/*
 *  Copyright (c) 2020 The WebRTC 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 "api/units/time_delta.h"
#include "modules/video_coding/utility/frame_sampler.h"
#ifdef RTC_ENABLE_VP9

#include "modules/video_coding/codecs/vp9/libvpx_vp9_encoder.h"

#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <iterator>
#include <memory>
#include <numeric>
#include <optional>
#include <span>
#include <string>
#include <utility>
#include <vector>

#include "absl/algorithm/container.h"
#include "absl/container/inlined_vector.h"
#include "api/environment/environment.h"
#include "api/fec_controller_override.h"
#include "api/field_trials_view.h"
#include "api/scoped_refptr.h"
#include "api/transport/rtp/dependency_descriptor.h"
#include "api/video/encoded_image.h"
#include "api/video/i010_buffer.h"
#include "api/video/render_resolution.h"
#include "api/video/video_bitrate_allocation.h"
#include "api/video/video_bitrate_allocator.h"
#include "api/video/video_codec_constants.h"
#include "api/video/video_codec_type.h"
#include "api/video/video_frame.h"
#include "api/video/video_frame_buffer.h"
#include "api/video/video_frame_type.h"
#include "api/video_codecs/scalability_mode.h"
#include "api/video_codecs/video_codec.h"
#include "api/video_codecs/video_encoder.h"
#include "api/video_codecs/vp9_profile.h"
#include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
#include "modules/video_coding/codecs/interface/common_constants.h"
#include "modules/video_coding/codecs/interface/libvpx_interface.h"
#include "modules/video_coding/codecs/vp9/include/vp9.h"
#include "modules/video_coding/codecs/vp9/include/vp9_globals.h"
#include "modules/video_coding/include/video_codec_interface.h"
#include "modules/video_coding/include/video_error_codes.h"
#include "modules/video_coding/svc/create_scalability_structure.h"
#include "modules/video_coding/svc/scalability_mode_util.h"
#include "modules/video_coding/svc/scalable_video_controller.h"
#include "modules/video_coding/svc/scalable_video_controller_no_layering.h"
#include "modules/video_coding/svc/simulcast_to_svc_converter.h"
#include "modules/video_coding/svc/svc_rate_allocator.h"
#include "modules/video_coding/utility/framerate_controller_deprecated.h"
#include "modules/video_coding/utility/simulcast_rate_allocator.h"
#include "rtc_base/checks.h"
#include "rtc_base/containers/flat_map.h"
#include "rtc_base/experiments/field_trial_list.h"
#include "rtc_base/experiments/field_trial_parser.h"
#include "rtc_base/experiments/rate_control_settings.h"
#include "rtc_base/logging.h"
#include "rtc_base/numerics/safe_conversions.h"
#include "rtc_base/strings/string_builder.h"
#include "rtc_base/trace_event.h"
#include "third_party/libvpx/source/libvpx/vpx/vp8cx.h"
#include "third_party/libvpx/source/libvpx/vpx/vpx_encoder.h"
#include "third_party/libvpx/source/libvpx/vpx/vpx_image.h"

#if (defined(WEBRTC_ARCH_ARM) || defined(WEBRTC_ARCH_ARM64)) && \
    (defined(WEBRTC_ANDROID) || defined(WEBRTC_IOS))
#define MOBILE_ARM
#endif

namespace webrtc {

namespace {
// Maps from gof_idx to encoder internal reference frame buffer index. These
// maps work for 1,2 and 3 temporal layers with GOF length of 1,2 and 4 frames.
uint8_t kRefBufIdx[4] = {0, 0, 0, 1};
uint8_t kUpdBufIdx[4] = {0, 0, 1, 0};

// Maximum allowed PID difference for differnet per-layer frame-rate case.
const int kMaxAllowedPidDiff = 30;

namespace variable_framerate_screenshare {
constexpr double kMinFps = 5.0;
constexpr int kMinQP = 32;
constexpr int kUndershootPct = 30;
constexpr int kFramesBeforeSteadyState = 5;
}  // namespace variable_framerate_screenshare

// TODO(ilink): Tune these thresholds further.
// Selected using ConverenceMotion_1280_720_50.yuv clip.
// No toggling observed on any link capacity from 100-2000kbps.
// HD was reached consistently when link capacity was 1500kbps.
// Set resolutions are a bit more conservative than svc_config.cc sets, e.g.
// for 300kbps resolution converged to 270p instead of 360p.
constexpr int kLowVp9QpThreshold = 149;
constexpr int kHighVp9QpThreshold = 205;

std::pair<size_t, size_t> GetActiveLayers(
    const VideoBitrateAllocation& allocation) {
  for (size_t sl_idx = 0; sl_idx < kMaxSpatialLayers; ++sl_idx) {
    if (allocation.GetSpatialLayerSum(sl_idx) > 0) {
      size_t last_layer = sl_idx + 1;
      while (last_layer < kMaxSpatialLayers &&
             allocation.GetSpatialLayerSum(last_layer) > 0) {
        ++last_layer;
      }
      return std::make_pair(sl_idx, last_layer);
    }
  }
  return {0, 0};
}

std::unique_ptr<ScalableVideoController> CreateVp9ScalabilityStructure(
    const VideoCodec& codec) {
  int num_spatial_layers = codec.VP9().numberOfSpatialLayers;
  int num_temporal_layers =
      std::max(1, int{codec.VP9().numberOfTemporalLayers});
  if (num_spatial_layers == 1 && num_temporal_layers == 1) {
    return std::make_unique<ScalableVideoControllerNoLayering>();
  }

  StringBuilder ss;
  if (codec.mode == VideoCodecMode::kScreensharing) {
    // TODO(bugs.webrtc.org/11999): Compose names of the structures when they
    // are implemented.
    return nullptr;
  } else if (codec.VP9().interLayerPred == InterLayerPredMode::kOn ||
             num_spatial_layers == 1) {
    ss << "L" << num_spatial_layers << "T" << num_temporal_layers;
  } else if (codec.VP9().interLayerPred == InterLayerPredMode::kOnKeyPic) {
    ss << "L" << num_spatial_layers << "T" << num_temporal_layers << "_KEY";
  } else {
    RTC_DCHECK_EQ(codec.VP9().interLayerPred, InterLayerPredMode::kOff);
    ss << "S" << num_spatial_layers << "T" << num_temporal_layers;
  }

  // Check spatial ratio.
  if (num_spatial_layers > 1) {
    if (codec.width != codec.spatialLayers[num_spatial_layers - 1].width ||
        codec.height != codec.spatialLayers[num_spatial_layers - 1].height) {
      RTC_LOG(LS_WARNING)
          << "Top layer resolution expected to match overall resolution";
      return nullptr;
    }
    // Check if the ratio is one of the supported.
    int numerator;
    int denominator;
    if (codec.spatialLayers[1].width == 2 * codec.spatialLayers[0].width) {
      numerator = 1;
      denominator = 2;
      // no suffix for 1:2 ratio.
    } else if (2 * codec.spatialLayers[1].width ==
               3 * codec.spatialLayers[0].width) {
      numerator = 2;
      denominator = 3;
      ss << "h";
    } else {
      RTC_LOG(LS_WARNING) << "Unsupported scalability ratio "
                          << codec.spatialLayers[0].width << ":"
                          << codec.spatialLayers[1].width;
      return nullptr;
    }
    // Validate ratio is consistent for all spatial layer transitions.
    for (int sid = 1; sid < num_spatial_layers; ++sid) {
      if (codec.spatialLayers[sid].width * numerator !=
              codec.spatialLayers[sid - 1].width * denominator ||
          codec.spatialLayers[sid].height * numerator !=
              codec.spatialLayers[sid - 1].height * denominator) {
        RTC_LOG(LS_WARNING) << "Inconsistent scalability ratio " << numerator
                            << ":" << denominator;
        return nullptr;
      }
    }
  }

  std::string name = ss.Release();
  std::optional<ScalabilityMode> scalability_mode =
      ScalabilityModeFromString(name);
  if (!scalability_mode.has_value()) {
    RTC_LOG(LS_WARNING) << "Invalid scalability mode " << name;
    return nullptr;
  }
  auto scalability_structure_controller =
      CreateScalabilityStructure(*scalability_mode);
  if (scalability_structure_controller == nullptr) {
    RTC_LOG(LS_WARNING) << "Unsupported scalability structure " << name;
  } else {
    RTC_LOG(LS_INFO) << "Created scalability structure " << name;
  }
  return scalability_structure_controller;
}

vpx_svc_ref_frame_config_t Vp9References(
    std::span<const ScalableVideoController::LayerFrameConfig> layers) {
  vpx_svc_ref_frame_config_t ref_config = {};
  for (const ScalableVideoController::LayerFrameConfig& layer_frame : layers) {
    const auto& buffers = layer_frame.Buffers();
    RTC_DCHECK_LE(buffers.size(), 3);
    int sid = layer_frame.SpatialId();
    if (!buffers.empty()) {
      ref_config.lst_fb_idx[sid] = buffers[0].id;
      ref_config.reference_last[sid] = buffers[0].referenced;
      if (buffers[0].updated) {
        ref_config.update_buffer_slot[sid] |= (1 << buffers[0].id);
      }
    }
    if (buffers.size() > 1) {
      ref_config.gld_fb_idx[sid] = buffers[1].id;
      ref_config.reference_golden[sid] = buffers[1].referenced;
      if (buffers[1].updated) {
        ref_config.update_buffer_slot[sid] |= (1 << buffers[1].id);
      }
    }
    if (buffers.size() > 2) {
      ref_config.alt_fb_idx[sid] = buffers[2].id;
      ref_config.reference_alt_ref[sid] = buffers[2].referenced;
      if (buffers[2].updated) {
        ref_config.update_buffer_slot[sid] |= (1 << buffers[2].id);
      }
    }
  }
  // TODO(bugs.webrtc.org/11999): Fill ref_config.duration
  return ref_config;
}

bool AllowDenoising() {
#ifdef MOBILE_ARM
  // Keep the denoiser disabled on mobile ARM devices. It increases encode time
  // by up to 16%.
  return false;
#else
  return true;
#endif
}

}  // namespace

void LibvpxVp9Encoder::EncoderOutputCodedPacketCallback(vpx_codec_cx_pkt* pkt,
                                                        void* user_data) {
  LibvpxVp9Encoder* enc = static_cast<LibvpxVp9Encoder*>(user_data);
  enc->GetEncodedLayerFrame(pkt);
}

LibvpxVp9Encoder::LibvpxVp9Encoder(const Environment& env,
                                   Vp9EncoderSettings settings,
                                   std::unique_ptr<LibvpxInterface> interface)
    : env_(env),
      libvpx_(std::move(interface)),
      encoded_image_(),
      encoded_complete_callback_(nullptr),
      profile_(settings.profile),
      inited_(false),
      timestamp_(0),
      rc_max_intra_target_(0),
      encoder_(nullptr),
      config_(nullptr),
      raw_(nullptr),
      input_image_(nullptr),
      force_key_frame_(true),
      pics_since_key_(0),
      num_temporal_layers_(0),
      num_spatial_layers_(0),
      num_active_spatial_layers_(0),
      first_active_layer_(0),
      layer_deactivation_requires_key_frame_(env.field_trials().IsEnabled(
          "WebRTC-Vp9IssueKeyFrameOnLayerDeactivation")),
      is_svc_(false),
      inter_layer_pred_(InterLayerPredMode::kOn),
      trusted_rate_controller_(RateControlSettings(env.field_trials())
                                   .LibvpxVp9TrustedRateController()),
      first_frame_in_picture_(true),
      ss_info_needed_(false),
      force_all_active_layers_(false),
      enable_svc_for_simulcast_(
          !env.field_trials().IsDisabled("WebRTC-VP9-SvcForSimulcast")),
      is_flexible_mode_(false),
      variable_framerate_controller_(variable_framerate_screenshare::kMinFps),
      quality_scaler_experiment_(ParseQualityScalerConfig(env.field_trials())),
      performance_flags_(ParsePerformanceFlagsFromTrials(env.field_trials())),
      num_steady_state_frames_(0),
      config_changed_(true),
      encoder_info_override_(env.field_trials()),
      psnr_frame_sampler_(FrameSampler::kDefaultPsnrFrameSamplingInterval),
      post_encode_frame_drop_(!env.field_trials().IsDisabled(
          "WebRTC-LibvpxVp9Encoder-PostEncodeFrameDrop")) {
  codec_ = {};
  memset(&svc_params_, 0, sizeof(vpx_svc_extra_cfg_t));
}

