vpx/vp8/encoder/denoising.c

/*
 *  Copyright (c) 2012 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 <limits.h>

#include "denoising.h"

#include "vp8/common/reconinter.h"
#include "vpx/vpx_integer.h"
#include "vpx_mem/vpx_mem.h"
#include "vp8_rtcd.h"

static const unsigned int NOISE_MOTION_THRESHOLD = 25 * 25;
/* SSE_DIFF_THRESHOLD is selected as ~95% confidence assuming
 * var(noise) ~= 100.
 */
static const unsigned int SSE_DIFF_THRESHOLD = 16 * 16 * 20;
static const unsigned int SSE_THRESHOLD = 16 * 16 * 40;
static const unsigned int SSE_THRESHOLD_HIGH = 16 * 16 * 60;

/*
 * The filter function was modified to reduce the computational complexity.
 * Step 1:
 * Instead of applying tap coefficients for each pixel, we calculated the
 * pixel adjustments vs. pixel diff value ahead of time.
 *     adjustment = filtered_value - current_raw
 *                = (filter_coefficient * diff + 128) >> 8
 * where
 *     filter_coefficient = (255 << 8) / (256 + ((absdiff * 330) >> 3));
 *     filter_coefficient += filter_coefficient /
 *                           (3 + motion_magnitude_adjustment);
 *     filter_coefficient is clamped to 0 ~ 255.
 *
 * Step 2:
 * The adjustment vs. diff curve becomes flat very quick when diff increases.
 * This allowed us to use only several levels to approximate the curve without
 * changing the filtering algorithm too much.
 * The adjustments were further corrected by checking the motion magnitude.
 * The levels used are:
 * diff       adjustment w/o motion correction   adjustment w/ motion correction
 * [-255, -16]           -6                                   -7
 * [-15, -8]             -4                                   -5
 * [-7, -4]              -3                                   -4
 * [-3, 3]               diff                                 diff
 * [4, 7]                 3                                    4
 * [8, 15]                4                                    5
 * [16, 255]              6                                    7
 */

int vp8_denoiser_filter_c(unsigned char *mc_running_avg_y, int mc_avg_y_stride,
                          unsigned char *running_avg_y, int avg_y_stride,
                          unsigned char *sig, int sig_stride,
                          unsigned int motion_magnitude,
                          int increase_denoising)
{
    unsigned char *running_avg_y_start = running_avg_y;
    unsigned char *sig_start = sig;
    int sum_diff_thresh;
    int r, c;
    int sum_diff = 0;
    int adj_val[3] = {3, 4, 6};
    int shift_inc1 = 0;
    int shift_inc2 = 1;
    int col_sum[16] = {0, 0, 0, 0,
                       0, 0, 0, 0,
                       0, 0, 0, 0,
                       0, 0, 0, 0};
    /* If motion_magnitude is small, making the denoiser more aggressive by
     * increasing the adjustment for each level. Add another increment for
     * blocks that are labeled for increase denoising. */
    if (motion_magnitude <= MOTION_MAGNITUDE_THRESHOLD)
    {
      if (increase_denoising) {
        shift_inc1 = 1;
        shift_inc2 = 2;
      }
      adj_val[0] += shift_inc2;
      adj_val[1] += shift_inc2;
      adj_val[2] += shift_inc2;
    }

    for (r = 0; r < 16; ++r)
    {
        for (c = 0; c < 16; ++c)
        {
            int diff = 0;
            int adjustment = 0;
            int absdiff = 0;

            diff = mc_running_avg_y[c] - sig[c];
            absdiff = abs(diff);

            // When |diff| <= |3 + shift_inc1|, use pixel value from
            // last denoised raw.
            if (absdiff <= 3 + shift_inc1)
            {
                running_avg_y[c] = mc_running_avg_y[c];
                col_sum[c] += diff;
            }
            else
            {
                if (absdiff >= 4 + shift_inc1 && absdiff <= 7)
                    adjustment = adj_val[0];
                else if (absdiff >= 8 && absdiff <= 15)
                    adjustment = adj_val[1];
                else
                    adjustment = adj_val[2];

                if (diff > 0)
                {
                    if ((sig[c] + adjustment) > 255)
                        running_avg_y[c] = 255;
                    else
                        running_avg_y[c] = sig[c] + adjustment;

                    col_sum[c] += adjustment;
                }
                else
                {
                    if ((sig[c] - adjustment) < 0)
                        running_avg_y[c] = 0;
                    else
                        running_avg_y[c] = sig[c] - adjustment;

