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 <limits.h>
  #include <math.h>
  #include <stdio.h>
  
  #include "./vpx_dsp_rtcd.h"
  #include "./vpx_scale_rtcd.h"
  
  #include "vpx_dsp/vpx_dsp_common.h"
  #include "vpx_mem/vpx_mem.h"
  #include "vpx_ports/mem.h"
  #include "vpx_ports/system_state.h"
  #include "vpx_scale/vpx_scale.h"
  #include "vpx_scale/yv12config.h"
  
  #include "vp9/common/vp9_entropymv.h"
  #include "vp9/common/vp9_quant_common.h"
  #include "vp9/common/vp9_reconinter.h"  // vp9_setup_dst_planes()
  #include "vp9/encoder/vp9_aq_variance.h"
  #include "vp9/encoder/vp9_block.h"
  #include "vp9/encoder/vp9_encodeframe.h"
  #include "vp9/encoder/vp9_encodemb.h"
  #include "vp9/encoder/vp9_encodemv.h"
  #include "vp9/encoder/vp9_encoder.h"
  #include "vp9/encoder/vp9_extend.h"
  #include "vp9/encoder/vp9_firstpass.h"
  #include "vp9/encoder/vp9_mcomp.h"
  #include "vp9/encoder/vp9_quantize.h"
  #include "vp9/encoder/vp9_rd.h"
  #include "vpx_dsp/variance.h"
  
  #define OUTPUT_FPF          0
  #define ARF_STATS_OUTPUT    0
  
  #define BOOST_BREAKOUT      12.5
  #define BOOST_FACTOR        12.5
  #define FACTOR_PT_LOW       0.70
  #define FACTOR_PT_HIGH      0.90
  #define FIRST_PASS_Q        10.0
  #define GF_MAX_BOOST        96.0
  #define INTRA_MODE_PENALTY  1024
  #define KF_MAX_BOOST        128.0
  #define MIN_ARF_GF_BOOST    240
  #define MIN_DECAY_FACTOR    0.01
  #define MIN_KF_BOOST        300
  #define NEW_MV_MODE_PENALTY 32
  #define SVC_FACTOR_PT_LOW   0.45
  #define DARK_THRESH         64
  #define DEFAULT_GRP_WEIGHT  1.0
  #define RC_FACTOR_MIN       0.75
  #define RC_FACTOR_MAX       1.75
  
  
  #define NCOUNT_INTRA_THRESH 8192
  #define NCOUNT_INTRA_FACTOR 3
  
  
  #define DOUBLE_DIVIDE_CHECK(x) ((x) < 0 ? (x) - 0.000001 : (x) + 0.000001)
  
  #if ARF_STATS_OUTPUT
  unsigned int arf_count = 0;
  #endif
  
  // Resets the first pass file to the given position using a relative seek from
  // the current position.
  static void reset_fpf_position(TWO_PASS *p,
                                 const FIRSTPASS_STATS *position) {
    p->stats_in = position;
  }
  
  // Read frame stats at an offset from the current position.
  static const FIRSTPASS_STATS *read_frame_stats(const TWO_PASS *p, int offset) {
    if ((offset >= 0 && p->stats_in + offset >= p->stats_in_end) ||
        (offset < 0 && p->stats_in + offset < p->stats_in_start)) {
      return NULL;
    }
  
    return &p->stats_in[offset];
  }
  
  static int input_stats(TWO_PASS *p, FIRSTPASS_STATS *fps) {
    if (p->stats_in >= p->stats_in_end)
      return EOF;
  
    *fps = *p->stats_in;
    ++p->stats_in;
    return 1;
  }
  
  static void output_stats(FIRSTPASS_STATS *stats,
                           struct vpx_codec_pkt_list *pktlist) {
    struct vpx_codec_cx_pkt pkt;
    pkt.kind = VPX_CODEC_STATS_PKT;
    pkt.data.twopass_stats.buf = stats;
    pkt.data.twopass_stats.sz = sizeof(FIRSTPASS_STATS);
    vpx_codec_pkt_list_add(pktlist, &pkt);
  
  // TEMP debug code
  #if OUTPUT_FPF
    {
      FILE *fpfile;
      fpfile = fopen("firstpass.stt", "a");
  
      fprintf(fpfile, "%12.0lf %12.4lf %12.0lf %12.0lf %12.0lf %12.4lf %12.4lf"
              "%12.4lf %12.4lf %12.4lf %12.4lf %12.4lf %12.4lf %12.4lf %12.4lf"
              "%12.4lf %12.4lf %12.4lf %12.0lf %12.0lf %12.0lf %12.4lf\n",
              stats->frame,
              stats->weight,
              stats->intra_error,
              stats->coded_error,
              stats->sr_coded_error,
              stats->pcnt_inter,
              stats->pcnt_motion,
              stats->pcnt_second_ref,
              stats->pcnt_neutral,
              stats->intra_skip_pct,
              stats->intra_smooth_pct,
              stats->inactive_zone_rows,
              stats->inactive_zone_cols,
              stats->MVr,
              stats->mvr_abs,
              stats->MVc,
              stats->mvc_abs,
              stats->MVrv,
              stats->MVcv,
              stats->mv_in_out_count,
              stats->new_mv_count,
              stats->count,
              stats->duration);
      fclose(fpfile);
    }
  #endif
  }
  
  #if CONFIG_FP_MB_STATS
  static void output_fpmb_stats(uint8_t *this_frame_mb_stats, VP9_COMMON *cm,
                           struct vpx_codec_pkt_list *pktlist) {
    struct vpx_codec_cx_pkt pkt;
    pkt.kind = VPX_CODEC_FPMB_STATS_PKT;
    pkt.data.firstpass_mb_stats.buf = this_frame_mb_stats;
    pkt.data.firstpass_mb_stats.sz = cm->initial_mbs * sizeof(uint8_t);
    vpx_codec_pkt_list_add(pktlist, &pkt);
  }
  #endif
  
  static void zero_stats(FIRSTPASS_STATS *section) {
    section->frame              = 0.0;
    section->weight             = 0.0;
    section->intra_error        = 0.0;
    section->coded_error        = 0.0;
    section->sr_coded_error     = 0.0;
    section->pcnt_inter         = 0.0;
    section->pcnt_motion        = 0.0;
    section->pcnt_second_ref    = 0.0;
    section->pcnt_neutral       = 0.0;
    section->intra_skip_pct     = 0.0;
    section->intra_smooth_pct   = 0.0;
    section->inactive_zone_rows = 0.0;
    section->inactive_zone_cols = 0.0;
    section->MVr                = 0.0;
    section->mvr_abs            = 0.0;
    section->MVc                = 0.0;
    section->mvc_abs            = 0.0;
    section->MVrv               = 0.0;
    section->MVcv               = 0.0;
    section->mv_in_out_count    = 0.0;
    section->new_mv_count       = 0.0;
    section->count              = 0.0;
    section->duration           = 1.0;
    section->spatial_layer_id   = 0;
  }
  
  static void accumulate_stats(FIRSTPASS_STATS *section,
                               const FIRSTPASS_STATS *frame) {
    section->frame              += frame->frame;
    section->weight             += frame->weight;
    section->spatial_layer_id    = frame->spatial_layer_id;
    section->intra_error        += frame->intra_error;
    section->coded_error        += frame->coded_error;
    section->sr_coded_error     += frame->sr_coded_error;
    section->pcnt_inter         += frame->pcnt_inter;
    section->pcnt_motion        += frame->pcnt_motion;
    section->pcnt_second_ref    += frame->pcnt_second_ref;
    section->pcnt_neutral       += frame->pcnt_neutral;
    section->intra_skip_pct     += frame->intra_skip_pct;
    section->intra_smooth_pct   += frame->intra_smooth_pct;
    section->inactive_zone_rows += frame->inactive_zone_rows;
    section->inactive_zone_cols += frame->inactive_zone_cols;
    section->MVr                += frame->MVr;
    section->mvr_abs            += frame->mvr_abs;
    section->MVc                += frame->MVc;
    section->mvc_abs            += frame->mvc_abs;
    section->MVrv               += frame->MVrv;
    section->MVcv               += frame->MVcv;
    section->mv_in_out_count    += frame->mv_in_out_count;
    section->new_mv_count       += frame->new_mv_count;
    section->count              += frame->count;
    section->duration           += frame->duration;
  }
  
  static void subtract_stats(FIRSTPASS_STATS *section,
                             const FIRSTPASS_STATS *frame) {
    section->frame              -= frame->frame;
    section->weight             -= frame->weight;
    section->intra_error        -= frame->intra_error;
    section->coded_error        -= frame->coded_error;
    section->sr_coded_error     -= frame->sr_coded_error;
    section->pcnt_inter         -= frame->pcnt_inter;
    section->pcnt_motion        -= frame->pcnt_motion;
    section->pcnt_second_ref    -= frame->pcnt_second_ref;
    section->pcnt_neutral       -= frame->pcnt_neutral;
    section->intra_skip_pct     -= frame->intra_skip_pct;
    section->intra_smooth_pct   -= frame->intra_smooth_pct;
    section->inactive_zone_rows -= frame->inactive_zone_rows;
    section->inactive_zone_cols -= frame->inactive_zone_cols;
    section->MVr                -= frame->MVr;
    section->mvr_abs            -= frame->mvr_abs;
    section->MVc                -= frame->MVc;
    section->mvc_abs            -= frame->mvc_abs;
    section->MVrv               -= frame->MVrv;
    section->MVcv               -= frame->MVcv;
    section->mv_in_out_count    -= frame->mv_in_out_count;
    section->new_mv_count       -= frame->new_mv_count;
    section->count              -= frame->count;
    section->duration           -= frame->duration;
  }
  
  // Calculate an active area of the image that discounts formatting
  // bars and partially discounts other 0 energy areas.
  #define MIN_ACTIVE_AREA 0.5
  #define MAX_ACTIVE_AREA 1.0
  static double calculate_active_area(const VP9_COMP *cpi,
                                      const FIRSTPASS_STATS *this_frame) {
    double active_pct;
  
    active_pct = 1.0 -
      ((this_frame->intra_skip_pct / 2) +
       ((this_frame->inactive_zone_rows * 2) / (double)cpi->common.mb_rows));
    return fclamp(active_pct, MIN_ACTIVE_AREA, MAX_ACTIVE_AREA);
  }
  
  // Calculate a modified Error used in distributing bits between easier and
  // harder frames.
  #define ACT_AREA_CORRECTION 0.5
  static double calculate_modified_err(const VP9_COMP *cpi,
                                       const TWO_PASS *twopass,
                                       const VP9EncoderConfig *oxcf,
                                       const FIRSTPASS_STATS *this_frame) {
    const FIRSTPASS_STATS *const stats = &twopass->total_stats;
    const double av_weight = stats->weight / stats->count;
    const double av_err = (stats->coded_error * av_weight) / stats->count;
    double modified_error =
      av_err * pow(this_frame->coded_error * this_frame->weight /
                   DOUBLE_DIVIDE_CHECK(av_err), oxcf->two_pass_vbrbias / 100.0);
  
    // Correction for active area. Frames with a reduced active area
    // (eg due to formatting bars) have a higher error per mb for the
    // remaining active MBs. The correction here assumes that coding
    // 0.5N blocks of complexity 2X is a little easier than coding N
    // blocks of complexity X.
    modified_error *=
      pow(calculate_active_area(cpi, this_frame), ACT_AREA_CORRECTION);
  
    return fclamp(modified_error,
                  twopass->modified_error_min, twopass->modified_error_max);
  }
  
  // This function returns the maximum target rate per frame.
  static int frame_max_bits(const RATE_CONTROL *rc,
                            const VP9EncoderConfig *oxcf) {
    int64_t max_bits = ((int64_t)rc->avg_frame_bandwidth *
                            (int64_t)oxcf->two_pass_vbrmax_section) / 100;
    if (max_bits < 0)
      max_bits = 0;
    else if (max_bits > rc->max_frame_bandwidth)
      max_bits = rc->max_frame_bandwidth;
  
    return (int)max_bits;
  }
  
  void vp9_init_first_pass(VP9_COMP *cpi) {
    zero_stats(&cpi->twopass.total_stats);
  }
  
  void vp9_end_first_pass(VP9_COMP *cpi) {
    if (is_two_pass_svc(cpi)) {
      int i;
      for (i = 0; i < cpi->svc.number_spatial_layers; ++i) {
        output_stats(&cpi->svc.layer_context[i].twopass.total_stats,
                     cpi->output_pkt_list);
      }
    } else {
      output_stats(&cpi->twopass.total_stats, cpi->output_pkt_list);
    }
  }
  
  static vpx_variance_fn_t get_block_variance_fn(BLOCK_SIZE bsize) {
    switch (bsize) {
      case BLOCK_8X8:
        return vpx_mse8x8;
      case BLOCK_16X8:
        return vpx_mse16x8;
      case BLOCK_8X16:
        return vpx_mse8x16;
      default:
        return vpx_mse16x16;
    }
  }
  
  static unsigned int get_prediction_error(BLOCK_SIZE bsize,
                                           const struct buf_2d *src,
                                           const struct buf_2d *ref) {
    unsigned int sse;
    const vpx_variance_fn_t fn = get_block_variance_fn(bsize);
    fn(src->buf, src->stride, ref->buf, ref->stride, &sse);
    return sse;
  }
  
  #if CONFIG_VP9_HIGHBITDEPTH
  static vpx_variance_fn_t highbd_get_block_variance_fn(BLOCK_SIZE bsize,
                                                        int bd) {
    switch (bd) {
      default:
        switch (bsize) {
          case BLOCK_8X8:
            return vpx_highbd_8_mse8x8;
          case BLOCK_16X8:
            return vpx_highbd_8_mse16x8;
          case BLOCK_8X16:
            return vpx_highbd_8_mse8x16;
          default:
            return vpx_highbd_8_mse16x16;
        }
        break;
      case 10:
        switch (bsize) {
          case BLOCK_8X8:
            return vpx_highbd_10_mse8x8;
          case BLOCK_16X8:
            return vpx_highbd_10_mse16x8;
          case BLOCK_8X16:
            return vpx_highbd_10_mse8x16;
          default:
            return vpx_highbd_10_mse16x16;
        }
        break;
      case 12:
        switch (bsize) {
          case BLOCK_8X8:
            return vpx_highbd_12_mse8x8;
          case BLOCK_16X8:
            return vpx_highbd_12_mse16x8;
          case BLOCK_8X16:
            return vpx_highbd_12_mse8x16;
          default:
            return vpx_highbd_12_mse16x16;
        }
        break;
    }
  }
  
  static unsigned int highbd_get_prediction_error(BLOCK_SIZE bsize,
                                                  const struct buf_2d *src,
                                                  const struct buf_2d *ref,
                                                  int bd) {
    unsigned int sse;
    const vpx_variance_fn_t fn = highbd_get_block_variance_fn(bsize, bd);
    fn(src->buf, src->stride, ref->buf, ref->stride, &sse);
    return sse;
  }
  #endif  // CONFIG_VP9_HIGHBITDEPTH
  