LibvpxVp9Encoder::~LibvpxVp9Encoder() {
  Release();
}

void LibvpxVp9Encoder::SetFecControllerOverride(FecControllerOverride*) {
  // Ignored.
}

int LibvpxVp9Encoder::Release() {
  int ret_val = WEBRTC_VIDEO_CODEC_OK;

  if (encoder_ != nullptr) {
    if (inited_) {
      if (libvpx_->codec_destroy(encoder_)) {
        ret_val = WEBRTC_VIDEO_CODEC_MEMORY;
      }
    }
    delete encoder_;
    encoder_ = nullptr;
  }
  if (config_ != nullptr) {
    delete config_;
    config_ = nullptr;
  }
  if (raw_ != nullptr) {
    libvpx_->img_free(raw_);
    raw_ = nullptr;
  }
  inited_ = false;
  return ret_val;
}

bool LibvpxVp9Encoder::SetSvcRates(
    const VideoBitrateAllocation& bitrate_allocation) {
  std::pair<size_t, size_t> current_layers =
      GetActiveLayers(current_bitrate_allocation_);
  std::pair<size_t, size_t> new_layers = GetActiveLayers(bitrate_allocation);

  const bool layer_activation_requires_key_frame =
      inter_layer_pred_ == InterLayerPredMode::kOff ||
      inter_layer_pred_ == InterLayerPredMode::kOnKeyPic;
  const bool lower_layers_enabled = new_layers.first < current_layers.first;
  const bool higher_layers_enabled = new_layers.second > current_layers.second;
  const bool disabled_layers = new_layers.first > current_layers.first ||
                               new_layers.second < current_layers.second;

  if (lower_layers_enabled ||
      (higher_layers_enabled && layer_activation_requires_key_frame) ||
      (disabled_layers && layer_deactivation_requires_key_frame_)) {
    force_key_frame_ = true;
  }

  if (current_layers != new_layers) {
    ss_info_needed_ = true;
  }

  config_->rc_target_bitrate = bitrate_allocation.get_sum_kbps();

  for (size_t sl_idx = 0; sl_idx < num_spatial_layers_; ++sl_idx) {
    if (config_->ss_target_bitrate[sl_idx] == 0) {
      // Reset frame rate controller if layer is resumed after pause.
      framerate_controller_[sl_idx].Reset();
    }

    config_->ss_target_bitrate[sl_idx] =
        bitrate_allocation.GetSpatialLayerSum(sl_idx) / 1000;

    for (size_t tl_idx = 0; tl_idx < num_temporal_layers_; ++tl_idx) {
      config_->layer_target_bitrate[sl_idx * num_temporal_layers_ + tl_idx] =
          bitrate_allocation.GetTemporalLayerSum(sl_idx, tl_idx) / 1000;
    }

    framerate_controller_[sl_idx].SetTargetRate(
        num_spatial_layers_ > 1 ? codec_.spatialLayers[sl_idx].maxFramerate
                                : codec_.maxFramerate);
  }

  num_active_spatial_layers_ = 0;
  first_active_layer_ = 0;
  bool seen_active_layer = false;
  bool expect_no_more_active_layers = false;
  for (int i = 0; i < num_spatial_layers_; ++i) {
    if (config_->ss_target_bitrate[i] > 0) {
      RTC_DCHECK(!expect_no_more_active_layers) << "Only middle layer is "
                                                   "deactivated.";
      if (!seen_active_layer) {
        first_active_layer_ = i;
      }
      num_active_spatial_layers_ = i + 1;
      seen_active_layer = true;
    } else {
      expect_no_more_active_layers = seen_active_layer;
    }
  }

  if (seen_active_layer && performance_flags_.use_per_layer_speed) {
    bool denoiser_on =
        AllowDenoising() && codec_.VP9()->denoisingOn &&
        performance_flags_by_spatial_index_[num_active_spatial_layers_ - 1]
            .allow_denoising;
    libvpx_->codec_control(encoder_, VP9E_SET_NOISE_SENSITIVITY,
                           denoiser_on ? 1 : 0);
  }

  if (higher_layers_enabled && !force_key_frame_) {
    // Prohibit drop of all layers for the next frame, so newly enabled
    // layer would have a valid spatial reference.
    for (size_t i = 0; i < num_spatial_layers_; ++i) {
      svc_drop_frame_.framedrop_thresh[i] = 0;
    }
    force_all_active_layers_ = true;
  }

  if (svc_controller_) {
    for (int sid = 0; sid < num_spatial_layers_; ++sid) {
      // Bitrates in `layer_target_bitrate` are accumulated for each temporal
      // layer but in `VideoBitrateAllocation` they should be separated.
      int previous_bitrate_kbps = 0;
      for (int tid = 0; tid < num_temporal_layers_; ++tid) {
        int accumulated_bitrate_kbps =
            config_->layer_target_bitrate[sid * num_temporal_layers_ + tid];
        int single_layer_bitrate_kbps =
            accumulated_bitrate_kbps - previous_bitrate_kbps;
        RTC_DCHECK_GE(single_layer_bitrate_kbps, 0);
        current_bitrate_allocation_.SetBitrate(
            sid, tid, single_layer_bitrate_kbps * 1'000);
        previous_bitrate_kbps = accumulated_bitrate_kbps;
      }
    }
    svc_controller_->OnRatesUpdated(current_bitrate_allocation_);
  } else {
    current_bitrate_allocation_ = bitrate_allocation;
  }
  config_changed_ = true;
  return true;
}

void LibvpxVp9Encoder::AdjustScalingFactorsForTopActiveLayer() {
  if (num_active_spatial_layers_ == 0 || num_spatial_layers_ <= 1 || !is_svc_ ||
      static_cast<int>(config_->g_w) ==
          codec_.spatialLayers[num_active_spatial_layers_ - 1].width) {
    return;
  }

  config_->g_w = codec_.spatialLayers[num_active_spatial_layers_ - 1].width;
  config_->g_h = codec_.spatialLayers[num_active_spatial_layers_ - 1].height;

  // Recalculate scaling factors ignoring top inactive layers.
  // Divide all by scaling factor of the last active layer.
  for (int i = 0; i < num_active_spatial_layers_; ++i) {
    int n = scaling_factors_num_[i] *
            scaling_factors_den_[num_active_spatial_layers_ - 1];
    int d = scaling_factors_den_[i] *
            scaling_factors_num_[num_active_spatial_layers_ - 1];
    int gcd = std::gcd(n, d);
    svc_params_.scaling_factor_num[i] = n / gcd;
    svc_params_.scaling_factor_den[i] = d / gcd;
  }
  for (int i = num_active_spatial_layers_; i < num_spatial_layers_; ++i) {
    svc_params_.scaling_factor_num[i] = 1;
    svc_params_.scaling_factor_den[i] = 1;
  }

  libvpx_->codec_control(encoder_, VP9E_SET_SVC_PARAMETERS, &svc_params_);
  config_changed_ = true;
}

void LibvpxVp9Encoder::DisableSpatialLayer(int sid) {
  RTC_DCHECK_LT(sid, num_spatial_layers_);
  if (config_->ss_target_bitrate[sid] == 0) {
    return;
  }
  config_->ss_target_bitrate[sid] = 0;
  for (int tid = 0; tid < num_temporal_layers_; ++tid) {
    config_->layer_target_bitrate[sid * num_temporal_layers_ + tid] = 0;
  }
  config_changed_ = true;
}

void LibvpxVp9Encoder::EnableSpatialLayer(int sid) {
  RTC_DCHECK_LT(sid, num_spatial_layers_);
  if (config_->ss_target_bitrate[sid] > 0) {
    return;
  }
  for (int tid = 0; tid < num_temporal_layers_; ++tid) {
    config_->layer_target_bitrate[sid * num_temporal_layers_ + tid] =
        current_bitrate_allocation_.GetTemporalLayerSum(sid, tid) / 1000;
  }
  config_->ss_target_bitrate[sid] =
      current_bitrate_allocation_.GetSpatialLayerSum(sid) / 1000;
  RTC_DCHECK_GT(config_->ss_target_bitrate[sid], 0);
  config_changed_ = true;
}

void LibvpxVp9Encoder::SetActiveSpatialLayers() {
  // Svc controller may decide to skip a frame at certain spatial layer even
  // when bitrate for it is non-zero, however libvpx uses configured bitrate as
  // a signal which layers should be produced.
  RTC_DCHECK(svc_controller_);
  RTC_DCHECK(!layer_frames_.empty());
  RTC_DCHECK(absl::c_is_sorted(
      layer_frames_, [](const ScalableVideoController::LayerFrameConfig& lhs,
                        const ScalableVideoController::LayerFrameConfig& rhs) {
        return lhs.SpatialId() < rhs.SpatialId();
      }));

  auto frame_it = layer_frames_.begin();
  for (int sid = 0; sid < num_spatial_layers_; ++sid) {
    if (frame_it != layer_frames_.end() && frame_it->SpatialId() == sid) {
      EnableSpatialLayer(sid);
      ++frame_it;
    } else {
      DisableSpatialLayer(sid);
    }
  }
}

void LibvpxVp9Encoder::SetRates(const RateControlParameters& parameters) {
  if (!inited_) {
    RTC_LOG(LS_WARNING) << "SetRates() called while uninitialized.";
    return;
  }
  if (encoder_->err) {
    RTC_LOG(LS_WARNING) << "Encoder in error state: " << encoder_->err;
    return;
  }
  if (parameters.framerate_fps < 1.0) {
    RTC_LOG(LS_WARNING) << "Unsupported framerate: "
                        << parameters.framerate_fps;
    return;
  }

  codec_.maxFramerate = static_cast<uint32_t>(parameters.framerate_fps + 0.5);

  bool res = SetSvcRates(parameters.bitrate);
  RTC_DCHECK(res) << "Failed to set new bitrate allocation";
  AdjustScalingFactorsForTopActiveLayer();
  config_changed_ = true;
}

// TODO(eladalon): s/inst/codec_settings/g.
int LibvpxVp9Encoder::InitEncode(const VideoCodec* inst,
                                 const Settings& settings) {
  if (inst == nullptr) {
    return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
  }
  if (inst->maxFramerate < 1) {
    return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
  }
  // Allow zero to represent an unspecified maxBitRate
  if (inst->maxBitrate > 0 && inst->startBitrate > inst->maxBitrate) {
    return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
  }
  if (inst->width < 1 || inst->height < 1) {
    return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
  }
  if (settings.number_of_cores < 1) {
    return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
  }
  if (inst->VP9().numberOfTemporalLayers > 3) {
    return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
  }
  // libvpx probably does not support more than 3 spatial layers.
  if (inst->VP9().numberOfSpatialLayers > 3) {
    return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
  }

  int ret_val = Release();
  if (ret_val < 0) {
    return ret_val;
  }
  if (encoder_ == nullptr) {
    encoder_ = new vpx_codec_ctx_t;
    memset(encoder_, 0, sizeof(*encoder_));
  }
  if (config_ == nullptr) {
    config_ = new vpx_codec_enc_cfg_t;
    memset(config_, 0, sizeof(*config_));
  }
  timestamp_ = 0;
  if (&codec_ != inst) {
    codec_ = *inst;
  }

  if (enable_svc_for_simulcast_ && codec_.numberOfSimulcastStreams > 1) {
    if (!SimulcastToSvcConverter::IsConfigSupported(codec_)) {
      return WEBRTC_VIDEO_CODEC_ERR_SIMULCAST_PARAMETERS_NOT_SUPPORTED;
    }
    RTC_LOG(LS_INFO) << "Rewriting simulcast config to SVC.";
    current_bitrate_allocation_ =
        SimulcastRateAllocator(env_, codec_)
            .Allocate(VideoBitrateAllocationParameters(
                codec_.startBitrate * 1000, codec_.maxFramerate));
    simulcast_to_svc_converter_.emplace(codec_);
    codec_ = simulcast_to_svc_converter_->GetConfig();
  } else {
    current_bitrate_allocation_ =
        SvcRateAllocator(codec_, env_.field_trials())
            .Allocate(VideoBitrateAllocationParameters(
                codec_.startBitrate * 1000, codec_.maxFramerate));
    simulcast_to_svc_converter_ = std::nullopt;
  }