                    col_sum[c] -= adjustment;
                }
            }
        }

        /* Update pointers for next iteration. */
        sig += sig_stride;
        mc_running_avg_y += mc_avg_y_stride;
        running_avg_y += avg_y_stride;
    }

    for (c = 0; c < 16; ++c) {
      // Below we clip the value in the same way which SSE code use.
      // When adopting aggressive denoiser, the adj_val for each pixel
      // could be at most 8 (this is current max adjustment of the map).
      // In SSE code, we calculate the sum of adj_val for
      // the columns, so the sum could be upto 128(16 rows). However,
      // the range of the value is -128 ~ 127 in SSE code, that's why
      // we do this change in C code.
      // We don't do this for UV denoiser, since there are only 8 rows,
      // and max adjustments <= 8, so the sum of the columns will not
      // exceed 64.
      if (col_sum[c] >= 128) {
        col_sum[c] = 127;
      }
      sum_diff += col_sum[c];
    }

    sum_diff_thresh= SUM_DIFF_THRESHOLD;
    if (increase_denoising) sum_diff_thresh = SUM_DIFF_THRESHOLD_HIGH;
    if (abs(sum_diff) > sum_diff_thresh) {
      // Before returning to copy the block (i.e., apply no denoising), check
      // if we can still apply some (weaker) temporal filtering to this block,
      // that would otherwise not be denoised at all. Simplest is to apply
      // an additional adjustment to running_avg_y to bring it closer to sig.
      // The adjustment is capped by a maximum delta, and chosen such that
      // in most cases the resulting sum_diff will be within the
      // accceptable range given by sum_diff_thresh.

      // The delta is set by the excess of absolute pixel diff over threshold.
      int delta = ((abs(sum_diff) - sum_diff_thresh) >> 8) + 1;
      // Only apply the adjustment for max delta up to 3.
      if (delta < 4) {
        sig -= sig_stride * 16;
        mc_running_avg_y -= mc_avg_y_stride * 16;
        running_avg_y -= avg_y_stride * 16;
        for (r = 0; r < 16; ++r) {
          for (c = 0; c < 16; ++c) {
            int diff = mc_running_avg_y[c] - sig[c];
            int adjustment = abs(diff);
            if (adjustment > delta)
              adjustment = delta;
            if (diff > 0) {
              // Bring denoised signal down.
              if (running_avg_y[c] - adjustment < 0)
                running_avg_y[c] = 0;
              else
                running_avg_y[c] = running_avg_y[c] - adjustment;
              col_sum[c] -= adjustment;
            } else if (diff < 0) {
              // Bring denoised signal up.
              if (running_avg_y[c] + adjustment > 255)
                running_avg_y[c] = 255;
              else
                running_avg_y[c] = running_avg_y[c] + adjustment;
              col_sum[c] += adjustment;
            }
          }
          // TODO(marpan): Check here if abs(sum_diff) has gone below the
          // threshold sum_diff_thresh, and if so, we can exit the row loop.
          sig += sig_stride;
          mc_running_avg_y += mc_avg_y_stride;
          running_avg_y += avg_y_stride;
        }

        sum_diff = 0;
        for (c = 0; c < 16; ++c) {
          if (col_sum[c] >= 128) {
            col_sum[c] = 127;
          }
          sum_diff += col_sum[c];
        }

        if (abs(sum_diff) > sum_diff_thresh)
          return COPY_BLOCK;
      } else {
        return COPY_BLOCK;
      }
    }

    vp8_copy_mem16x16(running_avg_y_start, avg_y_stride, sig_start, sig_stride);
    return FILTER_BLOCK;
}

int vp8_denoiser_filter_uv_c(unsigned char *mc_running_avg_uv,
                             int mc_avg_uv_stride,
                             unsigned char *running_avg_uv,
                             int avg_uv_stride,
                             unsigned char *sig,
                             int sig_stride,
                             unsigned int motion_magnitude,
                             int increase_denoising) {
    unsigned char *running_avg_uv_start = running_avg_uv;
    unsigned char *sig_start = sig;
    int sum_diff_thresh;
    int r, c;
    int sum_diff = 0;
    int sum_block = 0;
    int adj_val[3] = {3, 4, 6};
    int shift_inc1 = 0;
    int shift_inc2 = 1;
    /* If motion_magnitude is small, making the denoiser more aggressive by
     * increasing the adjustment for each level. Add another increment for
     * blocks that are labeled for increase denoising. */
    if (motion_magnitude <= MOTION_MAGNITUDE_THRESHOLD_UV) {
      if (increase_denoising) {
        shift_inc1 = 1;
        shift_inc2 = 2;
      }
      adj_val[0] += shift_inc2;
      adj_val[1] += shift_inc2;
      adj_val[2] += shift_inc2;
    }

