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 <assert.h>
  #include <limits.h>
  
  #include "./vpx_scale_rtcd.h"
  #include "vpx_dsp/psnr.h"
  #include "vpx_mem/vpx_mem.h"
  #include "vpx_ports/mem.h"
  
  #include "vp9/common/vp9_loopfilter.h"
  #include "vp9/common/vp9_onyxc_int.h"
  #include "vp9/common/vp9_quant_common.h"
  
  #include "vp9/encoder/vp9_encoder.h"
  #include "vp9/encoder/vp9_picklpf.h"
  #include "vp9/encoder/vp9_quantize.h"
  
  static int get_max_filter_level(const VP9_COMP *cpi) {
    if (cpi->oxcf.pass == 2) {
      return cpi->twopass.section_intra_rating > 8 ? MAX_LOOP_FILTER * 3 / 4
                                                   : MAX_LOOP_FILTER;
    } else {
      return MAX_LOOP_FILTER;
    }
  }
  
  static int64_t try_filter_frame(const YV12_BUFFER_CONFIG *sd,
                                  VP9_COMP *const cpi, int filt_level,
                                  int partial_frame) {
    VP9_COMMON *const cm = &cpi->common;
    int64_t filt_err;
  
    vp9_build_mask_frame(cm, filt_level, partial_frame);
  
    if (cpi->num_workers > 1)
      vp9_loop_filter_frame_mt(cm->frame_to_show, cm, cpi->td.mb.e_mbd.plane,
                               filt_level, 1, partial_frame, cpi->workers,
                               cpi->num_workers, &cpi->lf_row_sync);
    else
      vp9_loop_filter_frame(cm->frame_to_show, cm, &cpi->td.mb.e_mbd, filt_level,
                            1, partial_frame);
  
  #if CONFIG_VP9_HIGHBITDEPTH
    if (cm->use_highbitdepth) {
      filt_err = vpx_highbd_get_y_sse(sd, cm->frame_to_show);
    } else {
      filt_err = vpx_get_y_sse(sd, cm->frame_to_show);
    }
  #else
    filt_err = vpx_get_y_sse(sd, cm->frame_to_show);
  #endif  // CONFIG_VP9_HIGHBITDEPTH
  
    // Re-instate the unfiltered frame
    vpx_yv12_copy_y(&cpi->last_frame_uf, cm->frame_to_show);
  
    return filt_err;
  }
  
  static int search_filter_level(const YV12_BUFFER_CONFIG *sd, VP9_COMP *cpi,
                                 int partial_frame) {
    const VP9_COMMON *const cm = &cpi->common;
    const struct loopfilter *const lf = &cm->lf;
    const int min_filter_level = 0;
    const int max_filter_level = get_max_filter_level(cpi);
    int filt_direction = 0;
    int64_t best_err;
    int filt_best;
  
    // Start the search at the previous frame filter level unless it is now out of
    // range.
    int filt_mid = clamp(lf->last_filt_level, min_filter_level, max_filter_level);
    int filter_step = filt_mid < 16 ? 4 : filt_mid / 4;
    // Sum squared error at each filter level
    int64_t ss_err[MAX_LOOP_FILTER + 1];
  
    // Set each entry to -1
    memset(ss_err, 0xFF, sizeof(ss_err));
  
    //  Make a copy of the unfiltered / processed recon buffer
    vpx_yv12_copy_y(cm->frame_to_show, &cpi->last_frame_uf);
  
    best_err = try_filter_frame(sd, cpi, filt_mid, partial_frame);
    filt_best = filt_mid;
    ss_err[filt_mid] = best_err;
  
    while (filter_step > 0) {
      const int filt_high = VPXMIN(filt_mid + filter_step, max_filter_level);
      const int filt_low = VPXMAX(filt_mid - filter_step, min_filter_level);
  
      // Bias against raising loop filter in favor of lowering it.
      int64_t bias = (best_err >> (15 - (filt_mid / 8))) * filter_step;
  
      if ((cpi->oxcf.pass == 2) && (cpi->twopass.section_intra_rating < 20))
        bias = (bias * cpi->twopass.section_intra_rating) / 20;
  