  memset(&svc_params_, 0, sizeof(vpx_svc_extra_cfg_t));

  force_key_frame_ = true;
  pics_since_key_ = 0;

  scalability_mode_ = codec_.GetScalabilityMode();
  if (scalability_mode_.has_value()) {
    // Use settings from `ScalabilityMode` identifier.
    RTC_LOG(LS_INFO) << "Create scalability structure "
                     << ScalabilityModeToString(*scalability_mode_);
    svc_controller_ = CreateScalabilityStructure(*scalability_mode_);
    if (!svc_controller_) {
      RTC_LOG(LS_WARNING) << "Failed to create scalability structure.";
      return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
    }
    ScalableVideoController::StreamLayersConfig info =
        svc_controller_->StreamConfig();
    num_spatial_layers_ = info.num_spatial_layers;
    num_temporal_layers_ = info.num_temporal_layers;
    inter_layer_pred_ = ScalabilityModeToInterLayerPredMode(*scalability_mode_);
  } else {
    num_spatial_layers_ = codec_.VP9()->numberOfSpatialLayers;
    RTC_DCHECK_GT(num_spatial_layers_, 0);
    num_temporal_layers_ = codec_.VP9()->numberOfTemporalLayers;
    if (num_temporal_layers_ == 0) {
      num_temporal_layers_ = 1;
    }
    inter_layer_pred_ = codec_.VP9()->interLayerPred;
    svc_controller_ = CreateVp9ScalabilityStructure(codec_);
  }

  framerate_controller_ = std::vector<FramerateControllerDeprecated>(
      num_spatial_layers_, FramerateControllerDeprecated(codec_.maxFramerate));

  is_svc_ = (num_spatial_layers_ > 1 || num_temporal_layers_ > 1);

  // Populate encoder configuration with default values.
  if (libvpx_->codec_enc_config_default(vpx_codec_vp9_cx(), config_, 0)) {
    return WEBRTC_VIDEO_CODEC_ERROR;
  }

  switch (profile_) {
    case VP9Profile::kProfile0:
      config_->g_bit_depth = VPX_BITS_8;
      config_->g_profile = 0;
      config_->g_input_bit_depth = 8;
      break;
    case VP9Profile::kProfile1:
      // Encoding of profile 1 is not implemented. It would require extended
      // support for I444, I422, and I440 buffers.
      RTC_DCHECK_NOTREACHED();
      break;
    case VP9Profile::kProfile2:
      config_->g_bit_depth = VPX_BITS_10;
      config_->g_profile = 2;
      config_->g_input_bit_depth = 10;
      break;
    case VP9Profile::kProfile3:
      // Encoding of profile 3 is not implemented.
      RTC_DCHECK_NOTREACHED();
      break;
  }

  config_->g_w = codec_.width;
  config_->g_h = codec_.height;
  config_->rc_target_bitrate = codec_.startBitrate;  // in kbit/s
  config_->g_error_resilient = is_svc_ ? VPX_ERROR_RESILIENT_DEFAULT : 0;
  // Setting the time base of the codec.
  config_->g_timebase.num = 1;
  config_->g_timebase.den = kVideoPayloadTypeFrequency;
  config_->g_lag_in_frames = 0;  // 0- no frame lagging
  config_->g_threads = 1;
  // Rate control settings.
  config_->rc_dropframe_thresh = codec_.GetFrameDropEnabled() ? 30 : 0;
  config_->rc_end_usage = VPX_CBR;
  config_->g_pass = VPX_RC_ONE_PASS;
  config_->rc_min_quantizer =
      codec_.mode == VideoCodecMode::kScreensharing ? 8 : 2;
  config_->rc_max_quantizer = 52;
  config_->rc_undershoot_pct = 50;
  config_->rc_overshoot_pct = 50;
  config_->rc_buf_initial_sz = 500;
  config_->rc_buf_optimal_sz = 600;
  config_->rc_buf_sz = 1000;
  // Set the maximum target size of any key-frame.
  rc_max_intra_target_ = MaxIntraTarget(config_->rc_buf_optimal_sz);
  // Key-frame interval is enforced manually by this wrapper.
  config_->kf_mode = VPX_KF_DISABLED;
  // TODO(webm:1592): work-around for libvpx issue, as it can still
  // put some key-frames at will even in VPX_KF_DISABLED kf_mode.
  config_->kf_max_dist = codec_.VP9()->keyFrameInterval;
  config_->kf_min_dist = config_->kf_max_dist;
  if (quality_scaler_experiment_.enabled) {
    // In that experiment webrtc wide quality scaler is used instead of libvpx
    // internal scaler.
    config_->rc_resize_allowed = 0;
  } else {
    config_->rc_resize_allowed = codec_.VP9()->automaticResizeOn ? 1 : 0;
  }
  // Determine number of threads based on the image size and #cores.
  config_->g_threads =
      NumberOfThreads(config_->g_w, config_->g_h, settings.number_of_cores);

  is_flexible_mode_ = codec_.VP9()->flexibleMode;

  if (num_spatial_layers_ > 1 &&
      codec_.mode == VideoCodecMode::kScreensharing && !is_flexible_mode_) {
    RTC_LOG(LS_ERROR) << "Flexible mode is required for screenshare with "
                         "several spatial layers";
    return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
  }

  if (num_temporal_layers_ == 1) {
    gof_.SetGofInfoVP9(kTemporalStructureMode1);
    config_->temporal_layering_mode = VP9E_TEMPORAL_LAYERING_MODE_NOLAYERING;
    config_->ts_number_layers = 1;
    config_->ts_rate_decimator[0] = 1;
    config_->ts_periodicity = 1;
    config_->ts_layer_id[0] = 0;
  } else if (num_temporal_layers_ == 2) {
    gof_.SetGofInfoVP9(kTemporalStructureMode2);
    config_->temporal_layering_mode = VP9E_TEMPORAL_LAYERING_MODE_0101;
    config_->ts_number_layers = 2;
    config_->ts_rate_decimator[0] = 2;
    config_->ts_rate_decimator[1] = 1;
    config_->ts_periodicity = 2;
    config_->ts_layer_id[0] = 0;
    config_->ts_layer_id[1] = 1;
  } else if (num_temporal_layers_ == 3) {
    gof_.SetGofInfoVP9(kTemporalStructureMode3);
    config_->temporal_layering_mode = VP9E_TEMPORAL_LAYERING_MODE_0212;
    config_->ts_number_layers = 3;
    config_->ts_rate_decimator[0] = 4;
    config_->ts_rate_decimator[1] = 2;
    config_->ts_rate_decimator[2] = 1;
    config_->ts_periodicity = 4;
    config_->ts_layer_id[0] = 0;
    config_->ts_layer_id[1] = 2;
    config_->ts_layer_id[2] = 1;
    config_->ts_layer_id[3] = 2;
  } else {
    return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
  }

  config_->temporal_layering_mode = VP9E_TEMPORAL_LAYERING_MODE_BYPASS;
  if (num_temporal_layers_ > 1 && num_spatial_layers_ > 1 &&
      codec_.mode == VideoCodecMode::kScreensharing) {
    // External reference control for several temporal layers with different
    // frame rates on spatial layers is not implemented yet.
    return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
  }
  ref_buf_ = {};

  return InitAndSetControlSettings();
}

int LibvpxVp9Encoder::NumberOfThreads(int width,
                                      int height,
                                      int number_of_cores) {
  // Keep the number of encoder threads equal to the possible number of column
  // tiles, which is (1, 2, 4, 8). See comments below for VP9E_SET_TILE_COLUMNS.
  if (width * height >= 1280 * 720 && number_of_cores > 4) {
    return 4;
  } else if (width * height >= 640 * 360 && number_of_cores > 2) {
    return 2;
  } else {
// Use 2 threads for low res on mobile ARM.
#ifdef MOBILE_ARM
    if (width * height >= 320 * 180 && number_of_cores > 2) {
      return 2;
    }
#endif
    // 1 thread less than VGA.
    return 1;
  }
}

int LibvpxVp9Encoder::InitAndSetControlSettings() {
  // Set QP-min/max per spatial and temporal layer.
  int tot_num_layers = num_spatial_layers_ * num_temporal_layers_;
  scaling_factors_num_.resize(num_spatial_layers_);
  scaling_factors_den_.resize(num_spatial_layers_);
  for (int i = 0; i < tot_num_layers; ++i) {
    svc_params_.max_quantizers[i] = config_->rc_max_quantizer;
    svc_params_.min_quantizers[i] = config_->rc_min_quantizer;
  }
  config_->ss_number_layers = num_spatial_layers_;
  if (svc_controller_) {
    auto stream_config = svc_controller_->StreamConfig();
    for (int i = 0; i < stream_config.num_spatial_layers; ++i) {
      scaling_factors_num_[i] = svc_params_.scaling_factor_num[i] =
          stream_config.scaling_factor_num[i];
      scaling_factors_den_[i] = svc_params_.scaling_factor_den[i] =
          stream_config.scaling_factor_den[i];
    }
  } else if (num_spatial_layers_ > 1) {
    for (int i = 0; i < num_spatial_layers_; ++i) {
      const auto& layer = codec_.spatialLayers[i];
      RTC_CHECK_GT(layer.width, 0);
      const int scale_factor = codec_.width / layer.width;
      RTC_DCHECK_GT(scale_factor, 0);

      // Ensure scaler factor is integer.
      if (scale_factor * layer.width != codec_.width) {
        return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
      }

      // Ensure scale factor is the same in both dimensions.
      if (scale_factor * layer.height != codec_.height) {
        return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
      }

      // Ensure scale factor is power of two.
      const bool is_pow_of_two = (scale_factor & (scale_factor - 1)) == 0;
      if (!is_pow_of_two) {
        return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
      }

      scaling_factors_num_[i] = svc_params_.scaling_factor_num[i] = 1;
      scaling_factors_den_[i] = svc_params_.scaling_factor_den[i] =
          scale_factor;

      RTC_DCHECK_GT(codec_.spatialLayers[i].maxFramerate, 0);
      RTC_DCHECK_LE(codec_.spatialLayers[i].maxFramerate, codec_.maxFramerate);
      if (i > 0) {
        // Frame rate of high spatial layer is supposed to be equal or higher
        // than frame rate of low spatial layer.
        RTC_DCHECK_GE(codec_.spatialLayers[i].maxFramerate,
                      codec_.spatialLayers[i - 1].maxFramerate);
      }
    }
  }

  UpdatePerformanceFlags();
  RTC_DCHECK_EQ(performance_flags_by_spatial_index_.size(),
                static_cast<size_t>(num_spatial_layers_));