  // Refine the motion search range according to the frame dimension
  // for first pass test.
  static int get_search_range(const VP9_COMP *cpi) {
    int sr = 0;
    const int dim = VPXMIN(cpi->initial_width, cpi->initial_height);
  
    while ((dim << sr) < MAX_FULL_PEL_VAL)
      ++sr;
    return sr;
  }
  
  static void first_pass_motion_search(VP9_COMP *cpi, MACROBLOCK *x,
                                       const MV *ref_mv, MV *best_mv,
                                       int *best_motion_err) {
    MACROBLOCKD *const xd = &x->e_mbd;
    MV tmp_mv = {0, 0};
    MV ref_mv_full = {ref_mv->row >> 3, ref_mv->col >> 3};
    int num00, tmp_err, n;
    const BLOCK_SIZE bsize = xd->mi[0]->sb_type;
    vp9_variance_fn_ptr_t v_fn_ptr = cpi->fn_ptr[bsize];
    const int new_mv_mode_penalty = NEW_MV_MODE_PENALTY;
  
    int step_param = 3;
    int further_steps = (MAX_MVSEARCH_STEPS - 1) - step_param;
    const int sr = get_search_range(cpi);
    step_param += sr;
    further_steps -= sr;
  
    // Override the default variance function to use MSE.
    v_fn_ptr.vf = get_block_variance_fn(bsize);
  #if CONFIG_VP9_HIGHBITDEPTH
    if (xd->cur_buf->flags & YV12_FLAG_HIGHBITDEPTH) {
      v_fn_ptr.vf = highbd_get_block_variance_fn(bsize, xd->bd);
    }
  #endif  // CONFIG_VP9_HIGHBITDEPTH
  
    // Center the initial step/diamond search on best mv.
    tmp_err = cpi->diamond_search_sad(x, &cpi->ss_cfg, &ref_mv_full, &tmp_mv,
                                      step_param,
                                      x->sadperbit16, &num00, &v_fn_ptr, ref_mv);
    if (tmp_err < INT_MAX)
      tmp_err = vp9_get_mvpred_var(x, &tmp_mv, ref_mv, &v_fn_ptr, 1);
    if (tmp_err < INT_MAX - new_mv_mode_penalty)
      tmp_err += new_mv_mode_penalty;
  
    if (tmp_err < *best_motion_err) {
      *best_motion_err = tmp_err;
      *best_mv = tmp_mv;
    }
  
    // Carry out further step/diamond searches as necessary.
    n = num00;
    num00 = 0;
  
    while (n < further_steps) {
      ++n;
  
      if (num00) {
        --num00;
      } else {
        tmp_err = cpi->diamond_search_sad(x, &cpi->ss_cfg, &ref_mv_full, &tmp_mv,
                                          step_param + n, x->sadperbit16,
                                          &num00, &v_fn_ptr, ref_mv);
        if (tmp_err < INT_MAX)
          tmp_err = vp9_get_mvpred_var(x, &tmp_mv, ref_mv, &v_fn_ptr, 1);
        if (tmp_err < INT_MAX - new_mv_mode_penalty)
          tmp_err += new_mv_mode_penalty;
  
        if (tmp_err < *best_motion_err) {
          *best_motion_err = tmp_err;
          *best_mv = tmp_mv;
        }
      }
    }
  }
  
  static BLOCK_SIZE get_bsize(const VP9_COMMON *cm, int mb_row, int mb_col) {
    if (2 * mb_col + 1 < cm->mi_cols) {
      return 2 * mb_row + 1 < cm->mi_rows ? BLOCK_16X16
                                          : BLOCK_16X8;
    } else {
      return 2 * mb_row + 1 < cm->mi_rows ? BLOCK_8X16
                                          : BLOCK_8X8;
    }
  }
  
  static int find_fp_qindex(vpx_bit_depth_t bit_depth) {
    int i;
  
    for (i = 0; i < QINDEX_RANGE; ++i)
      if (vp9_convert_qindex_to_q(i, bit_depth) >= FIRST_PASS_Q)
        break;
  
    if (i == QINDEX_RANGE)
      i--;
  
    return i;
  }
  
  static void set_first_pass_params(VP9_COMP *cpi) {
    VP9_COMMON *const cm = &cpi->common;
    if (!cpi->refresh_alt_ref_frame &&
        (cm->current_video_frame == 0 ||
         (cpi->frame_flags & FRAMEFLAGS_KEY))) {
      cm->frame_type = KEY_FRAME;
    } else {
      cm->frame_type = INTER_FRAME;
    }
    // Do not use periodic key frames.
    cpi->rc.frames_to_key = INT_MAX;
  }
  
  // This threshold is used to track blocks where to all intents and purposes
  // the intra prediction error 0. Though the metric we test against
  // is technically a sse we are mainly interested in blocks where all the pixels
  // in the 8 bit domain have an error of <= 1 (where error = sse) so a
  // linear scaling for 10 and 12 bit gives similar results.
  #define UL_INTRA_THRESH 50
  static int get_ul_intra_threshold(VP9_COMMON *cm) {
    int ret_val = UL_INTRA_THRESH;
  #if CONFIG_VP9_HIGHBITDEPTH
    if (cm->use_highbitdepth) {
      switch (cm->bit_depth) {
        case VPX_BITS_8:
          ret_val = UL_INTRA_THRESH;
          break;
        case VPX_BITS_10:
          ret_val = UL_INTRA_THRESH << 2;
          break;
        case VPX_BITS_12:
          ret_val = UL_INTRA_THRESH << 4;
          break;
        default:
          assert(0 && "cm->bit_depth should be VPX_BITS_8, "
                      "VPX_BITS_10 or VPX_BITS_12");
      }
    }
  #else
    (void) cm;
  #endif  // CONFIG_VP9_HIGHBITDEPTH
    return ret_val;
  }
  
  #define SMOOTH_INTRA_THRESH 4000
  static int get_smooth_intra_threshold(VP9_COMMON *cm) {
    int ret_val = SMOOTH_INTRA_THRESH;
  #if CONFIG_VP9_HIGHBITDEPTH
    if (cm->use_highbitdepth) {
      switch (cm->bit_depth) {
        case VPX_BITS_8:
          ret_val = SMOOTH_INTRA_THRESH;
          break;
        case VPX_BITS_10:
          ret_val = SMOOTH_INTRA_THRESH << 4;
          break;
        case VPX_BITS_12:
          ret_val = SMOOTH_INTRA_THRESH << 8;
          break;
        default:
          assert(0 && "cm->bit_depth should be VPX_BITS_8, "
                      "VPX_BITS_10 or VPX_BITS_12");
      }
    }
  #else
    (void) cm;
  #endif  // CONFIG_VP9_HIGHBITDEPTH
    return ret_val;
  }
  
  #define INVALID_ROW -1
  void vp9_first_pass(VP9_COMP *cpi, const struct lookahead_entry *source) {
    int mb_row, mb_col;
    MACROBLOCK *const x = &cpi->td.mb;
    VP9_COMMON *const cm = &cpi->common;
    MACROBLOCKD *const xd = &x->e_mbd;
    TileInfo tile;
    struct macroblock_plane *const p = x->plane;
    struct macroblockd_plane *const pd = xd->plane;
    const PICK_MODE_CONTEXT *ctx = &cpi->td.pc_root->none;
    int i;
  
    int recon_yoffset, recon_uvoffset;
    int64_t intra_error = 0;
    int64_t coded_error = 0;
    int64_t sr_coded_error = 0;
  
    int sum_mvr = 0, sum_mvc = 0;
    int sum_mvr_abs = 0, sum_mvc_abs = 0;
    int64_t sum_mvrs = 0, sum_mvcs = 0;
    int mvcount = 0;
    int intercount = 0;
    int second_ref_count = 0;
    const int intrapenalty = INTRA_MODE_PENALTY;
    double neutral_count;
    int intra_skip_count = 0;
    int intra_smooth_count = 0;
    int image_data_start_row = INVALID_ROW;
    int new_mv_count = 0;
    int sum_in_vectors = 0;
    MV lastmv = {0, 0};
    TWO_PASS *twopass = &cpi->twopass;
    const MV zero_mv = {0, 0};
    int recon_y_stride, recon_uv_stride, uv_mb_height;
  
    YV12_BUFFER_CONFIG *const lst_yv12 = get_ref_frame_buffer(cpi, LAST_FRAME);
    YV12_BUFFER_CONFIG *gld_yv12 = get_ref_frame_buffer(cpi, GOLDEN_FRAME);
    YV12_BUFFER_CONFIG *const new_yv12 = get_frame_new_buffer(cm);
    const YV12_BUFFER_CONFIG *first_ref_buf = lst_yv12;
  
    LAYER_CONTEXT *const lc = is_two_pass_svc(cpi) ?
          &cpi->svc.layer_context[cpi->svc.spatial_layer_id] : NULL;
    double intra_factor;
    double brightness_factor;
    BufferPool *const pool = cm->buffer_pool;
    MODE_INFO mi_above, mi_left;
  
    // First pass code requires valid last and new frame buffers.
    assert(new_yv12 != NULL);
    assert((lc != NULL) || frame_is_intra_only(cm) || (lst_yv12 != NULL));
  
  #if CONFIG_FP_MB_STATS
    if (cpi->use_fp_mb_stats) {
      vp9_zero_array(cpi->twopass.frame_mb_stats_buf, cm->initial_mbs);
    }
  #endif
  
    vpx_clear_system_state();
  
    intra_factor = 0.0;
    brightness_factor = 0.0;
    neutral_count = 0.0;
  
    set_first_pass_params(cpi);
    vp9_set_quantizer(cm, find_fp_qindex(cm->bit_depth));
  
    if (lc != NULL) {
      twopass = &lc->twopass;
  
      cpi->lst_fb_idx = cpi->svc.spatial_layer_id;
      cpi->ref_frame_flags = VP9_LAST_FLAG;
  
      if (cpi->svc.number_spatial_layers + cpi->svc.spatial_layer_id <
          REF_FRAMES) {
        cpi->gld_fb_idx =
            cpi->svc.number_spatial_layers + cpi->svc.spatial_layer_id;
        cpi->ref_frame_flags |= VP9_GOLD_FLAG;
        cpi->refresh_golden_frame = (lc->current_video_frame_in_layer == 0);
      } else {
        cpi->refresh_golden_frame = 0;
      }
  
      if (lc->current_video_frame_in_layer == 0)
        cpi->ref_frame_flags = 0;
  
      vp9_scale_references(cpi);
  
      // Use either last frame or alt frame for motion search.
      if (cpi->ref_frame_flags & VP9_LAST_FLAG) {
        first_ref_buf = vp9_get_scaled_ref_frame(cpi, LAST_FRAME);
        if (first_ref_buf == NULL)
          first_ref_buf = get_ref_frame_buffer(cpi, LAST_FRAME);
      }
  
      if (cpi->ref_frame_flags & VP9_GOLD_FLAG) {
        gld_yv12 = vp9_get_scaled_ref_frame(cpi, GOLDEN_FRAME);
        if (gld_yv12 == NULL) {
          gld_yv12 = get_ref_frame_buffer(cpi, GOLDEN_FRAME);
        }
      } else {
        gld_yv12 = NULL;
      }
  
      set_ref_ptrs(cm, xd,
                   (cpi->ref_frame_flags & VP9_LAST_FLAG) ? LAST_FRAME: NONE,
                   (cpi->ref_frame_flags & VP9_GOLD_FLAG) ? GOLDEN_FRAME : NONE);
  
      cpi->Source = vp9_scale_if_required(cm, cpi->un_scaled_source,
                                          &cpi->scaled_source, 0);
    }
  
    vp9_setup_block_planes(&x->e_mbd, cm->subsampling_x, cm->subsampling_y);
  
    vp9_setup_src_planes(x, cpi->Source, 0, 0);
    vp9_setup_dst_planes(xd->plane, new_yv12, 0, 0);
  
    if (!frame_is_intra_only(cm)) {
      vp9_setup_pre_planes(xd, 0, first_ref_buf, 0, 0, NULL);
    }
  
    xd->mi = cm->mi_grid_visible;
    xd->mi[0] = cm->mi;
  
    vp9_frame_init_quantizer(cpi);
  
    for (i = 0; i < MAX_MB_PLANE; ++i) {
      p[i].coeff = ctx->coeff_pbuf[i][1];
      p[i].qcoeff = ctx->qcoeff_pbuf[i][1];
      pd[i].dqcoeff = ctx->dqcoeff_pbuf[i][1];
      p[i].eobs = ctx->eobs_pbuf[i][1];
    }
    x->skip_recode = 0;
  
    vp9_init_mv_probs(cm);
    vp9_initialize_rd_consts(cpi);
  
    // Tiling is ignored in the first pass.
    vp9_tile_init(&tile, cm, 0, 0);
  
    recon_y_stride = new_yv12->y_stride;
    recon_uv_stride = new_yv12->uv_stride;
    uv_mb_height = 16 >> (new_yv12->y_height > new_yv12->uv_height);
  
    for (mb_row = 0; mb_row < cm->mb_rows; ++mb_row) {
      MV best_ref_mv = {0, 0};
  
      // Reset above block coeffs.
      recon_yoffset = (mb_row * recon_y_stride * 16);
      recon_uvoffset = (mb_row * recon_uv_stride * uv_mb_height);
  
      // Set up limit values for motion vectors to prevent them extending
      // outside the UMV borders.
      x->mv_row_min = -((mb_row * 16) + BORDER_MV_PIXELS_B16);
      x->mv_row_max = ((cm->mb_rows - 1 - mb_row) * 16)
                      + BORDER_MV_PIXELS_B16;
  
      for (mb_col = 0; mb_col < cm->mb_cols; ++mb_col) {
        int this_error;
        const int use_dc_pred = (mb_col || mb_row) && (!mb_col || !mb_row);
        const BLOCK_SIZE bsize = get_bsize(cm, mb_row, mb_col);
        double log_intra;
        int level_sample;
  
  #if CONFIG_FP_MB_STATS
        const int mb_index = mb_row * cm->mb_cols + mb_col;
  #endif
  
        vpx_clear_system_state();
  
        xd->plane[0].dst.buf = new_yv12->y_buffer + recon_yoffset;
        xd->plane[1].dst.buf = new_yv12->u_buffer + recon_uvoffset;
        xd->plane[2].dst.buf = new_yv12->v_buffer + recon_uvoffset;
        xd->mi[0]->sb_type = bsize;
        xd->mi[0]->ref_frame[0] = INTRA_FRAME;
        set_mi_row_col(xd, &tile,
                       mb_row << 1, num_8x8_blocks_high_lookup[bsize],
                       mb_col << 1, num_8x8_blocks_wide_lookup[bsize],
                       cm->mi_rows, cm->mi_cols);
        // Are edges available for intra prediction?
        // Since the firstpass does not populate the mi_grid_visible,
        // above_mi/left_mi must be overwritten with a nonzero value when edges
        // are available.  Required by vp9_predict_intra_block().
        xd->above_mi = (mb_row != 0) ? &mi_above : NULL;
        xd->left_mi  = (mb_col > tile.mi_col_start) ? &mi_left : NULL;
  
        // Do intra 16x16 prediction.
        x->skip_encode = 0;
        xd->mi[0]->mode = DC_PRED;
        xd->mi[0]->tx_size = use_dc_pred ?
           (bsize >= BLOCK_16X16 ? TX_16X16 : TX_8X8) : TX_4X4;
        vp9_encode_intra_block_plane(x, bsize, 0, 0);
        this_error = vpx_get_mb_ss(x->plane[0].src_diff);
  
        // Keep a record of blocks that have almost no intra error residual
        // (i.e. are in effect completely flat and untextured in the intra
        // domain). In natural videos this is uncommon, but it is much more
        // common in animations, graphics and screen content, so may be used
        // as a signal to detect these types of content.
        if (this_error < get_ul_intra_threshold(cm)) {
          ++intra_skip_count;
        } else if ((mb_col > 0) && (image_data_start_row == INVALID_ROW)) {
          image_data_start_row = mb_row;
        }
        if (this_error < get_smooth_intra_threshold(cm)) {
          ++intra_smooth_count;
        }
  
