/*
 * Copyright (c) 2019, Alliance for Open Media. All rights reserved
 *
 * This source code is subject to the terms of the BSD 2 Clause License and
 * the Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License
 * was not distributed with this source code in the LICENSE file, you can
 * obtain it at www.aomedia.org/license/software. If the Alliance for Open
 * Media Patent License 1.0 was not distributed with this source code in the
 * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
 */

#include <stdint.h>

#include "av1/common/blockd.h"
#include "config/aom_config.h"
#include "config/aom_scale_rtcd.h"

#include "aom/aom_codec.h"
#include "aom/aom_encoder.h"

#if CONFIG_MISMATCH_DEBUG
#include "aom_util/debug_util.h"
#endif  // CONFIG_MISMATCH_DEBUG

#include "av1/common/av1_common_int.h"
#include "av1/common/reconinter.h"

#include "av1/encoder/encoder.h"
#include "av1/encoder/encode_strategy.h"
#include "av1/encoder/encodeframe.h"
#include "av1/encoder/encoder_alloc.h"
#include "av1/encoder/firstpass.h"
#include "av1/encoder/gop_structure.h"
#include "av1/encoder/pass2_strategy.h"
#include "av1/encoder/temporal_filter.h"
#if CONFIG_THREE_PASS
#include "av1/encoder/thirdpass.h"
#endif  // CONFIG_THREE_PASS
#include "av1/encoder/tpl_model.h"

#if CONFIG_TUNE_VMAF
#include "av1/encoder/tune_vmaf.h"
#endif

#define TEMPORAL_FILTER_KEY_FRAME (CONFIG_REALTIME_ONLY ? 0 : 1)

static INLINE void set_refresh_frame_flags(
    RefreshFrameInfo *const refresh_frame, bool refresh_gf, bool refresh_bwdref,
    bool refresh_arf) {
  refresh_frame->golden_frame = refresh_gf;
  refresh_frame->bwd_ref_frame = refresh_bwdref;
  refresh_frame->alt_ref_frame = refresh_arf;
}

void av1_configure_buffer_updates(AV1_COMP *const cpi,
                                  RefreshFrameInfo *const refresh_frame,
                                  const FRAME_UPDATE_TYPE type,
                                  const REFBUF_STATE refbuf_state,
                                  int force_refresh_all) {
  // NOTE(weitinglin): Should we define another function to take care of
  // cpi->rc.is_$Source_Type to make this function as it is in the comment?
  const ExtRefreshFrameFlagsInfo *const ext_refresh_frame_flags =
      &cpi->ext_flags.refresh_frame;
  cpi->rc.is_src_frame_alt_ref = 0;

  switch (type) {
    case KF_UPDATE:
      set_refresh_frame_flags(refresh_frame, true, true, true);
      break;

    case LF_UPDATE:
      set_refresh_frame_flags(refresh_frame, false, false, false);
      break;

    case GF_UPDATE:
      set_refresh_frame_flags(refresh_frame, true, false, false);
      break;

    case OVERLAY_UPDATE:
      if (refbuf_state == REFBUF_RESET)
        set_refresh_frame_flags(refresh_frame, true, true, true);
      else
        set_refresh_frame_flags(refresh_frame, true, false, false);

      cpi->rc.is_src_frame_alt_ref = 1;
      break;

    case ARF_UPDATE:
      // NOTE: BWDREF does not get updated along with ALTREF_FRAME.
      if (refbuf_state == REFBUF_RESET)
        set_refresh_frame_flags(refresh_frame, true, true, true);
      else
        set_refresh_frame_flags(refresh_frame, false, false, true);

      break;

    case INTNL_OVERLAY_UPDATE:
      set_refresh_frame_flags(refresh_frame, false, false, false);
      cpi->rc.is_src_frame_alt_ref = 1;
      break;

    case INTNL_ARF_UPDATE:
      set_refresh_frame_flags(refresh_frame, false, true, false);
      break;

    default: assert(0); break;
  }

  if (ext_refresh_frame_flags->update_pending &&
      (!is_stat_generation_stage(cpi))) {
    set_refresh_frame_flags(refresh_frame,
                            ext_refresh_frame_flags->golden_frame,
                            ext_refresh_frame_flags->bwd_ref_frame,
                            ext_refresh_frame_flags->alt_ref_frame);
    GF_GROUP *gf_group = &cpi->ppi->gf_group;
    if (ext_refresh_frame_flags->golden_frame)
      gf_group->update_type[cpi->gf_frame_index] = GF_UPDATE;
    if (ext_refresh_frame_flags->alt_ref_frame)
      gf_group->update_type[cpi->gf_frame_index] = ARF_UPDATE;
    if (ext_refresh_frame_flags->bwd_ref_frame)
      gf_group->update_type[cpi->gf_frame_index] = INTNL_ARF_UPDATE;
  }

  if (force_refresh_all)
    set_refresh_frame_flags(refresh_frame, true, true, true);
}

static void set_additional_frame_flags(const AV1_COMMON *const cm,
                                       unsigned int *const frame_flags) {
  if (frame_is_intra_only(cm)) {
    *frame_flags |= FRAMEFLAGS_INTRAONLY;
  }
  if (frame_is_sframe(cm)) {
    *frame_flags |= FRAMEFLAGS_SWITCH;
  }
  if (cm->features.error_resilient_mode) {
    *frame_flags |= FRAMEFLAGS_ERROR_RESILIENT;
  }
}

static void set_ext_overrides(AV1_COMMON *const cm,
                              EncodeFrameParams *const frame_params,
                              ExternalFlags *const ext_flags) {
  // Overrides the defaults with the externally supplied values with
  // av1_update_reference() and av1_update_entropy() calls
  // Note: The overrides are valid only for the next frame passed
  // to av1_encode_lowlevel()

  if (ext_flags->use_s_frame) {
    frame_params->frame_type = S_FRAME;
  }

  if (ext_flags->refresh_frame_context_pending) {
    cm->features.refresh_frame_context = ext_flags->refresh_frame_context;
    ext_flags->refresh_frame_context_pending = 0;
  }
  cm->features.allow_ref_frame_mvs = ext_flags->use_ref_frame_mvs;

  frame_params->error_resilient_mode = ext_flags->use_error_resilient;
  // A keyframe is already error resilient and keyframes with
  // error_resilient_mode interferes with the use of show_existing_frame
  // when forward reference keyframes are enabled.
  frame_params->error_resilient_mode &= frame_params->frame_type != KEY_FRAME;
  // For bitstream conformance, s-frames must be error-resilient
  frame_params->error_resilient_mode |= frame_params->frame_type == S_FRAME;
}

static int choose_primary_ref_frame(
    AV1_COMP *const cpi, const EncodeFrameParams *const frame_params) {
  const AV1_COMMON *const cm = &cpi->common;

  const int intra_only = frame_params->frame_type == KEY_FRAME ||
                         frame_params->frame_type == INTRA_ONLY_FRAME;
  if (intra_only || frame_params->error_resilient_mode ||
      cpi->ext_flags.use_primary_ref_none) {
    return PRIMARY_REF_NONE;
  }

#if !CONFIG_REALTIME_ONLY
  if (cpi->use_ducky_encode) {
    int wanted_fb = cpi->ppi->gf_group.primary_ref_idx[cpi->gf_frame_index];
    for (int ref_frame = LAST_FRAME; ref_frame <= ALTREF_FRAME; ref_frame++) {
      if (get_ref_frame_map_idx(cm, ref_frame) == wanted_fb)
        return ref_frame - LAST_FRAME;
    }

    return PRIMARY_REF_NONE;
  }
#endif  // !CONFIG_REALTIME_ONLY

  // In large scale case, always use Last frame's frame contexts.
  // Note(yunqing): In other cases, primary_ref_frame is chosen based on
  // cpi->ppi->gf_group.layer_depth[cpi->gf_frame_index], which also controls
  // frame bit allocation.
  if (cm->tiles.large_scale) return (LAST_FRAME - LAST_FRAME);

  if (cpi->ppi->use_svc) return av1_svc_primary_ref_frame(cpi);

  // Find the most recent reference frame with the same reference type as the
  // current frame
  const int current_ref_type = get_current_frame_ref_type(cpi);
  int wanted_fb = cpi->ppi->fb_of_context_type[current_ref_type];
#if CONFIG_FPMT_TEST
  if (cpi->ppi->fpmt_unit_test_cfg == PARALLEL_SIMULATION_ENCODE) {
    GF_GROUP *const gf_group = &cpi->ppi->gf_group;
    if (gf_group->update_type[cpi->gf_frame_index] == INTNL_ARF_UPDATE) {
      int frame_level = gf_group->frame_parallel_level[cpi->gf_frame_index];
      // Book keep wanted_fb of frame_parallel_level 1 frame in an FP2 set.
      if (frame_level == 1) {
        cpi->wanted_fb = wanted_fb;
      }
      // Use the wanted_fb of level 1 frame in an FP2 for a level 2 frame in the
      // set.
      if (frame_level == 2 &&
          gf_group->update_type[cpi->gf_frame_index - 1] == INTNL_ARF_UPDATE) {
        assert(gf_group->frame_parallel_level[cpi->gf_frame_index - 1] == 1);
        wanted_fb = cpi->wanted_fb;
      }
    }
  }
#endif  // CONFIG_FPMT_TEST
  int primary_ref_frame = PRIMARY_REF_NONE;
  for (int ref_frame = LAST_FRAME; ref_frame <= ALTREF_FRAME; ref_frame++) {
    if (get_ref_frame_map_idx(cm, ref_frame) == wanted_fb) {
      primary_ref_frame = ref_frame - LAST_FRAME;
    }
  }

  return primary_ref_frame;
}

static void adjust_frame_rate(AV1_COMP *cpi, int64_t ts_start, int64_t ts_end) {
  TimeStamps *time_stamps = &cpi->time_stamps;
  int64_t this_duration;
  int step = 0;