  // `current_bitrate_allocation_` is set in InitEncode and may have used
  // simulcast configuration.
  if (!SetSvcRates(current_bitrate_allocation_)) {
    return WEBRTC_VIDEO_CODEC_ERR_PARAMETER;
  }

  vpx_codec_flags_t flags =
      config_->g_bit_depth == VPX_BITS_8 ? 0 : VPX_CODEC_USE_HIGHBITDEPTH;

  const vpx_codec_err_t rv =
      libvpx_->codec_enc_init(encoder_, vpx_codec_vp9_cx(), config_, flags);
  if (rv != VPX_CODEC_OK) {
    RTC_LOG(LS_ERROR) << "Init error: " << libvpx_->codec_err_to_string(rv);
    return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
  }

  if (performance_flags_.use_per_layer_speed) {
    for (int si = 0; si < num_spatial_layers_; ++si) {
      svc_params_.speed_per_layer[si] =
          performance_flags_by_spatial_index_[si].base_layer_speed;
      svc_params_.loopfilter_ctrl[si] =
          performance_flags_by_spatial_index_[si].deblock_mode;
    }
    bool denoiser_on =
        AllowDenoising() && codec_.VP9()->denoisingOn &&
        performance_flags_by_spatial_index_[num_spatial_layers_ - 1]
            .allow_denoising;
    libvpx_->codec_control(encoder_, VP9E_SET_NOISE_SENSITIVITY,
                           denoiser_on ? 1 : 0);
  }

  libvpx_->codec_control(encoder_, VP8E_SET_MAX_INTRA_BITRATE_PCT,
                         rc_max_intra_target_);
  libvpx_->codec_control(encoder_, VP9E_SET_AQ_MODE,
                         codec_.VP9()->adaptiveQpMode ? 3 : 0);

  libvpx_->codec_control(encoder_, VP9E_SET_FRAME_PARALLEL_DECODING, 0);
  libvpx_->codec_control(encoder_, VP9E_SET_SVC_GF_TEMPORAL_REF, 0);

  if (is_svc_) {
    libvpx_->codec_control(encoder_, VP9E_SET_SVC, 1);
    libvpx_->codec_control(encoder_, VP9E_SET_SVC_PARAMETERS, &svc_params_);
  }
  if (!is_svc_ || !performance_flags_.use_per_layer_speed) {
    libvpx_->codec_control(
        encoder_, VP8E_SET_CPUUSED,
        performance_flags_by_spatial_index_.rbegin()->base_layer_speed);
  }

  if (num_spatial_layers_ > 1) {
    switch (inter_layer_pred_) {
      case InterLayerPredMode::kOn:
        libvpx_->codec_control(encoder_, VP9E_SET_SVC_INTER_LAYER_PRED, 0);
        break;
      case InterLayerPredMode::kOff:
        libvpx_->codec_control(encoder_, VP9E_SET_SVC_INTER_LAYER_PRED, 1);
        break;
      case InterLayerPredMode::kOnKeyPic:
        libvpx_->codec_control(encoder_, VP9E_SET_SVC_INTER_LAYER_PRED, 2);
        break;
      default:
        RTC_DCHECK_NOTREACHED();
    }

    memset(&svc_drop_frame_, 0, sizeof(svc_drop_frame_));
    const bool reverse_constrained_drop_mode =
        inter_layer_pred_ == InterLayerPredMode::kOn &&
        codec_.mode == VideoCodecMode::kScreensharing;
    if (reverse_constrained_drop_mode) {
      // Screenshare dropping mode: drop a layer only together with all lower
      // layers. This ensures that drops on lower layers won't reduce frame-rate
      // for higher layers and reference structure is RTP-compatible.
      svc_drop_frame_.framedrop_mode = CONSTRAINED_FROM_ABOVE_DROP;
      svc_drop_frame_.max_consec_drop = 5;
      for (size_t i = 0; i < num_spatial_layers_; ++i) {
        svc_drop_frame_.framedrop_thresh[i] = config_->rc_dropframe_thresh;
      }
    } else {
      if (is_flexible_mode_ && svc_controller_ &&
          (inter_layer_pred_ == InterLayerPredMode::kOff ||
           inter_layer_pred_ == InterLayerPredMode::kOnKeyPic)) {
        // SVC controller is required since it properly accounts for dropped
        // refs (unlike SetReferences(), which assumes full superframe drop).
        svc_drop_frame_.framedrop_mode = LAYER_DROP;
      } else {
        // Configure encoder to drop entire superframe whenever it needs to drop
        // a layer. This mode is preferred over per-layer dropping which causes
        // quality flickering and is not compatible with RTP non-flexible mode.
        svc_drop_frame_.framedrop_mode = FULL_SUPERFRAME_DROP;
      }
      svc_drop_frame_.max_consec_drop = 2;
      for (size_t i = 0; i < num_spatial_layers_; ++i) {
        svc_drop_frame_.framedrop_thresh[i] = config_->rc_dropframe_thresh;
      }
    }
    libvpx_->codec_control(encoder_, VP9E_SET_SVC_FRAME_DROP_LAYER,
                           &svc_drop_frame_);
  }

  // Register callback for getting each spatial layer.
  vpx_codec_priv_output_cx_pkt_cb_pair_t cbp = {
      .output_cx_pkt = LibvpxVp9Encoder::EncoderOutputCodedPacketCallback,
      .user_priv = reinterpret_cast<void*>(this)};
  libvpx_->codec_control(encoder_, VP9E_REGISTER_CX_CALLBACK,
                         reinterpret_cast<void*>(&cbp));

  // Control function to set the number of column tiles in encoding a frame, in
  // log2 unit: e.g., 0 = 1 tile column, 1 = 2 tile columns, 2 = 4 tile columns.
  // The number tile columns will be capped by the encoder based on image size
  // (minimum width of tile column is 256 pixels, maximum is 4096).
  libvpx_->codec_control(encoder_, VP9E_SET_TILE_COLUMNS,
                         static_cast<int>((config_->g_threads >> 1)));

  // Turn on row-based multithreading.
  libvpx_->codec_control(encoder_, VP9E_SET_ROW_MT, 1);

  if (AllowDenoising() && !performance_flags_.use_per_layer_speed) {
    libvpx_->codec_control(encoder_, VP9E_SET_NOISE_SENSITIVITY,
                           codec_.VP9()->denoisingOn ? 1 : 0);
  }

  if (codec_.mode == VideoCodecMode::kScreensharing) {
    // Adjust internal parameters to screen content.
    libvpx_->codec_control(encoder_, VP9E_SET_TUNE_CONTENT, 1);
  }
  // Enable encoder skip of static/low content blocks.
  libvpx_->codec_control(encoder_, VP8E_SET_STATIC_THRESHOLD, 1);

  if (post_encode_frame_drop_) {
    libvpx_->codec_control(encoder_, VP9E_SET_POSTENCODE_DROP, 1);
  }

  // This has to be done after the initial setup is completed.
  AdjustScalingFactorsForTopActiveLayer();

  inited_ = true;
  config_changed_ = true;
  return WEBRTC_VIDEO_CODEC_OK;
}

uint32_t LibvpxVp9Encoder::MaxIntraTarget(uint32_t optimal_buffer_size) {
  // Set max to the optimal buffer level (normalized by target BR),
  // and scaled by a scale_par.
  // Max target size = scale_par * optimal_buffer_size * targetBR[Kbps].
  // This value is presented in percentage of perFrameBw:
  // perFrameBw = targetBR[Kbps] * 1000 / framerate.
  // The target in % is as follows:
  float scale_par = 0.5;
  uint32_t target_pct =
      optimal_buffer_size * scale_par * codec_.maxFramerate / 10;
  // Don't go below 3 times the per frame bandwidth.
  const uint32_t min_intra_size = 300;
  return (target_pct < min_intra_size) ? min_intra_size : target_pct;
}

int LibvpxVp9Encoder::Encode(const VideoFrame& input_image,
                             const std::vector<VideoFrameType>* frame_types) {
  if (!inited_) {
    return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
  }
  if (encoded_complete_callback_ == nullptr) {
    return WEBRTC_VIDEO_CODEC_UNINITIALIZED;
  }
  if (num_active_spatial_layers_ == 0) {
    // All spatial layers are disabled, return without encoding anything.
    return WEBRTC_VIDEO_CODEC_OK;
  }

  // A keyframe request on any stream triggers a keyframe on all streams
  // in order to keep the temporal layering structure aligned.
  if (frame_types &&
      absl::c_linear_search(*frame_types, VideoFrameType::kVideoFrameKey)) {
    force_key_frame_ = true;
  }

  if (pics_since_key_ + 1 ==
      static_cast<size_t>(codec_.VP9()->keyFrameInterval)) {
    force_key_frame_ = true;
  }

  if (svc_controller_) {
    layer_frames_ = svc_controller_->NextFrameConfig(force_key_frame_);
    if (simulcast_to_svc_converter_) {
      simulcast_to_svc_converter_->EncodeStarted(force_key_frame_);
    }
    if (layer_frames_.empty()) {
      return WEBRTC_VIDEO_CODEC_ERROR;
    }
    if (layer_frames_.front().IsKeyframe()) {
      force_key_frame_ = true;
    }
  }

  vpx_svc_layer_id_t layer_id = {.spatial_layer_id = 0};
  if (!force_key_frame_) {
    const size_t gof_idx = (pics_since_key_ + 1) % gof_.num_frames_in_gof;
    layer_id.temporal_layer_id = gof_.temporal_idx[gof_idx];

    if (codec_.mode == VideoCodecMode::kScreensharing) {
      const uint32_t frame_timestamp_ms =
          1000 * input_image.rtp_timestamp() / kVideoPayloadTypeFrequency;

      // To ensure that several rate-limiters with different limits don't
      // interfere, they must be queried in order of increasing limit.

      bool use_steady_state_limiter =
          input_image.update_rect().IsEmpty() &&
          num_steady_state_frames_ >=
              variable_framerate_screenshare::kFramesBeforeSteadyState;

      // Need to check all frame limiters, even if lower layers are disabled,
      // because variable frame-rate limiter should be checked after the first
      // layer. It's easier to overwrite active layers after, then check all
      // cases.
      for (uint8_t sl_idx = 0; sl_idx < num_active_spatial_layers_; ++sl_idx) {
        const float layer_fps =
            framerate_controller_[layer_id.spatial_layer_id].GetTargetRate();
        // Use steady state rate-limiter at the correct place.
        if (use_steady_state_limiter &&
            layer_fps > variable_framerate_screenshare::kMinFps - 1e-9) {
          if (variable_framerate_controller_.DropFrame(frame_timestamp_ms)) {
            layer_id.spatial_layer_id = num_active_spatial_layers_;
          }
          // Break always: if rate limiter triggered frame drop, no need to
          // continue; otherwise, the rate is less than the next limiters.
          break;
        }
        if (framerate_controller_[sl_idx].DropFrame(frame_timestamp_ms)) {
          ++layer_id.spatial_layer_id;
        } else {
          break;
        }
      }

      if (use_steady_state_limiter &&
          layer_id.spatial_layer_id < num_active_spatial_layers_) {
        variable_framerate_controller_.AddFrame(frame_timestamp_ms);
      }
    }

    if (force_all_active_layers_) {
      layer_id.spatial_layer_id = first_active_layer_;
      force_all_active_layers_ = false;
    }

    RTC_DCHECK_LE(layer_id.spatial_layer_id, num_active_spatial_layers_);
    if (layer_id.spatial_layer_id >= num_active_spatial_layers_) {
      // Drop entire picture.
      return WEBRTC_VIDEO_CODEC_OK;
    }
  }

  // Need to set temporal layer id on ALL layers, even disabled ones.
  // Otherwise libvpx might produce frames on a disabled layer:
  // http://crbug.com/1051476
  for (int sl_idx = 0; sl_idx < num_spatial_layers_; ++sl_idx) {
    layer_id.temporal_layer_id_per_spatial[sl_idx] = layer_id.temporal_layer_id;
  }

  if (layer_id.spatial_layer_id < first_active_layer_) {
    layer_id.spatial_layer_id = first_active_layer_;
  }

  if (svc_controller_) {
    layer_id.spatial_layer_id = layer_frames_.front().SpatialId();
    layer_id.temporal_layer_id = layer_frames_.front().TemporalId();
    for (const auto& layer : layer_frames_) {
      layer_id.temporal_layer_id_per_spatial[layer.SpatialId()] =
          layer.TemporalId();
    }
    SetActiveSpatialLayers();
  }

  if (is_svc_ && performance_flags_.use_per_layer_speed) {
    // Update speed settings that might depend on temporal index.
    bool speed_updated = false;
    for (int sl_idx = 0; sl_idx < num_spatial_layers_; ++sl_idx) {
      const int target_speed =
          layer_id.temporal_layer_id_per_spatial[sl_idx] == 0
              ? performance_flags_by_spatial_index_[sl_idx].base_layer_speed
              : performance_flags_by_spatial_index_[sl_idx].high_layer_speed;
      if (svc_params_.speed_per_layer[sl_idx] != target_speed) {
        svc_params_.speed_per_layer[sl_idx] = target_speed;
        speed_updated = true;
      }
    }
    if (speed_updated) {
      libvpx_->codec_control(encoder_, VP9E_SET_SVC_PARAMETERS, &svc_params_);
    }
  }

  libvpx_->codec_control(encoder_, VP9E_SET_SVC_LAYER_ID, &layer_id);

  if (num_spatial_layers_ > 1) {
    // Update frame dropping settings as they may change on per-frame basis.
    libvpx_->codec_control(encoder_, VP9E_SET_SVC_FRAME_DROP_LAYER,
                           &svc_drop_frame_);
  }

  if (config_changed_) {
    if (libvpx_->codec_enc_config_set(encoder_, config_)) {
      return WEBRTC_VIDEO_CODEC_ERROR;
    }

    if (!performance_flags_.use_per_layer_speed) {
      // Not setting individual speeds per layer, find the highest active
      // resolution instead and base the speed on that.
      for (int i = num_spatial_layers_ - 1; i >= 0; --i) {
        if (config_->ss_target_bitrate[i] > 0) {
          int width = (scaling_factors_num_[i] * codec_.width) /
                      scaling_factors_den_[i];
          int height = (scaling_factors_num_[i] * codec_.height) /
                       scaling_factors_den_[i];
          int speed =
              std::prev(performance_flags_.settings_by_resolution.lower_bound(
                            width * height))
                  ->second.base_layer_speed;
          libvpx_->codec_control(encoder_, VP8E_SET_CPUUSED, speed);
          break;
        }
      }
    }
    config_changed_ = false;
  }

