text: /*
   *  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 "modules/video_coding/codecs/av1/scalability_structure_l2t2_key_shift.h"
  
  #include <utility>
  #include <vector>
  
  #include "absl/base/macros.h"
  #include "api/transport/rtp/dependency_descriptor.h"
  #include "rtc_base/checks.h"
  #include "rtc_base/logging.h"
  
  namespace webrtc {
  namespace {
  
  constexpr auto kNotPresent = DecodeTargetIndication::kNotPresent;
  constexpr auto kDiscardable = DecodeTargetIndication::kDiscardable;
  constexpr auto kSwitch = DecodeTargetIndication::kSwitch;
  
  constexpr DecodeTargetIndication kDtis[6][4] = {
      {kSwitch, kSwitch, kSwitch, kSwitch},                   //    kKey, S0T0
      {kNotPresent, kNotPresent, kSwitch, kSwitch},           //    kKey, S1T0
      {kSwitch, kSwitch, kNotPresent, kNotPresent},           //    kDelta0, S0T0
      {kNotPresent, kNotPresent, kNotPresent, kDiscardable},  //    kDelta0, S1T1
      {kNotPresent, kDiscardable, kNotPresent, kNotPresent},  //    kDelta1, S0T1
      {kNotPresent, kNotPresent, kSwitch, kSwitch},           //    kDelta1, S1T0
  };
  
  }  // namespace
  
  ScalabilityStructureL2T2KeyShift::~ScalabilityStructureL2T2KeyShift() = default;
  
  ScalableVideoController::StreamLayersConfig
  ScalabilityStructureL2T2KeyShift::StreamConfig() const {
    StreamLayersConfig result;
    result.num_spatial_layers = 2;
    result.num_temporal_layers = 2;
    result.scaling_factor_num[0] = 1;
    result.scaling_factor_den[0] = 2;
    return result;
  }
  
  FrameDependencyStructure ScalabilityStructureL2T2KeyShift::DependencyStructure()
      const {
    FrameDependencyStructure structure;
    structure.num_decode_targets = 4;
    structure.num_chains = 2;
    structure.decode_target_protected_by_chain = {0, 0, 1, 1};
    structure.templates.resize(7);
    auto& templates = structure.templates;
    templates[0].S(0).T(0).Dtis("SSSS").ChainDiffs({0, 0});
    templates[1].S(0).T(0).Dtis("SS--").ChainDiffs({2, 1}).FrameDiffs({2});
    templates[2].S(0).T(0).Dtis("SS--").ChainDiffs({4, 1}).FrameDiffs({4});
    templates[3].S(0).T(1).Dtis("-D--").ChainDiffs({2, 3}).FrameDiffs({2});
    templates[4].S(1).T(0).Dtis("--SS").ChainDiffs({1, 1}).FrameDiffs({1});
    templates[5].S(1).T(0).Dtis("--SS").ChainDiffs({3, 4}).FrameDiffs({4});
    templates[6].S(1).T(1).Dtis("---D").ChainDiffs({1, 2}).FrameDiffs({2});
    return structure;
  }
  
  ScalableVideoController::LayerFrameConfig
  ScalabilityStructureL2T2KeyShift::KeyFrameConfig() const {
    return LayerFrameConfig().Id(0).Keyframe().S(0).T(0).Update(0);
  }
  
  std::vector<ScalableVideoController::LayerFrameConfig>
  ScalabilityStructureL2T2KeyShift::NextFrameConfig(bool restart) {
    if (restart) {
      next_pattern_ = kKey;
    }
    std::vector<LayerFrameConfig> result(2);
  
    // Buffer0 keeps latest S0T0 frame,
    // Buffer1 keeps latest S1T0 frame.
    switch (next_pattern_) {
      case kKey:
        result[0] = KeyFrameConfig();
        result[1].Id(1).S(1).T(0).Reference(0).Update(1);
        next_pattern_ = kDelta0;
        break;
      case kDelta0:
        result[0].Id(2).S(0).T(0).ReferenceAndUpdate(0);
        result[1].Id(3).S(1).T(1).Reference(1);
        next_pattern_ = kDelta1;
        break;
      case kDelta1:
        result[0].Id(4).S(0).T(1).Reference(0);
        result[1].Id(5).S(1).T(0).ReferenceAndUpdate(1);
        next_pattern_ = kDelta0;
        break;
    }
    return result;
  }
  
  absl::optional<GenericFrameInfo> ScalabilityStructureL2T2KeyShift::OnEncodeDone(
      LayerFrameConfig config) {
    if (config.IsKeyframe()) {
      config = KeyFrameConfig();
    }
  
    absl::optional<GenericFrameInfo> frame_info;
    if (config.Id() < 0 || config.Id() >= int{ABSL_ARRAYSIZE(kDtis)}) {
      RTC_LOG(LS_ERROR) << "Unexpected config id " << config.Id();
      return frame_info;
    }
    frame_info.emplace();
    frame_info->spatial_id = config.SpatialId();
    frame_info->temporal_id = config.TemporalId();
    frame_info->encoder_buffers = config.Buffers();
    frame_info->decode_target_indications.assign(std::begin(kDtis[config.Id()]),
                                                 std::end(kDtis[config.Id()]));
    if (config.IsKeyframe()) {
      frame_info->part_of_chain = {true, true};
    } else if (config.TemporalId() == 0) {
      frame_info->part_of_chain = {config.SpatialId() == 0,
                                   config.SpatialId() == 1};
    } else {
      frame_info->part_of_chain = {false, false};
    }
    return frame_info;
  }
  
  }  // namespace webrtc
  