  // Clear down mmx registers

  if (cpi->ppi->use_svc && cpi->svc.spatial_layer_id > 0) {
    cpi->framerate = cpi->svc.base_framerate;
    av1_rc_update_framerate(cpi, cpi->common.width, cpi->common.height);
    return;
  }

  if (ts_start == time_stamps->first_ts_start) {
    this_duration = ts_end - ts_start;
    step = 1;
  } else {
    int64_t last_duration =
        time_stamps->prev_ts_end - time_stamps->prev_ts_start;

    this_duration = ts_end - time_stamps->prev_ts_end;

    // do a step update if the duration changes by 10%
    if (last_duration)
      step = (int)((this_duration - last_duration) * 10 / last_duration);
  }

  if (this_duration) {
    if (step) {
      cpi->new_framerate = 10000000.0 / this_duration;
      av1_new_framerate(cpi, cpi->new_framerate);
    } else {
      // Average this frame's rate into the last second's average
      // frame rate. If we haven't seen 1 second yet, then average
      // over the whole interval seen.
      const double interval =
          AOMMIN((double)(ts_end - time_stamps->first_ts_start), 10000000.0);
      double avg_duration = 10000000.0 / cpi->framerate;
      avg_duration *= (interval - avg_duration + this_duration);
      avg_duration /= interval;
      cpi->new_framerate = (10000000.0 / avg_duration);
      // For parallel frames update cpi->framerate with new_framerate
      // during av1_post_encode_updates()
      double framerate =
          (cpi->ppi->gf_group.frame_parallel_level[cpi->gf_frame_index] > 0)
              ? cpi->framerate
              : cpi->new_framerate;
      av1_new_framerate(cpi, framerate);
    }
  }

  time_stamps->prev_ts_start = ts_start;
  time_stamps->prev_ts_end = ts_end;
}

// Determine whether there is a forced keyframe pending in the lookahead buffer
int is_forced_keyframe_pending(struct lookahead_ctx *lookahead,
                               const int up_to_index,
                               const COMPRESSOR_STAGE compressor_stage) {
  for (int i = 0; i <= up_to_index; i++) {
    const struct lookahead_entry *e =
        av1_lookahead_peek(lookahead, i, compressor_stage);
    if (e == NULL) {
      // We have reached the end of the lookahead buffer and not early-returned
      // so there isn't a forced key-frame pending.
      return -1;
    } else if (e->flags == AOM_EFLAG_FORCE_KF) {
      return i;
    } else {
      continue;
    }
  }
  return -1;  // Never reached
}

// Check if we should encode an ARF or internal ARF.  If not, try a LAST
// Do some setup associated with the chosen source
// temporal_filtered, flush, and frame_update_type are outputs.
// Return the frame source, or NULL if we couldn't find one
static struct lookahead_entry *choose_frame_source(
    AV1_COMP *const cpi, int *const flush, int *pop_lookahead,
    struct lookahead_entry **last_source,
    EncodeFrameParams *const frame_params) {
  AV1_COMMON *const cm = &cpi->common;
  const GF_GROUP *const gf_group = &cpi->ppi->gf_group;
  struct lookahead_entry *source = NULL;

  // Source index in lookahead buffer.
  int src_index = gf_group->arf_src_offset[cpi->gf_frame_index];

  // TODO(Aasaipriya): Forced key frames need to be fixed when rc_mode != AOM_Q
  if (src_index &&
      (is_forced_keyframe_pending(cpi->ppi->lookahead, src_index,
                                  cpi->compressor_stage) != -1) &&
      cpi->oxcf.rc_cfg.mode != AOM_Q && !is_stat_generation_stage(cpi)) {
    src_index = 0;
    *flush = 1;
  }

  // If the current frame is arf, then we should not pop from the lookahead
  // buffer. If the current frame is not arf, then pop it. This assumes the
  // first frame in the GF group is not arf. May need to change if it is not
  // true.
  *pop_lookahead = (src_index == 0);
  // If this is a key frame and keyframe filtering is enabled with overlay,
  // then do not pop.
  if (*pop_lookahead && cpi->oxcf.kf_cfg.enable_keyframe_filtering > 1 &&
      gf_group->update_type[cpi->gf_frame_index] == ARF_UPDATE &&
      !is_stat_generation_stage(cpi) && cpi->ppi->lookahead) {
    if (cpi->ppi->lookahead->read_ctxs[cpi->compressor_stage].sz &&
        (*flush ||
         cpi->ppi->lookahead->read_ctxs[cpi->compressor_stage].sz ==
             cpi->ppi->lookahead->read_ctxs[cpi->compressor_stage].pop_sz)) {
      *pop_lookahead = 0;
    }
  }

  // LAP stage does not have ARFs or forward key-frames,
  // hence, always pop_lookahead here.
  if (is_stat_generation_stage(cpi)) {
    *pop_lookahead = 1;
    src_index = 0;
  }

  frame_params->show_frame = *pop_lookahead;

#if CONFIG_FPMT_TEST
  if (cpi->ppi->fpmt_unit_test_cfg == PARALLEL_ENCODE) {
#else
  {
#endif  // CONFIG_FPMT_TEST
    // Future frame in parallel encode set
    if (gf_group->src_offset[cpi->gf_frame_index] != 0 &&
        !is_stat_generation_stage(cpi))
      src_index = gf_group->src_offset[cpi->gf_frame_index];
  }
  if (frame_params->show_frame) {
    // show frame, pop from buffer
    // Get last frame source.
    if (cm->current_frame.frame_number > 0) {
      *last_source = av1_lookahead_peek(cpi->ppi->lookahead, src_index - 1,
                                        cpi->compressor_stage);
    }
    // Read in the source frame.
    source = av1_lookahead_peek(cpi->ppi->lookahead, src_index,
                                cpi->compressor_stage);
  } else {
    // no show frames are arf frames
    source = av1_lookahead_peek(cpi->ppi->lookahead, src_index,
                                cpi->compressor_stage);
    if (source != NULL) {
      cm->showable_frame = 1;
    }
  }
  return source;
}

// Don't allow a show_existing_frame to coincide with an error resilient or
// S-Frame. An exception can be made in the case of a keyframe, since it does
// not depend on any previous frames.
static int allow_show_existing(const AV1_COMP *const cpi,
                               unsigned int frame_flags) {
  if (cpi->common.current_frame.frame_number == 0) return 0;

  const struct lookahead_entry *lookahead_src =
      av1_lookahead_peek(cpi->ppi->lookahead, 0, cpi->compressor_stage);
  if (lookahead_src == NULL) return 1;

  const int is_error_resilient =
      cpi->oxcf.tool_cfg.error_resilient_mode ||
      (lookahead_src->flags & AOM_EFLAG_ERROR_RESILIENT);
  const int is_s_frame = cpi->oxcf.kf_cfg.enable_sframe ||
                         (lookahead_src->flags & AOM_EFLAG_SET_S_FRAME);
  const int is_key_frame =
      (cpi->rc.frames_to_key == 0) || (frame_flags & FRAMEFLAGS_KEY);
  return !(is_error_resilient || is_s_frame) || is_key_frame;
}

// Update frame_flags to tell the encoder's caller what sort of frame was
// encoded.
static void update_frame_flags(const AV1_COMMON *const cm,
                               const RefreshFrameInfo *const refresh_frame,
                               unsigned int *frame_flags) {
  if (encode_show_existing_frame(cm)) {
    *frame_flags &= ~FRAMEFLAGS_GOLDEN;
    *frame_flags &= ~FRAMEFLAGS_BWDREF;
    *frame_flags &= ~FRAMEFLAGS_ALTREF;
    *frame_flags &= ~FRAMEFLAGS_KEY;
    return;
  }

  if (refresh_frame->golden_frame) {
    *frame_flags |= FRAMEFLAGS_GOLDEN;
  } else {
    *frame_flags &= ~FRAMEFLAGS_GOLDEN;
  }

  if (refresh_frame->alt_ref_frame) {
    *frame_flags |= FRAMEFLAGS_ALTREF;
  } else {
    *frame_flags &= ~FRAMEFLAGS_ALTREF;
  }

  if (refresh_frame->bwd_ref_frame) {
    *frame_flags |= FRAMEFLAGS_BWDREF;
  } else {
    *frame_flags &= ~FRAMEFLAGS_BWDREF;
  }

  if (cm->current_frame.frame_type == KEY_FRAME) {
    *frame_flags |= FRAMEFLAGS_KEY;
  } else {
    *frame_flags &= ~FRAMEFLAGS_KEY;
  }
}

#define DUMP_REF_FRAME_IMAGES 0

#if DUMP_REF_FRAME_IMAGES == 1
static int dump_one_image(AV1_COMMON *cm,
                          const YV12_BUFFER_CONFIG *const ref_buf,
                          char *file_name) {
  int h;
  FILE *f_ref = NULL;

  if (ref_buf == NULL) {
    printf("Frame data buffer is NULL.\n");
    return AOM_CODEC_MEM_ERROR;
  }

  if ((f_ref = fopen(file_name, "wb")) == NULL) {
    printf("Unable to open file %s to write.\n", file_name);
    return AOM_CODEC_MEM_ERROR;
  }