  // Set input image for use in the callback.
  // This was necessary since you need some information from input_image.
  // You can save only the necessary information (such as timestamp) instead of
  // doing this.
  input_image_ = &input_image;

  scoped_refptr<VideoFrameBuffer> scaled_image;
  if (!is_svc_ || num_active_spatial_layers_ == num_spatial_layers_) {
    scaled_image = input_image.video_frame_buffer();
  } else {
    scaled_image = input_image.video_frame_buffer()->Scale(
        codec_.spatialLayers[num_active_spatial_layers_ - 1].width,
        codec_.spatialLayers[num_active_spatial_layers_ - 1].height);
  }

  RTC_DCHECK_EQ(scaled_image->width(), config_->g_w);
  RTC_DCHECK_EQ(scaled_image->height(), config_->g_h);

  // In case we need to map the buffer, `mapped_buffer` is used to keep it alive
  // through reference counting until after encoding has finished.
  scoped_refptr<const VideoFrameBuffer> mapped_buffer;
  const I010BufferInterface* i010_buffer;
  scoped_refptr<const I010BufferInterface> i010_copy;
  switch (profile_) {
    case VP9Profile::kProfile0: {
      mapped_buffer = PrepareBufferForProfile0(scaled_image);
      if (!mapped_buffer) {
        return WEBRTC_VIDEO_CODEC_ERROR;
      }
      break;
    }
    case VP9Profile::kProfile1: {
      RTC_DCHECK_NOTREACHED();
      break;
    }
    case VP9Profile::kProfile2: {
      // We can inject kI010 frames directly for encode. All other formats
      // should be converted to it.
      switch (input_image.video_frame_buffer()->type()) {
        case VideoFrameBuffer::Type::kI010: {
          i010_buffer = scaled_image->GetI010();
          break;
        }
        default: {
          auto i420_buffer = scaled_image->ToI420();
          if (!i420_buffer) {
            RTC_LOG(LS_ERROR) << "Failed to convert "
                              << VideoFrameBufferTypeToString(
                                     input_image.video_frame_buffer()->type())
                              << " image to I420. Can't encode frame.";
            return WEBRTC_VIDEO_CODEC_ERROR;
          }
          i010_copy = I010Buffer::Copy(*i420_buffer);
          i010_buffer = i010_copy.get();
        }
      }

      // TODO: crbug.com/492213293 - Remove once the root cause is fixed.
      if (i010_buffer->StrideU() != i010_buffer->StrideV()) {
        RTC_LOG(LS_ERROR) << "Libvpx requires the U and V strides to be equal.";
        return WEBRTC_VIDEO_CODEC_ERROR;
      }

      MaybeRewrapRawWithFormat(VPX_IMG_FMT_I42016, i010_buffer->width(),
                               i010_buffer->height());
      raw_->planes[VPX_PLANE_Y] = const_cast<uint8_t*>(
          reinterpret_cast<const uint8_t*>(i010_buffer->DataY()));
      raw_->planes[VPX_PLANE_U] = const_cast<uint8_t*>(
          reinterpret_cast<const uint8_t*>(i010_buffer->DataU()));
      raw_->planes[VPX_PLANE_V] = const_cast<uint8_t*>(
          reinterpret_cast<const uint8_t*>(i010_buffer->DataV()));
      raw_->stride[VPX_PLANE_Y] = i010_buffer->StrideY() * 2;
      raw_->stride[VPX_PLANE_U] = i010_buffer->StrideU() * 2;
      raw_->stride[VPX_PLANE_V] = i010_buffer->StrideV() * 2;
      break;
    }
    case VP9Profile::kProfile3: {
      RTC_DCHECK_NOTREACHED();
      break;
    }
  }

  vpx_enc_frame_flags_t flags = 0;
  if (force_key_frame_) {
    flags = VPX_EFLAG_FORCE_KF;
  }
#if defined(WEBRTC_ENCODER_PSNR_STATS) && defined(VPX_EFLAG_CALCULATE_PSNR)
  if (psnr_frame_sampler_.ShouldBeSampled(input_image)) {
    flags |= VPX_EFLAG_CALCULATE_PSNR;
  }
#endif

  if (svc_controller_) {
    vpx_svc_ref_frame_config_t ref_config = Vp9References(layer_frames_);
    libvpx_->codec_control(encoder_, VP9E_SET_SVC_REF_FRAME_CONFIG,
                           &ref_config);
  } else {
    vpx_svc_ref_frame_config_t ref_config =
        SetReferences(force_key_frame_, layer_id.spatial_layer_id);

    if (VideoCodecMode::kScreensharing == codec_.mode) {
      for (uint8_t sl_idx = 0; sl_idx < num_active_spatial_layers_; ++sl_idx) {
        ref_config.duration[sl_idx] = static_cast<int64_t>(
            kVideoPayloadTypeFrequency /
            (std::min(static_cast<float>(codec_.maxFramerate),
                      framerate_controller_[sl_idx].GetTargetRate())));
      }
    }

    libvpx_->codec_control(encoder_, VP9E_SET_SVC_REF_FRAME_CONFIG,
                           &ref_config);
  }

  first_frame_in_picture_ = true;

  // TODO(ssilkin): Frame duration should be specified per spatial layer
  // since their frame rate can be different. For now calculate frame duration
  // based on target frame rate of the highest spatial layer, which frame rate
  // is supposed to be equal or higher than frame rate of low spatial layers.
  // Also, timestamp should represent actual time passed since previous frame
  // (not 'expected' time). Then rate controller can drain buffer more
  // accurately.
  RTC_DCHECK_GE(framerate_controller_.size(), num_active_spatial_layers_);
  float target_framerate_fps =
      (codec_.mode == VideoCodecMode::kScreensharing)
          ? std::min(static_cast<float>(codec_.maxFramerate),
                     framerate_controller_[num_active_spatial_layers_ - 1]
                         .GetTargetRate())
          : codec_.maxFramerate;
  uint32_t duration =
      static_cast<uint32_t>(kVideoPayloadTypeFrequency / target_framerate_fps);
  const vpx_codec_err_t rv = libvpx_->codec_encode(
      encoder_, raw_, timestamp_, duration, flags, VPX_DL_REALTIME);
  if (rv != VPX_CODEC_OK) {
    RTC_LOG(LS_ERROR) << "Encoding error: " << libvpx_->codec_err_to_string(rv)
                      << "\n"
                         "Details: "
                      << libvpx_->codec_error(encoder_) << "\n"
                      << libvpx_->codec_error_detail(encoder_);
    return WEBRTC_VIDEO_CODEC_ERROR;
  }
  timestamp_ += duration;

  return WEBRTC_VIDEO_CODEC_OK;
}

bool LibvpxVp9Encoder::PopulateCodecSpecific(CodecSpecificInfo* codec_specific,
                                             std::optional<int>* spatial_idx,
                                             std::optional<int>* temporal_idx,
                                             const vpx_codec_cx_pkt& pkt) {
  RTC_CHECK(codec_specific != nullptr);
  codec_specific->codecType = kVideoCodecVP9;
  CodecSpecificInfoVP9* vp9_info = &(codec_specific->codecSpecific.VP9);

  vp9_info->first_frame_in_picture = first_frame_in_picture_;
  vp9_info->flexible_mode = is_flexible_mode_;

  if (pkt.data.frame.flags & VPX_FRAME_IS_KEY) {
    pics_since_key_ = 0;
  } else if (first_frame_in_picture_) {
    ++pics_since_key_;
  }

  vpx_svc_layer_id_t layer_id = {.spatial_layer_id = 0};
  libvpx_->codec_control(encoder_, VP9E_GET_SVC_LAYER_ID, &layer_id);

  // Can't have keyframe with non-zero temporal layer.
  RTC_DCHECK(pics_since_key_ != 0 || layer_id.temporal_layer_id == 0);

  RTC_CHECK_GT(num_temporal_layers_, 0);
  RTC_CHECK_GT(num_active_spatial_layers_, 0);
  if (num_temporal_layers_ == 1) {
    RTC_CHECK_EQ(layer_id.temporal_layer_id, 0);
    vp9_info->temporal_idx = kNoTemporalIdx;
    *temporal_idx = std::nullopt;
  } else {
    vp9_info->temporal_idx = layer_id.temporal_layer_id;
    *temporal_idx = layer_id.temporal_layer_id;
  }
  if (num_active_spatial_layers_ == 1) {
    RTC_CHECK_EQ(layer_id.spatial_layer_id, 0);
    *spatial_idx = std::nullopt;
  } else {
    *spatial_idx = layer_id.spatial_layer_id;
  }

  const bool is_key_pic = (pics_since_key_ == 0);
  const bool is_inter_layer_pred_allowed =
      (inter_layer_pred_ == InterLayerPredMode::kOn ||
       (inter_layer_pred_ == InterLayerPredMode::kOnKeyPic && is_key_pic));

  // Always set inter_layer_predicted to true on high layer frame if inter-layer
  // prediction (ILP) is allowed even if encoder didn't actually use it.
  // Setting inter_layer_predicted to false would allow receiver to decode high
  // layer frame without decoding low layer frame. If that would happen (e.g.
  // if low layer frame is lost) then receiver won't be able to decode next high
  // layer frame which uses ILP.
  vp9_info->inter_layer_predicted =
      first_frame_in_picture_ ? false : is_inter_layer_pred_allowed;

  // Mark all low spatial layer frames as references (not just frames of
  // active low spatial layers) if inter-layer prediction is enabled since
  // these frames are indirect references of high spatial layer, which can
  // later be enabled without key frame.
  vp9_info->non_ref_for_inter_layer_pred =
      !is_inter_layer_pred_allowed ||
      layer_id.spatial_layer_id + 1 == num_spatial_layers_;

  // Always populate this, so that the packetizer can properly set the marker
  // bit.
  vp9_info->num_spatial_layers = num_active_spatial_layers_;
  vp9_info->first_active_layer = first_active_layer_;

  vp9_info->num_ref_pics = 0;
  FillReferenceIndices(pkt, pics_since_key_, vp9_info->inter_layer_predicted,
                       vp9_info);
  if (vp9_info->flexible_mode) {
    vp9_info->gof_idx = kNoGofIdx;
    if (!svc_controller_) {
      if (num_temporal_layers_ == 1) {
        vp9_info->temporal_up_switch = true;
      } else {
        // In flexible mode with > 1 temporal layer but no SVC controller we
        // can't techincally determine if a frame is an upswitch point, use
        // gof-based data as proxy for now.
        // TODO(sprang): Remove once SVC controller is the only choice.
        vp9_info->gof_idx =
            static_cast<uint8_t>(pics_since_key_ % gof_.num_frames_in_gof);
        vp9_info->temporal_up_switch =
            gof_.temporal_up_switch[vp9_info->gof_idx];
      }
    }
  } else {
    vp9_info->gof_idx =
        static_cast<uint8_t>(pics_since_key_ % gof_.num_frames_in_gof);
    vp9_info->temporal_up_switch = gof_.temporal_up_switch[vp9_info->gof_idx];
    RTC_DCHECK(vp9_info->num_ref_pics == gof_.num_ref_pics[vp9_info->gof_idx] ||
               vp9_info->num_ref_pics == 0);
  }

  vp9_info->inter_pic_predicted = (!is_key_pic && vp9_info->num_ref_pics > 0);

