= 0xfffffff8;
      mi_rows_to_filter = MAX(cm->mi_rows / 8, 8);
    }
    end_mi_row = start_mi_row + mi_rows_to_filter;
    vp9_loop_filter_frame_init(cm, frame_filter_level);
    vp9_loop_filter_rows(cm->frame_to_show, cm, xd,
                         start_mi_row, end_mi_row,
                         y_only);
  }
  
  int vp9_loop_filter_worker(void *arg1, void *arg2) {
    LFWorkerData *const lf_data = (LFWorkerData*)arg1;
    (void)arg2;
    vp9_loop_filter_rows(lf_data->frame_buffer, lf_data->cm, &lf_data->xd,
                         lf_data->start, lf_data->stop, lf_data->y_only);
    return 1;
  }
  