modules/video_coding/svc/scalability_structure_l2t1_key.cc

/*
 *  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/svc/scalability_structure_l2t1_key.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 kSwitch = DecodeTargetIndication::kSwitch;

constexpr DecodeTargetIndication kDtis[3][2] = {
    {kSwitch, kSwitch},      // Key, S0
    {kSwitch, kNotPresent},  // Delta, S0
    {kNotPresent, kSwitch},  // Key and Delta, S1
};

}  // namespace

ScalabilityStructureL2T1Key::~ScalabilityStructureL2T1Key() = default;

ScalableVideoController::StreamLayersConfig
ScalabilityStructureL2T1Key::StreamConfig() const {
  StreamLayersConfig result;
  result.num_spatial_layers = 2;
  result.num_temporal_layers = 1;
  result.scaling_factor_num[0] = 1;
  result.scaling_factor_den[0] = 2;
  return result;
}

FrameDependencyStructure ScalabilityStructureL2T1Key::DependencyStructure()
    const {
  FrameDependencyStructure structure;
  structure.num_decode_targets = 2;
  structure.num_chains = 2;
  structure.decode_target_protected_by_chain = {0, 1};
  structure.templates.resize(4);
  structure.templates[0].S(0).Dtis("S-").ChainDiffs({2, 1}).FrameDiffs({2});
  structure.templates[1].S(0).Dtis("SS").ChainDiffs({0, 0});
  structure.templates[2].S(1).Dtis("-S").ChainDiffs({1, 2}).FrameDiffs({2});
  structure.templates[3].S(1).Dtis("-S").ChainDiffs({1, 1}).FrameDiffs({1});
  return structure;
}

ScalableVideoController::LayerFrameConfig
ScalabilityStructureL2T1Key::KeyFrameConfig() const {
  return LayerFrameConfig().Id(0).S(0).Keyframe().Update(0);
}

std::vector<ScalableVideoController::LayerFrameConfig>
ScalabilityStructureL2T1Key::NextFrameConfig(bool restart) {
  std::vector<LayerFrameConfig> result(2);

  // Buffer0 keeps latest S0T0 frame, Buffer1 keeps latest S1T0 frame.
  if (restart || keyframe_) {
    result[0] = KeyFrameConfig();
    result[1].Id(2).S(1).Reference(0).Update(1);
    keyframe_ = false;
  } else {
    result[0].Id(1).S(0).ReferenceAndUpdate(0);
    result[1].Id(2).S(1).ReferenceAndUpdate(1);
  }
  return result;
}

GenericFrameInfo ScalabilityStructureL2T1Key::OnEncodeDone(
    const LayerFrameConfig& config) {
  RTC_CHECK_GE(config.Id(), 0);
  RTC_CHECK_LT(config.Id(), ABSL_ARRAYSIZE(kDtis));

  GenericFrameInfo frame_info;
  frame_info.spatial_id = config.SpatialId();
  frame_info.temporal_id = config.TemporalId();
  frame_info.encoder_buffers = config.Buffers();
  int config_id = config.IsKeyframe() ? 0 : config.Id();
  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 {
    frame_info.part_of_chain = {config.SpatialId() == 0,
                                config.SpatialId() == 1};
  }
  return frame_info;
}

}  // namespace webrtc