  // Write SS on key frame of independently coded spatial layers and on base
  // temporal/spatial layer frame if number of layers changed without issuing
  // of key picture (inter-layer prediction is enabled).
  const bool is_key_frame = is_key_pic && !vp9_info->inter_layer_predicted;
  if (is_key_frame || (ss_info_needed_ && layer_id.temporal_layer_id == 0 &&
                       layer_id.spatial_layer_id == first_active_layer_)) {
    vp9_info->ss_data_available = true;
    vp9_info->spatial_layer_resolution_present = true;
    // Signal disabled layers.
    for (size_t i = 0; i < first_active_layer_; ++i) {
      vp9_info->width[i] = 0;
      vp9_info->height[i] = 0;
    }
    for (size_t i = first_active_layer_; i < num_active_spatial_layers_; ++i) {
      vp9_info->width[i] =
          codec_.width * scaling_factors_num_[i] / scaling_factors_den_[i];
      vp9_info->height[i] =
          codec_.height * scaling_factors_num_[i] / scaling_factors_den_[i];
    }
    if (vp9_info->flexible_mode) {
      vp9_info->gof.num_frames_in_gof = 0;
    } else {
      vp9_info->gof.CopyGofInfoVP9(gof_);
    }

    ss_info_needed_ = false;
  } else {
    vp9_info->ss_data_available = false;
  }

  first_frame_in_picture_ = false;

  // Populate codec-agnostic section in the codec specific structure.
  if (svc_controller_) {
    auto it = absl::c_find_if(
        layer_frames_,
        [&](const ScalableVideoController::LayerFrameConfig& config) {
          return config.SpatialId() == layer_id.spatial_layer_id;
        });
    if (it == layer_frames_.end()) {
      RTC_LOG(LS_ERROR) << "Encoder produced a frame for layer S"
                        << layer_id.spatial_layer_id << "T"
                        << layer_id.temporal_layer_id
                        << " that wasn't requested.";
      return false;
    }
    codec_specific->generic_frame_info = svc_controller_->OnEncodeDone(*it);
    if (is_key_frame) {
      codec_specific->template_structure =
          svc_controller_->DependencyStructure();
      auto& resolutions = codec_specific->template_structure->resolutions;
      resolutions.resize(num_spatial_layers_);
      for (int sid = 0; sid < num_spatial_layers_; ++sid) {
        resolutions[sid] = RenderResolution(
            /*width=*/codec_.width * scaling_factors_num_[sid] /
                scaling_factors_den_[sid],
            /*height=*/codec_.height * scaling_factors_num_[sid] /
                scaling_factors_den_[sid]);
      }
    }
    if (is_flexible_mode_) {
      // Populate data for legacy temporal-upswitch state.
      // We can switch up to a higher temporal layer only if all temporal layers
      // higher than this (within the current spatial layer) are switch points.
      vp9_info->temporal_up_switch = true;
      for (int i = layer_id.temporal_layer_id + 1; i < num_temporal_layers_;
           ++i) {
        // Assumes decode targets are always ordered first by spatial then by
        // temporal id.
        size_t dti_index =
            (layer_id.spatial_layer_id * num_temporal_layers_) + i;
        vp9_info->temporal_up_switch &=
            (codec_specific->generic_frame_info
                 ->decode_target_indications[dti_index] ==
             DecodeTargetIndication::kSwitch);
      }
    }
  }
  // If returned the configured scalability mode in standard mode, otherwise
  // create one if it is based on layer activation.
  if (scalability_mode_) {
    codec_specific->scalability_mode = scalability_mode_;
  } else {
    codec_specific_.scalability_mode = MakeScalabilityMode(
        num_active_spatial_layers_, num_temporal_layers_, inter_layer_pred_,
        num_active_spatial_layers_ > 1
            ? std::make_optional(ScalabilityModeResolutionRatio::kTwoToOne)
            : std::nullopt,
        /*shift=*/false);
  }

  return true;
}

void LibvpxVp9Encoder::FillReferenceIndices(const vpx_codec_cx_pkt& pkt,
                                            const size_t pic_num,
                                            const bool inter_layer_predicted,
                                            CodecSpecificInfoVP9* vp9_info) {
  vpx_svc_layer_id_t layer_id = {.spatial_layer_id = 0};
  libvpx_->codec_control(encoder_, VP9E_GET_SVC_LAYER_ID, &layer_id);

  const bool is_key_frame =
      (pkt.data.frame.flags & VPX_FRAME_IS_KEY) ? true : false;

  std::vector<RefFrameBuffer> ref_buf_list;

  if (is_svc_) {
    vpx_svc_ref_frame_config_t enc_layer_conf = {.lst_fb_idx = {0}};
    libvpx_->codec_control(encoder_, VP9E_GET_SVC_REF_FRAME_CONFIG,
                           &enc_layer_conf);
    char ref_buf_flags[] = "00000000";
    // There should be one character per buffer + 1 termination '\0'.
    static_assert(sizeof(ref_buf_flags) == kNumVp9Buffers + 1);

    if (enc_layer_conf.reference_last[layer_id.spatial_layer_id]) {
      const size_t fb_idx =
          enc_layer_conf.lst_fb_idx[layer_id.spatial_layer_id];
      RTC_DCHECK_LT(fb_idx, ref_buf_.size());
      if (std::find(ref_buf_list.begin(), ref_buf_list.end(),
                    ref_buf_[fb_idx]) == ref_buf_list.end()) {
        ref_buf_list.push_back(ref_buf_[fb_idx]);
        ref_buf_flags[fb_idx] = '1';
      }
    }

    if (enc_layer_conf.reference_alt_ref[layer_id.spatial_layer_id]) {
      const size_t fb_idx =
          enc_layer_conf.alt_fb_idx[layer_id.spatial_layer_id];
      RTC_DCHECK_LT(fb_idx, ref_buf_.size());
      if (std::find(ref_buf_list.begin(), ref_buf_list.end(),
                    ref_buf_[fb_idx]) == ref_buf_list.end()) {
        ref_buf_list.push_back(ref_buf_[fb_idx]);
        ref_buf_flags[fb_idx] = '1';
      }
    }

    if (enc_layer_conf.reference_golden[layer_id.spatial_layer_id]) {
      const size_t fb_idx =
          enc_layer_conf.gld_fb_idx[layer_id.spatial_layer_id];
      RTC_DCHECK_LT(fb_idx, ref_buf_.size());
      if (std::find(ref_buf_list.begin(), ref_buf_list.end(),
                    ref_buf_[fb_idx]) == ref_buf_list.end()) {
        ref_buf_list.push_back(ref_buf_[fb_idx]);
        ref_buf_flags[fb_idx] = '1';
      }
    }

    RTC_LOG(LS_VERBOSE) << "Frame " << pic_num << " sl "
                        << layer_id.spatial_layer_id << " tl "
                        << layer_id.temporal_layer_id << " refered buffers "
                        << ref_buf_flags;

  } else if (!is_key_frame) {
    RTC_DCHECK_EQ(num_spatial_layers_, 1);
    RTC_DCHECK_EQ(num_temporal_layers_, 1);
    // In non-SVC mode encoder doesn't provide reference list. Assume each frame
    // refers previous one, which is stored in buffer 0.
    ref_buf_list.push_back(ref_buf_[0]);
  }

  std::vector<size_t> ref_pid_list;

  vp9_info->num_ref_pics = 0;
  for (const RefFrameBuffer& ref_buf : ref_buf_list) {
    RTC_DCHECK_LE(ref_buf.pic_num, pic_num);
    if (ref_buf.pic_num < pic_num) {
      if (inter_layer_pred_ != InterLayerPredMode::kOn) {
        // RTP spec limits temporal prediction to the same spatial layer.
        // It is safe to ignore this requirement if inter-layer prediction is
        // enabled for all frames when all base frames are relayed to receiver.
        RTC_DCHECK_EQ(ref_buf.spatial_layer_id, layer_id.spatial_layer_id);
      } else {
        RTC_DCHECK_LE(ref_buf.spatial_layer_id, layer_id.spatial_layer_id);
      }
      RTC_DCHECK_LE(ref_buf.temporal_layer_id, layer_id.temporal_layer_id);

      // Encoder may reference several spatial layers on the same previous
      // frame in case if some spatial layers are skipped on the current frame.
      // We shouldn't put duplicate references as it may break some old
      // clients and isn't RTP compatible.
      if (std::find(ref_pid_list.begin(), ref_pid_list.end(),
                    ref_buf.pic_num) != ref_pid_list.end()) {
        continue;
      }
      ref_pid_list.push_back(ref_buf.pic_num);

      const size_t p_diff = pic_num - ref_buf.pic_num;
      RTC_DCHECK_LE(p_diff, 127UL);

      vp9_info->p_diff[vp9_info->num_ref_pics] = static_cast<uint8_t>(p_diff);
      ++vp9_info->num_ref_pics;
    } else {
      RTC_DCHECK(inter_layer_predicted);
      // RTP spec only allows to use previous spatial layer for inter-layer
      // prediction.
      RTC_DCHECK_EQ(ref_buf.spatial_layer_id + 1, layer_id.spatial_layer_id);
    }
  }
}

void LibvpxVp9Encoder::UpdateReferenceBuffers(const vpx_codec_cx_pkt& /* pkt */,
                                              const size_t pic_num) {
  vpx_svc_layer_id_t layer_id = {.spatial_layer_id = 0};
  libvpx_->codec_control(encoder_, VP9E_GET_SVC_LAYER_ID, &layer_id);

  RefFrameBuffer frame_buf = {.pic_num = pic_num,
                              .spatial_layer_id = layer_id.spatial_layer_id,
                              .temporal_layer_id = layer_id.temporal_layer_id};

  if (is_svc_) {
    vpx_svc_ref_frame_config_t enc_layer_conf = {.lst_fb_idx = {0}};
    libvpx_->codec_control(encoder_, VP9E_GET_SVC_REF_FRAME_CONFIG,
                           &enc_layer_conf);
    const int update_buffer_slot =
        enc_layer_conf.update_buffer_slot[layer_id.spatial_layer_id];

    for (size_t i = 0; i < ref_buf_.size(); ++i) {
      if (update_buffer_slot & (1 << i)) {
        ref_buf_[i] = frame_buf;
      }
    }

    RTC_LOG(LS_VERBOSE) << "Frame " << pic_num << " sl "
                        << layer_id.spatial_layer_id << " tl "
                        << layer_id.temporal_layer_id << " updated buffers "
                        << (update_buffer_slot & (1 << 0) ? 1 : 0)
                        << (update_buffer_slot & (1 << 1) ? 1 : 0)
                        << (update_buffer_slot & (1 << 2) ? 1 : 0)
                        << (update_buffer_slot & (1 << 3) ? 1 : 0)
                        << (update_buffer_slot & (1 << 4) ? 1 : 0)
                        << (update_buffer_slot & (1 << 5) ? 1 : 0)
                        << (update_buffer_slot & (1 << 6) ? 1 : 0)
                        << (update_buffer_slot & (1 << 7) ? 1 : 0);
  } else {
    RTC_DCHECK_EQ(num_spatial_layers_, 1);
    RTC_DCHECK_EQ(num_temporal_layers_, 1);
    // In non-svc mode encoder doesn't provide reference list. Assume each frame
    // is reference and stored in buffer 0.
    ref_buf_[0] = frame_buf;
  }
}

vpx_svc_ref_frame_config_t LibvpxVp9Encoder::SetReferences(
    bool is_key_pic,
    int first_active_spatial_layer_id) {
  // kRefBufIdx, kUpdBufIdx need to be updated to support longer GOFs.
  RTC_DCHECK_LE(gof_.num_frames_in_gof, 4);

  vpx_svc_ref_frame_config_t ref_config;
  memset(&ref_config, 0, sizeof(ref_config));

  const size_t num_temporal_refs = std::max(1, num_temporal_layers_ - 1);
  const bool is_inter_layer_pred_allowed =
      inter_layer_pred_ == InterLayerPredMode::kOn ||
      (inter_layer_pred_ == InterLayerPredMode::kOnKeyPic && is_key_pic);
  std::optional<int> last_updated_buf_idx;

  // Put temporal reference to LAST and spatial reference to GOLDEN. Update
  // frame buffer (i.e. store encoded frame) if current frame is a temporal
  // reference (i.e. it belongs to a low temporal layer) or it is a spatial
  // reference. In later case, always store spatial reference in the last
  // reference frame buffer.
  // For the case of 3 temporal and 3 spatial layers we need 6 frame buffers
  // for temporal references plus 1 buffer for spatial reference. 7 buffers
  // in total.