  #if CONFIG_VP9_HIGHBITDEPTH
        if (cm->use_highbitdepth) {
          switch (cm->bit_depth) {
            case VPX_BITS_8:
              break;
            case VPX_BITS_10:
              this_error >>= 4;
              break;
            case VPX_BITS_12:
              this_error >>= 8;
              break;
            default:
              assert(0 && "cm->bit_depth should be VPX_BITS_8, "
                          "VPX_BITS_10 or VPX_BITS_12");
              return;
          }
        }
  #endif  // CONFIG_VP9_HIGHBITDEPTH
  
        vpx_clear_system_state();
        log_intra = log(this_error + 1.0);
        if (log_intra < 10.0)
          intra_factor += 1.0 + ((10.0 - log_intra) * 0.05);
        else
          intra_factor += 1.0;
  
  #if CONFIG_VP9_HIGHBITDEPTH
        if (cm->use_highbitdepth)
          level_sample = CONVERT_TO_SHORTPTR(x->plane[0].src.buf)[0];
        else
          level_sample = x->plane[0].src.buf[0];
  #else
        level_sample = x->plane[0].src.buf[0];
  #endif
        if ((level_sample < DARK_THRESH) && (log_intra < 9.0))
          brightness_factor += 1.0 + (0.01 * (DARK_THRESH - level_sample));
        else
          brightness_factor += 1.0;
  
        // Intrapenalty below deals with situations where the intra and inter
        // error scores are very low (e.g. a plain black frame).
        // We do not have special cases in first pass for 0,0 and nearest etc so
        // all inter modes carry an overhead cost estimate for the mv.
        // When the error score is very low this causes us to pick all or lots of
        // INTRA modes and throw lots of key frames.
        // This penalty adds a cost matching that of a 0,0 mv to the intra case.
        this_error += intrapenalty;
  
        // Accumulate the intra error.
        intra_error += (int64_t)this_error;
  
  #if CONFIG_FP_MB_STATS
        if (cpi->use_fp_mb_stats) {
          // initialization
          cpi->twopass.frame_mb_stats_buf[mb_index] = 0;
        }
  #endif
  
        // Set up limit values for motion vectors to prevent them extending
        // outside the UMV borders.
        x->mv_col_min = -((mb_col * 16) + BORDER_MV_PIXELS_B16);
        x->mv_col_max = ((cm->mb_cols - 1 - mb_col) * 16) + BORDER_MV_PIXELS_B16;
  
        // Other than for the first frame do a motion search.
        if ((lc == NULL && cm->current_video_frame > 0) ||
            (lc != NULL && lc->current_video_frame_in_layer > 0)) {
          int tmp_err, motion_error, raw_motion_error;
          // Assume 0,0 motion with no mv overhead.
          MV mv = {0, 0} , tmp_mv = {0, 0};
          struct buf_2d unscaled_last_source_buf_2d;
  
          xd->plane[0].pre[0].buf = first_ref_buf->y_buffer + recon_yoffset;
  #if CONFIG_VP9_HIGHBITDEPTH
          if (xd->cur_buf->flags & YV12_FLAG_HIGHBITDEPTH) {
            motion_error = highbd_get_prediction_error(
                bsize, &x->plane[0].src, &xd->plane[0].pre[0], xd->bd);
          } else {
            motion_error = get_prediction_error(
                bsize, &x->plane[0].src, &xd->plane[0].pre[0]);
          }
  #else
          motion_error = get_prediction_error(
              bsize, &x->plane[0].src, &xd->plane[0].pre[0]);
  #endif  // CONFIG_VP9_HIGHBITDEPTH
  
          // Compute the motion error of the 0,0 motion using the last source
          // frame as the reference. Skip the further motion search on
          // reconstructed frame if this error is small.
          unscaled_last_source_buf_2d.buf =
              cpi->unscaled_last_source->y_buffer + recon_yoffset;
          unscaled_last_source_buf_2d.stride =
              cpi->unscaled_last_source->y_stride;
  #if CONFIG_VP9_HIGHBITDEPTH
          if (xd->cur_buf->flags & YV12_FLAG_HIGHBITDEPTH) {
            raw_motion_error = highbd_get_prediction_error(
                bsize, &x->plane[0].src, &unscaled_last_source_buf_2d, xd->bd);
          } else {
            raw_motion_error = get_prediction_error(
                bsize, &x->plane[0].src, &unscaled_last_source_buf_2d);
          }
  #else
          raw_motion_error = get_prediction_error(
              bsize, &x->plane[0].src, &unscaled_last_source_buf_2d);
  #endif  // CONFIG_VP9_HIGHBITDEPTH
  
          // TODO(pengchong): Replace the hard-coded threshold
          if (raw_motion_error > 25 || lc != NULL) {
            // Test last reference frame using the previous best mv as the
            // starting point (best reference) for the search.
            first_pass_motion_search(cpi, x, &best_ref_mv, &mv, &motion_error);
  
            // If the current best reference mv is not centered on 0,0 then do a
            // 0,0 based search as well.
            if (!is_zero_mv(&best_ref_mv)) {
              tmp_err = INT_MAX;
              first_pass_motion_search(cpi, x, &zero_mv, &tmp_mv, &tmp_err);
  
              if (tmp_err < motion_error) {
                motion_error = tmp_err;
                mv = tmp_mv;
              }
            }
  
            // Search in an older reference frame.
            if (((lc == NULL && cm->current_video_frame > 1) ||
                 (lc != NULL && lc->current_video_frame_in_layer > 1))
                && gld_yv12 != NULL) {
              // Assume 0,0 motion with no mv overhead.
              int gf_motion_error;
  
              xd->plane[0].pre[0].buf = gld_yv12->y_buffer + recon_yoffset;
  #if CONFIG_VP9_HIGHBITDEPTH
              if (xd->cur_buf->flags & YV12_FLAG_HIGHBITDEPTH) {
                gf_motion_error = highbd_get_prediction_error(
                    bsize, &x->plane[0].src, &xd->plane[0].pre[0], xd->bd);
              } else {
                gf_motion_error = get_prediction_error(
                    bsize, &x->plane[0].src, &xd->plane[0].pre[0]);
              }
  #else
              gf_motion_error = get_prediction_error(
                  bsize, &x->plane[0].src, &xd->plane[0].pre[0]);
  #endif  // CONFIG_VP9_HIGHBITDEPTH
  
              first_pass_motion_search(cpi, x, &zero_mv, &tmp_mv,
                                       &gf_motion_error);
  
              if (gf_motion_error < motion_error && gf_motion_error < this_error)
                ++second_ref_count;
  
              // Reset to last frame as reference buffer.
              xd->plane[0].pre[0].buf = first_ref_buf->y_buffer + recon_yoffset;
              xd->plane[1].pre[0].buf = first_ref_buf->u_buffer + recon_uvoffset;
              xd->plane[2].pre[0].buf = first_ref_buf->v_buffer + recon_uvoffset;
  
              // In accumulating a score for the older reference frame take the
              // best of the motion predicted score and the intra coded error
              // (just as will be done for) accumulation of "coded_error" for
              // the last frame.
              if (gf_motion_error < this_error)
                sr_coded_error += gf_motion_error;
              else
                sr_coded_error += this_error;
            } else {
              sr_coded_error += motion_error;
            }
          } else {
            sr_coded_error += motion_error;
          }
  
          // Start by assuming that intra mode is best.
          best_ref_mv.row = 0;
          best_ref_mv.col = 0;
  
  #if CONFIG_FP_MB_STATS
          if (cpi->use_fp_mb_stats) {
            // intra predication statistics
            cpi->twopass.frame_mb_stats_buf[mb_index] = 0;
            cpi->twopass.frame_mb_stats_buf[mb_index] |= FPMB_DCINTRA_MASK;
            cpi->twopass.frame_mb_stats_buf[mb_index] |= FPMB_MOTION_ZERO_MASK;
            if (this_error > FPMB_ERROR_LARGE_TH) {
              cpi->twopass.frame_mb_stats_buf[mb_index] |= FPMB_ERROR_LARGE_MASK;
            } else if (this_error < FPMB_ERROR_SMALL_TH) {
              cpi->twopass.frame_mb_stats_buf[mb_index] |= FPMB_ERROR_SMALL_MASK;
            }
          }
  #endif
  
          if (motion_error <= this_error) {
            vpx_clear_system_state();
  
            // Keep a count of cases where the inter and intra were very close
            // and very low. This helps with scene cut detection for example in
            // cropped clips with black bars at the sides or top and bottom.
            if (((this_error - intrapenalty) * 9 <= motion_error * 10) &&
                (this_error < (2 * intrapenalty))) {
              neutral_count += 1.0;
            // Also track cases where the intra is not much worse than the inter
            // and use this in limiting the GF/arf group length.
            } else if ((this_error > NCOUNT_INTRA_THRESH) &&
                       (this_error < (NCOUNT_INTRA_FACTOR * motion_error))) {
              neutral_count += (double)motion_error /
                               DOUBLE_DIVIDE_CHECK((double)this_error);
            }
  
            mv.row *= 8;
            mv.col *= 8;
            this_error = motion_error;
            xd->mi[0]->mode = NEWMV;
            xd->mi[0]->mv[0].as_mv = mv;
            xd->mi[0]->tx_size = TX_4X4;
            xd->mi[0]->ref_frame[0] = LAST_FRAME;
            xd->mi[0]->ref_frame[1] = NONE;
            vp9_build_inter_predictors_sby(xd, mb_row << 1, mb_col << 1, bsize);
            vp9_encode_sby_pass1(x, bsize);
            sum_mvr += mv.row;
            sum_mvr_abs += abs(mv.row);
            sum_mvc += mv.col;
            sum_mvc_abs += abs(mv.col);
            sum_mvrs += mv.row * mv.row;
            sum_mvcs += mv.col * mv.col;
            ++intercount;
  
            best_ref_mv = mv;
  
  #if CONFIG_FP_MB_STATS
            if (cpi->use_fp_mb_stats) {
              // inter predication statistics
              cpi->twopass.frame_mb_stats_buf[mb_index] = 0;
              cpi->twopass.frame_mb_stats_buf[mb_index] &= ~FPMB_DCINTRA_MASK;
              cpi->twopass.frame_mb_stats_buf[mb_index] |= FPMB_MOTION_ZERO_MASK;
              if (this_error > FPMB_ERROR_LARGE_TH) {
                cpi->twopass.frame_mb_stats_buf[mb_index] |=
                    FPMB_ERROR_LARGE_MASK;
              } else if (this_error < FPMB_ERROR_SMALL_TH) {
                cpi->twopass.frame_mb_stats_buf[mb_index] |=
                    FPMB_ERROR_SMALL_MASK;
              }
            }
  #endif
  
            if (!is_zero_mv(&mv)) {
              ++mvcount;
  
  #if CONFIG_FP_MB_STATS
              if (cpi->use_fp_mb_stats) {
                cpi->twopass.frame_mb_stats_buf[mb_index] &=
                    ~FPMB_MOTION_ZERO_MASK;
                // check estimated motion direction
                if (mv.as_mv.col > 0 && mv.as_mv.col >= abs(mv.as_mv.row)) {
                  // right direction
                  cpi->twopass.frame_mb_stats_buf[mb_index] |=
                      FPMB_MOTION_RIGHT_MASK;
                } else if (mv.as_mv.row < 0 &&
                           abs(mv.as_mv.row) >= abs(mv.as_mv.col)) {
                  // up direction
                  cpi->twopass.frame_mb_stats_buf[mb_index] |=
                      FPMB_MOTION_UP_MASK;
                } else if (mv.as_mv.col < 0 &&
                           abs(mv.as_mv.col) >= abs(mv.as_mv.row)) {
                  // left direction
                  cpi->twopass.frame_mb_stats_buf[mb_index] |=
                      FPMB_MOTION_LEFT_MASK;
                } else {
                  // down direction
                  cpi->twopass.frame_mb_stats_buf[mb_index] |=
                      FPMB_MOTION_DOWN_MASK;
                }
              }
  #endif
  
              // Non-zero vector, was it different from the last non zero vector?
              if (!is_equal_mv(&mv, &lastmv))
                ++new_mv_count;
              lastmv = mv;
  
              // Does the row vector point inwards or outwards?
              if (mb_row < cm->mb_rows / 2) {
                if (mv.row > 0)
                  --sum_in_vectors;
                else if (mv.row < 0)
                  ++sum_in_vectors;
              } else if (mb_row > cm->mb_rows / 2) {
                if (mv.row > 0)
                  ++sum_in_vectors;
                else if (mv.row < 0)
                  --sum_in_vectors;
              }
  
              // Does the col vector point inwards or outwards?
              if (mb_col < cm->mb_cols / 2) {
                if (mv.col > 0)
                  --sum_in_vectors;
                else if (mv.col < 0)
                  ++sum_in_vectors;
              } else if (mb_col > cm->mb_cols / 2) {
                if (mv.col > 0)
                  ++sum_in_vectors;
                else if (mv.col < 0)
                  --sum_in_vectors;
              }
            }
          }
        } else {
          sr_coded_error += (int64_t)this_error;
        }
        coded_error += (int64_t)this_error;
  
        // Adjust to the next column of MBs.
        x->plane[0].src.buf += 16;
        x->plane[1].src.buf += uv_mb_height;
        x->plane[2].src.buf += uv_mb_height;
  
        recon_yoffset += 16;
        recon_uvoffset += uv_mb_height;
      }
  
      // Adjust to the next row of MBs.
      x->plane[0].src.buf += 16 * x->plane[0].src.stride - 16 * cm->mb_cols;
      x->plane[1].src.buf += uv_mb_height * x->plane[1].src.stride -
                             uv_mb_height * cm->mb_cols;
      x->plane[2].src.buf += uv_mb_height * x->plane[1].src.stride -
                             uv_mb_height * cm->mb_cols;
  
      vpx_clear_system_state();
    }
  
    // Clamp the image start to rows/2. This number of rows is discarded top
    // and bottom as dead data so rows / 2 means the frame is blank.
    if ((image_data_start_row > cm->mb_rows / 2) ||
        (image_data_start_row == INVALID_ROW)) {
      image_data_start_row = cm->mb_rows / 2;
    }
    // Exclude any image dead zone
    if (image_data_start_row > 0) {
      intra_skip_count =
          VPXMAX(0, intra_skip_count - (image_data_start_row * cm->mb_cols * 2));
    }
  