  // --- Y ---
  for (h = 0; h < cm->height; ++h) {
    fwrite(&ref_buf->y_buffer[h * ref_buf->y_stride], 1, cm->width, f_ref);
  }
  // --- U ---
  for (h = 0; h < (cm->height >> 1); ++h) {
    fwrite(&ref_buf->u_buffer[h * ref_buf->uv_stride], 1, (cm->width >> 1),
           f_ref);
  }
  // --- V ---
  for (h = 0; h < (cm->height >> 1); ++h) {
    fwrite(&ref_buf->v_buffer[h * ref_buf->uv_stride], 1, (cm->width >> 1),
           f_ref);
  }

  fclose(f_ref);

  return AOM_CODEC_OK;
}

static void dump_ref_frame_images(AV1_COMP *cpi) {
  AV1_COMMON *const cm = &cpi->common;
  MV_REFERENCE_FRAME ref_frame;

  for (ref_frame = LAST_FRAME; ref_frame <= ALTREF_FRAME; ++ref_frame) {
    char file_name[256] = "";
    snprintf(file_name, sizeof(file_name), "/tmp/enc_F%d_ref_%d.yuv",
             cm->current_frame.frame_number, ref_frame);
    dump_one_image(cm, get_ref_frame_yv12_buf(cpi, ref_frame), file_name);
  }
}
#endif  // DUMP_REF_FRAME_IMAGES == 1

int av1_get_refresh_ref_frame_map(int refresh_frame_flags) {
  int ref_map_index;

  for (ref_map_index = 0; ref_map_index < REF_FRAMES; ++ref_map_index)
    if ((refresh_frame_flags >> ref_map_index) & 1) break;

  if (ref_map_index == REF_FRAMES) ref_map_index = INVALID_IDX;
  return ref_map_index;
}

static int get_free_ref_map_index(RefFrameMapPair ref_map_pairs[REF_FRAMES]) {
  for (int idx = 0; idx < REF_FRAMES; ++idx)
    if (ref_map_pairs[idx].disp_order == -1) return idx;
  return INVALID_IDX;
}

static int get_refresh_idx(RefFrameMapPair ref_frame_map_pairs[REF_FRAMES],
                           int update_arf, GF_GROUP *gf_group, int gf_index,
                           int enable_refresh_skip, int cur_frame_disp) {
  int arf_count = 0;
  int oldest_arf_order = INT32_MAX;
  int oldest_arf_idx = -1;

  int oldest_frame_order = INT32_MAX;
  int oldest_idx = -1;

  for (int map_idx = 0; map_idx < REF_FRAMES; map_idx++) {
    RefFrameMapPair ref_pair = ref_frame_map_pairs[map_idx];
    if (ref_pair.disp_order == -1) continue;
    const int frame_order = ref_pair.disp_order;
    const int reference_frame_level = ref_pair.pyr_level;
    // Keep future frames and three closest previous frames in output order.
    if (frame_order > cur_frame_disp - 3) continue;

    if (enable_refresh_skip) {
      int skip_frame = 0;
      // Prevent refreshing a frame in gf_group->skip_frame_refresh.
      for (int i = 0; i < REF_FRAMES; i++) {
        int frame_to_skip = gf_group->skip_frame_refresh[gf_index][i];
        if (frame_to_skip == INVALID_IDX) break;
        if (frame_order == frame_to_skip) {
          skip_frame = 1;
          break;
        }
      }
      if (skip_frame) continue;
    }

    // Keep track of the oldest level 1 frame if the current frame is also level
    // 1.
    if (reference_frame_level == 1) {
      // If there are more than 2 level 1 frames in the reference list,
      // discard the oldest.
      if (frame_order < oldest_arf_order) {
        oldest_arf_order = frame_order;
        oldest_arf_idx = map_idx;
      }
      arf_count++;
      continue;
    }

    // Update the overall oldest reference frame.
    if (frame_order < oldest_frame_order) {
      oldest_frame_order = frame_order;
      oldest_idx = map_idx;
    }
  }
  if (update_arf && arf_count > 2) return oldest_arf_idx;
  if (oldest_idx >= 0) return oldest_idx;
  if (oldest_arf_idx >= 0) return oldest_arf_idx;
  if (oldest_idx == -1) {
    assert(arf_count > 2 && enable_refresh_skip);
    return oldest_arf_idx;
  }
  assert(0 && "No valid refresh index found");
  return -1;
}

// Computes the reference refresh index for INTNL_ARF_UPDATE frame.
int av1_calc_refresh_idx_for_intnl_arf(
    AV1_COMP *cpi, RefFrameMapPair ref_frame_map_pairs[REF_FRAMES],
    int gf_index) {
  GF_GROUP *const gf_group = &cpi->ppi->gf_group;

  // Search for the open slot to store the current frame.
  int free_fb_index = get_free_ref_map_index(ref_frame_map_pairs);

  // Use a free slot if available.
  if (free_fb_index != INVALID_IDX) {
    return free_fb_index;
  } else {
    int enable_refresh_skip = !is_one_pass_rt_params(cpi);
    int refresh_idx =
        get_refresh_idx(ref_frame_map_pairs, 0, gf_group, gf_index,
                        enable_refresh_skip, gf_group->display_idx[gf_index]);
    return refresh_idx;
  }
}

int av1_get_refresh_frame_flags(
    const AV1_COMP *const cpi, const EncodeFrameParams *const frame_params,
    FRAME_UPDATE_TYPE frame_update_type, int gf_index, int cur_disp_order,
    RefFrameMapPair ref_frame_map_pairs[REF_FRAMES]) {
  const AV1_COMMON *const cm = &cpi->common;
  const ExtRefreshFrameFlagsInfo *const ext_refresh_frame_flags =
      &cpi->ext_flags.refresh_frame;

  GF_GROUP *gf_group = &cpi->ppi->gf_group;
  if (gf_group->refbuf_state[gf_index] == REFBUF_RESET)
    return SELECT_ALL_BUF_SLOTS;

  // TODO(jingning): Deprecate the following operations.
  // Switch frames and shown key-frames overwrite all reference slots
  if (frame_params->frame_type == S_FRAME) return SELECT_ALL_BUF_SLOTS;

  // show_existing_frames don't actually send refresh_frame_flags so set the
  // flags to 0 to keep things consistent.
  if (frame_params->show_existing_frame) return 0;

  const RTC_REF *const rtc_ref = &cpi->rtc_ref;
  if (is_frame_droppable(rtc_ref, ext_refresh_frame_flags)) return 0;

#if !CONFIG_REALTIME_ONLY
  if (cpi->use_ducky_encode &&
      cpi->ducky_encode_info.frame_info.gop_mode == DUCKY_ENCODE_GOP_MODE_RCL) {
    int new_fb_map_idx = cpi->ppi->gf_group.update_ref_idx[gf_index];
    if (new_fb_map_idx == INVALID_IDX) return 0;
    return 1 << new_fb_map_idx;
  }
#endif  // !CONFIG_REALTIME_ONLY

  int refresh_mask = 0;
  if (ext_refresh_frame_flags->update_pending) {
    if (rtc_ref->set_ref_frame_config ||
        use_rtc_reference_structure_one_layer(cpi)) {
      for (unsigned int i = 0; i < INTER_REFS_PER_FRAME; i++) {
        int ref_frame_map_idx = rtc_ref->ref_idx[i];
        refresh_mask |= rtc_ref->refresh[ref_frame_map_idx]
                        << ref_frame_map_idx;
      }
      return refresh_mask;
    }
    // Unfortunately the encoder interface reflects the old refresh_*_frame
    // flags so we have to replicate the old refresh_frame_flags logic here in
    // order to preserve the behaviour of the flag overrides.
    int ref_frame_map_idx = get_ref_frame_map_idx(cm, LAST_FRAME);
    if (ref_frame_map_idx != INVALID_IDX)
      refresh_mask |= ext_refresh_frame_flags->last_frame << ref_frame_map_idx;

    ref_frame_map_idx = get_ref_frame_map_idx(cm, EXTREF_FRAME);
    if (ref_frame_map_idx != INVALID_IDX)
      refresh_mask |= ext_refresh_frame_flags->bwd_ref_frame
                      << ref_frame_map_idx;

    ref_frame_map_idx = get_ref_frame_map_idx(cm, ALTREF2_FRAME);
    if (ref_frame_map_idx != INVALID_IDX)
      refresh_mask |= ext_refresh_frame_flags->alt2_ref_frame
                      << ref_frame_map_idx;

    if (frame_update_type == OVERLAY_UPDATE) {
      ref_frame_map_idx = get_ref_frame_map_idx(cm, ALTREF_FRAME);
      if (ref_frame_map_idx != INVALID_IDX)
        refresh_mask |= ext_refresh_frame_flags->golden_frame
                        << ref_frame_map_idx;
    } else {
      ref_frame_map_idx = get_ref_frame_map_idx(cm, GOLDEN_FRAME);
      if (ref_frame_map_idx != INVALID_IDX)
        refresh_mask |= ext_refresh_frame_flags->golden_frame
                        << ref_frame_map_idx;

      ref_frame_map_idx = get_ref_frame_map_idx(cm, ALTREF_FRAME);
      if (ref_frame_map_idx != INVALID_IDX)
        refresh_mask |= ext_refresh_frame_flags->alt_ref_frame
                        << ref_frame_map_idx;
    }
    return refresh_mask;
  }