    // Avoid denoising color signal if its close to average level.
    for (r = 0; r < 8; ++r) {
      for (c = 0; c < 8; ++c) {
        sum_block += sig[c];
      }
      sig += sig_stride;
    }
    if (abs(sum_block - (128 * 8 * 8)) < SUM_DIFF_FROM_AVG_THRESH_UV) {
      return COPY_BLOCK;
    }

    sig -= sig_stride * 8;
    for (r = 0; r < 8; ++r) {
      for (c = 0; c < 8; ++c) {
        int diff = 0;
        int adjustment = 0;
        int absdiff = 0;

        diff = mc_running_avg_uv[c] - sig[c];
        absdiff = abs(diff);

        // When |diff| <= |3 + shift_inc1|, use pixel value from
        // last denoised raw.
        if (absdiff <= 3 + shift_inc1) {
          running_avg_uv[c] = mc_running_avg_uv[c];
          sum_diff += diff;
        } else {
          if (absdiff >= 4 && absdiff <= 7)
            adjustment = adj_val[0];
          else if (absdiff >= 8 && absdiff <= 15)
            adjustment = adj_val[1];
          else
            adjustment = adj_val[2];
          if (diff > 0) {
            if ((sig[c] + adjustment) > 255)
              running_avg_uv[c] = 255;
            else
              running_avg_uv[c] = sig[c] + adjustment;
            sum_diff += adjustment;
          } else {
            if ((sig[c] - adjustment) < 0)
              running_avg_uv[c] = 0;
            else
              running_avg_uv[c] = sig[c] - adjustment;
            sum_diff -= adjustment;
          }
        }
      }
      /* Update pointers for next iteration. */
      sig += sig_stride;
      mc_running_avg_uv += mc_avg_uv_stride;
      running_avg_uv += avg_uv_stride;
    }

    sum_diff_thresh= SUM_DIFF_THRESHOLD_UV;
    if (increase_denoising) sum_diff_thresh = SUM_DIFF_THRESHOLD_HIGH_UV;
    if (abs(sum_diff) > sum_diff_thresh) {
      // Before returning to copy the block (i.e., apply no denoising), check
      // if we can still apply some (weaker) temporal filtering to this block,
      // that would otherwise not be denoised at all. Simplest is to apply
      // an additional adjustment to running_avg_y to bring it closer to sig.
      // The adjustment is capped by a maximum delta, and chosen such that
      // in most cases the resulting sum_diff will be within the
      // accceptable range given by sum_diff_thresh.

      // The delta is set by the excess of absolute pixel diff over threshold.
      int delta = ((abs(sum_diff) - sum_diff_thresh) >> 8) + 1;
      // Only apply the adjustment for max delta up to 3.
      if (delta < 4) {
        sig -= sig_stride * 8;
        mc_running_avg_uv -= mc_avg_uv_stride * 8;
        running_avg_uv -= avg_uv_stride * 8;
        for (r = 0; r < 8; ++r) {
          for (c = 0; c < 8; ++c) {
            int diff = mc_running_avg_uv[c] - sig[c];
            int adjustment = abs(diff);
            if (adjustment > delta)
              adjustment = delta;
            if (diff > 0) {
              // Bring denoised signal down.
              if (running_avg_uv[c] - adjustment < 0)
                running_avg_uv[c] = 0;
              else
                running_avg_uv[c] = running_avg_uv[c] - adjustment;
              sum_diff -= adjustment;
            } else if (diff < 0) {
              // Bring denoised signal up.
              if (running_avg_uv[c] + adjustment > 255)
                running_avg_uv[c] = 255;
              else
                running_avg_uv[c] = running_avg_uv[c] + adjustment;
              sum_diff += adjustment;
            }
          }
          // TODO(marpan): Check here if abs(sum_diff) has gone below the
          // threshold sum_diff_thresh, and if so, we can exit the row loop.
          sig += sig_stride;
          mc_running_avg_uv += mc_avg_uv_stride;
          running_avg_uv += avg_uv_stride;
        }
        if (abs(sum_diff) > sum_diff_thresh)
          return COPY_BLOCK;
      } else {
        return COPY_BLOCK;
      }
    }