    {
      FIRSTPASS_STATS fps;
      // The minimum error here insures some bit allocation to frames even
      // in static regions. The allocation per MB declines for larger formats
      // where the typical "real" energy per MB also falls.
      // Initial estimate here uses sqrt(mbs) to define the min_err, where the
      // number of mbs is proportional to the image area.
      const int num_mbs = (cpi->oxcf.resize_mode != RESIZE_NONE)
                          ? cpi->initial_mbs : cpi->common.MBs;
      const double min_err = 200 * sqrt(num_mbs);
  
      intra_factor = intra_factor / (double)num_mbs;
      brightness_factor = brightness_factor / (double)num_mbs;
      fps.weight = intra_factor * brightness_factor;
  
      fps.frame = cm->current_video_frame;
      fps.spatial_layer_id = cpi->svc.spatial_layer_id;
      fps.coded_error = (double)(coded_error >> 8) + min_err;
      fps.sr_coded_error = (double)(sr_coded_error >> 8) + min_err;
      fps.intra_error = (double)(intra_error >> 8) + min_err;
      fps.count = 1.0;
      fps.pcnt_inter = (double)intercount / num_mbs;
      fps.pcnt_second_ref = (double)second_ref_count / num_mbs;
      fps.pcnt_neutral = (double)neutral_count / num_mbs;
      fps.intra_skip_pct = (double)intra_skip_count / num_mbs;
      fps.intra_smooth_pct = (double)intra_smooth_count / num_mbs;
      fps.inactive_zone_rows = (double)image_data_start_row;
      // Currently set to 0 as most issues relate to letter boxing.
      fps.inactive_zone_cols = (double)0;
  
      if (mvcount > 0) {
        fps.MVr = (double)sum_mvr / mvcount;
        fps.mvr_abs = (double)sum_mvr_abs / mvcount;
        fps.MVc = (double)sum_mvc / mvcount;
        fps.mvc_abs = (double)sum_mvc_abs / mvcount;
        fps.MVrv = ((double)sum_mvrs -
                    ((double)sum_mvr * sum_mvr / mvcount)) / mvcount;
        fps.MVcv = ((double)sum_mvcs -
                    ((double)sum_mvc * sum_mvc / mvcount)) / mvcount;
        fps.mv_in_out_count = (double)sum_in_vectors / (mvcount * 2);
        fps.new_mv_count = new_mv_count;
        fps.pcnt_motion = (double)mvcount / num_mbs;
      } else {
        fps.MVr = 0.0;
        fps.mvr_abs = 0.0;
        fps.MVc = 0.0;
        fps.mvc_abs = 0.0;
        fps.MVrv = 0.0;
        fps.MVcv = 0.0;
        fps.mv_in_out_count = 0.0;
        fps.new_mv_count = 0.0;
        fps.pcnt_motion = 0.0;
      }
  
      // Dont allow a value of 0 for duration.
      // (Section duration is also defaulted to minimum of 1.0).
      fps.duration = VPXMAX(1.0, (double)(source->ts_end - source->ts_start));
  
      // Don't want to do output stats with a stack variable!
      twopass->this_frame_stats = fps;
      output_stats(&twopass->this_frame_stats, cpi->output_pkt_list);
      accumulate_stats(&twopass->total_stats, &fps);
  
  #if CONFIG_FP_MB_STATS
      if (cpi->use_fp_mb_stats) {
        output_fpmb_stats(twopass->frame_mb_stats_buf, cm, cpi->output_pkt_list);
      }
  #endif
    }
  
    // Copy the previous Last Frame back into gf and and arf buffers if
    // the prediction is good enough... but also don't allow it to lag too far.
    if ((twopass->sr_update_lag > 3) ||
        ((cm->current_video_frame > 0) &&
         (twopass->this_frame_stats.pcnt_inter > 0.20) &&
         ((twopass->this_frame_stats.intra_error /
           DOUBLE_DIVIDE_CHECK(twopass->this_frame_stats.coded_error)) > 2.0))) {
      if (gld_yv12 != NULL) {
        ref_cnt_fb(pool->frame_bufs, &cm->ref_frame_map[cpi->gld_fb_idx],
                   cm->ref_frame_map[cpi->lst_fb_idx]);
      }
      twopass->sr_update_lag = 1;
    } else {
      ++twopass->sr_update_lag;
    }
  
    vpx_extend_frame_borders(new_yv12);
  
    if (lc != NULL) {
      vp9_update_reference_frames(cpi);
    } else {
      // The frame we just compressed now becomes the last frame.
      ref_cnt_fb(pool->frame_bufs, &cm->ref_frame_map[cpi->lst_fb_idx],
                 cm->new_fb_idx);
    }
  
    // Special case for the first frame. Copy into the GF buffer as a second
    // reference.
    if (cm->current_video_frame == 0 && cpi->gld_fb_idx != INVALID_IDX &&
        lc == NULL) {
      ref_cnt_fb(pool->frame_bufs, &cm->ref_frame_map[cpi->gld_fb_idx],
                 cm->ref_frame_map[cpi->lst_fb_idx]);
    }
  
    // Use this to see what the first pass reconstruction looks like.
    if (0) {
      char filename[512];
      FILE *recon_file;
      snprintf(filename, sizeof(filename), "enc%04d.yuv",
               (int)cm->current_video_frame);
  
      if (cm->current_video_frame == 0)
        recon_file = fopen(filename, "wb");
      else
        recon_file = fopen(filename, "ab");
  
      (void)fwrite(lst_yv12->buffer_alloc, lst_yv12->frame_size, 1, recon_file);
      fclose(recon_file);
    }
  
    ++cm->current_video_frame;
    if (cpi->use_svc)
      vp9_inc_frame_in_layer(cpi);
  }
  
  static double calc_correction_factor(double err_per_mb,
                                       double err_divisor,
                                       double pt_low,
                                       double pt_high,
                                       int q,
                                       vpx_bit_depth_t bit_depth) {
    const double error_term = err_per_mb / err_divisor;
  
    // Adjustment based on actual quantizer to power term.
    const double power_term =
        VPXMIN(vp9_convert_qindex_to_q(q, bit_depth) * 0.01 + pt_low, pt_high);
  
    // Calculate correction factor.
    if (power_term < 1.0)
      assert(error_term >= 0.0);
  
    return fclamp(pow(error_term, power_term), 0.05, 5.0);
  }
  
  #define ERR_DIVISOR         115.0
  static int get_twopass_worst_quality(VP9_COMP *cpi,
                                       const double section_err,
                                       double inactive_zone,
                                       int section_target_bandwidth) {
    const RATE_CONTROL *const rc = &cpi->rc;
    const VP9EncoderConfig *const oxcf = &cpi->oxcf;
    TWO_PASS *const twopass = &cpi->twopass;
  
    // Clamp the target rate to VBR min / max limts.
    const int target_rate =
        vp9_rc_clamp_pframe_target_size(cpi, section_target_bandwidth);
  
    inactive_zone = fclamp(inactive_zone, 0.0, 1.0);
  
    if (target_rate <= 0) {
      return rc->worst_quality;  // Highest value allowed
    } else {
      const int num_mbs = (cpi->oxcf.resize_mode != RESIZE_NONE)
                          ? cpi->initial_mbs : cpi->common.MBs;
      const int active_mbs = VPXMAX(1, num_mbs - (int)(num_mbs * inactive_zone));
      const double av_err_per_mb = section_err / active_mbs;
      const double speed_term = 1.0 + 0.04 * oxcf->speed;
      double last_group_rate_err;
      const int target_norm_bits_per_mb = ((uint64_t)target_rate <<
                                           BPER_MB_NORMBITS) / active_mbs;
      int q;
      int is_svc_upper_layer = 0;
  
      if (is_two_pass_svc(cpi) && cpi->svc.spatial_layer_id > 0)
        is_svc_upper_layer = 1;
  
      // based on recent history adjust expectations of bits per macroblock.
      last_group_rate_err = (double)twopass->rolling_arf_group_actual_bits /
          DOUBLE_DIVIDE_CHECK((double)twopass->rolling_arf_group_target_bits);
      last_group_rate_err =
          VPXMAX(0.25, VPXMIN(4.0, last_group_rate_err));
      twopass->bpm_factor *= (3.0 + last_group_rate_err) / 4.0;
      twopass->bpm_factor =
          VPXMAX(0.25, VPXMIN(4.0, twopass->bpm_factor));
  
      // Try and pick a max Q that will be high enough to encode the
      // content at the given rate.
      for (q = rc->best_quality; q < rc->worst_quality; ++q) {
        const double factor =
            calc_correction_factor(av_err_per_mb,
                                   ERR_DIVISOR,
                                   is_svc_upper_layer ? SVC_FACTOR_PT_LOW :
                                   FACTOR_PT_LOW, FACTOR_PT_HIGH, q,
                                   cpi->common.bit_depth);
        const int bits_per_mb =
          vp9_rc_bits_per_mb(INTER_FRAME, q,
                             factor * speed_term * cpi->twopass.bpm_factor,
                             cpi->common.bit_depth);
        if (bits_per_mb <= target_norm_bits_per_mb)
          break;
      }
  
      // Restriction on active max q for constrained quality mode.
      if (cpi->oxcf.rc_mode == VPX_CQ)
        q = VPXMAX(q, oxcf->cq_level);
      return q;
    }
  }
  
  static void setup_rf_level_maxq(VP9_COMP *cpi) {
    int i;
    RATE_CONTROL *const rc = &cpi->rc;
    for (i = INTER_NORMAL; i < RATE_FACTOR_LEVELS; ++i) {
      int qdelta = vp9_frame_type_qdelta(cpi, i, rc->worst_quality);
      rc->rf_level_maxq[i] = VPXMAX(rc->worst_quality + qdelta, rc->best_quality);
    }
  }
  
  static void init_subsampling(VP9_COMP *cpi) {
    const VP9_COMMON *const cm = &cpi->common;
    RATE_CONTROL *const rc = &cpi->rc;
    const int w = cm->width;
    const int h = cm->height;
    int i;
  
    for (i = 0; i < FRAME_SCALE_STEPS; ++i) {
      // Note: Frames with odd-sized dimensions may result from this scaling.
      rc->frame_width[i] = (w * 16) / frame_scale_factor[i];
      rc->frame_height[i] = (h * 16) / frame_scale_factor[i];
    }
  
    setup_rf_level_maxq(cpi);
  }
  
  void calculate_coded_size(VP9_COMP *cpi,
                            int *scaled_frame_width,
                            int *scaled_frame_height) {
    RATE_CONTROL *const rc = &cpi->rc;
    *scaled_frame_width = rc->frame_width[rc->frame_size_selector];
    *scaled_frame_height = rc->frame_height[rc->frame_size_selector];
  }
  
  void vp9_init_second_pass(VP9_COMP *cpi) {
    SVC *const svc = &cpi->svc;
    const VP9EncoderConfig *const oxcf = &cpi->oxcf;
    const int is_two_pass_svc = (svc->number_spatial_layers > 1) ||
                                (svc->number_temporal_layers > 1);
    RATE_CONTROL *const rc = &cpi->rc;
    TWO_PASS *const twopass = is_two_pass_svc ?
        &svc->layer_context[svc->spatial_layer_id].twopass : &cpi->twopass;
    double frame_rate;
    FIRSTPASS_STATS *stats;
  
    zero_stats(&twopass->total_stats);
    zero_stats(&twopass->total_left_stats);
  
    if (!twopass->stats_in_end)
      return;
  
    stats = &twopass->total_stats;
  
    *stats = *twopass->stats_in_end;
    twopass->total_left_stats = *stats;
  
    frame_rate = 10000000.0 * stats->count / stats->duration;
    // Each frame can have a different duration, as the frame rate in the source
    // isn't guaranteed to be constant. The frame rate prior to the first frame
    // encoded in the second pass is a guess. However, the sum duration is not.
    // It is calculated based on the actual durations of all frames from the
    // first pass.
  
    if (is_two_pass_svc) {
      vp9_update_spatial_layer_framerate(cpi, frame_rate);
      twopass->bits_left = (int64_t)(stats->duration *
          svc->layer_context[svc->spatial_layer_id].target_bandwidth /
          10000000.0);
    } else {
      vp9_new_framerate(cpi, frame_rate);
      twopass->bits_left = (int64_t)(stats->duration * oxcf->target_bandwidth /
                               10000000.0);
    }
  
    // This variable monitors how far behind the second ref update is lagging.
    twopass->sr_update_lag = 1;
  
    // Scan the first pass file and calculate a modified total error based upon
    // the bias/power function used to allocate bits.
    {
      const double avg_error = stats->coded_error /
                               DOUBLE_DIVIDE_CHECK(stats->count);
      const FIRSTPASS_STATS *s = twopass->stats_in;
      double modified_error_total = 0.0;
      twopass->modified_error_min = (avg_error *
                                        oxcf->two_pass_vbrmin_section) / 100;
      twopass->modified_error_max = (avg_error *
                                        oxcf->two_pass_vbrmax_section) / 100;
      while (s < twopass->stats_in_end) {
        modified_error_total += calculate_modified_err(cpi, twopass, oxcf, s);
        ++s;
      }
      twopass->modified_error_left = modified_error_total;
    }
  
    // Reset the vbr bits off target counters
    rc->vbr_bits_off_target = 0;
    rc->vbr_bits_off_target_fast = 0;
    rc->rate_error_estimate = 0;
  
    // Static sequence monitor variables.
    twopass->kf_zeromotion_pct = 100;
    twopass->last_kfgroup_zeromotion_pct = 100;
  
    // Initialize bits per macro_block estimate correction factor.
    twopass->bpm_factor = 1.0;
    // Initiallize actual and target bits counters for ARF groups so that
    // at the start we have a neutral bpm adjustment.
    twopass->rolling_arf_group_target_bits = 1;
    twopass->rolling_arf_group_actual_bits = 1;
  
    if (oxcf->resize_mode != RESIZE_NONE) {
      init_subsampling(cpi);
    }
  }
  
  #define SR_DIFF_PART 0.0015
  #define INTRA_PART 0.005
  #define DEFAULT_DECAY_LIMIT 0.75
  #define LOW_SR_DIFF_TRHESH 0.1
  #define SR_DIFF_MAX 128.0
  #define LOW_CODED_ERR_PER_MB 10.0
  #define NCOUNT_FRAME_II_THRESH 6.0
  
  static double get_sr_decay_rate(const VP9_COMP *cpi,
                                  const FIRSTPASS_STATS *frame) {
    const int num_mbs = (cpi->oxcf.resize_mode != RESIZE_NONE)
                        ? cpi->initial_mbs : cpi->common.MBs;
    double sr_diff =
        (frame->sr_coded_error - frame->coded_error) / num_mbs;
    double sr_decay = 1.0;
    double modified_pct_inter;
    double modified_pcnt_intra;
    const double motion_amplitude_part =
        frame->pcnt_motion *
        ((frame->mvc_abs + frame->mvr_abs) /
         (cpi->initial_height + cpi->initial_width));
  
    modified_pct_inter = frame->pcnt_inter;
    if (((frame->coded_error / num_mbs) > LOW_CODED_ERR_PER_MB) &&
        ((frame->intra_error / DOUBLE_DIVIDE_CHECK(frame->coded_error)) <
         (double)NCOUNT_FRAME_II_THRESH)) {
      modified_pct_inter = frame->pcnt_inter - frame->pcnt_neutral;
    }
    modified_pcnt_intra = 100 * (1.0 - modified_pct_inter);
  
  
    if ((sr_diff > LOW_SR_DIFF_TRHESH)) {
      sr_diff = VPXMIN(sr_diff, SR_DIFF_MAX);
      sr_decay = 1.0 - (SR_DIFF_PART * sr_diff) -
                 motion_amplitude_part -
                 (INTRA_PART * modified_pcnt_intra);
    }
    return VPXMAX(sr_decay, VPXMIN(DEFAULT_DECAY_LIMIT, modified_pct_inter));
  }
  
  // This function gives an estimate of how badly we believe the prediction
  // quality is decaying from frame to frame.
  static double get_zero_motion_factor(const VP9_COMP *cpi,
                                       const FIRSTPASS_STATS *frame) {
    const double zero_motion_pct = frame->pcnt_inter -
                                   frame->pcnt_motion;
    double sr_decay = get_sr_decay_rate(cpi, frame);
    return VPXMIN(sr_decay, zero_motion_pct);
  }
  
