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 "denoising.h"

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

static const unsigned int NOISE_MOTION_THRESHOLD = 20*20;
static const unsigned int NOISE_DIFF2_THRESHOLD = 75;
// 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 uint8_t blend(uint8_t state, uint8_t sample, uint8_t factor_q8)
{
  return (uint8_t)(
      (((uint16_t)factor_q8 * ((uint16_t)state) +  // Q8
        (uint16_t)(256 - factor_q8) * ((uint16_t)sample)) + 128)  // Q8
      >> 8);
}

static unsigned int denoiser_motion_compensate(YV12_BUFFER_CONFIG* src,
                                               YV12_BUFFER_CONFIG* dst,
                                               MACROBLOCK* x,
                                               unsigned int best_sse,
                                               unsigned int zero_mv_sse,
                                               int recon_yoffset,
                                               int recon_uvoffset)
{
  MACROBLOCKD filter_xd = x->e_mbd;
  int mv_col;
  int mv_row;
  int sse_diff = zero_mv_sse - best_sse;
  // 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;
  // Use the best MV for the compensation.
  filter_xd.mode_info_context->mbmi.ref_frame = LAST_FRAME;
  filter_xd.mode_info_context->mbmi.mode = filter_xd.best_sse_inter_mode;
  filter_xd.mode_info_context->mbmi.mv = filter_xd.best_sse_mv;
  filter_xd.mode_info_context->mbmi.need_to_clamp_mvs =
      filter_xd.need_to_clamp_best_mvs;
  mv_col = filter_xd.best_sse_mv.as_mv.col;
  mv_row = filter_xd.best_sse_mv.as_mv.row;
  if (filter_xd.mode_info_context->mbmi.mode <= B_PRED ||
      (mv_row*mv_row + mv_col*mv_col <= NOISE_MOTION_THRESHOLD &&
       sse_diff < SSE_DIFF_THRESHOLD))
  {
    // 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.
    filter_xd.mode_info_context->mbmi.ref_frame = LAST_FRAME;
    filter_xd.mode_info_context->mbmi.mode = ZEROMV;
    filter_xd.mode_info_context->mbmi.mv.as_int = 0;
    x->e_mbd.best_sse_inter_mode = ZEROMV;
    x->e_mbd.best_sse_mv.as_int = 0;
    best_sse = zero_mv_sse;
  }
  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);
  }
  return best_sse;
}

static void denoiser_filter(YV12_BUFFER_CONFIG* mc_running_avg,
                            YV12_BUFFER_CONFIG* running_avg,
                            MACROBLOCK* signal,
                            unsigned int motion_magnitude2,
                            int y_offset,
                            int uv_offset)
{
  unsigned char* sig = signal->thismb;
  int sig_stride = 16;
  unsigned char* mc_running_avg_y = mc_running_avg->y_buffer + y_offset;
  int mc_avg_y_stride = mc_running_avg->y_stride;
  unsigned char* running_avg_y = running_avg->y_buffer + y_offset;
  int avg_y_stride = running_avg->y_stride;
  int r, c;
  for (r = 0; r < 16; r++)
  {
    for (c = 0; c < 16; c++)
    {
      int diff;
      int absdiff = 0;
      unsigned int filter_coefficient;
      absdiff = sig[c] - mc_running_avg_y[c];
      absdiff = absdiff > 0 ? absdiff : -absdiff;
      assert(absdiff >= 0 && absdiff < 256);
      filter_coefficient = (255 << 8) / (256 + ((absdiff * 330) >> 3));
      // Allow some additional filtering of static blocks, or blocks with very
      // small motion vectors.
      filter_coefficient += filter_coefficient / (3 + (motion_magnitude2 >> 3));
      filter_coefficient = filter_coefficient > 255 ? 255 : filter_coefficient;

      running_avg_y[c] = blend(mc_running_avg_y[c], sig[c], filter_coefficient);
      diff = sig[c] - running_avg_y[c];

      if (diff * diff < NOISE_DIFF2_THRESHOLD)
      {
        // Replace with mean to suppress the noise.
        sig[c] = running_avg_y[c];
      }
      else
      {
        // Replace the filter state with the signal since the change in this
        // pixel isn't classified as noise.
        running_avg_y[c] = sig[c];
      }
    }
    sig += sig_stride;
    mc_running_avg_y += mc_avg_y_stride;
    running_avg_y += avg_y_stride;
  }
}

int vp8_denoiser_allocate(VP8_DENOISER *denoiser, int width, int height)
{
  assert(denoiser);
  denoiser->yv12_running_avg.flags = 0;
  if (vp8_yv12_alloc_frame_buffer(&(denoiser->yv12_running_avg), width,
                                  height, VP8BORDERINPIXELS) < 0)
  {
      vp8_denoiser_free(denoiser);
      return 1;
  }
  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_running_avg.buffer_alloc, 0,
             denoiser->yv12_running_avg.frame_size);
  vpx_memset(denoiser->yv12_mc_running_avg.buffer_alloc, 0,
             denoiser->yv12_mc_running_avg.frame_size);
  return 0;
}

void vp8_denoiser_free(VP8_DENOISER *denoiser)
{
  assert(denoiser);
  vp8_yv12_de_alloc_frame_buffer(&denoiser->yv12_running_avg);
  vp8_yv12_de_alloc_frame_buffer(&denoiser->yv12_mc_running_avg);
}

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) {
  int mv_row;
  int mv_col;
  unsigned int motion_magnitude2;
  // Motion compensate the running average.
  best_sse = denoiser_motion_compensate(&denoiser->yv12_running_avg,
                                        &denoiser->yv12_mc_running_avg,
                                        x,
                                        best_sse,
                                        zero_mv_sse,
                                        recon_yoffset,
                                        recon_uvoffset);

  mv_row = x->e_mbd.best_sse_mv.as_mv.row;
  mv_col = x->e_mbd.best_sse_mv.as_mv.col;
  motion_magnitude2 = mv_row*mv_row + mv_col*mv_col;
  if (best_sse > SSE_THRESHOLD ||
      motion_magnitude2 > 8 * NOISE_MOTION_THRESHOLD)
  {
    // No filtering of this block since 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.y_buffer + recon_yoffset,
                      denoiser->yv12_running_avg.y_stride);
    return;
  }
  // Filter.
  denoiser_filter(&denoiser->yv12_mc_running_avg,
                  &denoiser->yv12_running_avg,
                  x,
                  motion_magnitude2,
                  recon_yoffset,
                  recon_uvoffset);
}