  for (int sl_idx = first_active_spatial_layer_id;
       sl_idx < num_active_spatial_layers_; ++sl_idx) {
    const size_t curr_pic_num = is_key_pic ? 0 : pics_since_key_ + 1;
    const size_t gof_idx = curr_pic_num % gof_.num_frames_in_gof;

    if (!is_key_pic) {
      // Set up temporal reference.
      const int buf_idx = sl_idx * num_temporal_refs + kRefBufIdx[gof_idx];

      // Last reference frame buffer is reserved for spatial reference. It is
      // not supposed to be used for temporal prediction.
      RTC_DCHECK_LT(buf_idx, kNumVp9Buffers - 1);

      const int pid_diff = curr_pic_num - ref_buf_[buf_idx].pic_num;
      // Incorrect spatial layer may be in the buffer due to a key-frame.
      const bool same_spatial_layer =
          ref_buf_[buf_idx].spatial_layer_id == sl_idx;
      bool correct_pid = false;
      if (is_flexible_mode_) {
        correct_pid = pid_diff > 0 && pid_diff < kMaxAllowedPidDiff;
      } else {
        // Below code assumes single temporal referecence.
        RTC_DCHECK_EQ(gof_.num_ref_pics[gof_idx], 1);
        correct_pid = pid_diff == gof_.pid_diff[gof_idx][0];
      }

      if (same_spatial_layer && correct_pid) {
        ref_config.lst_fb_idx[sl_idx] = buf_idx;
        ref_config.reference_last[sl_idx] = 1;
      } else {
        // This reference doesn't match with one specified by GOF. This can
        // only happen if spatial layer is enabled dynamically without key
        // frame. Spatial prediction is supposed to be enabled in this case.
        RTC_DCHECK(is_inter_layer_pred_allowed &&
                   sl_idx > first_active_spatial_layer_id);
      }
    }

    if (is_inter_layer_pred_allowed && sl_idx > first_active_spatial_layer_id) {
      // Set up spatial reference.
      RTC_DCHECK(last_updated_buf_idx);
      ref_config.gld_fb_idx[sl_idx] = *last_updated_buf_idx;
      ref_config.reference_golden[sl_idx] = 1;
    } else {
      RTC_DCHECK(ref_config.reference_last[sl_idx] != 0 ||
                 sl_idx == first_active_spatial_layer_id ||
                 inter_layer_pred_ == InterLayerPredMode::kOff);
    }

    last_updated_buf_idx.reset();

    if (gof_.temporal_idx[gof_idx] < num_temporal_layers_ - 1 ||
        num_temporal_layers_ == 1) {
      last_updated_buf_idx = sl_idx * num_temporal_refs + kUpdBufIdx[gof_idx];

      // Ensure last frame buffer is not used for temporal prediction (it is
      // reserved for spatial reference).
      RTC_DCHECK_LT(*last_updated_buf_idx, kNumVp9Buffers - 1);
    } else if (is_inter_layer_pred_allowed) {
      last_updated_buf_idx = kNumVp9Buffers - 1;
    }

    if (last_updated_buf_idx) {
      ref_config.update_buffer_slot[sl_idx] = 1 << *last_updated_buf_idx;
    }
  }

  return ref_config;
}

void LibvpxVp9Encoder::GetEncodedLayerFrame(const vpx_codec_cx_pkt* pkt) {
  RTC_DCHECK_EQ(pkt->kind, VPX_CODEC_CX_FRAME_PKT);

  vpx_svc_layer_id_t layer_id = {.spatial_layer_id = 0};
  libvpx_->codec_control(encoder_, VP9E_GET_SVC_LAYER_ID, &layer_id);

  // This encoder doesn't mark the last encoded frame with end_of_picture -
  // meaning that if per-layer frame dropping is enabled and the last layer
  // drops the frame, there will be no encoded image with end_of_picture set.
  // In those cases the receiver will have to figure that out based on the
  // absence of a picture when the next frame arrives.
  // We should consider changing this behavior - but that necessitates buffering
  // and so introduces latency. If FULL_SUPERFRAME_DROP is used, this is a non-
  // issue.
  // Due to this behavior, end_of_temporal_unit is the same thing as
  // end_of_picture.
  const bool end_of_picture =
      layer_id.spatial_layer_id + 1 == num_active_spatial_layers_;

  if (pkt->data.frame.sz == 0) {
    encoded_complete_callback_->OnFrameDropped(input_image_->rtp_timestamp(),
                                               layer_id.spatial_layer_id,
                                               end_of_picture);
    return;
  }

  encoded_image_.SetEncodedData(EncodedImageBuffer::Create(
      static_cast<const uint8_t*>(pkt->data.frame.buf), pkt->data.frame.sz));

  codec_specific_ = {};
  std::optional<int> spatial_index;
  std::optional<int> temporal_index;
  if (!PopulateCodecSpecific(&codec_specific_, &spatial_index, &temporal_index,
                             *pkt)) {
    // Drop the frame.
    encoded_image_.set_size(0);
    return;
  }
  encoded_image_.SetSpatialIndex(spatial_index);
  encoded_image_.SetTemporalIndex(temporal_index);

  const bool is_key_frame =
      ((pkt->data.frame.flags & VPX_FRAME_IS_KEY) ? true : false) &&
      !codec_specific_.codecSpecific.VP9.inter_layer_predicted;

  // Ensure encoder issued key frame on request.
  RTC_DCHECK(is_key_frame || !force_key_frame_);

  // Check if encoded frame is a key frame.
  encoded_image_.set_frame_type(VideoFrameType::kVideoFrameDelta);
  if (is_key_frame) {
    encoded_image_.set_frame_type(VideoFrameType::kVideoFrameKey);
    force_key_frame_ = false;
  }

  UpdateReferenceBuffers(*pkt, pics_since_key_);

  TRACE_COUNTER1("webrtc", "EncodedFrameSize", encoded_image_.size());
  encoded_image_.SetRtpTimestamp(input_image_->rtp_timestamp());
  encoded_image_.SetPresentationTimestamp(
      input_image_->presentation_timestamp());
  encoded_image_.SetColorSpace(input_image_->color_space());
  encoded_image_._encodedHeight =
      pkt->data.frame.height[layer_id.spatial_layer_id];
  encoded_image_._encodedWidth =
      pkt->data.frame.width[layer_id.spatial_layer_id];
  int qp = -1;
  libvpx_->codec_control(encoder_, VP8E_GET_LAST_QUANTIZER, &qp);
  encoded_image_.qp_ = qp;
  // Pull PSNR which is not pushed for VP9.
  // TODO: bugs.webrtc.org/388070060 - check SVC behavior.
  // TODO: bugs.webrtc.org/388070060 - this is broken for simulcast which seems
  // to be using kSVC.
  vpx_codec_iter_t iter = nullptr;
  const vpx_codec_cx_pkt_t* cx_data = nullptr;
  encoded_image_.set_psnr(std::nullopt);
  while ((cx_data = libvpx_->codec_get_cx_data(encoder_, &iter)) != nullptr) {
    if (cx_data->kind == VPX_CODEC_PSNR_PKT) {
      // PSNR index: 0: total, 1: Y, 2: U, 3: V
      encoded_image_.set_psnr(
          EncodedImage::Psnr({.y = cx_data->data.psnr.psnr[1],
                              .u = cx_data->data.psnr.psnr[2],
                              .v = cx_data->data.psnr.psnr[3]}));
    }
  }

  encoded_image_.set_end_of_temporal_unit(end_of_picture);
  DeliverBufferedFrame(end_of_picture);
}

void LibvpxVp9Encoder::DeliverBufferedFrame(bool end_of_picture) {
  if (encoded_image_.size() > 0) {
    if (num_spatial_layers_ > 1) {
      // Restore frame dropping settings, as dropping may be temporary forbidden
      // due to dynamically enabled layers.
      for (size_t i = 0; i < num_spatial_layers_; ++i) {
        svc_drop_frame_.framedrop_thresh[i] = config_->rc_dropframe_thresh;
      }
    }

    codec_specific_.end_of_picture = end_of_picture;

    if (!simulcast_to_svc_converter_) {
      encoded_image_.SetSimulcastIndex(std::nullopt);
    } else {
      simulcast_to_svc_converter_->ConvertFrame(encoded_image_,
                                                codec_specific_);
    }

    encoded_complete_callback_->OnEncodedImage(encoded_image_,
                                               &codec_specific_);

    if (codec_.mode == VideoCodecMode::kScreensharing) {
      const uint8_t spatial_idx = encoded_image_.SpatialIndex().value_or(0);
      const uint32_t frame_timestamp_ms =
          1000 * encoded_image_.RtpTimestamp() / kVideoPayloadTypeFrequency;
      framerate_controller_[spatial_idx].AddFrame(frame_timestamp_ms);

      const size_t steady_state_size = SteadyStateSize(
          spatial_idx, codec_specific_.codecSpecific.VP9.temporal_idx);

      // Only frames on spatial layers, which may be limited in a steady state
      // are considered for steady state detection.
      if (framerate_controller_[spatial_idx].GetTargetRate() >
          variable_framerate_screenshare::kMinFps + 1e-9) {
        if (encoded_image_.qp_ <= variable_framerate_screenshare::kMinQP &&
            encoded_image_.size() <= steady_state_size) {
          ++num_steady_state_frames_;
        } else {
          num_steady_state_frames_ = 0;
        }
      }
    }
    encoded_image_.set_size(0);
  }
}

int LibvpxVp9Encoder::RegisterEncodeCompleteCallback(
    EncodedImageCallback* callback) {
  encoded_complete_callback_ = callback;
  return WEBRTC_VIDEO_CODEC_OK;
}

VideoEncoder::EncoderInfo LibvpxVp9Encoder::GetEncoderInfo() const {
  EncoderInfo info;
  info.supports_native_handle = false;
  info.supports_simulcast = true;
  info.implementation_name = "libvpx";
  if (quality_scaler_experiment_.enabled && inited_ &&
      codec_.VP9().automaticResizeOn) {
    info.scaling_settings = VideoEncoder::ScalingSettings(
        quality_scaler_experiment_.low_qp, quality_scaler_experiment_.high_qp);
  } else {
    info.scaling_settings = VideoEncoder::ScalingSettings::kOff;
  }
  info.has_trusted_rate_controller = trusted_rate_controller_;
  info.is_hardware_accelerated = false;
  if (inited_) {
    // Find the max configured fps of any active spatial layer.
    float max_fps = 0.0;
    for (size_t si = 0; si < num_spatial_layers_; ++si) {
      if (codec_.spatialLayers[si].active &&
          codec_.spatialLayers[si].maxFramerate > max_fps) {
        max_fps = codec_.spatialLayers[si].maxFramerate;
      }
    }
    if (num_active_spatial_layers_ > 0) {
      info.mapped_resolution =
          VideoEncoder::Resolution(config_->g_w, config_->g_h);
    }

    for (size_t si = 0; si < num_spatial_layers_; ++si) {
      info.fps_allocation[si].clear();
      if (!codec_.spatialLayers[si].active) {
        continue;
      }

      // This spatial layer may already use a fraction of the total frame rate.
      const float sl_fps_fraction =
          codec_.spatialLayers[si].maxFramerate / max_fps;
      for (size_t ti = 0; ti < num_temporal_layers_; ++ti) {
        const uint32_t decimator =
            num_temporal_layers_ <= 1 ? 1 : config_->ts_rate_decimator[ti];
        RTC_DCHECK_GT(decimator, 0);
        info.fps_allocation[si].push_back(
            saturated_cast<uint8_t>(EncoderInfo::kMaxFramerateFraction *
                                    (sl_fps_fraction / decimator)));
      }
    }
    if (profile_ == VP9Profile::kProfile0) {
      info.preferred_pixel_formats = {VideoFrameBuffer::Type::kI420,
                                      VideoFrameBuffer::Type::kNV12};
    }

    if (codec_.mode == VideoCodecMode::kScreensharing) {
      info.min_qp = variable_framerate_screenshare::kMinQP;
    }
  }
  if (!encoder_info_override_.resolution_bitrate_limits().empty()) {
    info.resolution_bitrate_limits =
        encoder_info_override_.resolution_bitrate_limits();
  }
  return info;
}

size_t LibvpxVp9Encoder::SteadyStateSize(int sid, int tid) {
  const size_t bitrate_bps = current_bitrate_allocation_.GetBitrate(
      sid, tid == kNoTemporalIdx ? 0 : tid);
  const float fps = (codec_.mode == VideoCodecMode::kScreensharing)
                        ? std::min(static_cast<float>(codec_.maxFramerate),
                                   framerate_controller_[sid].GetTargetRate())
                        : codec_.maxFramerate;
  return static_cast<size_t>(
      bitrate_bps / (8 * fps) *
          (100 - variable_framerate_screenshare::kUndershootPct) / 100 +
      0.5);
}