  // Search for the open slot to store the current frame.
  int free_fb_index = get_free_ref_map_index(ref_frame_map_pairs);

  // No refresh necessary for these frame types.
  if (frame_update_type == OVERLAY_UPDATE ||
      frame_update_type == INTNL_OVERLAY_UPDATE)
    return refresh_mask;

  // If there is an open slot, refresh that one instead of replacing a
  // reference.
  if (free_fb_index != INVALID_IDX) {
    refresh_mask = 1 << free_fb_index;
    return refresh_mask;
  }
  const int enable_refresh_skip = !is_one_pass_rt_params(cpi);
  const int update_arf = frame_update_type == ARF_UPDATE;
  const int refresh_idx =
      get_refresh_idx(ref_frame_map_pairs, update_arf, &cpi->ppi->gf_group,
                      gf_index, enable_refresh_skip, cur_disp_order);
  return 1 << refresh_idx;
}

#if !CONFIG_REALTIME_ONLY
void setup_mi(AV1_COMP *const cpi, YV12_BUFFER_CONFIG *src) {
  AV1_COMMON *const cm = &cpi->common;
  const int num_planes = av1_num_planes(cm);
  MACROBLOCK *const x = &cpi->td.mb;
  MACROBLOCKD *const xd = &x->e_mbd;

  av1_setup_src_planes(x, src, 0, 0, num_planes, cm->seq_params->sb_size);

  av1_setup_block_planes(xd, cm->seq_params->subsampling_x,
                         cm->seq_params->subsampling_y, num_planes);

  set_mi_offsets(&cm->mi_params, xd, 0, 0);
}

// Apply temporal filtering to source frames and encode the filtered frame.
// If the current frame does not require filtering, this function is identical
// to av1_encode() except that tpl is not performed.
static int denoise_and_encode(AV1_COMP *const cpi, uint8_t *const dest,
                              EncodeFrameInput *const frame_input,
                              EncodeFrameParams *const frame_params,
                              EncodeFrameResults *const frame_results) {
#if CONFIG_COLLECT_COMPONENT_TIMING
  if (cpi->oxcf.pass == 2) start_timing(cpi, denoise_and_encode_time);
#endif
  const AV1EncoderConfig *const oxcf = &cpi->oxcf;
  AV1_COMMON *const cm = &cpi->common;
  GF_GROUP *const gf_group = &cpi->ppi->gf_group;
  FRAME_UPDATE_TYPE update_type =
      get_frame_update_type(&cpi->ppi->gf_group, cpi->gf_frame_index);
  const int is_second_arf =
      av1_gop_is_second_arf(gf_group, cpi->gf_frame_index);

  // Decide whether to apply temporal filtering to the source frame.
  int apply_filtering =
      av1_is_temporal_filter_on(oxcf) && !is_stat_generation_stage(cpi);
  if (update_type != KF_UPDATE && update_type != ARF_UPDATE && !is_second_arf) {
    apply_filtering = 0;
  }
  if (apply_filtering) {
    if (frame_params->frame_type == KEY_FRAME) {
      // TODO(angiebird): Move the noise level check to av1_tf_info_filtering.
      // Decide whether it is allowed to perform key frame filtering
      int allow_kf_filtering = oxcf->kf_cfg.enable_keyframe_filtering &&
                               !frame_params->show_existing_frame &&
                               !is_lossless_requested(&oxcf->rc_cfg);
      if (allow_kf_filtering) {
        const double y_noise_level = av1_estimate_noise_from_single_plane(
            frame_input->source, 0, cm->seq_params->bit_depth,
            NOISE_ESTIMATION_EDGE_THRESHOLD);
        apply_filtering = y_noise_level > 0;
      } else {
        apply_filtering = 0;
      }
      // If we are doing kf filtering, set up a few things.
      if (apply_filtering) {
        av1_setup_past_independence(cm);
      }
    } else if (is_second_arf) {
      apply_filtering = cpi->sf.hl_sf.second_alt_ref_filtering;
    }
  }

#if CONFIG_COLLECT_COMPONENT_TIMING
  if (cpi->oxcf.pass == 2) start_timing(cpi, apply_filtering_time);
#endif
  // Save the pointer to the original source image.
  YV12_BUFFER_CONFIG *source_buffer = frame_input->source;
  // apply filtering to frame
  if (apply_filtering) {
    int show_existing_alt_ref = 0;
    FRAME_DIFF frame_diff;
    int top_index = 0;
    int bottom_index = 0;
    const int q_index = av1_rc_pick_q_and_bounds(
        cpi, cpi->oxcf.frm_dim_cfg.width, cpi->oxcf.frm_dim_cfg.height,
        cpi->gf_frame_index, &bottom_index, &top_index);

    // TODO(bohanli): figure out why we need frame_type in cm here.
    cm->current_frame.frame_type = frame_params->frame_type;
    if (update_type == KF_UPDATE || update_type == ARF_UPDATE) {
      YV12_BUFFER_CONFIG *tf_buf = av1_tf_info_get_filtered_buf(
          &cpi->ppi->tf_info, cpi->gf_frame_index, &frame_diff);
      if (tf_buf != NULL) {
        frame_input->source = tf_buf;
        show_existing_alt_ref = av1_check_show_filtered_frame(
            tf_buf, &frame_diff, q_index, cm->seq_params->bit_depth);
        if (show_existing_alt_ref) {
          cpi->common.showable_frame |= 1;
        }
      }
      if (gf_group->frame_type[cpi->gf_frame_index] != KEY_FRAME) {
        cpi->ppi->show_existing_alt_ref = show_existing_alt_ref;
      }
    }

    if (is_second_arf) {
      // Allocate the memory for tf_buf_second_arf buffer, only when it is
      // required.
      int ret = aom_realloc_frame_buffer(
          &cpi->ppi->tf_info.tf_buf_second_arf, oxcf->frm_dim_cfg.width,
          oxcf->frm_dim_cfg.height, cm->seq_params->subsampling_x,
          cm->seq_params->subsampling_y, cm->seq_params->use_highbitdepth,
          cpi->oxcf.border_in_pixels, cm->features.byte_alignment, NULL, NULL,
          NULL, cpi->oxcf.tool_cfg.enable_global_motion, 0);
      if (ret)
        aom_internal_error(cm->error, AOM_CODEC_MEM_ERROR,
                           "Failed to allocate tf_buf_second_arf");

      YV12_BUFFER_CONFIG *tf_buf_second_arf =
          &cpi->ppi->tf_info.tf_buf_second_arf;
      // We didn't apply temporal filtering for second arf ahead in
      // av1_tf_info_filtering().
      const int arf_src_index = gf_group->arf_src_offset[cpi->gf_frame_index];
      // Right now, we are still using tf_buf_second_arf due to
      // implementation complexity.
      // TODO(angiebird): Reuse tf_info->tf_buf here.
      av1_temporal_filter(cpi, arf_src_index, cpi->gf_frame_index, &frame_diff,
                          tf_buf_second_arf);
      show_existing_alt_ref = av1_check_show_filtered_frame(
          tf_buf_second_arf, &frame_diff, q_index, cm->seq_params->bit_depth);
      if (show_existing_alt_ref) {
        aom_extend_frame_borders(tf_buf_second_arf, av1_num_planes(cm));
        frame_input->source = tf_buf_second_arf;
      }
      // Currently INTNL_ARF_UPDATE only do show_existing.
      cpi->common.showable_frame |= 1;
    }

    // Copy source metadata to the temporal filtered frame
    if (source_buffer->metadata &&
        aom_copy_metadata_to_frame_buffer(frame_input->source,
                                          source_buffer->metadata)) {
      aom_internal_error(
          cm->error, AOM_CODEC_MEM_ERROR,
          "Failed to copy source metadata to the temporal filtered frame");
    }
  }
#if CONFIG_COLLECT_COMPONENT_TIMING
  if (cpi->oxcf.pass == 2) end_timing(cpi, apply_filtering_time);
#endif

  int set_mv_params = frame_params->frame_type == KEY_FRAME ||
                      update_type == ARF_UPDATE || update_type == GF_UPDATE;
  cm->show_frame = frame_params->show_frame;
  cm->current_frame.frame_type = frame_params->frame_type;
  // TODO(bohanli): Why is this? what part of it is necessary?
  av1_set_frame_size(cpi, cm->superres_upscaled_width,
                     cm->superres_upscaled_height);
  if (set_mv_params) av1_set_mv_search_params(cpi);

