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diff --git a/third_party/libwebrtc/api/transport/rtp/dependency_descriptor.h b/third_party/libwebrtc/api/transport/rtp/dependency_descriptor.h
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index 0000000000..0db600918e
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+++ b/third_party/libwebrtc/api/transport/rtp/dependency_descriptor.h
@@ -0,0 +1,129 @@
+/*
+ *  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.
+ */
+
+#ifndef API_TRANSPORT_RTP_DEPENDENCY_DESCRIPTOR_H_
+#define API_TRANSPORT_RTP_DEPENDENCY_DESCRIPTOR_H_
+
+#include <stdint.h>
+
+#include <initializer_list>
+#include <memory>
+#include <vector>
+
+#include "absl/container/inlined_vector.h"
+#include "absl/strings/string_view.h"
+#include "absl/types/optional.h"
+#include "api/video/render_resolution.h"
+
+namespace webrtc {
+// Structures to build and parse dependency descriptor as described in
+// https://aomediacodec.github.io/av1-rtp-spec/#dependency-descriptor-rtp-header-extension
+
+// Relationship of a frame to a Decode target.
+enum class DecodeTargetIndication {
+  kNotPresent = 0,   // DecodeTargetInfo symbol '-'
+  kDiscardable = 1,  // DecodeTargetInfo symbol 'D'
+  kSwitch = 2,       // DecodeTargetInfo symbol 'S'
+  kRequired = 3      // DecodeTargetInfo symbol 'R'
+};
+
+struct FrameDependencyTemplate {
+  // Setters are named briefly to chain them when building the template.
+  FrameDependencyTemplate& S(int spatial_layer);
+  FrameDependencyTemplate& T(int temporal_layer);
+  FrameDependencyTemplate& Dtis(absl::string_view dtis);
+  FrameDependencyTemplate& FrameDiffs(std::initializer_list<int> diffs);
+  FrameDependencyTemplate& ChainDiffs(std::initializer_list<int> diffs);
+
+  friend bool operator==(const FrameDependencyTemplate& lhs,
+                         const FrameDependencyTemplate& rhs) {
+    return lhs.spatial_id == rhs.spatial_id &&
+           lhs.temporal_id == rhs.temporal_id &&
+           lhs.decode_target_indications == rhs.decode_target_indications &&
+           lhs.frame_diffs == rhs.frame_diffs &&
+           lhs.chain_diffs == rhs.chain_diffs;
+  }
+
+  int spatial_id = 0;
+  int temporal_id = 0;
+  absl::InlinedVector<DecodeTargetIndication, 10> decode_target_indications;
+  absl::InlinedVector<int, 4> frame_diffs;
+  absl::InlinedVector<int, 4> chain_diffs;
+};
+
+struct FrameDependencyStructure {
+  friend bool operator==(const FrameDependencyStructure& lhs,
+                         const FrameDependencyStructure& rhs) {
+    return lhs.num_decode_targets == rhs.num_decode_targets &&
+           lhs.num_chains == rhs.num_chains &&
+           lhs.decode_target_protected_by_chain ==
+               rhs.decode_target_protected_by_chain &&
+           lhs.resolutions == rhs.resolutions && lhs.templates == rhs.templates;
+  }
+
+  int structure_id = 0;
+  int num_decode_targets = 0;
+  int num_chains = 0;
+  // If chains are used (num_chains > 0), maps decode target index into index of
+  // the chain protecting that target.
+  absl::InlinedVector<int, 10> decode_target_protected_by_chain;
+  absl::InlinedVector<RenderResolution, 4> resolutions;
+  std::vector<FrameDependencyTemplate> templates;
+};
+
+struct DependencyDescriptor {
+  static constexpr int kMaxSpatialIds = 4;
+  static constexpr int kMaxTemporalIds = 8;
+  static constexpr int kMaxDecodeTargets = 32;
+  static constexpr int kMaxTemplates = 64;
+
+  bool first_packet_in_frame = true;
+  bool last_packet_in_frame = true;
+  int frame_number = 0;
+  FrameDependencyTemplate frame_dependencies;
+  absl::optional<RenderResolution> resolution;
+  absl::optional<uint32_t> active_decode_targets_bitmask;
+  std::unique_ptr<FrameDependencyStructure> attached_structure;
+};
+
+// Below are implementation details.
+namespace webrtc_impl {
+absl::InlinedVector<DecodeTargetIndication, 10> StringToDecodeTargetIndications(
+    absl::string_view indication_symbols);
+}  // namespace webrtc_impl
+
+inline FrameDependencyTemplate& FrameDependencyTemplate::S(int spatial_layer) {
+  this->spatial_id = spatial_layer;
+  return *this;
+}
+inline FrameDependencyTemplate& FrameDependencyTemplate::T(int temporal_layer) {
+  this->temporal_id = temporal_layer;
+  return *this;
+}
+inline FrameDependencyTemplate& FrameDependencyTemplate::Dtis(
+    absl::string_view dtis) {
+  this->decode_target_indications =
+      webrtc_impl::StringToDecodeTargetIndications(dtis);
+  return *this;
+}
+inline FrameDependencyTemplate& FrameDependencyTemplate::FrameDiffs(
+    std::initializer_list<int> diffs) {
+  this->frame_diffs.assign(diffs.begin(), diffs.end());
+  return *this;
+}
+inline FrameDependencyTemplate& FrameDependencyTemplate::ChainDiffs(
+    std::initializer_list<int> diffs) {
+  this->chain_diffs.assign(diffs.begin(), diffs.end());
+  return *this;
+}
+
+}  // namespace webrtc
+
+#endif  // API_TRANSPORT_RTP_DEPENDENCY_DESCRIPTOR_H_