    vp8_copy_mem8x8(running_avg_uv_start, avg_uv_stride, sig_start,
                    sig_stride);
    return FILTER_BLOCK;
}

void vp8_denoiser_set_parameters(VP8_DENOISER *denoiser, int mode) {
  assert(mode > 0);  // Denoiser is allocated only if mode > 0.
  if (mode == 1) {
    denoiser->denoiser_mode = kDenoiserOnYOnly;
  } else if (mode == 2) {
    denoiser->denoiser_mode = kDenoiserOnYUV;
  } else if (mode == 3) {
    denoiser->denoiser_mode = kDenoiserOnYUVAggressive;
  } else {
    denoiser->denoiser_mode = kDenoiserOnAdaptive;
  }
  if (denoiser->denoiser_mode != kDenoiserOnYUVAggressive) {
    denoiser->denoise_pars.scale_sse_thresh = 1;
    denoiser->denoise_pars.scale_motion_thresh = 8;
    denoiser->denoise_pars.scale_increase_filter = 0;
    denoiser->denoise_pars.denoise_mv_bias = 95;
    denoiser->denoise_pars.pickmode_mv_bias = 100;
    denoiser->denoise_pars.qp_thresh = 0;
    denoiser->denoise_pars.consec_zerolast = UINT_MAX;
  } else {
    denoiser->denoise_pars.scale_sse_thresh = 2;
    denoiser->denoise_pars.scale_motion_thresh = 16;
    denoiser->denoise_pars.scale_increase_filter = 1;
    denoiser->denoise_pars.denoise_mv_bias = 60;
    denoiser->denoise_pars.pickmode_mv_bias = 60;
    denoiser->denoise_pars.qp_thresh = 100;
    denoiser->denoise_pars.consec_zerolast = 10;
  }
}

int vp8_denoiser_allocate(VP8_DENOISER *denoiser, int width, int height,
                          int num_mb_rows, int num_mb_cols, int mode)
{
    int i;
    assert(denoiser);
    denoiser->num_mb_cols = num_mb_cols;

    for (i = 0; i < MAX_REF_FRAMES; i++)
    {
        denoiser->yv12_running_avg[i].flags = 0;

        if (vp8_yv12_alloc_frame_buffer(&(denoiser->yv12_running_avg[i]), width,
                                        height, VP8BORDERINPIXELS)
            < 0)
        {
            vp8_denoiser_free(denoiser);
            return 1;
        }
        vpx_memset(denoiser->yv12_running_avg[i].buffer_alloc, 0,
                   denoiser->yv12_running_avg[i].frame_size);

    }
    denoiser->yv12_mc_running_avg.flags = 0;

    if (vp8_yv12_alloc_frame_buffer(&(denoiser->yv12_mc_running_avg), width,
                                   height, VP8BORDERINPIXELS) < 0)
    {
        vp8_denoiser_free(denoiser);
        return 1;
    }

    vpx_memset(denoiser->yv12_mc_running_avg.buffer_alloc, 0,
               denoiser->yv12_mc_running_avg.frame_size);

    if (vp8_yv12_alloc_frame_buffer(&denoiser->yv12_last_source, width,
                                    height, VP8BORDERINPIXELS) < 0) {
      vp8_denoiser_free(denoiser);
      return 1;
    }
    vpx_memset(denoiser->yv12_last_source.buffer_alloc, 0,
               denoiser->yv12_last_source.frame_size);

    denoiser->denoise_state = vpx_calloc((num_mb_rows * num_mb_cols), 1);
    vpx_memset(denoiser->denoise_state, 0, (num_mb_rows * num_mb_cols));
    vp8_denoiser_set_parameters(denoiser, mode);
    denoiser->nmse_source_diff = 0;
    denoiser->nmse_source_diff_count = 0;
    denoiser->qp_avg = 0;
    // QP threshold below which we can go up to aggressive mode.
    denoiser->qp_threshold_up = 80;
    // QP threshold above which we can go back down to normal mode.
    // For now keep this second threshold high, so not used currently.
    denoiser->qp_threshold_down = 128;
    // Bitrate thresholds and noise metric (nmse) thresholds for switching to
    // aggressive mode.
    // TODO(marpan): Adjust thresholds, including effect on resolution.
    denoiser->bitrate_threshold = 200000;  // (bits/sec).
    denoiser->threshold_aggressive_mode = 35;
    if (width * height > 640 * 480) {
      denoiser->bitrate_threshold = 500000;
      denoiser->threshold_aggressive_mode = 100;
    } else if (width * height > 960 * 540) {
      denoiser->bitrate_threshold = 800000;
      denoiser->threshold_aggressive_mode = 150;
    } else if (width * height > 1280 * 720) {
      denoiser->bitrate_threshold = 2000000;
      denoiser->threshold_aggressive_mode = 1400;
    }
    return 0;
}