#if CONFIG_RD_COMMAND
  if (frame_params->frame_type == KEY_FRAME) {
    char filepath[] = "rd_command.txt";
    av1_read_rd_command(filepath, &cpi->rd_command);
  }
#endif  // CONFIG_RD_COMMAND
  if (cpi->gf_frame_index == 0 && !is_stat_generation_stage(cpi)) {
    // perform tpl after filtering
    int allow_tpl =
        oxcf->gf_cfg.lag_in_frames > 1 && oxcf->algo_cfg.enable_tpl_model;
    if (gf_group->size > MAX_LENGTH_TPL_FRAME_STATS) {
      allow_tpl = 0;
    }
    if (frame_params->frame_type == KEY_FRAME) {
      // TODO(angiebird): handle disable_filtered_key_tpl properly
      allow_tpl = allow_tpl && !cpi->sf.tpl_sf.disable_filtered_key_tpl;
    } else {
      // In rare case, it's possible to have non ARF/GF update_type here.
      // We should set allow_tpl to zero in the situation
      allow_tpl =
          allow_tpl && (update_type == ARF_UPDATE || update_type == GF_UPDATE ||
                        (cpi->use_ducky_encode &&
                         cpi->ducky_encode_info.frame_info.gop_mode ==
                             DUCKY_ENCODE_GOP_MODE_RCL));
    }

    if (allow_tpl) {
      if (!cpi->skip_tpl_setup_stats) {
        av1_tpl_preload_rc_estimate(cpi, frame_params);
        av1_tpl_setup_stats(cpi, 0, frame_params);
#if CONFIG_BITRATE_ACCURACY && !CONFIG_THREE_PASS
        assert(cpi->gf_frame_index == 0);
        av1_vbr_rc_update_q_index_list(&cpi->vbr_rc_info, &cpi->ppi->tpl_data,
                                       gf_group, cm->seq_params->bit_depth);
#endif
      }
    } else {
      av1_init_tpl_stats(&cpi->ppi->tpl_data);
    }
#if CONFIG_BITRATE_ACCURACY && CONFIG_THREE_PASS
    if (cpi->oxcf.pass == AOM_RC_SECOND_PASS &&
        cpi->second_pass_log_stream != NULL) {
      TPL_INFO *tpl_info;
      AOM_CHECK_MEM_ERROR(cm->error, tpl_info, aom_malloc(sizeof(*tpl_info)));
      av1_pack_tpl_info(tpl_info, gf_group, &cpi->ppi->tpl_data);
      av1_write_tpl_info(tpl_info, cpi->second_pass_log_stream,
                         cpi->common.error);
      aom_free(tpl_info);
    }
#endif  // CONFIG_BITRATE_ACCURACY && CONFIG_THREE_PASS
  }

  if (av1_encode(cpi, dest, frame_input, frame_params, frame_results) !=
      AOM_CODEC_OK) {
    return AOM_CODEC_ERROR;
  }

  // Set frame_input source to true source for psnr calculation.
  if (apply_filtering && is_psnr_calc_enabled(cpi)) {
    cpi->source = av1_realloc_and_scale_if_required(
        cm, source_buffer, &cpi->scaled_source, cm->features.interp_filter, 0,
        false, true, cpi->oxcf.border_in_pixels,
        cpi->oxcf.tool_cfg.enable_global_motion);
    cpi->unscaled_source = source_buffer;
  }
#if CONFIG_COLLECT_COMPONENT_TIMING
  if (cpi->oxcf.pass == 2) end_timing(cpi, denoise_and_encode_time);
#endif
  return AOM_CODEC_OK;
}
#endif  // !CONFIG_REALTIME_ONLY

/*!\cond */
// Struct to keep track of relevant reference frame data.
typedef struct {
  int map_idx;
  int disp_order;
  int pyr_level;
  int used;
} RefBufMapData;
/*!\endcond */

// Comparison function to sort reference frames in ascending display order.
static int compare_map_idx_pair_asc(const void *a, const void *b) {
  if (((RefBufMapData *)a)->disp_order == ((RefBufMapData *)b)->disp_order) {
    return 0;
  } else if (((const RefBufMapData *)a)->disp_order >
             ((const RefBufMapData *)b)->disp_order) {
    return 1;
  } else {
    return -1;
  }
}

// Checks to see if a particular reference frame is already in the reference
// frame map.
static int is_in_ref_map(RefBufMapData *map, int disp_order, int n_frames) {
  for (int i = 0; i < n_frames; i++) {
    if (disp_order == map[i].disp_order) return 1;
  }
  return 0;
}

// Add a reference buffer index to a named reference slot.
static void add_ref_to_slot(RefBufMapData *ref, int *const remapped_ref_idx,
                            int frame) {
  remapped_ref_idx[frame - LAST_FRAME] = ref->map_idx;
  ref->used = 1;
}

// Threshold dictating when we are allowed to start considering
// leaving lowest level frames unmapped.
#define LOW_LEVEL_FRAMES_TR 5

// Find which reference buffer should be left out of the named mapping.
// This is because there are 8 reference buffers and only 7 named slots.
static void set_unmapped_ref(RefBufMapData *buffer_map, int n_bufs,
                             int n_min_level_refs, int min_level,
                             int cur_frame_disp) {
  int max_dist = 0;
  int unmapped_idx = -1;
  if (n_bufs <= ALTREF_FRAME) return;
  for (int i = 0; i < n_bufs; i++) {
    if (buffer_map[i].used) continue;
    if (buffer_map[i].pyr_level != min_level ||
        n_min_level_refs >= LOW_LEVEL_FRAMES_TR) {
      int dist = abs(cur_frame_disp - buffer_map[i].disp_order);
      if (dist > max_dist) {
        max_dist = dist;
        unmapped_idx = i;
      }
    }
  }
  assert(unmapped_idx >= 0 && "Unmapped reference not found");
  buffer_map[unmapped_idx].used = 1;
}

void av1_get_ref_frames(RefFrameMapPair ref_frame_map_pairs[REF_FRAMES],
                        int cur_frame_disp, const AV1_COMP *cpi, int gf_index,
                        int is_parallel_encode,
                        int remapped_ref_idx[REF_FRAMES]) {
  int buf_map_idx = 0;

  // Initialize reference frame mappings.
  for (int i = 0; i < REF_FRAMES; ++i) remapped_ref_idx[i] = INVALID_IDX;

#if !CONFIG_REALTIME_ONLY
  if (cpi->use_ducky_encode &&
      cpi->ducky_encode_info.frame_info.gop_mode == DUCKY_ENCODE_GOP_MODE_RCL) {
    for (int i = 0; i < REF_FRAMES; ++i) remapped_ref_idx[i] = 0;
    for (int rf = LAST_FRAME; rf < REF_FRAMES; ++rf) {
      if (cpi->ppi->gf_group.ref_frame_list[gf_index][rf] != INVALID_IDX) {
        remapped_ref_idx[rf - LAST_FRAME] =
            cpi->ppi->gf_group.ref_frame_list[gf_index][rf];
      }
    }

    return;
  }
#endif  // !CONFIG_REALTIME_ONLY

  RefBufMapData buffer_map[REF_FRAMES];
  int n_bufs = 0;
  memset(buffer_map, 0, REF_FRAMES * sizeof(buffer_map[0]));
  int min_level = MAX_ARF_LAYERS;
  int max_level = 0;
  GF_GROUP *gf_group = &cpi->ppi->gf_group;
  int skip_ref_unmapping = 0;
  int is_one_pass_rt = is_one_pass_rt_params(cpi);

  // Go through current reference buffers and store display order, pyr level,
  // and map index.
  for (int map_idx = 0; map_idx < REF_FRAMES; map_idx++) {
    // Get reference frame buffer.
    RefFrameMapPair ref_pair = ref_frame_map_pairs[map_idx];
    if (ref_pair.disp_order == -1) continue;
    const int frame_order = ref_pair.disp_order;
    // Avoid duplicates.
    if (is_in_ref_map(buffer_map, frame_order, n_bufs)) continue;
    const int reference_frame_level = ref_pair.pyr_level;

    // Keep track of the lowest and highest levels that currently exist.
    if (reference_frame_level < min_level) min_level = reference_frame_level;
    if (reference_frame_level > max_level) max_level = reference_frame_level;

    buffer_map[n_bufs].map_idx = map_idx;
    buffer_map[n_bufs].disp_order = frame_order;
    buffer_map[n_bufs].pyr_level = reference_frame_level;
    buffer_map[n_bufs].used = 0;
    n_bufs++;
  }

  // Sort frames in ascending display order.
  qsort(buffer_map, n_bufs, sizeof(buffer_map[0]), compare_map_idx_pair_asc);

  int n_min_level_refs = 0;
  int closest_past_ref = -1;
  int golden_idx = -1;
  int altref_idx = -1;

  // Find the GOLDEN_FRAME and BWDREF_FRAME.
  // Also collect various stats about the reference frames for the remaining
  // mappings.
  for (int i = n_bufs - 1; i >= 0; i--) {
    if (buffer_map[i].pyr_level == min_level) {
      // Keep track of the number of lowest level frames.
      n_min_level_refs++;
      if (buffer_map[i].disp_order < cur_frame_disp && golden_idx == -1 &&
          remapped_ref_idx[GOLDEN_FRAME - LAST_FRAME] == INVALID_IDX) {
        // Save index for GOLDEN.
        golden_idx = i;
      } else if (buffer_map[i].disp_order > cur_frame_disp &&
                 altref_idx == -1 &&
                 remapped_ref_idx[ALTREF_FRAME - LAST_FRAME] == INVALID_IDX) {
        // Save index for ALTREF.
        altref_idx = i;
      }
    } else if (buffer_map[i].disp_order == cur_frame_disp) {
      // Map the BWDREF_FRAME if this is the show_existing_frame.
      add_ref_to_slot(&buffer_map[i], remapped_ref_idx, BWDREF_FRAME);
    }