  #define ZM_POWER_FACTOR 0.75
  
  static double get_prediction_decay_rate(const VP9_COMP *cpi,
                                          const FIRSTPASS_STATS *next_frame) {
    const double sr_decay_rate = get_sr_decay_rate(cpi, next_frame);
    const double zero_motion_factor =
      (0.95 * pow((next_frame->pcnt_inter - next_frame->pcnt_motion),
                  ZM_POWER_FACTOR));
  
    return VPXMAX(zero_motion_factor,
                  (sr_decay_rate + ((1.0 - sr_decay_rate) * zero_motion_factor)));
  }
  
  // Function to test for a condition where a complex transition is followed
  // by a static section. For example in slide shows where there is a fade
  // between slides. This is to help with more optimal kf and gf positioning.
  static int detect_transition_to_still(VP9_COMP *cpi,
                                        int frame_interval, int still_interval,
                                        double loop_decay_rate,
                                        double last_decay_rate) {
    TWO_PASS *const twopass = &cpi->twopass;
    RATE_CONTROL *const rc = &cpi->rc;
  
    // Break clause to detect very still sections after motion
    // For example a static image after a fade or other transition
    // instead of a clean scene cut.
    if (frame_interval > rc->min_gf_interval &&
        loop_decay_rate >= 0.999 &&
        last_decay_rate < 0.9) {
      int j;
  
      // Look ahead a few frames to see if static condition persists...
      for (j = 0; j < still_interval; ++j) {
        const FIRSTPASS_STATS *stats = &twopass->stats_in[j];
        if (stats >= twopass->stats_in_end)
          break;
  
        if (stats->pcnt_inter - stats->pcnt_motion < 0.999)
          break;
      }
  
      // Only if it does do we signal a transition to still.
      return j == still_interval;
    }
  
    return 0;
  }
  
  // This function detects a flash through the high relative pcnt_second_ref
  // score in the frame following a flash frame. The offset passed in should
  // reflect this.
  static int detect_flash(const TWO_PASS *twopass, int offset) {
    const FIRSTPASS_STATS *const next_frame = read_frame_stats(twopass, offset);
  
    // What we are looking for here is a situation where there is a
    // brief break in prediction (such as a flash) but subsequent frames
    // are reasonably well predicted by an earlier (pre flash) frame.
    // The recovery after a flash is indicated by a high pcnt_second_ref
    // compared to pcnt_inter.
    return next_frame != NULL &&
           next_frame->pcnt_second_ref > next_frame->pcnt_inter &&
           next_frame->pcnt_second_ref >= 0.5;
  }
  
  // Update the motion related elements to the GF arf boost calculation.
  static void accumulate_frame_motion_stats(const FIRSTPASS_STATS *stats,
                                            double *mv_in_out,
                                            double *mv_in_out_accumulator,
                                            double *abs_mv_in_out_accumulator,
                                            double *mv_ratio_accumulator) {
    const double pct = stats->pcnt_motion;
  
    // Accumulate Motion In/Out of frame stats.
    *mv_in_out = stats->mv_in_out_count * pct;
    *mv_in_out_accumulator += *mv_in_out;
    *abs_mv_in_out_accumulator += fabs(*mv_in_out);
  
    // Accumulate a measure of how uniform (or conversely how random) the motion
    // field is (a ratio of abs(mv) / mv).
    if (pct > 0.05) {
      const double mvr_ratio = fabs(stats->mvr_abs) /
                                   DOUBLE_DIVIDE_CHECK(fabs(stats->MVr));
      const double mvc_ratio = fabs(stats->mvc_abs) /
                                   DOUBLE_DIVIDE_CHECK(fabs(stats->MVc));
  
      *mv_ratio_accumulator += pct * (mvr_ratio < stats->mvr_abs ?
                                         mvr_ratio : stats->mvr_abs);
      *mv_ratio_accumulator += pct * (mvc_ratio < stats->mvc_abs ?
                                         mvc_ratio : stats->mvc_abs);
    }
  }
  
  #define BASELINE_ERR_PER_MB 1000.0
  static double calc_frame_boost(VP9_COMP *cpi,
                                 const FIRSTPASS_STATS *this_frame,
                                 double this_frame_mv_in_out,
                                 double max_boost) {
    double frame_boost;
    const double lq =
      vp9_convert_qindex_to_q(cpi->rc.avg_frame_qindex[INTER_FRAME],
                              cpi->common.bit_depth);
    const double boost_q_correction = VPXMIN((0.5 + (lq * 0.015)), 1.5);
    int num_mbs = (cpi->oxcf.resize_mode != RESIZE_NONE)
                  ? cpi->initial_mbs : cpi->common.MBs;
  
    // Correct for any inactive region in the image
    num_mbs = (int)VPXMAX(1, num_mbs * calculate_active_area(cpi, this_frame));
  
    // Underlying boost factor is based on inter error ratio.
    frame_boost = (BASELINE_ERR_PER_MB * num_mbs) /
                  DOUBLE_DIVIDE_CHECK(this_frame->coded_error);
    frame_boost = frame_boost * BOOST_FACTOR * boost_q_correction;
  
    // Increase boost for frames where new data coming into frame (e.g. zoom out).
    // Slightly reduce boost if there is a net balance of motion out of the frame
    // (zoom in). The range for this_frame_mv_in_out is -1.0 to +1.0.
    if (this_frame_mv_in_out > 0.0)
      frame_boost += frame_boost * (this_frame_mv_in_out * 2.0);
    // In the extreme case the boost is halved.
    else
      frame_boost += frame_boost * (this_frame_mv_in_out / 2.0);
  
    return VPXMIN(frame_boost, max_boost * boost_q_correction);
  }
  
  static int calc_arf_boost(VP9_COMP *cpi, int offset,
                            int f_frames, int b_frames,
                            int *f_boost, int *b_boost) {
    TWO_PASS *const twopass = &cpi->twopass;
    int i;
    double boost_score = 0.0;
    double mv_ratio_accumulator = 0.0;
    double decay_accumulator = 1.0;
    double this_frame_mv_in_out = 0.0;
    double mv_in_out_accumulator = 0.0;
    double abs_mv_in_out_accumulator = 0.0;
    int arf_boost;
    int flash_detected = 0;
  
    // Search forward from the proposed arf/next gf position.
    for (i = 0; i < f_frames; ++i) {
      const FIRSTPASS_STATS *this_frame = read_frame_stats(twopass, i + offset);
      if (this_frame == NULL)
        break;
  
      // Update the motion related elements to the boost calculation.
      accumulate_frame_motion_stats(this_frame,
                                    &this_frame_mv_in_out, &mv_in_out_accumulator,
                                    &abs_mv_in_out_accumulator,
                                    &mv_ratio_accumulator);
  
      // We want to discount the flash frame itself and the recovery
      // frame that follows as both will have poor scores.
      flash_detected = detect_flash(twopass, i + offset) ||
                       detect_flash(twopass, i + offset + 1);
  
      // Accumulate the effect of prediction quality decay.
      if (!flash_detected) {
        decay_accumulator *= get_prediction_decay_rate(cpi, this_frame);
        decay_accumulator = decay_accumulator < MIN_DECAY_FACTOR
                            ? MIN_DECAY_FACTOR : decay_accumulator;
      }
  
      boost_score += decay_accumulator * calc_frame_boost(cpi, this_frame,
                                                          this_frame_mv_in_out,
                                                          GF_MAX_BOOST);
    }
  
    *f_boost = (int)boost_score;
  
    // Reset for backward looking loop.
    boost_score = 0.0;
    mv_ratio_accumulator = 0.0;
    decay_accumulator = 1.0;
    this_frame_mv_in_out = 0.0;
    mv_in_out_accumulator = 0.0;
    abs_mv_in_out_accumulator = 0.0;
  
    // Search backward towards last gf position.
    for (i = -1; i >= -b_frames; --i) {
      const FIRSTPASS_STATS *this_frame = read_frame_stats(twopass, i + offset);
      if (this_frame == NULL)
        break;
  
      // Update the motion related elements to the boost calculation.
      accumulate_frame_motion_stats(this_frame,
                                    &this_frame_mv_in_out, &mv_in_out_accumulator,
                                    &abs_mv_in_out_accumulator,
                                    &mv_ratio_accumulator);
  
      // We want to discount the the flash frame itself and the recovery
      // frame that follows as both will have poor scores.
      flash_detected = detect_flash(twopass, i + offset) ||
                       detect_flash(twopass, i + offset + 1);
  
      // Cumulative effect of prediction quality decay.
      if (!flash_detected) {
        decay_accumulator *= get_prediction_decay_rate(cpi, this_frame);
        decay_accumulator = decay_accumulator < MIN_DECAY_FACTOR
                                ? MIN_DECAY_FACTOR : decay_accumulator;
      }
  
      boost_score += decay_accumulator * calc_frame_boost(cpi, this_frame,
                                                          this_frame_mv_in_out,
                                                          GF_MAX_BOOST);
    }
    *b_boost = (int)boost_score;
  
    arf_boost = (*f_boost + *b_boost);
    if (arf_boost < ((b_frames + f_frames) * 20))
      arf_boost = ((b_frames + f_frames) * 20);
    arf_boost = VPXMAX(arf_boost, MIN_ARF_GF_BOOST);
  
    return arf_boost;
  }
  
  // Calculate a section intra ratio used in setting max loop filter.
  static int calculate_section_intra_ratio(const FIRSTPASS_STATS *begin,
                                           const FIRSTPASS_STATS *end,
                                           int section_length) {
    const FIRSTPASS_STATS *s = begin;
    double intra_error = 0.0;
    double coded_error = 0.0;
    int i = 0;
  
    while (s < end && i < section_length) {
      intra_error += s->intra_error;
      coded_error += s->coded_error;
      ++s;
      ++i;
    }
  
    return (int)(intra_error / DOUBLE_DIVIDE_CHECK(coded_error));
  }
  
  // Calculate the total bits to allocate in this GF/ARF group.
  static int64_t calculate_total_gf_group_bits(VP9_COMP *cpi,
                                               double gf_group_err) {
    const RATE_CONTROL *const rc = &cpi->rc;
    const TWO_PASS *const twopass = &cpi->twopass;
    const int max_bits = frame_max_bits(rc, &cpi->oxcf);
    int64_t total_group_bits;
  
    // Calculate the bits to be allocated to the group as a whole.
    if ((twopass->kf_group_bits > 0) && (twopass->kf_group_error_left > 0)) {
      total_group_bits = (int64_t)(twopass->kf_group_bits *
                                   (gf_group_err / twopass->kf_group_error_left));
    } else {
      total_group_bits = 0;
    }
  
    // Clamp odd edge cases.
    total_group_bits = (total_group_bits < 0) ?
       0 : (total_group_bits > twopass->kf_group_bits) ?
       twopass->kf_group_bits : total_group_bits;
  
    // Clip based on user supplied data rate variability limit.
    if (total_group_bits > (int64_t)max_bits * rc->baseline_gf_interval)
      total_group_bits = (int64_t)max_bits * rc->baseline_gf_interval;
  
    return total_group_bits;
  }
  
  // Calculate the number bits extra to assign to boosted frames in a group.
  static int calculate_boost_bits(int frame_count,
                                  int boost, int64_t total_group_bits) {
    int allocation_chunks;
  
    // return 0 for invalid inputs (could arise e.g. through rounding errors)
    if (!boost || (total_group_bits <= 0) || (frame_count <= 0) )
      return 0;
  
    allocation_chunks = (frame_count * 100) + boost;
  
    // Prevent overflow.
    if (boost > 1023) {
      int divisor = boost >> 10;
      boost /= divisor;
      allocation_chunks /= divisor;
    }
  
    // Calculate the number of extra bits for use in the boosted frame or frames.
    return VPXMAX((int)(((int64_t)boost * total_group_bits) / allocation_chunks),
                  0);
  }
  
  // Current limit on maximum number of active arfs in a GF/ARF group.
  #define MAX_ACTIVE_ARFS 2
  #define ARF_SLOT1 2
  #define ARF_SLOT2 3
  // This function indirects the choice of buffers for arfs.
  // At the moment the values are fixed but this may change as part of
  // the integration process with other codec features that swap buffers around.
  static void get_arf_buffer_indices(unsigned char *arf_buffer_indices) {
    arf_buffer_indices[0] = ARF_SLOT1;
    arf_buffer_indices[1] = ARF_SLOT2;
  }
  
  static void allocate_gf_group_bits(VP9_COMP *cpi, int64_t gf_group_bits,
                                     double group_error, int gf_arf_bits) {
    RATE_CONTROL *const rc = &cpi->rc;
    const VP9EncoderConfig *const oxcf = &cpi->oxcf;
    TWO_PASS *const twopass = &cpi->twopass;
    GF_GROUP *const gf_group = &twopass->gf_group;
    FIRSTPASS_STATS frame_stats;
    int i;
    int frame_index = 1;
    int target_frame_size;
    int key_frame;
    const int max_bits = frame_max_bits(&cpi->rc, &cpi->oxcf);
    int64_t total_group_bits = gf_group_bits;
    double modified_err = 0.0;
    double err_fraction;
    int mid_boost_bits = 0;
    int mid_frame_idx;
    unsigned char arf_buffer_indices[MAX_ACTIVE_ARFS];
    int alt_frame_index = frame_index;
    int has_temporal_layers = is_two_pass_svc(cpi) &&
                              cpi->svc.number_temporal_layers > 1;
  
    // Only encode alt reference frame in temporal base layer.
    if (has_temporal_layers)
      alt_frame_index = cpi->svc.number_temporal_layers;
  
    key_frame = cpi->common.frame_type == KEY_FRAME ||
                vp9_is_upper_layer_key_frame(cpi);
  
    get_arf_buffer_indices(arf_buffer_indices);
  
    // For key frames the frame target rate is already set and it
    // is also the golden frame.
    if (!key_frame) {
      if (rc->source_alt_ref_active) {
        gf_group->update_type[0] = OVERLAY_UPDATE;
        gf_group->rf_level[0] = INTER_NORMAL;
        gf_group->bit_allocation[0] = 0;
      } else {
        gf_group->update_type[0] = GF_UPDATE;
        gf_group->rf_level[0] = GF_ARF_STD;
        gf_group->bit_allocation[0] = gf_arf_bits;
      }
      gf_group->arf_update_idx[0] = arf_buffer_indices[0];
      gf_group->arf_ref_idx[0] = arf_buffer_indices[0];
  
      // Step over the golden frame / overlay frame
      if (EOF == input_stats(twopass, &frame_stats))
        return;
    }
  
    // Deduct the boost bits for arf (or gf if it is not a key frame)
    // from the group total.
    if (rc->source_alt_ref_pending || !key_frame)
      total_group_bits -= gf_arf_bits;
  
    // Store the bits to spend on the ARF if there is one.
    if (rc->source_alt_ref_pending) {
      gf_group->update_type[alt_frame_index] = ARF_UPDATE;
      gf_group->rf_level[alt_frame_index] = GF_ARF_STD;
      gf_group->bit_allocation[alt_frame_index] = gf_arf_bits;
  
      if (has_temporal_layers)
        gf_group->arf_src_offset[alt_frame_index] =
            (unsigned char)(rc->baseline_gf_interval -
                            cpi->svc.number_temporal_layers);
      else
        gf_group->arf_src_offset[alt_frame_index] =
            (unsigned char)(rc->baseline_gf_interval - 1);
  
      gf_group->arf_update_idx[alt_frame_index] = arf_buffer_indices[0];
      gf_group->arf_ref_idx[alt_frame_index] =
        arf_buffer_indices[cpi->multi_arf_last_grp_enabled &&
                           rc->source_alt_ref_active];
      if (!has_temporal_layers)
        ++frame_index;
  
      if (cpi->multi_arf_enabled) {
        // Set aside a slot for a level 1 arf.
        gf_group->update_type[frame_index] = ARF_UPDATE;
        gf_group->rf_level[frame_index] = GF_ARF_LOW;
        gf_group->arf_src_offset[frame_index] =
          (unsigned char)((rc->baseline_gf_interval >> 1) - 1);
        gf_group->arf_update_idx[frame_index] = arf_buffer_indices[1];
        gf_group->arf_ref_idx[frame_index] = arf_buffer_indices[0];
        ++frame_index;
      }
    }
  