void vp8_denoiser_free(VP8_DENOISER *denoiser)
{
    int i;
    assert(denoiser);

    for (i = 0; i < MAX_REF_FRAMES ; i++)
    {
        vp8_yv12_de_alloc_frame_buffer(&denoiser->yv12_running_avg[i]);
    }
    vp8_yv12_de_alloc_frame_buffer(&denoiser->yv12_mc_running_avg);
    vp8_yv12_de_alloc_frame_buffer(&denoiser->yv12_last_source);
    vpx_free(denoiser->denoise_state);
}


void vp8_denoiser_denoise_mb(VP8_DENOISER *denoiser,
                             MACROBLOCK *x,
                             unsigned int best_sse,
                             unsigned int zero_mv_sse,
                             int recon_yoffset,
                             int recon_uvoffset,
                             loop_filter_info_n *lfi_n,
                             int mb_row,
                             int mb_col,
                             int block_index)

{
    int mv_row;
    int mv_col;
    unsigned int motion_threshold;
    unsigned int motion_magnitude2;
    unsigned int sse_thresh;
    int sse_diff_thresh = 0;
    // Spatial loop filter: only applied selectively based on
    // temporal filter state of block relative to top/left neighbors.
    int apply_spatial_loop_filter = 1;
    MV_REFERENCE_FRAME frame = x->best_reference_frame;
    MV_REFERENCE_FRAME zero_frame = x->best_zeromv_reference_frame;

    enum vp8_denoiser_decision decision = FILTER_BLOCK;
    enum vp8_denoiser_decision decision_u = COPY_BLOCK;
    enum vp8_denoiser_decision decision_v = COPY_BLOCK;

    if (zero_frame)
    {
        YV12_BUFFER_CONFIG *src = &denoiser->yv12_running_avg[frame];
        YV12_BUFFER_CONFIG *dst = &denoiser->yv12_mc_running_avg;
        YV12_BUFFER_CONFIG saved_pre,saved_dst;
        MB_MODE_INFO saved_mbmi;
        MACROBLOCKD *filter_xd = &x->e_mbd;
        MB_MODE_INFO *mbmi = &filter_xd->mode_info_context->mbmi;
        int sse_diff = 0;
        // Bias on zero motion vector sse.
        const int zero_bias = denoiser->denoise_pars.denoise_mv_bias;
        zero_mv_sse = (unsigned int)((int64_t)zero_mv_sse * zero_bias / 100);
        sse_diff = zero_mv_sse - best_sse;

        saved_mbmi = *mbmi;

        /* Use the best MV for the compensation. */
        mbmi->ref_frame = x->best_reference_frame;
        mbmi->mode = x->best_sse_inter_mode;
        mbmi->mv = x->best_sse_mv;
        mbmi->need_to_clamp_mvs = x->need_to_clamp_best_mvs;
        mv_col = x->best_sse_mv.as_mv.col;
        mv_row = x->best_sse_mv.as_mv.row;
        // Bias to zero_mv if small amount of motion.
        // Note sse_diff_thresh is intialized to zero, so this ensures
        // we will always choose zero_mv for denoising if
        // zero_mv_see <= best_sse (i.e., sse_diff <= 0).
        if ((unsigned int)(mv_row * mv_row + mv_col * mv_col)
            <= NOISE_MOTION_THRESHOLD)
            sse_diff_thresh = (int)SSE_DIFF_THRESHOLD;

        if (frame == INTRA_FRAME ||
            sse_diff <= sse_diff_thresh)
        {
            /*
             * Handle intra blocks as referring to last frame with zero motion
             * and let the absolute pixel difference affect the filter factor.
             * Also consider small amount of motion as being random walk due
             * to noise, if it doesn't mean that we get a much bigger error.
             * Note that any changes to the mode info only affects the
             * denoising.
             */
            mbmi->ref_frame =
                    x->best_zeromv_reference_frame;

            src = &denoiser->yv12_running_avg[zero_frame];

            mbmi->mode = ZEROMV;
            mbmi->mv.as_int = 0;
            x->best_sse_inter_mode = ZEROMV;
            x->best_sse_mv.as_int = 0;
            best_sse = zero_mv_sse;
        }

        saved_pre = filter_xd->pre;
        saved_dst = filter_xd->dst;

