1 files changed, 177 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/video_coding/svc/scalability_structure_l2t2_key_shift.cc b/third_party/libwebrtc/modules/video_coding/svc/scalability_structure_l2t2_key_shift.cc
new file mode 100644
index 0000000000..4d15942d3e
--- /dev/null
+++ b/third_party/libwebrtc/modules/video_coding/svc/scalability_structure_l2t2_key_shift.cc
@@ -0,0 +1,177 @@
+/*
+ *  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_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 {
+
+DecodeTargetIndication
+Dti(int sid, int tid, const ScalableVideoController::LayerFrameConfig& config) {
+  if (config.IsKeyframe()) {
+    RTC_DCHECK_EQ(config.TemporalId(), 0);
+    return sid < config.SpatialId() ? DecodeTargetIndication::kNotPresent
+                                    : DecodeTargetIndication::kSwitch;
+  }
+
+  if (sid != config.SpatialId() || tid < config.TemporalId()) {
+    return DecodeTargetIndication::kNotPresent;
+  }
+  if (tid == config.TemporalId() && tid > 0) {
+    return DecodeTargetIndication::kDiscardable;
+  }
+  return DecodeTargetIndication::kSwitch;
+}
+
+}  // namespace
+
+constexpr int ScalabilityStructureL2T2KeyShift::kNumSpatialLayers;
+constexpr int ScalabilityStructureL2T2KeyShift::kNumTemporalLayers;
+
+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;
+  result.uses_reference_scaling = true;
+  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;
+}
+
+std::vector<ScalableVideoController::LayerFrameConfig>
+ScalabilityStructureL2T2KeyShift::NextFrameConfig(bool restart) {
+  std::vector<LayerFrameConfig> configs;
+  configs.reserve(2);
+  if (restart) {
+    next_pattern_ = kKey;
+  }
+
+  // Buffer0 keeps latest S0T0 frame,
+  // Buffer1 keeps latest S1T0 frame.
+  switch (next_pattern_) {
+    case kKey:
+      if (DecodeTargetIsActive(/*sid=*/0, /*tid=*/0)) {
+        configs.emplace_back();
+        configs.back().S(0).T(0).Update(0).Keyframe();
+      }
+      if (DecodeTargetIsActive(/*sid=*/1, /*tid=*/0)) {
+        configs.emplace_back();
+        configs.back().S(1).T(0).Update(1);
+        if (DecodeTargetIsActive(/*sid=*/0, /*tid=*/0)) {
+          configs.back().Reference(0);
+        } else {
+          configs.back().Keyframe();
+        }
+      }
+      next_pattern_ = kDelta0;
+      break;
+    case kDelta0:
+      if (DecodeTargetIsActive(/*sid=*/0, /*tid=*/0)) {
+        configs.emplace_back();
+        configs.back().S(0).T(0).ReferenceAndUpdate(0);
+      }
+      if (DecodeTargetIsActive(/*sid=*/1, /*tid=*/1)) {
+        configs.emplace_back();
+        configs.back().S(1).T(1).Reference(1);
+      }
+      if (configs.empty() && DecodeTargetIsActive(/*sid=*/1, /*tid=*/0)) {
+        configs.emplace_back();
+        configs.back().S(1).T(0).ReferenceAndUpdate(1);
+      }
+      next_pattern_ = kDelta1;
+      break;
+    case kDelta1:
+      if (DecodeTargetIsActive(/*sid=*/0, /*tid=*/1)) {
+        configs.emplace_back();
+        configs.back().S(0).T(1).Reference(0);
+      }
+      if (DecodeTargetIsActive(/*sid=*/1, /*tid=*/0)) {
+        configs.emplace_back();
+        configs.back().S(1).T(0).ReferenceAndUpdate(1);
+      }
+      if (configs.empty() && DecodeTargetIsActive(/*sid=*/0, /*tid=*/0)) {
+        configs.emplace_back();
+        configs.back().S(0).T(0).ReferenceAndUpdate(0);
+      }
+      next_pattern_ = kDelta0;
+      break;
+  }
+
+  RTC_DCHECK(!configs.empty() || active_decode_targets_.none());
+  return configs;
+}
+
+GenericFrameInfo ScalabilityStructureL2T2KeyShift::OnEncodeDone(
+    const LayerFrameConfig& config) {
+  GenericFrameInfo frame_info;
+  frame_info.spatial_id = config.SpatialId();
+  frame_info.temporal_id = config.TemporalId();
+  frame_info.encoder_buffers = config.Buffers();
+  for (int sid = 0; sid < kNumSpatialLayers; ++sid) {
+    for (int tid = 0; tid < kNumTemporalLayers; ++tid) {
+      frame_info.decode_target_indications.push_back(Dti(sid, tid, config));
+    }
+  }
+  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;
+}
+
+void ScalabilityStructureL2T2KeyShift::OnRatesUpdated(
+    const VideoBitrateAllocation& bitrates) {
+  for (int sid = 0; sid < kNumSpatialLayers; ++sid) {
+    // Enable/disable spatial layers independetely.
+    bool active = bitrates.GetBitrate(sid, /*tid=*/0) > 0;
+    if (!DecodeTargetIsActive(sid, /*tid=*/0) && active) {
+      // Key frame is required to reenable any spatial layer.
+      next_pattern_ = kKey;
+    }
+
+    SetDecodeTargetIsActive(sid, /*tid=*/0, active);
+    SetDecodeTargetIsActive(sid, /*tid=*/1,
+                            active && bitrates.GetBitrate(sid, /*tid=*/1) > 0);
+  }
+}
+
+}  // namespace webrtc