      // yx, bias less for large block size
      if (cm->tx_mode != ONLY_4X4) bias >>= 1;
  
      if (filt_direction <= 0 && filt_low != filt_mid) {
        // Get Low filter error score
        if (ss_err[filt_low] < 0) {
          ss_err[filt_low] = try_filter_frame(sd, cpi, filt_low, partial_frame);
        }
        // If value is close to the best so far then bias towards a lower loop
        // filter value.
        if ((ss_err[filt_low] - bias) < best_err) {
          // Was it actually better than the previous best?
          if (ss_err[filt_low] < best_err) best_err = ss_err[filt_low];
  
          filt_best = filt_low;
        }
      }
  
      // Now look at filt_high
      if (filt_direction >= 0 && filt_high != filt_mid) {
        if (ss_err[filt_high] < 0) {
          ss_err[filt_high] = try_filter_frame(sd, cpi, filt_high, partial_frame);
        }
        // Was it better than the previous best?
        if (ss_err[filt_high] < (best_err - bias)) {
          best_err = ss_err[filt_high];
          filt_best = filt_high;
        }
      }
  
      // Half the step distance if the best filter value was the same as last time
      if (filt_best == filt_mid) {
        filter_step /= 2;
        filt_direction = 0;
      } else {
        filt_direction = (filt_best < filt_mid) ? -1 : 1;
        filt_mid = filt_best;
      }
    }
  
    return filt_best;
  }
  
  void vp9_pick_filter_level(const YV12_BUFFER_CONFIG *sd, VP9_COMP *cpi,
                             LPF_PICK_METHOD method) {
    VP9_COMMON *const cm = &cpi->common;
    struct loopfilter *const lf = &cm->lf;
  
    lf->sharpness_level = 0;
  
    if (method == LPF_PICK_MINIMAL_LPF && lf->filter_level) {
      lf->filter_level = 0;
    } else if (method >= LPF_PICK_FROM_Q) {
      const int min_filter_level = 0;
      const int max_filter_level = get_max_filter_level(cpi);
      const int q = vp9_ac_quant(cm->base_qindex, 0, cm->bit_depth);
  // These values were determined by linear fitting the result of the
  // searched level, filt_guess = q * 0.316206 + 3.87252
  #if CONFIG_VP9_HIGHBITDEPTH
      int filt_guess;
      switch (cm->bit_depth) {
        case VPX_BITS_8:
          filt_guess = ROUND_POWER_OF_TWO(q * 20723 + 1015158, 18);
          break;
        case VPX_BITS_10:
          filt_guess = ROUND_POWER_OF_TWO(q * 20723 + 4060632, 20);
          break;
        default:
          assert(cm->bit_depth == VPX_BITS_12);
          filt_guess = ROUND_POWER_OF_TWO(q * 20723 + 16242526, 22);
          break;
      }
  #else
      int filt_guess = ROUND_POWER_OF_TWO(q * 20723 + 1015158, 18);
  #endif  // CONFIG_VP9_HIGHBITDEPTH
      if (cpi->oxcf.pass == 0 && cpi->oxcf.rc_mode == VPX_CBR &&
          cpi->oxcf.aq_mode == CYCLIC_REFRESH_AQ && cm->seg.enabled &&
          (cm->base_qindex < 200 || cm->width * cm->height > 320 * 240) &&
          cpi->oxcf.content != VP9E_CONTENT_SCREEN && cm->frame_type != KEY_FRAME)
        filt_guess = 5 * filt_guess >> 3;
  
      if (cm->frame_type == KEY_FRAME) filt_guess -= 4;
      lf->filter_level = clamp(filt_guess, min_filter_level, max_filter_level);
    } else {
      lf->filter_level =
          search_filter_level(sd, cpi, method == LPF_PICK_FROM_SUBIMAGE);
    }
  }
  