        /* Compensate the running average. */
        filter_xd->pre.y_buffer = src->y_buffer + recon_yoffset;
        filter_xd->pre.u_buffer = src->u_buffer + recon_uvoffset;
        filter_xd->pre.v_buffer = src->v_buffer + recon_uvoffset;
        /* Write the compensated running average to the destination buffer. */
        filter_xd->dst.y_buffer = dst->y_buffer + recon_yoffset;
        filter_xd->dst.u_buffer = dst->u_buffer + recon_uvoffset;
        filter_xd->dst.v_buffer = dst->v_buffer + recon_uvoffset;

        if (!x->skip)
        {
            vp8_build_inter_predictors_mb(filter_xd);
        }
        else
        {
            vp8_build_inter16x16_predictors_mb(filter_xd,
                                               filter_xd->dst.y_buffer,
                                               filter_xd->dst.u_buffer,
                                               filter_xd->dst.v_buffer,
                                               filter_xd->dst.y_stride,
                                               filter_xd->dst.uv_stride);
        }
        filter_xd->pre = saved_pre;
        filter_xd->dst = saved_dst;
        *mbmi = saved_mbmi;

    }

    mv_row = x->best_sse_mv.as_mv.row;
    mv_col = x->best_sse_mv.as_mv.col;
    motion_magnitude2 = mv_row * mv_row + mv_col * mv_col;
    motion_threshold = denoiser->denoise_pars.scale_motion_thresh *
        NOISE_MOTION_THRESHOLD;

    if (motion_magnitude2 <
        denoiser->denoise_pars.scale_increase_filter * NOISE_MOTION_THRESHOLD)
      x->increase_denoising = 1;

    sse_thresh = denoiser->denoise_pars.scale_sse_thresh * SSE_THRESHOLD;
    if (x->increase_denoising)
      sse_thresh = denoiser->denoise_pars.scale_sse_thresh * SSE_THRESHOLD_HIGH;

    if (best_sse > sse_thresh || motion_magnitude2 > motion_threshold)
      decision = COPY_BLOCK;

    if (decision == FILTER_BLOCK)
    {
        unsigned char *mc_running_avg_y =
            denoiser->yv12_mc_running_avg.y_buffer + recon_yoffset;
        int mc_avg_y_stride = denoiser->yv12_mc_running_avg.y_stride;
        unsigned char *running_avg_y =
            denoiser->yv12_running_avg[INTRA_FRAME].y_buffer + recon_yoffset;
        int avg_y_stride = denoiser->yv12_running_avg[INTRA_FRAME].y_stride;