    // During parallel encodes of lower layer frames, exclude the first frame
    // (frame_parallel_level 1) from being used for the reference assignment of
    // the second frame (frame_parallel_level 2).
    if (!is_one_pass_rt && gf_group->frame_parallel_level[gf_index] == 2 &&
        gf_group->frame_parallel_level[gf_index - 1] == 1 &&
        gf_group->update_type[gf_index - 1] == INTNL_ARF_UPDATE) {
      assert(gf_group->update_type[gf_index] == INTNL_ARF_UPDATE);
#if CONFIG_FPMT_TEST
      is_parallel_encode = (cpi->ppi->fpmt_unit_test_cfg == PARALLEL_ENCODE)
                               ? is_parallel_encode
                               : 0;
#endif  // CONFIG_FPMT_TEST
      // If parallel cpis are active, use ref_idx_to_skip, else, use display
      // index.
      assert(IMPLIES(is_parallel_encode, cpi->ref_idx_to_skip != INVALID_IDX));
      assert(IMPLIES(!is_parallel_encode,
                     gf_group->skip_frame_as_ref[gf_index] != INVALID_IDX));
      buffer_map[i].used = is_parallel_encode
                               ? (buffer_map[i].map_idx == cpi->ref_idx_to_skip)
                               : (buffer_map[i].disp_order ==
                                  gf_group->skip_frame_as_ref[gf_index]);
      // In case a ref frame is excluded from being used during assignment,
      // skip the call to set_unmapped_ref(). Applicable in steady state.
      if (buffer_map[i].used) skip_ref_unmapping = 1;
    }

    // Keep track of where the frames change from being past frames to future
    // frames.
    if (buffer_map[i].disp_order < cur_frame_disp && closest_past_ref < 0)
      closest_past_ref = i;
  }

  // Do not map GOLDEN and ALTREF based on their pyramid level if all reference
  // frames have the same level.
  if (n_min_level_refs <= n_bufs) {
    // Map the GOLDEN_FRAME.
    if (golden_idx > -1)
      add_ref_to_slot(&buffer_map[golden_idx], remapped_ref_idx, GOLDEN_FRAME);
    // Map the ALTREF_FRAME.
    if (altref_idx > -1)
      add_ref_to_slot(&buffer_map[altref_idx], remapped_ref_idx, ALTREF_FRAME);
  }

  // Find the buffer to be excluded from the mapping.
  if (!skip_ref_unmapping)
    set_unmapped_ref(buffer_map, n_bufs, n_min_level_refs, min_level,
                     cur_frame_disp);

  // Place past frames in LAST_FRAME, LAST2_FRAME, and LAST3_FRAME.
  for (int frame = LAST_FRAME; frame < GOLDEN_FRAME; frame++) {
    // Continue if the current ref slot is already full.
    if (remapped_ref_idx[frame - LAST_FRAME] != INVALID_IDX) continue;
    // Find the next unmapped reference buffer
    // in decreasing ouptut order relative to current picture.
    int next_buf_max = 0;
    int next_disp_order = INT_MIN;
    for (buf_map_idx = n_bufs - 1; buf_map_idx >= 0; buf_map_idx--) {
      if (!buffer_map[buf_map_idx].used &&
          buffer_map[buf_map_idx].disp_order < cur_frame_disp &&
          buffer_map[buf_map_idx].disp_order > next_disp_order) {
        next_disp_order = buffer_map[buf_map_idx].disp_order;
        next_buf_max = buf_map_idx;
      }
    }
    buf_map_idx = next_buf_max;
    if (buf_map_idx < 0) break;
    if (buffer_map[buf_map_idx].used) break;
    add_ref_to_slot(&buffer_map[buf_map_idx], remapped_ref_idx, frame);
  }

  // Place future frames (if there are any) in BWDREF_FRAME and ALTREF2_FRAME.
  for (int frame = BWDREF_FRAME; frame < REF_FRAMES; frame++) {
    // Continue if the current ref slot is already full.
    if (remapped_ref_idx[frame - LAST_FRAME] != INVALID_IDX) continue;
    // Find the next unmapped reference buffer
    // in increasing ouptut order relative to current picture.
    int next_buf_max = 0;
    int next_disp_order = INT_MAX;
    for (buf_map_idx = n_bufs - 1; buf_map_idx >= 0; buf_map_idx--) {
      if (!buffer_map[buf_map_idx].used &&
          buffer_map[buf_map_idx].disp_order > cur_frame_disp &&
          buffer_map[buf_map_idx].disp_order < next_disp_order) {
        next_disp_order = buffer_map[buf_map_idx].disp_order;
        next_buf_max = buf_map_idx;
      }
    }
    buf_map_idx = next_buf_max;
    if (buf_map_idx < 0) break;
    if (buffer_map[buf_map_idx].used) break;
    add_ref_to_slot(&buffer_map[buf_map_idx], remapped_ref_idx, frame);
  }

  // Place remaining past frames.
  buf_map_idx = closest_past_ref;
  for (int frame = LAST_FRAME; frame < REF_FRAMES; frame++) {
    // Continue if the current ref slot is already full.
    if (remapped_ref_idx[frame - LAST_FRAME] != INVALID_IDX) continue;
    // Find the next unmapped reference buffer.
    for (; buf_map_idx >= 0; buf_map_idx--) {
      if (!buffer_map[buf_map_idx].used) break;
    }
    if (buf_map_idx < 0) break;
    if (buffer_map[buf_map_idx].used) break;
    add_ref_to_slot(&buffer_map[buf_map_idx], remapped_ref_idx, frame);
  }

  // Place remaining future frames.
  buf_map_idx = n_bufs - 1;
  for (int frame = ALTREF_FRAME; frame >= LAST_FRAME; frame--) {
    // Continue if the current ref slot is already full.
    if (remapped_ref_idx[frame - LAST_FRAME] != INVALID_IDX) continue;
    // Find the next unmapped reference buffer.
    for (; buf_map_idx > closest_past_ref; buf_map_idx--) {
      if (!buffer_map[buf_map_idx].used) break;
    }
    if (buf_map_idx < 0) break;
    if (buffer_map[buf_map_idx].used) break;
    add_ref_to_slot(&buffer_map[buf_map_idx], remapped_ref_idx, frame);
  }

  // Fill any slots that are empty (should only happen for the first 7 frames).
  for (int i = 0; i < REF_FRAMES; ++i)
    if (remapped_ref_idx[i] == INVALID_IDX) remapped_ref_idx[i] = 0;
}

int av1_encode_strategy(AV1_COMP *const cpi, size_t *const size,
                        uint8_t *const dest, unsigned int *frame_flags,
                        int64_t *const time_stamp, int64_t *const time_end,
                        const aom_rational64_t *const timestamp_ratio,
                        int *const pop_lookahead, int flush) {
  AV1EncoderConfig *const oxcf = &cpi->oxcf;
  AV1_COMMON *const cm = &cpi->common;
  GF_GROUP *gf_group = &cpi->ppi->gf_group;
  ExternalFlags *const ext_flags = &cpi->ext_flags;
  GFConfig *const gf_cfg = &oxcf->gf_cfg;

  EncodeFrameInput frame_input;
  EncodeFrameParams frame_params;
  EncodeFrameResults frame_results;
  memset(&frame_input, 0, sizeof(frame_input));
  memset(&frame_params, 0, sizeof(frame_params));
  memset(&frame_results, 0, sizeof(frame_results));

#if CONFIG_BITRATE_ACCURACY && CONFIG_THREE_PASS
  VBR_RATECTRL_INFO *vbr_rc_info = &cpi->vbr_rc_info;
  if (oxcf->pass == AOM_RC_THIRD_PASS && vbr_rc_info->ready == 0) {
    THIRD_PASS_FRAME_INFO frame_info[MAX_THIRD_PASS_BUF];
    av1_open_second_pass_log(cpi, 1);
    FILE *second_pass_log_stream = cpi->second_pass_log_stream;
    fseek(second_pass_log_stream, 0, SEEK_END);
    size_t file_size = ftell(second_pass_log_stream);
    rewind(second_pass_log_stream);
    size_t read_size = 0;
    while (read_size < file_size) {
      THIRD_PASS_GOP_INFO gop_info;
      struct aom_internal_error_info *error = cpi->common.error;
      // Read in GOP information from the second pass file.
      av1_read_second_pass_gop_info(second_pass_log_stream, &gop_info, error);
      TPL_INFO *tpl_info;
      AOM_CHECK_MEM_ERROR(cm->error, tpl_info, aom_malloc(sizeof(*tpl_info)));
      av1_read_tpl_info(tpl_info, second_pass_log_stream, error);
      // Read in per-frame info from second-pass encoding
      av1_read_second_pass_per_frame_info(second_pass_log_stream, frame_info,
                                          gop_info.num_frames, error);
      av1_vbr_rc_append_tpl_info(vbr_rc_info, tpl_info);
      read_size = ftell(second_pass_log_stream);
      aom_free(tpl_info);
    }
    av1_close_second_pass_log(cpi);
    if (cpi->oxcf.rc_cfg.mode == AOM_Q) {
      vbr_rc_info->base_q_index = cpi->oxcf.rc_cfg.cq_level;
      av1_vbr_rc_compute_q_indices(
          vbr_rc_info->base_q_index, vbr_rc_info->total_frame_count,
          vbr_rc_info->qstep_ratio_list, cm->seq_params->bit_depth,
          vbr_rc_info->q_index_list);
    } else {
      vbr_rc_info->base_q_index = av1_vbr_rc_info_estimate_base_q(
          vbr_rc_info->total_bit_budget, cm->seq_params->bit_depth,
          vbr_rc_info->scale_factors, vbr_rc_info->total_frame_count,
          vbr_rc_info->update_type_list, vbr_rc_info->qstep_ratio_list,
          vbr_rc_info->txfm_stats_list, vbr_rc_info->q_index_list, NULL);
    }
    vbr_rc_info->ready = 1;
#if CONFIG_RATECTRL_LOG
    rc_log_record_chunk_info(&cpi->rc_log, vbr_rc_info->base_q_index,
                             vbr_rc_info->total_frame_count);
#endif  // CONFIG_RATECTRL_LOG
  }
#endif  // CONFIG_BITRATE_ACCURACY && CONFIG_THREE_PASS