// static
LibvpxVp9Encoder::QualityScalerExperiment
LibvpxVp9Encoder::ParseQualityScalerConfig(const FieldTrialsView& trials) {
  FieldTrialFlag disabled = FieldTrialFlag("Disabled");
  FieldTrialParameter<int> low_qp("low_qp", kLowVp9QpThreshold);
  FieldTrialParameter<int> high_qp("hihg_qp", kHighVp9QpThreshold);
  ParseFieldTrial({&disabled, &low_qp, &high_qp},
                  trials.Lookup("WebRTC-VP9QualityScaler"));
  QualityScalerExperiment config;
  config.enabled = !disabled.Get();
  RTC_LOG(LS_INFO) << "Webrtc quality scaler for vp9 is "
                   << (config.enabled ? "enabled." : "disabled");
  config.low_qp = low_qp.Get();
  config.high_qp = high_qp.Get();

  return config;
}

void LibvpxVp9Encoder::UpdatePerformanceFlags() {
  flat_map<int, PerformanceFlags::ParameterSet> params_by_resolution;
  if (codec_.GetVideoEncoderComplexity() ==
      VideoCodecComplexity::kComplexityLow) {
    // For low tier devices, always use speed 9. Only disable upper
    // layer deblocking below QCIF.
    params_by_resolution[0] = {.base_layer_speed = 9,
                               .high_layer_speed = 9,
                               .deblock_mode = 1,
                               .allow_denoising = true};
    params_by_resolution[352 * 288] = {.base_layer_speed = 9,
                                       .high_layer_speed = 9,
                                       .deblock_mode = 0,
                                       .allow_denoising = true};
  } else {
    params_by_resolution = performance_flags_.settings_by_resolution;
  }

  const auto find_speed = [&](int min_pixel_count) {
    RTC_DCHECK(!params_by_resolution.empty());
    auto it = params_by_resolution.upper_bound(min_pixel_count);
    return std::prev(it)->second;
  };
  performance_flags_by_spatial_index_.clear();

  if (is_svc_) {
    for (int si = 0; si < num_spatial_layers_; ++si) {
      performance_flags_by_spatial_index_.push_back(find_speed(
          codec_.spatialLayers[si].width * codec_.spatialLayers[si].height));
    }
  } else {
    performance_flags_by_spatial_index_.push_back(
        find_speed(codec_.width * codec_.height));
  }
}

// static
LibvpxVp9Encoder::PerformanceFlags
LibvpxVp9Encoder::ParsePerformanceFlagsFromTrials(
    const FieldTrialsView& trials) {
  struct Params : public PerformanceFlags::ParameterSet {
    int min_pixel_count = 0;
  };

  FieldTrialStructList<Params> trials_list(
      {FieldTrialStructMember("min_pixel_count",
                              [](Params* p) { return &p->min_pixel_count; }),
       FieldTrialStructMember("high_layer_speed",
                              [](Params* p) { return &p->high_layer_speed; }),
       FieldTrialStructMember("base_layer_speed",
                              [](Params* p) { return &p->base_layer_speed; }),
       FieldTrialStructMember("deblock_mode",
                              [](Params* p) { return &p->deblock_mode; }),
       FieldTrialStructMember("denoiser",
                              [](Params* p) { return &p->allow_denoising; })},
      {});

  FieldTrialFlag per_layer_speed("use_per_layer_speed");

  ParseFieldTrial({&trials_list, &per_layer_speed},
                  trials.Lookup("WebRTC-VP9-PerformanceFlags"));

  PerformanceFlags flags;
  flags.use_per_layer_speed = per_layer_speed.Get();

  constexpr int kMinSpeed = 1;
  constexpr int kMaxSpeed = 9;
  for (auto& f : trials_list.Get()) {
    if (f.base_layer_speed < kMinSpeed || f.base_layer_speed > kMaxSpeed ||
        f.high_layer_speed < kMinSpeed || f.high_layer_speed > kMaxSpeed ||
        f.deblock_mode < 0 || f.deblock_mode > 2) {
      RTC_LOG(LS_WARNING) << "Ignoring invalid performance flags: "
                          << "min_pixel_count = " << f.min_pixel_count
                          << ", high_layer_speed = " << f.high_layer_speed
                          << ", base_layer_speed = " << f.base_layer_speed
                          << ", deblock_mode = " << f.deblock_mode;
      continue;
    }
    flags.settings_by_resolution[f.min_pixel_count] = f;
  }

  if (flags.settings_by_resolution.empty()) {
    return GetDefaultPerformanceFlags();
  }

  return flags;
}

// static
LibvpxVp9Encoder::PerformanceFlags
LibvpxVp9Encoder::GetDefaultPerformanceFlags() {
  PerformanceFlags flags;
  flags.use_per_layer_speed = true;
#ifdef MOBILE_ARM
  // Speed 8 on all layers for all resolutions.
  flags.settings_by_resolution[0] = {.base_layer_speed = 8,
                                     .high_layer_speed = 8,
                                     .deblock_mode = 0,
                                     .allow_denoising = true};
#else

  // For smaller resolutions, use lower speed setting for the temporal base
  // layer (get some coding gain at the cost of increased encoding complexity).
  // Set encoder Speed 5 for TL0, encoder Speed 8 for upper temporal layers, and
  // disable deblocking for upper-most temporal layers.
  flags.settings_by_resolution[0] = {.base_layer_speed = 5,
                                     .high_layer_speed = 8,
                                     .deblock_mode = 1,
                                     .allow_denoising = true};

  // Use speed 7 for QCIF and above.
  // Set encoder Speed 7 for TL0, encoder Speed 8 for upper temporal layers, and
  // enable deblocking for all temporal layers.
  flags.settings_by_resolution[352 * 288] = {.base_layer_speed = 7,
                                             .high_layer_speed = 8,
                                             .deblock_mode = 0,
                                             .allow_denoising = true};

  // For very high resolution (1080p and up), turn the speed all the way up
  // since this is very CPU intensive. Also disable denoising to save CPU, at
  // these resolutions denoising appear less effective and hopefully you also
  // have a less noisy video source at this point.
  flags.settings_by_resolution[1920 * 1080] = {.base_layer_speed = 9,
                                               .high_layer_speed = 9,
                                               .deblock_mode = 0,
                                               .allow_denoising = false};

#endif
  return flags;
}

void LibvpxVp9Encoder::MaybeRewrapRawWithFormat(const vpx_img_fmt fmt,
                                                unsigned int width,
                                                unsigned int height) {
  if (!raw_) {
    raw_ = libvpx_->img_wrap(nullptr, fmt, width, height, 1, nullptr);
    RTC_LOG(LS_INFO) << "Configured VP9 encoder pixel format to "
                     << (fmt == VPX_IMG_FMT_NV12 ? "NV12" : "I420") << " "
                     << width << "x" << height;
  } else if (raw_->fmt != fmt || raw_->d_w != width || raw_->d_h != height) {
    RTC_LOG(LS_INFO) << "Switching VP9 encoder pixel format to "
                     << (fmt == VPX_IMG_FMT_NV12 ? "NV12" : "I420") << " "
                     << width << "x" << height;
    libvpx_->img_free(raw_);
    raw_ = libvpx_->img_wrap(nullptr, fmt, width, height, 1, nullptr);
  }
  // else no-op since the image is already in the right format.
  raw_->bit_depth = (fmt == VPX_IMG_FMT_I42016) ? 16 : 8;
}

scoped_refptr<VideoFrameBuffer> LibvpxVp9Encoder::PrepareBufferForProfile0(
    scoped_refptr<VideoFrameBuffer> buffer) {
  absl::InlinedVector<VideoFrameBuffer::Type, kMaxPreferredPixelFormats>
      supported_formats = {VideoFrameBuffer::Type::kI420,
                           VideoFrameBuffer::Type::kNV12};

  scoped_refptr<VideoFrameBuffer> mapped_buffer;
  if (buffer->type() != VideoFrameBuffer::Type::kNative) {
    // `buffer` is already mapped.
    mapped_buffer = buffer;
  } else {
    // Attempt to map to one of the supported formats.
    mapped_buffer = buffer->GetMappedFrameBuffer(supported_formats);
  }
  if (!mapped_buffer ||
      (absl::c_find(supported_formats, mapped_buffer->type()) ==
           supported_formats.end() &&
       mapped_buffer->type() != VideoFrameBuffer::Type::kI420A)) {
    // Unknown pixel format or unable to map, convert to I420 and prepare that
    // buffer instead to ensure Scale() is safe to use.
    auto converted_buffer = buffer->ToI420();
    if (!converted_buffer) {
      RTC_LOG(LS_ERROR) << "Failed to convert "
                        << VideoFrameBufferTypeToString(buffer->type())
                        << " image to I420. Can't encode frame.";
      return {};
    }
    RTC_CHECK(converted_buffer->type() == VideoFrameBuffer::Type::kI420 ||
              converted_buffer->type() == VideoFrameBuffer::Type::kI420A);

    // Because `buffer` had to be converted, use `converted_buffer` instead.
    buffer = mapped_buffer = converted_buffer;
  }

  // Prepare `raw_` from `mapped_buffer`.
  switch (mapped_buffer->type()) {
    case VideoFrameBuffer::Type::kI420:
    case VideoFrameBuffer::Type::kI420A: {
      MaybeRewrapRawWithFormat(VPX_IMG_FMT_I420, mapped_buffer->width(),
                               mapped_buffer->height());
      const I420BufferInterface* i420_buffer = mapped_buffer->GetI420();
      RTC_DCHECK(i420_buffer);

      // TODO: crbug.com/492213293 - Remove once the root cause is fixed.
      if (i420_buffer->StrideU() != i420_buffer->StrideV()) {
        RTC_LOG(LS_ERROR) << "Libvpx requires the U and V strides to be equal.";
        return {};
      }

      raw_->planes[VPX_PLANE_Y] = const_cast<uint8_t*>(i420_buffer->DataY());
      raw_->planes[VPX_PLANE_U] = const_cast<uint8_t*>(i420_buffer->DataU());
      raw_->planes[VPX_PLANE_V] = const_cast<uint8_t*>(i420_buffer->DataV());
      raw_->stride[VPX_PLANE_Y] = i420_buffer->StrideY();
      raw_->stride[VPX_PLANE_U] = i420_buffer->StrideU();
      raw_->stride[VPX_PLANE_V] = i420_buffer->StrideV();
      break;
    }
    case VideoFrameBuffer::Type::kNV12: {
      MaybeRewrapRawWithFormat(VPX_IMG_FMT_NV12, mapped_buffer->width(),
                               mapped_buffer->height());
      const NV12BufferInterface* nv12_buffer = mapped_buffer->GetNV12();
      RTC_DCHECK(nv12_buffer);
      raw_->planes[VPX_PLANE_Y] = const_cast<uint8_t*>(nv12_buffer->DataY());
      raw_->planes[VPX_PLANE_U] = const_cast<uint8_t*>(nv12_buffer->DataUV());
      raw_->planes[VPX_PLANE_V] = raw_->planes[VPX_PLANE_U] + 1;
      raw_->stride[VPX_PLANE_Y] = nv12_buffer->StrideY();
      raw_->stride[VPX_PLANE_U] = nv12_buffer->StrideUV();
      raw_->stride[VPX_PLANE_V] = nv12_buffer->StrideUV();
      break;
    }
    default:
      RTC_DCHECK_NOTREACHED();
  }
  return mapped_buffer;
}

}  // namespace webrtc

#endif  // RTC_ENABLE_VP9