        /* Filter. */
        decision = vp8_denoiser_filter(mc_running_avg_y, mc_avg_y_stride,
                                       running_avg_y, avg_y_stride,
                                       x->thismb, 16, motion_magnitude2,
                                       x->increase_denoising);
        denoiser->denoise_state[block_index] = motion_magnitude2 > 0 ?
            kFilterNonZeroMV : kFilterZeroMV;
        // Only denoise UV for zero motion, and if y channel was denoised.
        if (denoiser->denoiser_mode != kDenoiserOnYOnly &&
            motion_magnitude2 == 0 &&
            decision == FILTER_BLOCK) {
          unsigned char *mc_running_avg_u =
              denoiser->yv12_mc_running_avg.u_buffer + recon_uvoffset;
          unsigned char *running_avg_u =
              denoiser->yv12_running_avg[INTRA_FRAME].u_buffer + recon_uvoffset;
          unsigned char *mc_running_avg_v =
              denoiser->yv12_mc_running_avg.v_buffer + recon_uvoffset;
          unsigned char *running_avg_v =
              denoiser->yv12_running_avg[INTRA_FRAME].v_buffer + recon_uvoffset;
          int mc_avg_uv_stride = denoiser->yv12_mc_running_avg.uv_stride;
          int avg_uv_stride = denoiser->yv12_running_avg[INTRA_FRAME].uv_stride;
          int signal_stride = x->block[16].src_stride;
          decision_u =
              vp8_denoiser_filter_uv(mc_running_avg_u, mc_avg_uv_stride,
                                      running_avg_u, avg_uv_stride,
                                      x->block[16].src + *x->block[16].base_src,
                                      signal_stride, motion_magnitude2, 0);
          decision_v =
              vp8_denoiser_filter_uv(mc_running_avg_v, mc_avg_uv_stride,
                                      running_avg_v, avg_uv_stride,
                                      x->block[20].src + *x->block[20].base_src,
                                      signal_stride, motion_magnitude2, 0);
        }
    }
    if (decision == COPY_BLOCK)
    {
        /* No filtering of this block; it differs too much from the predictor,
         * or the motion vector magnitude is considered too big.
         */
        vp8_copy_mem16x16(
                x->thismb, 16,
                denoiser->yv12_running_avg[INTRA_FRAME].y_buffer + recon_yoffset,
                denoiser->yv12_running_avg[INTRA_FRAME].y_stride);
        denoiser->denoise_state[block_index] = kNoFilter;
    }
    if (denoiser->denoiser_mode != kDenoiserOnYOnly) {
      if (decision_u == COPY_BLOCK) {
        vp8_copy_mem8x8(
            x->block[16].src + *x->block[16].base_src, x->block[16].src_stride,
            denoiser->yv12_running_avg[INTRA_FRAME].u_buffer + recon_uvoffset,
            denoiser->yv12_running_avg[INTRA_FRAME].uv_stride);
      }
      if (decision_v == COPY_BLOCK) {
        vp8_copy_mem8x8(
            x->block[20].src + *x->block[20].base_src, x->block[16].src_stride,
            denoiser->yv12_running_avg[INTRA_FRAME].v_buffer + recon_uvoffset,
            denoiser->yv12_running_avg[INTRA_FRAME].uv_stride);
      }
    }
    // Option to selectively deblock the denoised signal, for y channel only.
    if (apply_spatial_loop_filter) {
      loop_filter_info lfi;
      int apply_filter_col = 0;
      int apply_filter_row = 0;
      int apply_filter = 0;
      int y_stride = denoiser->yv12_running_avg[INTRA_FRAME].y_stride;
      int uv_stride =denoiser->yv12_running_avg[INTRA_FRAME].uv_stride;

      // Fix filter level to some nominal value for now.
      int filter_level = 32;

      int hev_index = lfi_n->hev_thr_lut[INTER_FRAME][filter_level];
      lfi.mblim = lfi_n->mblim[filter_level];
      lfi.blim = lfi_n->blim[filter_level];
      lfi.lim = lfi_n->lim[filter_level];
      lfi.hev_thr = lfi_n->hev_thr[hev_index];

      // Apply filter if there is a difference in the denoiser filter state
      // between the current and left/top block, or if non-zero motion vector
      // is used for the motion-compensated filtering.
      if (mb_col > 0) {
        apply_filter_col = !((denoiser->denoise_state[block_index] ==
            denoiser->denoise_state[block_index - 1]) &&
            denoiser->denoise_state[block_index] != kFilterNonZeroMV);
        if (apply_filter_col) {
          // Filter left vertical edge.
          apply_filter = 1;
          vp8_loop_filter_mbv(
              denoiser->yv12_running_avg[INTRA_FRAME].y_buffer + recon_yoffset,
              NULL, NULL, y_stride, uv_stride, &lfi);
        }
      }
      if (mb_row > 0) {
        apply_filter_row = !((denoiser->denoise_state[block_index] ==
            denoiser->denoise_state[block_index - denoiser->num_mb_cols]) &&
            denoiser->denoise_state[block_index] != kFilterNonZeroMV);
        if (apply_filter_row) {
          // Filter top horizontal edge.
          apply_filter = 1;
          vp8_loop_filter_mbh(
              denoiser->yv12_running_avg[INTRA_FRAME].y_buffer + recon_yoffset,
              NULL, NULL, y_stride, uv_stride, &lfi);
        }
      }
      if (apply_filter) {
        // Update the signal block |x|. Pixel changes are only to top and/or
        // left boundary pixels: can we avoid full block copy here.
        vp8_copy_mem16x16(
            denoiser->yv12_running_avg[INTRA_FRAME].y_buffer + recon_yoffset,
            y_stride, x->thismb, 16);
      }
    }
}