  // Check if we need to stuff more src frames
  if (flush == 0) {
    int srcbuf_size =
        av1_lookahead_depth(cpi->ppi->lookahead, cpi->compressor_stage);
    int pop_size =
        av1_lookahead_pop_sz(cpi->ppi->lookahead, cpi->compressor_stage);

    // Continue buffering look ahead buffer.
    if (srcbuf_size < pop_size) return -1;
  }

  if (!av1_lookahead_peek(cpi->ppi->lookahead, 0, cpi->compressor_stage)) {
#if !CONFIG_REALTIME_ONLY
    if (flush && oxcf->pass == AOM_RC_FIRST_PASS &&
        !cpi->ppi->twopass.first_pass_done) {
      av1_end_first_pass(cpi); /* get last stats packet */
      cpi->ppi->twopass.first_pass_done = 1;
    }
#endif
    return -1;
  }

  // TODO(sarahparker) finish bit allocation for one pass pyramid
  if (has_no_stats_stage(cpi)) {
    gf_cfg->gf_max_pyr_height =
        AOMMIN(gf_cfg->gf_max_pyr_height, USE_ALTREF_FOR_ONE_PASS);
    gf_cfg->gf_min_pyr_height =
        AOMMIN(gf_cfg->gf_min_pyr_height, gf_cfg->gf_max_pyr_height);
  }

  // Allocation of mi buffers.
  alloc_mb_mode_info_buffers(cpi);

  cpi->skip_tpl_setup_stats = 0;
#if !CONFIG_REALTIME_ONLY
  if (oxcf->pass != AOM_RC_FIRST_PASS) {
    TplParams *const tpl_data = &cpi->ppi->tpl_data;
    if (tpl_data->tpl_stats_pool[0] == NULL) {
      av1_setup_tpl_buffers(cpi->ppi, &cm->mi_params, oxcf->frm_dim_cfg.width,
                            oxcf->frm_dim_cfg.height, 0,
                            oxcf->gf_cfg.lag_in_frames);
    }
  }
  cpi->twopass_frame.this_frame = NULL;
  const int use_one_pass_rt_params = is_one_pass_rt_params(cpi);
  if (!use_one_pass_rt_params && !is_stat_generation_stage(cpi)) {
#if CONFIG_COLLECT_COMPONENT_TIMING
    start_timing(cpi, av1_get_second_pass_params_time);
#endif

    // Initialise frame_level_rate_correction_factors with value previous
    // to the parallel frames.
    if (cpi->ppi->gf_group.frame_parallel_level[cpi->gf_frame_index] > 0) {
      for (int i = 0; i < RATE_FACTOR_LEVELS; i++) {
        cpi->rc.frame_level_rate_correction_factors[i] =
#if CONFIG_FPMT_TEST
            (cpi->ppi->fpmt_unit_test_cfg == PARALLEL_SIMULATION_ENCODE)
                ? cpi->ppi->p_rc.temp_rate_correction_factors[i]
                :
#endif  // CONFIG_FPMT_TEST
                cpi->ppi->p_rc.rate_correction_factors[i];
      }
    }

    // copy mv_stats from ppi to frame_level cpi.
    cpi->mv_stats = cpi->ppi->mv_stats;
    av1_get_second_pass_params(cpi, &frame_params, *frame_flags);
#if CONFIG_COLLECT_COMPONENT_TIMING
    end_timing(cpi, av1_get_second_pass_params_time);
#endif
  }
#endif

  if (!is_stat_generation_stage(cpi)) {
    // TODO(jingning): fwd key frame always uses show existing frame?
    if (gf_group->update_type[cpi->gf_frame_index] == OVERLAY_UPDATE &&
        gf_group->refbuf_state[cpi->gf_frame_index] == REFBUF_RESET) {
      frame_params.show_existing_frame = 1;
    } else {
      frame_params.show_existing_frame =
          (cpi->ppi->show_existing_alt_ref &&
           gf_group->update_type[cpi->gf_frame_index] == OVERLAY_UPDATE) ||
          gf_group->update_type[cpi->gf_frame_index] == INTNL_OVERLAY_UPDATE;
    }
    frame_params.show_existing_frame &= allow_show_existing(cpi, *frame_flags);

    // Reset show_existing_alt_ref decision to 0 after it is used.
    if (gf_group->update_type[cpi->gf_frame_index] == OVERLAY_UPDATE) {
      cpi->ppi->show_existing_alt_ref = 0;
    }
  } else {
    frame_params.show_existing_frame = 0;
  }

  struct lookahead_entry *source = NULL;
  struct lookahead_entry *last_source = NULL;
  if (frame_params.show_existing_frame) {
    source = av1_lookahead_peek(cpi->ppi->lookahead, 0, cpi->compressor_stage);
    *pop_lookahead = 1;
    frame_params.show_frame = 1;
  } else {
    source = choose_frame_source(cpi, &flush, pop_lookahead, &last_source,
                                 &frame_params);
  }

  if (source == NULL) {  // If no source was found, we can't encode a frame.
#if !CONFIG_REALTIME_ONLY
    if (flush && oxcf->pass == AOM_RC_FIRST_PASS &&
        !cpi->ppi->twopass.first_pass_done) {
      av1_end_first_pass(cpi); /* get last stats packet */
      cpi->ppi->twopass.first_pass_done = 1;
    }
#endif
    return -1;
  }

  // reset src_offset to allow actual encode call for this frame to get its
  // source.
  gf_group->src_offset[cpi->gf_frame_index] = 0;

  // Source may be changed if temporal filtered later.
  frame_input.source = &source->img;
  frame_input.last_source = last_source != NULL ? &last_source->img : NULL;
  frame_input.ts_duration = source->ts_end - source->ts_start;
  // Save unfiltered source. It is used in av1_get_second_pass_params().
  cpi->unfiltered_source = frame_input.source;

  *time_stamp = source->ts_start;
  *time_end = source->ts_end;
  if (source->ts_start < cpi->time_stamps.first_ts_start) {
    cpi->time_stamps.first_ts_start = source->ts_start;
    cpi->time_stamps.prev_ts_end = source->ts_start;
  }

  av1_apply_encoding_flags(cpi, source->flags);
  *frame_flags = (source->flags & AOM_EFLAG_FORCE_KF) ? FRAMEFLAGS_KEY : 0;

#if CONFIG_FPMT_TEST
  if (cpi->ppi->fpmt_unit_test_cfg == PARALLEL_SIMULATION_ENCODE) {
    if (cpi->ppi->gf_group.frame_parallel_level[cpi->gf_frame_index] > 0) {
      cpi->framerate = cpi->temp_framerate;
    }
  }
#endif  // CONFIG_FPMT_TEST

  // Shown frames and arf-overlay frames need frame-rate considering
  if (frame_params.show_frame)
    adjust_frame_rate(cpi, source->ts_start, source->ts_end);

  if (!frame_params.show_existing_frame) {
    if (cpi->film_grain_table) {
      cm->cur_frame->film_grain_params_present = aom_film_grain_table_lookup(
          cpi->film_grain_table, *time_stamp, *time_end, 0 /* =erase */,
          &cm->film_grain_params);
    } else {
      cm->cur_frame->film_grain_params_present =
          cm->seq_params->film_grain_params_present;
    }
    // only one operating point supported now
    const int64_t pts64 = ticks_to_timebase_units(timestamp_ratio, *time_stamp);
    if (pts64 < 0 || pts64 > UINT32_MAX) return AOM_CODEC_ERROR;

    cm->frame_presentation_time = (uint32_t)pts64;
  }

#if CONFIG_COLLECT_COMPONENT_TIMING
  start_timing(cpi, av1_get_one_pass_rt_params_time);
#endif
#if CONFIG_REALTIME_ONLY
  av1_get_one_pass_rt_params(cpi, &frame_params, &frame_input, *frame_flags);
  if (use_rtc_reference_structure_one_layer(cpi))
    av1_set_rtc_reference_structure_one_layer(cpi, cpi->gf_frame_index == 0);
#else
  if (use_one_pass_rt_params) {
    av1_get_one_pass_rt_params(cpi, &frame_params, &frame_input, *frame_flags);
    if (use_rtc_reference_structure_one_layer(cpi))
      av1_set_rtc_reference_structure_one_layer(cpi, cpi->gf_frame_index == 0);
  }
#endif
#if CONFIG_COLLECT_COMPONENT_TIMING
  end_timing(cpi, av1_get_one_pass_rt_params_time);
#endif

  FRAME_UPDATE_TYPE frame_update_type =
      get_frame_update_type(gf_group, cpi->gf_frame_index);

  if (frame_params.show_existing_frame &&
      frame_params.frame_type != KEY_FRAME) {
    // Force show-existing frames to be INTER, except forward keyframes
    frame_params.frame_type = INTER_FRAME;
  }

  // Per-frame encode speed.  In theory this can vary, but things may have
  // been written assuming speed-level will not change within a sequence, so
  // this parameter should be used with caution.
  frame_params.speed = oxcf->speed;