    // Define middle frame
    mid_frame_idx = frame_index + (rc->baseline_gf_interval >> 1) - 1;
  
    // Allocate bits to the other frames in the group.
    for (i = 0; i < rc->baseline_gf_interval - rc->source_alt_ref_pending; ++i) {
      int arf_idx = 0;
      if (EOF == input_stats(twopass, &frame_stats))
        break;
  
      if (has_temporal_layers && frame_index == alt_frame_index) {
        ++frame_index;
      }
  
      modified_err = calculate_modified_err(cpi, twopass, oxcf, &frame_stats);
  
      if (group_error > 0)
        err_fraction = modified_err / DOUBLE_DIVIDE_CHECK(group_error);
      else
        err_fraction = 0.0;
  
      target_frame_size = (int)((double)total_group_bits * err_fraction);
  
      if (rc->source_alt_ref_pending && cpi->multi_arf_enabled) {
        mid_boost_bits += (target_frame_size >> 4);
        target_frame_size -= (target_frame_size >> 4);
  
        if (frame_index <= mid_frame_idx)
          arf_idx = 1;
      }
      gf_group->arf_update_idx[frame_index] = arf_buffer_indices[arf_idx];
      gf_group->arf_ref_idx[frame_index] = arf_buffer_indices[arf_idx];
  
      target_frame_size = clamp(target_frame_size, 0,
                                VPXMIN(max_bits, (int)total_group_bits));
  
      gf_group->update_type[frame_index] = LF_UPDATE;
      gf_group->rf_level[frame_index] = INTER_NORMAL;
  
      gf_group->bit_allocation[frame_index] = target_frame_size;
      ++frame_index;
    }
  
    // Note:
    // We need to configure the frame at the end of the sequence + 1 that will be
    // the start frame for the next group. Otherwise prior to the call to
    // vp9_rc_get_second_pass_params() the data will be undefined.
    gf_group->arf_update_idx[frame_index] = arf_buffer_indices[0];
    gf_group->arf_ref_idx[frame_index] = arf_buffer_indices[0];
  
    if (rc->source_alt_ref_pending) {
      gf_group->update_type[frame_index] = OVERLAY_UPDATE;
      gf_group->rf_level[frame_index] = INTER_NORMAL;
  
      // Final setup for second arf and its overlay.
      if (cpi->multi_arf_enabled) {
        gf_group->bit_allocation[2] =
            gf_group->bit_allocation[mid_frame_idx] + mid_boost_bits;
        gf_group->update_type[mid_frame_idx] = OVERLAY_UPDATE;
        gf_group->bit_allocation[mid_frame_idx] = 0;
      }
    } else {
      gf_group->update_type[frame_index] = GF_UPDATE;
      gf_group->rf_level[frame_index] = GF_ARF_STD;
    }
  
    // Note whether multi-arf was enabled this group for next time.
    cpi->multi_arf_last_grp_enabled = cpi->multi_arf_enabled;
  }
  
  // Analyse and define a gf/arf group.
  static void define_gf_group(VP9_COMP *cpi, FIRSTPASS_STATS *this_frame) {
    VP9_COMMON *const cm = &cpi->common;
    RATE_CONTROL *const rc = &cpi->rc;
    VP9EncoderConfig *const oxcf = &cpi->oxcf;
    TWO_PASS *const twopass = &cpi->twopass;
    FIRSTPASS_STATS next_frame;
    const FIRSTPASS_STATS *const start_pos = twopass->stats_in;
    int i;
  
    double boost_score = 0.0;
    double old_boost_score = 0.0;
    double gf_group_err = 0.0;
    double gf_group_raw_error = 0.0;
    double gf_group_skip_pct = 0.0;
    double gf_group_inactive_zone_rows = 0.0;
    double gf_first_frame_err = 0.0;
    double mod_frame_err = 0.0;
  
    double mv_ratio_accumulator = 0.0;
    double decay_accumulator = 1.0;
    double zero_motion_accumulator = 1.0;
  
    double loop_decay_rate = 1.00;
    double last_loop_decay_rate = 1.00;
  
    double this_frame_mv_in_out = 0.0;
    double mv_in_out_accumulator = 0.0;
    double abs_mv_in_out_accumulator = 0.0;
    double mv_ratio_accumulator_thresh;
    unsigned int allow_alt_ref = is_altref_enabled(cpi);
  
    int f_boost = 0;
    int b_boost = 0;
    int flash_detected;
    int active_max_gf_interval;
    int active_min_gf_interval;
    int64_t gf_group_bits;
    double gf_group_error_left;
    int gf_arf_bits;
    const int is_key_frame = frame_is_intra_only(cm);
    const int arf_active_or_kf = is_key_frame || rc->source_alt_ref_active;
  
    // Reset the GF group data structures unless this is a key
    // frame in which case it will already have been done.
    if (is_key_frame == 0) {
      vp9_zero(twopass->gf_group);
    }
  
    vpx_clear_system_state();
    vp9_zero(next_frame);
  
    // Load stats for the current frame.
    mod_frame_err = calculate_modified_err(cpi, twopass, oxcf, this_frame);
  
    // Note the error of the frame at the start of the group. This will be
    // the GF frame error if we code a normal gf.
    gf_first_frame_err = mod_frame_err;
  
    // If this is a key frame or the overlay from a previous arf then
    // the error score / cost of this frame has already been accounted for.
    if (arf_active_or_kf) {
      gf_group_err -= gf_first_frame_err;
      gf_group_raw_error -= this_frame->coded_error;
      gf_group_skip_pct -= this_frame->intra_skip_pct;
      gf_group_inactive_zone_rows -= this_frame->inactive_zone_rows;
    }
  
    // Motion breakout threshold for loop below depends on image size.
    mv_ratio_accumulator_thresh =
        (cpi->initial_height + cpi->initial_width) / 4.0;
  
    // Set a maximum and minimum interval for the GF group.
    // If the image appears almost completely static we can extend beyond this.
    {
      int int_max_q =
        (int)(vp9_convert_qindex_to_q(twopass->active_worst_quality,
                                     cpi->common.bit_depth));
      int int_lbq =
        (int)(vp9_convert_qindex_to_q(rc->last_boosted_qindex,
                                     cpi->common.bit_depth));
      active_min_gf_interval =
        rc->min_gf_interval + arf_active_or_kf + VPXMIN(2, int_max_q / 200);
      if (active_min_gf_interval > rc->max_gf_interval)
        active_min_gf_interval = rc->max_gf_interval;
  
      if (cpi->multi_arf_allowed) {
        active_max_gf_interval = rc->max_gf_interval;
      } else {
        // The value chosen depends on the active Q range. At low Q we have
        // bits to spare and are better with a smaller interval and smaller boost.
        // At high Q when there are few bits to spare we are better with a longer
        // interval to spread the cost of the GF.
        active_max_gf_interval =
          12 + arf_active_or_kf + VPXMIN(4, (int_lbq / 6));
  
        // We have: active_min_gf_interval <= rc->max_gf_interval
        if (active_max_gf_interval < active_min_gf_interval)
          active_max_gf_interval = active_min_gf_interval;
        else if (active_max_gf_interval > rc->max_gf_interval)
          active_max_gf_interval = rc->max_gf_interval;
  
        // Would the active max drop us out just before the near the next kf?
        if ((active_max_gf_interval <= rc->frames_to_key) &&
            (active_max_gf_interval >=
                (rc->frames_to_key - rc->min_gf_interval)))
          active_max_gf_interval = rc->frames_to_key / 2;
      }
    }
  
    i = 0;
    while (i < rc->static_scene_max_gf_interval && i < rc->frames_to_key) {
      ++i;
  
      // Accumulate error score of frames in this gf group.
      mod_frame_err = calculate_modified_err(cpi, twopass, oxcf, this_frame);
      gf_group_err += mod_frame_err;
      gf_group_raw_error += this_frame->coded_error;
      gf_group_skip_pct += this_frame->intra_skip_pct;
      gf_group_inactive_zone_rows += this_frame->inactive_zone_rows;
  
      if (EOF == input_stats(twopass, &next_frame))
        break;
  
      // Test for the case where there is a brief flash but the prediction
      // quality back to an earlier frame is then restored.
      flash_detected = detect_flash(twopass, 0);
  
      // Update the motion related elements to the boost calculation.
      accumulate_frame_motion_stats(&next_frame,
                                    &this_frame_mv_in_out, &mv_in_out_accumulator,
                                    &abs_mv_in_out_accumulator,
                                    &mv_ratio_accumulator);
  
      // Accumulate the effect of prediction quality decay.
      if (!flash_detected) {
        last_loop_decay_rate = loop_decay_rate;
        loop_decay_rate = get_prediction_decay_rate(cpi, &next_frame);
  
        decay_accumulator = decay_accumulator * loop_decay_rate;
  
        // Monitor for static sections.
        zero_motion_accumulator = VPXMIN(
            zero_motion_accumulator, get_zero_motion_factor(cpi, &next_frame));
  
        // Break clause to detect very still sections after motion. For example,
        // a static image after a fade or other transition.
        if (detect_transition_to_still(cpi, i, 5, loop_decay_rate,
                                       last_loop_decay_rate)) {
          allow_alt_ref = 0;
          break;
        }
      }
  
      // Calculate a boost number for this frame.
      boost_score += decay_accumulator * calc_frame_boost(cpi, &next_frame,
                                                          this_frame_mv_in_out,
                                                          GF_MAX_BOOST);
  
      // Break out conditions.
      if (
        // Break at active_max_gf_interval unless almost totally static.
        ((i >= active_max_gf_interval) &&
         (zero_motion_accumulator < 0.995)) ||
        (
          // Don't break out with a very short interval.
          (i >= active_min_gf_interval) &&
          // If possible dont break very close to a kf
          ((rc->frames_to_key - i) >= rc->min_gf_interval) &&
          (!flash_detected) &&
          ((mv_ratio_accumulator > mv_ratio_accumulator_thresh) ||
           (abs_mv_in_out_accumulator > 3.0) ||
           (mv_in_out_accumulator < -2.0) ||
           ((boost_score - old_boost_score) < BOOST_BREAKOUT)))) {
        boost_score = old_boost_score;
        break;
      }
  
      *this_frame = next_frame;
      old_boost_score = boost_score;
    }
  
    // Was the group length constrained by the requirement for a new KF?
    rc->constrained_gf_group = (i >= rc->frames_to_key) ? 1 : 0;
  
    // Should we use the alternate reference frame.
    if (allow_alt_ref &&
      (i < cpi->oxcf.lag_in_frames) &&
      (i >= rc->min_gf_interval)) {
      // Calculate the boost for alt ref.
      rc->gfu_boost = calc_arf_boost(cpi, 0, (i - 1), (i - 1), &f_boost,
        &b_boost);
      rc->source_alt_ref_pending = 1;
  
      // Test to see if multi arf is appropriate.
      cpi->multi_arf_enabled =
        (cpi->multi_arf_allowed && (rc->baseline_gf_interval >= 6) &&
        (zero_motion_accumulator < 0.995)) ? 1 : 0;
    } else {
      rc->gfu_boost = VPXMAX((int)boost_score, MIN_ARF_GF_BOOST);
      rc->source_alt_ref_pending = 0;
    }
  
    // Set the interval until the next gf.
    rc->baseline_gf_interval = i - (is_key_frame || rc->source_alt_ref_pending);
  
    // Only encode alt reference frame in temporal base layer. So
    // baseline_gf_interval should be multiple of a temporal layer group
    // (typically the frame distance between two base layer frames)
    if (is_two_pass_svc(cpi) && cpi->svc.number_temporal_layers > 1) {
      int count = (1 << (cpi->svc.number_temporal_layers - 1)) - 1;
      int new_gf_interval = (rc->baseline_gf_interval + count) & (~count);
      int j;
      for (j = 0; j < new_gf_interval - rc->baseline_gf_interval; ++j) {
        if (EOF == input_stats(twopass, this_frame))
          break;
        gf_group_err += calculate_modified_err(cpi, twopass, oxcf, this_frame);
        gf_group_raw_error += this_frame->coded_error;
        gf_group_skip_pct += this_frame->intra_skip_pct;
        gf_group_inactive_zone_rows += this_frame->inactive_zone_rows;
      }
      rc->baseline_gf_interval = new_gf_interval;
    }
  
    rc->frames_till_gf_update_due = rc->baseline_gf_interval;
  
    // Reset the file position.
    reset_fpf_position(twopass, start_pos);
  
    // Calculate the bits to be allocated to the gf/arf group as a whole
    gf_group_bits = calculate_total_gf_group_bits(cpi, gf_group_err);
  
    // Calculate an estimate of the maxq needed for the group.
    // We are more agressive about correcting for sections
    // where there could be significant overshoot than for easier
    // sections where we do not wish to risk creating an overshoot
    // of the allocated bit budget.
    if ((cpi->oxcf.rc_mode != VPX_Q) && (rc->baseline_gf_interval > 1)) {
      const int vbr_group_bits_per_frame =
        (int)(gf_group_bits / rc->baseline_gf_interval);
      const double group_av_err = gf_group_raw_error  / rc->baseline_gf_interval;
      const double group_av_skip_pct =
        gf_group_skip_pct / rc->baseline_gf_interval;
      const double group_av_inactive_zone =
        ((gf_group_inactive_zone_rows * 2) /
         (rc->baseline_gf_interval * (double)cm->mb_rows));
      int tmp_q =
          get_twopass_worst_quality(cpi, group_av_err,
                                    (group_av_skip_pct + group_av_inactive_zone),
                                    vbr_group_bits_per_frame);
      twopass->active_worst_quality =
          (tmp_q + (twopass->active_worst_quality * 3)) >> 2;
    }
  
    // Calculate the extra bits to be used for boosted frame(s)
    gf_arf_bits = calculate_boost_bits(rc->baseline_gf_interval,
                                       rc->gfu_boost, gf_group_bits);
  
    // Adjust KF group bits and error remaining.
    twopass->kf_group_error_left -= (int64_t)gf_group_err;
  
    // If this is an arf update we want to remove the score for the overlay
    // frame at the end which will usually be very cheap to code.
    // The overlay frame has already, in effect, been coded so we want to spread
    // the remaining bits among the other frames.
    // For normal GFs remove the score for the GF itself unless this is
    // also a key frame in which case it has already been accounted for.
    if (rc->source_alt_ref_pending) {
      gf_group_error_left = gf_group_err - mod_frame_err;
    } else if (is_key_frame == 0) {
      gf_group_error_left = gf_group_err - gf_first_frame_err;
    } else {
      gf_group_error_left = gf_group_err;
    }
  
    // Allocate bits to each of the frames in the GF group.
    allocate_gf_group_bits(cpi, gf_group_bits, gf_group_error_left, gf_arf_bits);
  
    // Reset the file position.
    reset_fpf_position(twopass, start_pos);
  