  // Work out some encoding parameters specific to the pass:
  if (has_no_stats_stage(cpi) && oxcf->q_cfg.aq_mode == CYCLIC_REFRESH_AQ) {
    av1_cyclic_refresh_update_parameters(cpi);
  } else if (is_stat_generation_stage(cpi)) {
    cpi->td.mb.e_mbd.lossless[0] = is_lossless_requested(&oxcf->rc_cfg);
    // Current frame is coded as a key-frame for any of the following cases:
    // 1) First frame of a video
    // 2) For all-intra frame encoding
    // 3) When a key-frame is forced
    const int kf_requested =
        (cm->current_frame.frame_number == 0 ||
         oxcf->kf_cfg.key_freq_max == 0 || (*frame_flags & FRAMEFLAGS_KEY));
    if (kf_requested && frame_update_type != OVERLAY_UPDATE &&
        frame_update_type != INTNL_OVERLAY_UPDATE) {
      frame_params.frame_type = KEY_FRAME;
    } else {
      frame_params.frame_type = INTER_FRAME;
    }
  } else if (is_stat_consumption_stage(cpi)) {
#if CONFIG_MISMATCH_DEBUG
    mismatch_move_frame_idx_w();
#endif
#if TXCOEFF_COST_TIMER
    cm->txcoeff_cost_timer = 0;
    cm->txcoeff_cost_count = 0;
#endif
  }

  if (!is_stat_generation_stage(cpi))
    set_ext_overrides(cm, &frame_params, ext_flags);

  // Shown keyframes and S frames refresh all reference buffers
  const int force_refresh_all =
      ((frame_params.frame_type == KEY_FRAME && frame_params.show_frame) ||
       frame_params.frame_type == S_FRAME) &&
      !frame_params.show_existing_frame;

  av1_configure_buffer_updates(
      cpi, &frame_params.refresh_frame, frame_update_type,
      gf_group->refbuf_state[cpi->gf_frame_index], force_refresh_all);

  if (!is_stat_generation_stage(cpi)) {
    const YV12_BUFFER_CONFIG *ref_frame_buf[INTER_REFS_PER_FRAME];

    RefFrameMapPair ref_frame_map_pairs[REF_FRAMES];
    init_ref_map_pair(cpi, ref_frame_map_pairs);
    const int order_offset = gf_group->arf_src_offset[cpi->gf_frame_index];
    const int cur_frame_disp =
        cpi->common.current_frame.frame_number + order_offset;

    int get_ref_frames = 0;
#if CONFIG_FPMT_TEST
    get_ref_frames =
        (cpi->ppi->fpmt_unit_test_cfg == PARALLEL_SIMULATION_ENCODE) ? 1 : 0;
#endif  // CONFIG_FPMT_TEST
    if (get_ref_frames ||
        gf_group->frame_parallel_level[cpi->gf_frame_index] == 0) {
      if (!ext_flags->refresh_frame.update_pending) {
        av1_get_ref_frames(ref_frame_map_pairs, cur_frame_disp, cpi,
                           cpi->gf_frame_index, 1, cm->remapped_ref_idx);
      } else if (cpi->rtc_ref.set_ref_frame_config ||
                 use_rtc_reference_structure_one_layer(cpi)) {
        for (unsigned int i = 0; i < INTER_REFS_PER_FRAME; i++)
          cm->remapped_ref_idx[i] = cpi->rtc_ref.ref_idx[i];
      }
    }

    // Get the reference frames
    bool has_ref_frames = false;
    for (int i = 0; i < INTER_REFS_PER_FRAME; ++i) {
      const RefCntBuffer *ref_frame =
          get_ref_frame_buf(cm, ref_frame_priority_order[i]);
      ref_frame_buf[i] = ref_frame != NULL ? &ref_frame->buf : NULL;
      if (ref_frame != NULL) has_ref_frames = true;
    }
    if (!has_ref_frames && (frame_params.frame_type == INTER_FRAME ||
                            frame_params.frame_type == S_FRAME)) {
      return AOM_CODEC_ERROR;
    }

    // Work out which reference frame slots may be used.
    frame_params.ref_frame_flags =
        get_ref_frame_flags(&cpi->sf, is_one_pass_rt_params(cpi), ref_frame_buf,
                            ext_flags->ref_frame_flags);

    // Set primary_ref_frame of non-reference frames as PRIMARY_REF_NONE.
    if (cpi->ppi->gf_group.is_frame_non_ref[cpi->gf_frame_index]) {
      frame_params.primary_ref_frame = PRIMARY_REF_NONE;
    } else {
      frame_params.primary_ref_frame =
          choose_primary_ref_frame(cpi, &frame_params);
    }

    frame_params.order_offset = gf_group->arf_src_offset[cpi->gf_frame_index];

    // Call av1_get_refresh_frame_flags() if refresh index not available.
    if (!cpi->refresh_idx_available) {
      frame_params.refresh_frame_flags = av1_get_refresh_frame_flags(
          cpi, &frame_params, frame_update_type, cpi->gf_frame_index,
          cur_frame_disp, ref_frame_map_pairs);
    } else {
      assert(cpi->ref_refresh_index != INVALID_IDX);
      frame_params.refresh_frame_flags = (1 << cpi->ref_refresh_index);
    }

    // Make the frames marked as is_frame_non_ref to non-reference frames.
    if (gf_group->is_frame_non_ref[cpi->gf_frame_index])
      frame_params.refresh_frame_flags = 0;

    frame_params.existing_fb_idx_to_show = INVALID_IDX;
    // Find the frame buffer to show based on display order.
    if (frame_params.show_existing_frame) {
      for (int frame = 0; frame < REF_FRAMES; frame++) {
        const RefCntBuffer *const buf = cm->ref_frame_map[frame];
        if (buf == NULL) continue;
        const int frame_order = (int)buf->display_order_hint;
        if (frame_order == cur_frame_disp)
          frame_params.existing_fb_idx_to_show = frame;
      }
    }
  }

  // The way frame_params->remapped_ref_idx is setup is a placeholder.
  // Currently, reference buffer assignment is done by update_ref_frame_map()
  // which is called by high-level strategy AFTER encoding a frame.  It
  // modifies cm->remapped_ref_idx.  If you want to use an alternative method
  // to determine reference buffer assignment, just put your assignments into
  // frame_params->remapped_ref_idx here and they will be used when encoding
  // this frame.  If frame_params->remapped_ref_idx is setup independently of
  // cm->remapped_ref_idx then update_ref_frame_map() will have no effect.
  memcpy(frame_params.remapped_ref_idx, cm->remapped_ref_idx,
         REF_FRAMES * sizeof(*cm->remapped_ref_idx));

  cpi->td.mb.delta_qindex = 0;

  if (!frame_params.show_existing_frame) {
    cm->quant_params.using_qmatrix = oxcf->q_cfg.using_qm;
  }

#if CONFIG_REALTIME_ONLY
  if (av1_encode(cpi, dest, &frame_input, &frame_params, &frame_results) !=
      AOM_CODEC_OK) {
    return AOM_CODEC_ERROR;
  }
#else
  if (has_no_stats_stage(cpi) && oxcf->mode == REALTIME &&
      gf_cfg->lag_in_frames == 0) {
    if (av1_encode(cpi, dest, &frame_input, &frame_params, &frame_results) !=
        AOM_CODEC_OK) {
      return AOM_CODEC_ERROR;
    }
  } else if (denoise_and_encode(cpi, dest, &frame_input, &frame_params,
                                &frame_results) != AOM_CODEC_OK) {
    return AOM_CODEC_ERROR;
  }
#endif  // CONFIG_REALTIME_ONLY

  // This is used in rtc temporal filter case. Use true source in the PSNR
  // calculation.
  if (is_psnr_calc_enabled(cpi) && cpi->sf.rt_sf.use_rtc_tf &&
      cpi->common.current_frame.frame_type != KEY_FRAME) {
    assert(cpi->orig_source.buffer_alloc_sz > 0);
    cpi->source = &cpi->orig_source;
  }

  if (!is_stat_generation_stage(cpi)) {
    // First pass doesn't modify reference buffer assignment or produce frame
    // flags
    update_frame_flags(&cpi->common, &cpi->refresh_frame, frame_flags);
    set_additional_frame_flags(cm, frame_flags);
  }

#if !CONFIG_REALTIME_ONLY
#if TXCOEFF_COST_TIMER
  if (!is_stat_generation_stage(cpi)) {
    cm->cum_txcoeff_cost_timer += cm->txcoeff_cost_timer;
    fprintf(stderr,
            "\ntxb coeff cost block number: %ld, frame time: %ld, cum time %ld "
            "in us\n",
            cm->txcoeff_cost_count, cm->txcoeff_cost_timer,
            cm->cum_txcoeff_cost_timer);
  }
#endif
#endif  // !CONFIG_REALTIME_ONLY

#if CONFIG_TUNE_VMAF
  if (!is_stat_generation_stage(cpi) &&
      (oxcf->tune_cfg.tuning >= AOM_TUNE_VMAF_WITH_PREPROCESSING &&
       oxcf->tune_cfg.tuning <= AOM_TUNE_VMAF_NEG_MAX_GAIN)) {
    av1_update_vmaf_curve(cpi);
  }
#endif

  // Unpack frame_results:
  *size = frame_results.size;

  // Leave a signal for a higher level caller about if this frame is droppable
  if (*size > 0) {
    cpi->droppable =
        is_frame_droppable(&cpi->rtc_ref, &ext_flags->refresh_frame);
  }

  return AOM_CODEC_OK;
}