    // Calculate a section intra ratio used in setting max loop filter.
    if (cpi->common.frame_type != KEY_FRAME) {
      twopass->section_intra_rating =
          calculate_section_intra_ratio(start_pos, twopass->stats_in_end,
                                        rc->baseline_gf_interval);
    }
  
    if (oxcf->resize_mode == RESIZE_DYNAMIC) {
      // Default to starting GF groups at normal frame size.
      cpi->rc.next_frame_size_selector = UNSCALED;
    }
  
    // Reset rolling actual and target bits counters for ARF groups.
    twopass->rolling_arf_group_target_bits = 0;
    twopass->rolling_arf_group_actual_bits = 0;
  }
  
  // Threshold for use of the lagging second reference frame. High second ref
  // usage may point to a transient event like a flash or occlusion rather than
  // a real scene cut.
  #define SECOND_REF_USEAGE_THRESH 0.1
  // Minimum % intra coding observed in first pass (1.0 = 100%)
  #define MIN_INTRA_LEVEL 0.25
  // Minimum ratio between the % of intra coding and inter coding in the first
  // pass after discounting neutral blocks (discounting neutral blocks in this
  // way helps catch scene cuts in clips with very flat areas or letter box
  // format clips with image padding.
  #define INTRA_VS_INTER_THRESH 2.0
  // Hard threshold where the first pass chooses intra for almost all blocks.
  // In such a case even if the frame is not a scene cut coding a key frame
  // may be a good option.
  #define VERY_LOW_INTER_THRESH 0.05
  // Maximum threshold for the relative ratio of intra error score vs best
  // inter error score.
  #define KF_II_ERR_THRESHOLD 2.5
  // In real scene cuts there is almost always a sharp change in the intra
  // or inter error score.
  #define ERR_CHANGE_THRESHOLD 0.4
  // For real scene cuts we expect an improvment in the intra inter error
  // ratio in the next frame.
  #define II_IMPROVEMENT_THRESHOLD 3.5
  #define KF_II_MAX 128.0
  
  static int test_candidate_kf(TWO_PASS *twopass,
                               const FIRSTPASS_STATS *last_frame,
                               const FIRSTPASS_STATS *this_frame,
                               const FIRSTPASS_STATS *next_frame) {
    int is_viable_kf = 0;
    double pcnt_intra = 1.0 - this_frame->pcnt_inter;
    double modified_pcnt_inter =
      this_frame->pcnt_inter - this_frame->pcnt_neutral;
  
    // Does the frame satisfy the primary criteria of a key frame?
    // See above for an explanation of the test criteria.
    // If so, then examine how well it predicts subsequent frames.
    if ((this_frame->pcnt_second_ref < SECOND_REF_USEAGE_THRESH) &&
        (next_frame->pcnt_second_ref < SECOND_REF_USEAGE_THRESH) &&
        ((this_frame->pcnt_inter < VERY_LOW_INTER_THRESH) ||
         ((pcnt_intra > MIN_INTRA_LEVEL) &&
          (pcnt_intra > (INTRA_VS_INTER_THRESH * modified_pcnt_inter)) &&
          ((this_frame->intra_error /
            DOUBLE_DIVIDE_CHECK(this_frame->coded_error)) <
            KF_II_ERR_THRESHOLD) &&
          ((fabs(last_frame->coded_error - this_frame->coded_error) /
            DOUBLE_DIVIDE_CHECK(this_frame->coded_error) >
            ERR_CHANGE_THRESHOLD) ||
           (fabs(last_frame->intra_error - this_frame->intra_error) /
            DOUBLE_DIVIDE_CHECK(this_frame->intra_error) >
            ERR_CHANGE_THRESHOLD) ||
           ((next_frame->intra_error /
            DOUBLE_DIVIDE_CHECK(next_frame->coded_error)) >
            II_IMPROVEMENT_THRESHOLD))))) {
      int i;
      const FIRSTPASS_STATS *start_pos = twopass->stats_in;
      FIRSTPASS_STATS local_next_frame = *next_frame;
      double boost_score = 0.0;
      double old_boost_score = 0.0;
      double decay_accumulator = 1.0;
  
      // Examine how well the key frame predicts subsequent frames.
      for (i = 0; i < 16; ++i) {
        double next_iiratio = (BOOST_FACTOR * local_next_frame.intra_error /
                               DOUBLE_DIVIDE_CHECK(local_next_frame.coded_error));
  
        if (next_iiratio > KF_II_MAX)
          next_iiratio = KF_II_MAX;
  
        // Cumulative effect of decay in prediction quality.
        if (local_next_frame.pcnt_inter > 0.85)
          decay_accumulator *= local_next_frame.pcnt_inter;
        else
          decay_accumulator *= (0.85 + local_next_frame.pcnt_inter) / 2.0;
  
        // Keep a running total.
        boost_score += (decay_accumulator * next_iiratio);
  
        // Test various breakout clauses.
        if ((local_next_frame.pcnt_inter < 0.05) ||
            (next_iiratio < 1.5) ||
            (((local_next_frame.pcnt_inter -
               local_next_frame.pcnt_neutral) < 0.20) &&
             (next_iiratio < 3.0)) ||
            ((boost_score - old_boost_score) < 3.0) ||
            (local_next_frame.intra_error < 200)) {
          break;
        }
  
        old_boost_score = boost_score;
  
        // Get the next frame details
        if (EOF == input_stats(twopass, &local_next_frame))
          break;
      }
  
      // If there is tolerable prediction for at least the next 3 frames then
      // break out else discard this potential key frame and move on
      if (boost_score > 30.0 && (i > 3)) {
        is_viable_kf = 1;
      } else {
        // Reset the file position
        reset_fpf_position(twopass, start_pos);
  
        is_viable_kf = 0;
      }
    }
  
    return is_viable_kf;
  }
  
  #define FRAMES_TO_CHECK_DECAY 8
  
  static void find_next_key_frame(VP9_COMP *cpi, FIRSTPASS_STATS *this_frame) {
    int i, j;
    RATE_CONTROL *const rc = &cpi->rc;
    TWO_PASS *const twopass = &cpi->twopass;
    GF_GROUP *const gf_group = &twopass->gf_group;
    const VP9EncoderConfig *const oxcf = &cpi->oxcf;
    const FIRSTPASS_STATS first_frame = *this_frame;
    const FIRSTPASS_STATS *const start_position = twopass->stats_in;
    FIRSTPASS_STATS next_frame;
    FIRSTPASS_STATS last_frame;
    int kf_bits = 0;
    int loop_decay_counter = 0;
    double decay_accumulator = 1.0;
    double av_decay_accumulator = 0.0;
    double zero_motion_accumulator = 1.0;
    double boost_score = 0.0;
    double kf_mod_err = 0.0;
    double kf_group_err = 0.0;
    double recent_loop_decay[FRAMES_TO_CHECK_DECAY];
  
    vp9_zero(next_frame);
  
    cpi->common.frame_type = KEY_FRAME;
  
    // Reset the GF group data structures.
    vp9_zero(*gf_group);
  
    // Is this a forced key frame by interval.
    rc->this_key_frame_forced = rc->next_key_frame_forced;
  
    // Clear the alt ref active flag and last group multi arf flags as they
    // can never be set for a key frame.
    rc->source_alt_ref_active = 0;
    cpi->multi_arf_last_grp_enabled = 0;
  
    // KF is always a GF so clear frames till next gf counter.
    rc->frames_till_gf_update_due = 0;
  
    rc->frames_to_key = 1;
  
    twopass->kf_group_bits = 0;        // Total bits available to kf group
    twopass->kf_group_error_left = 0;  // Group modified error score.
  
    kf_mod_err = calculate_modified_err(cpi, twopass, oxcf, this_frame);
  
    // Initialize the decay rates for the recent frames to check
    for (j = 0; j < FRAMES_TO_CHECK_DECAY; ++j)
      recent_loop_decay[j] = 1.0;
  
    // Find the next keyframe.
    i = 0;
    while (twopass->stats_in < twopass->stats_in_end &&
           rc->frames_to_key < cpi->oxcf.key_freq) {
      // Accumulate kf group error.
      kf_group_err += calculate_modified_err(cpi, twopass, oxcf, this_frame);
  
      // Load the next frame's stats.
      last_frame = *this_frame;
      input_stats(twopass, this_frame);
  
      // Provided that we are not at the end of the file...
      if (cpi->oxcf.auto_key && twopass->stats_in < twopass->stats_in_end) {
        double loop_decay_rate;
  
        // Check for a scene cut.
        if (test_candidate_kf(twopass, &last_frame, this_frame,
                              twopass->stats_in))
          break;
  
        // How fast is the prediction quality decaying?
        loop_decay_rate = get_prediction_decay_rate(cpi, twopass->stats_in);
  
        // We want to know something about the recent past... rather than
        // as used elsewhere where we are concerned with decay in prediction
        // quality since the last GF or KF.
        recent_loop_decay[i % FRAMES_TO_CHECK_DECAY] = loop_decay_rate;
        decay_accumulator = 1.0;
        for (j = 0; j < FRAMES_TO_CHECK_DECAY; ++j)
          decay_accumulator *= recent_loop_decay[j];
  
        // Special check for transition or high motion followed by a
        // static scene.
        if (detect_transition_to_still(cpi, i, cpi->oxcf.key_freq - i,
                                       loop_decay_rate, decay_accumulator))
          break;
  
        // Step on to the next frame.
        ++rc->frames_to_key;
  
        // If we don't have a real key frame within the next two
        // key_freq intervals then break out of the loop.
        if (rc->frames_to_key >= 2 * cpi->oxcf.key_freq)
          break;
      } else {
        ++rc->frames_to_key;
      }
      ++i;
    }
  
    // If there is a max kf interval set by the user we must obey it.
    // We already breakout of the loop above at 2x max.
    // This code centers the extra kf if the actual natural interval
    // is between 1x and 2x.
    if (cpi->oxcf.auto_key &&
        rc->frames_to_key > cpi->oxcf.key_freq) {
      FIRSTPASS_STATS tmp_frame = first_frame;
  
      rc->frames_to_key /= 2;
  
      // Reset to the start of the group.
      reset_fpf_position(twopass, start_position);
  
      kf_group_err = 0.0;
  
      // Rescan to get the correct error data for the forced kf group.
      for (i = 0; i < rc->frames_to_key; ++i) {
        kf_group_err += calculate_modified_err(cpi, twopass, oxcf, &tmp_frame);
        input_stats(twopass, &tmp_frame);
      }
      rc->next_key_frame_forced = 1;
    } else if (twopass->stats_in == twopass->stats_in_end ||
               rc->frames_to_key >= cpi->oxcf.key_freq) {
      rc->next_key_frame_forced = 1;
    } else {
      rc->next_key_frame_forced = 0;
    }
  
    if (is_two_pass_svc(cpi) && cpi->svc.number_temporal_layers > 1) {
      int count = (1 << (cpi->svc.number_temporal_layers - 1)) - 1;
      int new_frame_to_key = (rc->frames_to_key + count) & (~count);
      int j;
      for (j = 0; j < new_frame_to_key - rc->frames_to_key; ++j) {
        if (EOF == input_stats(twopass, this_frame))
          break;
        kf_group_err += calculate_modified_err(cpi, twopass, oxcf, this_frame);
      }
      rc->frames_to_key = new_frame_to_key;
    }
  
    // Special case for the last key frame of the file.
    if (twopass->stats_in >= twopass->stats_in_end) {
      // Accumulate kf group error.
      kf_group_err += calculate_modified_err(cpi, twopass, oxcf, this_frame);
    }
  
    // Calculate the number of bits that should be assigned to the kf group.
    if (twopass->bits_left > 0 && twopass->modified_error_left > 0.0) {
      // Maximum number of bits for a single normal frame (not key frame).
      const int max_bits = frame_max_bits(rc, &cpi->oxcf);
  
      // Maximum number of bits allocated to the key frame group.
      int64_t max_grp_bits;
  
      // Default allocation based on bits left and relative
      // complexity of the section.
      twopass->kf_group_bits = (int64_t)(twopass->bits_left *
         (kf_group_err / twopass->modified_error_left));
  
      // Clip based on maximum per frame rate defined by the user.
      max_grp_bits = (int64_t)max_bits * (int64_t)rc->frames_to_key;
      if (twopass->kf_group_bits > max_grp_bits)
        twopass->kf_group_bits = max_grp_bits;
    } else {
      twopass->kf_group_bits = 0;
    }
    twopass->kf_group_bits = VPXMAX(0, twopass->kf_group_bits);
  
    // Reset the first pass file position.
    reset_fpf_position(twopass, start_position);
  
    // Scan through the kf group collating various stats used to determine
    // how many bits to spend on it.
    decay_accumulator = 1.0;
    boost_score = 0.0;
    for (i = 0; i < (rc->frames_to_key - 1); ++i) {
      if (EOF == input_stats(twopass, &next_frame))
        break;
  
      // Monitor for static sections.
      zero_motion_accumulator = VPXMIN(
          zero_motion_accumulator, get_zero_motion_factor(cpi, &next_frame));
  
      // Not all frames in the group are necessarily used in calculating boost.
      if ((i <= rc->max_gf_interval) ||
          ((i <= (rc->max_gf_interval * 4)) && (decay_accumulator > 0.5))) {
        const double frame_boost =
          calc_frame_boost(cpi, &next_frame, 0, KF_MAX_BOOST);
  
        // How fast is prediction quality decaying.
        if (!detect_flash(twopass, 0)) {
          const double loop_decay_rate =
            get_prediction_decay_rate(cpi, &next_frame);
          decay_accumulator *= loop_decay_rate;
          decay_accumulator = VPXMAX(decay_accumulator, MIN_DECAY_FACTOR);
          av_decay_accumulator += decay_accumulator;
          ++loop_decay_counter;
        }
        boost_score += (decay_accumulator * frame_boost);
      }
    }
    av_decay_accumulator /= (double)loop_decay_counter;
  
    reset_fpf_position(twopass, start_position);
  
    // Store the zero motion percentage
    twopass->kf_zeromotion_pct = (int)(zero_motion_accumulator * 100.0);
  
    // Calculate a section intra ratio used in setting max loop filter.
    twopass->section_intra_rating =
        calculate_section_intra_ratio(start_position, twopass->stats_in_end,
                                      rc->frames_to_key);
  
    // Apply various clamps for min and max boost
    rc->kf_boost = (int)(av_decay_accumulator * boost_score);
    rc->kf_boost = VPXMAX(rc->kf_boost, (rc->frames_to_key * 3));
    rc->kf_boost = VPXMAX(rc->kf_boost, MIN_KF_BOOST);
  
    // Work out how many bits to allocate for the key frame itself.
    kf_bits = calculate_boost_bits((rc->frames_to_key - 1),
                                    rc->kf_boost, twopass->kf_group_bits);
  
    twopass->kf_group_bits -= kf_bits;
  
    // Save the bits to spend on the key frame.
    gf_group->bit_allocation[0] = kf_bits;
    gf_group->update_type[0] = KF_UPDATE;
    gf_group->rf_level[0] = KF_STD;
  
    // Note the total error score of the kf group minus the key frame itself.
    twopass->kf_group_error_left = (int)(kf_group_err - kf_mod_err);
  
    // Adjust the count of total modified error left.
    // The count of bits left is adjusted elsewhere based on real coded frame
    // sizes.
    twopass->modified_error_left -= kf_group_err;
  
    if (oxcf->resize_mode == RESIZE_DYNAMIC) {
      // Default to normal-sized frame on keyframes.
      cpi->rc.next_frame_size_selector = UNSCALED;
    }
  }
  
  // Define the reference buffers that will be updated post encode.
  static void configure_buffer_updates(VP9_COMP *cpi) {
    TWO_PASS *const twopass = &cpi->twopass;
  
    cpi->rc.is_src_frame_alt_ref = 0;
    switch (twopass->gf_group.update_type[twopass->gf_group.index]) {
      case KF_UPDATE:
        cpi->refresh_last_frame = 1;
        cpi->refresh_golden_frame = 1;
        cpi->refresh_alt_ref_frame = 1;
        break;
      case LF_UPDATE:
        cpi->refresh_last_frame = 1;
        cpi->refresh_golden_frame = 0;
        cpi->refresh_alt_ref_frame = 0;
        break;
      case GF_UPDATE:
        cpi->refresh_last_frame = 1;
        cpi->refresh_golden_frame = 1;
        cpi->refresh_alt_ref_frame = 0;
        break;
      case OVERLAY_UPDATE:
        cpi->refresh_last_frame = 0;
        cpi->refresh_golden_frame = 1;
        cpi->refresh_alt_ref_frame = 0;
        cpi->rc.is_src_frame_alt_ref = 1;
        break;
      case ARF_UPDATE:
        cpi->refresh_last_frame = 0;
        cpi->refresh_golden_frame = 0;
        cpi->refresh_alt_ref_frame = 1;
        break;
      default:
        assert(0);
        break;
    }
    if (is_two_pass_svc(cpi)) {
      if (cpi->svc.temporal_layer_id > 0) {
        cpi->refresh_last_frame = 0;
        cpi->refresh_golden_frame = 0;
      }
      if (cpi->svc.layer_context[cpi->svc.spatial_layer_id].gold_ref_idx < 0)
        cpi->refresh_golden_frame = 0;
      if (cpi->alt_ref_source == NULL)
        cpi->refresh_alt_ref_frame = 0;
    }
  }
  
  static int is_skippable_frame(const VP9_COMP *cpi) {
    // If the current frame does not have non-zero motion vector detected in the
    // first  pass, and so do its previous and forward frames, then this frame
    // can be skipped for partition check, and the partition size is assigned
    // according to the variance
    const SVC *const svc = &cpi->svc;
    const TWO_PASS *const twopass = is_two_pass_svc(cpi) ?
        &svc->layer_context[svc->spatial_layer_id].twopass : &cpi->twopass;
  
    return (!frame_is_intra_only(&cpi->common) &&
      twopass->stats_in - 2 > twopass->stats_in_start &&
      twopass->stats_in < twopass->stats_in_end &&
      (twopass->stats_in - 1)->pcnt_inter - (twopass->stats_in - 1)->pcnt_motion
      == 1 &&
      (twopass->stats_in - 2)->pcnt_inter - (twopass->stats_in - 2)->pcnt_motion
      == 1 &&
      twopass->stats_in->pcnt_inter - twopass->stats_in->pcnt_motion == 1);
  }
  
  void vp9_rc_get_second_pass_params(VP9_COMP *cpi) {
    VP9_COMMON *const cm = &cpi->common;
    RATE_CONTROL *const rc = &cpi->rc;
    TWO_PASS *const twopass = &cpi->twopass;
    GF_GROUP *const gf_group = &twopass->gf_group;
    FIRSTPASS_STATS this_frame;
  
    int target_rate;
    LAYER_CONTEXT *const lc = is_two_pass_svc(cpi) ?
          &cpi->svc.layer_context[cpi->svc.spatial_layer_id] : 0;
  
    if (!twopass->stats_in)
      return;
  
    // If this is an arf frame then we dont want to read the stats file or
    // advance the input pointer as we already have what we need.
    if (gf_group->update_type[gf_group->index] == ARF_UPDATE) {
      int target_rate;
      configure_buffer_updates(cpi);
      target_rate = gf_group->bit_allocation[gf_group->index];
      target_rate = vp9_rc_clamp_pframe_target_size(cpi, target_rate);
      rc->base_frame_target = target_rate;
  
      cm->frame_type = INTER_FRAME;
  
      if (lc != NULL) {
        if (cpi->svc.spatial_layer_id == 0) {
          lc->is_key_frame = 0;
        } else {
          lc->is_key_frame = cpi->svc.layer_context[0].is_key_frame;
  
          if (lc->is_key_frame)
            cpi->ref_frame_flags &= (~VP9_LAST_FLAG);
        }
      }
  
      // Do the firstpass stats indicate that this frame is skippable for the
      // partition search?
      if (cpi->sf.allow_partition_search_skip &&
          cpi->oxcf.pass == 2 && (!cpi->use_svc || is_two_pass_svc(cpi))) {
        cpi->partition_search_skippable_frame = is_skippable_frame(cpi);
      }
  
      return;
    }
  
    vpx_clear_system_state();
  
    if (cpi->oxcf.rc_mode == VPX_Q) {
      twopass->active_worst_quality = cpi->oxcf.cq_level;
    } else if (cm->current_video_frame == 0 ||
               (lc != NULL && lc->current_video_frame_in_layer == 0)) {
      const int frames_left = (int)(twopass->total_stats.count -
          ((lc != NULL) ? lc->current_video_frame_in_layer
                        : cm->current_video_frame));
      // Special case code for first frame.
      const int section_target_bandwidth = (int)(twopass->bits_left /
                                                 frames_left);
      const double section_length = twopass->total_left_stats.count;
      const double section_error =
        twopass->total_left_stats.coded_error / section_length;
      const double section_intra_skip =
        twopass->total_left_stats.intra_skip_pct / section_length;
      const double section_inactive_zone =
        (twopass->total_left_stats.inactive_zone_rows * 2) /
        ((double)cm->mb_rows * section_length);
      int tmp_q;
  
      tmp_q = get_twopass_worst_quality(cpi, section_error,
          section_intra_skip + section_inactive_zone, section_target_bandwidth);
  
      twopass->active_worst_quality = tmp_q;
      twopass->baseline_active_worst_quality = tmp_q;
      rc->ni_av_qi = tmp_q;
      rc->last_q[INTER_FRAME] = tmp_q;
      rc->avg_q = vp9_convert_qindex_to_q(tmp_q, cm->bit_depth);
      rc->avg_frame_qindex[INTER_FRAME] = tmp_q;
      rc->last_q[KEY_FRAME] = (tmp_q + cpi->oxcf.best_allowed_q) / 2;
      rc->avg_frame_qindex[KEY_FRAME] = rc->last_q[KEY_FRAME];
    }
    vp9_zero(this_frame);
    if (EOF == input_stats(twopass, &this_frame))
      return;
  
    // Set the frame content type flag.
    if (this_frame.intra_skip_pct >= FC_ANIMATION_THRESH)
      twopass->fr_content_type = FC_GRAPHICS_ANIMATION;
    else
      twopass->fr_content_type = FC_NORMAL;
  
    // Keyframe and section processing.
    if (rc->frames_to_key == 0 || (cpi->frame_flags & FRAMEFLAGS_KEY)) {
      FIRSTPASS_STATS this_frame_copy;
      this_frame_copy = this_frame;
      // Define next KF group and assign bits to it.
      find_next_key_frame(cpi, &this_frame);
      this_frame = this_frame_copy;
    } else {
      cm->frame_type = INTER_FRAME;
    }
  
    if (lc != NULL) {
      if (cpi->svc.spatial_layer_id == 0) {
        lc->is_key_frame = (cm->frame_type == KEY_FRAME);
        if (lc->is_key_frame) {
          cpi->ref_frame_flags &=
              (~VP9_LAST_FLAG & ~VP9_GOLD_FLAG & ~VP9_ALT_FLAG);
          lc->frames_from_key_frame = 0;
          // Encode an intra only empty frame since we have a key frame.
          cpi->svc.encode_intra_empty_frame = 1;
        }
      } else {
        cm->frame_type = INTER_FRAME;
        lc->is_key_frame = cpi->svc.layer_context[0].is_key_frame;
  
        if (lc->is_key_frame) {
          cpi->ref_frame_flags &= (~VP9_LAST_FLAG);
          lc->frames_from_key_frame = 0;
        }
      }
    }
  
    // Define a new GF/ARF group. (Should always enter here for key frames).
    if (rc->frames_till_gf_update_due == 0) {
      define_gf_group(cpi, &this_frame);
  
      rc->frames_till_gf_update_due = rc->baseline_gf_interval;
      if (lc != NULL)
        cpi->refresh_golden_frame = 1;
  
  #if ARF_STATS_OUTPUT
      {
        FILE *fpfile;
        fpfile = fopen("arf.stt", "a");
        ++arf_count;
        fprintf(fpfile, "%10d %10ld %10d %10d %10ld\n",
                cm->current_video_frame, rc->frames_till_gf_update_due,
                rc->kf_boost, arf_count, rc->gfu_boost);
  
        fclose(fpfile);
      }
  #endif
    }
  
    configure_buffer_updates(cpi);
  
    // Do the firstpass stats indicate that this frame is skippable for the
    // partition search?
    if (cpi->sf.allow_partition_search_skip && cpi->oxcf.pass == 2 &&
        (!cpi->use_svc || is_two_pass_svc(cpi))) {
      cpi->partition_search_skippable_frame = is_skippable_frame(cpi);
    }
  
    target_rate = gf_group->bit_allocation[gf_group->index];
    rc->base_frame_target = target_rate;
  
    {
      const int num_mbs = (cpi->oxcf.resize_mode != RESIZE_NONE)
                          ? cpi->initial_mbs : cpi->common.MBs;
      // The multiplication by 256 reverses a scaling factor of (>> 8)
      // applied when combining MB error values for the frame.
      twopass->mb_av_energy =
        log(((this_frame.intra_error * 256.0) / num_mbs) + 1.0);
      twopass->mb_smooth_pct = this_frame.intra_smooth_pct;
    }
  
    // Update the total stats remaining structure.
    subtract_stats(&twopass->total_left_stats, &this_frame);
  }
  
  #define MINQ_ADJ_LIMIT 48
  #define MINQ_ADJ_LIMIT_CQ 20
  #define HIGH_UNDERSHOOT_RATIO 2
  void vp9_twopass_postencode_update(VP9_COMP *cpi) {
    TWO_PASS *const twopass = &cpi->twopass;
    RATE_CONTROL *const rc = &cpi->rc;
    VP9_COMMON *const cm = &cpi->common;
    const int bits_used = rc->base_frame_target;
  
    // VBR correction is done through rc->vbr_bits_off_target. Based on the
    // sign of this value, a limited % adjustment is made to the target rate
    // of subsequent frames, to try and push it back towards 0. This method
    // is designed to prevent extreme behaviour at the end of a clip
    // or group of frames.
    rc->vbr_bits_off_target += rc->base_frame_target - rc->projected_frame_size;
    twopass->bits_left = VPXMAX(twopass->bits_left - bits_used, 0);
  
    // Target vs actual bits for this arf group.
    twopass->rolling_arf_group_target_bits += rc->this_frame_target;
    twopass->rolling_arf_group_actual_bits += rc->projected_frame_size;
  
    // Calculate the pct rc error.
    if (rc->total_actual_bits) {
      rc->rate_error_estimate =
        (int)((rc->vbr_bits_off_target * 100) / rc->total_actual_bits);
      rc->rate_error_estimate = clamp(rc->rate_error_estimate, -100, 100);
    } else {
      rc->rate_error_estimate = 0;
    }
  
    if (cpi->common.frame_type != KEY_FRAME &&
        !vp9_is_upper_layer_key_frame(cpi)) {
      twopass->kf_group_bits -= bits_used;
      twopass->last_kfgroup_zeromotion_pct = twopass->kf_zeromotion_pct;
    }
    twopass->kf_group_bits = VPXMAX(twopass->kf_group_bits, 0);
  
    // Increment the gf group index ready for the next frame.
    ++twopass->gf_group.index;
  
    // If the rate control is drifting consider adjustment to min or maxq.
    if ((cpi->oxcf.rc_mode != VPX_Q) &&
        !cpi->rc.is_src_frame_alt_ref) {
      const int maxq_adj_limit =
        rc->worst_quality - twopass->active_worst_quality;
      const int minq_adj_limit =
          (cpi->oxcf.rc_mode == VPX_CQ ? MINQ_ADJ_LIMIT_CQ : MINQ_ADJ_LIMIT);
      int aq_extend_min = 0;
      int aq_extend_max = 0;
  
      // Extend min or Max Q range to account for imbalance from the base
      // value when using AQ.
      if (cpi->oxcf.aq_mode != NO_AQ) {
        if (cm->seg.aq_av_offset < 0) {
          // The balance of the AQ map tends towarda lowering the average Q.
          aq_extend_min = 0;
          aq_extend_max = VPXMIN(maxq_adj_limit, -cm->seg.aq_av_offset);
        } else {
          // The balance of the AQ map tends towards raising the average Q.
          aq_extend_min = VPXMIN(minq_adj_limit, cm->seg.aq_av_offset);
          aq_extend_max = 0;
        }
      }
  
      // Undershoot.
      if (rc->rate_error_estimate > cpi->oxcf.under_shoot_pct) {
        --twopass->extend_maxq;
        if (rc->rolling_target_bits >= rc->rolling_actual_bits)
          ++twopass->extend_minq;
      // Overshoot.
      } else if (rc->rate_error_estimate < -cpi->oxcf.over_shoot_pct) {
        --twopass->extend_minq;
        if (rc->rolling_target_bits < rc->rolling_actual_bits)
          ++twopass->extend_maxq;
      } else {
        // Adjustment for extreme local overshoot.
        if (rc->projected_frame_size > (2 * rc->base_frame_target) &&
            rc->projected_frame_size > (2 * rc->avg_frame_bandwidth))
          ++twopass->extend_maxq;
  
        // Unwind undershoot or overshoot adjustment.
        if (rc->rolling_target_bits < rc->rolling_actual_bits)
          --twopass->extend_minq;
        else if (rc->rolling_target_bits > rc->rolling_actual_bits)
          --twopass->extend_maxq;
      }
  
      twopass->extend_minq =
          clamp(twopass->extend_minq, aq_extend_min, minq_adj_limit);
      twopass->extend_maxq =
          clamp(twopass->extend_maxq, aq_extend_max, maxq_adj_limit);
  
      // If there is a big and undexpected undershoot then feed the extra
      // bits back in quickly. One situation where this may happen is if a
      // frame is unexpectedly almost perfectly predicted by the ARF or GF
      // but not very well predcited by the previous frame.
      if (!frame_is_kf_gf_arf(cpi) && !cpi->rc.is_src_frame_alt_ref) {
        int fast_extra_thresh = rc->base_frame_target / HIGH_UNDERSHOOT_RATIO;
        if (rc->projected_frame_size < fast_extra_thresh) {
          rc->vbr_bits_off_target_fast +=
            fast_extra_thresh - rc->projected_frame_size;
          rc->vbr_bits_off_target_fast =
            VPXMIN(rc->vbr_bits_off_target_fast, (4 * rc->avg_frame_bandwidth));
  
          // Fast adaptation of minQ if necessary to use up the extra bits.
          if (rc->avg_frame_bandwidth) {
            twopass->extend_minq_fast =
              (int)(rc->vbr_bits_off_target_fast * 8 / rc->avg_frame_bandwidth);
          }
          twopass->extend_minq_fast = VPXMIN(
              twopass->extend_minq_fast, minq_adj_limit - twopass->extend_minq);
        } else if (rc->vbr_bits_off_target_fast) {
          twopass->extend_minq_fast = VPXMIN(
              twopass->extend_minq_fast, minq_adj_limit - twopass->extend_minq);
        } else {
          twopass->extend_minq_fast = 0;
        }
      }
    }
  }
  