api/video/rtp_video_frame_assembler.cc - src/ - Git at Google

 /*
  *  Copyright (c) 2021 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/video/rtp_video_frame_assembler.h"

 #include <algorithm>
 #include <cstdint>
 #include <map>
 #include <memory>
 #include <utility>
 #include <vector>

 #include "absl/container/inlined_vector.h"
 #include "absl/types/optional.h"
 #include "modules/rtp_rtcp/source/frame_object.h"
 #include "modules/rtp_rtcp/source/rtp_dependency_descriptor_extension.h"
 #include "modules/rtp_rtcp/source/rtp_generic_frame_descriptor_extension.h"
 #include "modules/rtp_rtcp/source/rtp_packet_received.h"
 #include "modules/rtp_rtcp/source/video_rtp_depacketizer_av1.h"
 #include "modules/rtp_rtcp/source/video_rtp_depacketizer_generic.h"
 #include "modules/rtp_rtcp/source/video_rtp_depacketizer_h264.h"
 #include "modules/rtp_rtcp/source/video_rtp_depacketizer_raw.h"
 #include "modules/rtp_rtcp/source/video_rtp_depacketizer_vp8.h"
 #include "modules/rtp_rtcp/source/video_rtp_depacketizer_vp9.h"
 #include "modules/video_coding/packet_buffer.h"
 #include "modules/video_coding/rtp_frame_reference_finder.h"
 #include "rtc_base/logging.h"
 #include "rtc_base/numerics/sequence_number_unwrapper.h"

 namespace webrtc {
 namespace {
 std::unique_ptr<VideoRtpDepacketizer> CreateDepacketizer(
     RtpVideoFrameAssembler::PayloadFormat payload_format) {
   switch (payload_format) {
     case RtpVideoFrameAssembler::kRaw:
       return std::make_unique<VideoRtpDepacketizerRaw>();
     case RtpVideoFrameAssembler::kH264:
       return std::make_unique<VideoRtpDepacketizerH264>();
     case RtpVideoFrameAssembler::kVp8:
       return std::make_unique<VideoRtpDepacketizerVp8>();
     case RtpVideoFrameAssembler::kVp9:
       return std::make_unique<VideoRtpDepacketizerVp9>();
     case RtpVideoFrameAssembler::kAv1:
       return std::make_unique<VideoRtpDepacketizerAv1>();
     case RtpVideoFrameAssembler::kGeneric:
       return std::make_unique<VideoRtpDepacketizerGeneric>();
     case RtpVideoFrameAssembler::kH265:
       // TODO(bugs.webrtc.org/13485): Implement VideoRtpDepacketizerH265
       RTC_DCHECK_NOTREACHED();
       return nullptr;
   }
   RTC_DCHECK_NOTREACHED();
   return nullptr;
 }
 }  // namespace

 class RtpVideoFrameAssembler::Impl {
  public:
   explicit Impl(std::unique_ptr<VideoRtpDepacketizer> depacketizer);
   ~Impl() = default;

   FrameVector InsertPacket(const RtpPacketReceived& packet);

  private:
   using RtpFrameVector =
       absl::InlinedVector<std::unique_ptr<RtpFrameObject>, 3>;

   RtpFrameVector AssembleFrames(
       video_coding::PacketBuffer::InsertResult insert_result);
   FrameVector FindReferences(RtpFrameVector frames);
   FrameVector UpdateWithPadding(uint16_t seq_num);
   bool ParseDependenciesDescriptorExtension(const RtpPacketReceived& rtp_packet,
                                             RTPVideoHeader& video_header);
   bool ParseGenericDescriptorExtension(const RtpPacketReceived& rtp_packet,
                                        RTPVideoHeader& video_header);
   void ClearOldData(uint16_t incoming_seq_num);

   std::unique_ptr<FrameDependencyStructure> video_structure_;
   SeqNumUnwrapper<uint16_t> frame_id_unwrapper_;
   absl::optional<int64_t> video_structure_frame_id_;
   std::unique_ptr<VideoRtpDepacketizer> depacketizer_;
   video_coding::PacketBuffer packet_buffer_;
   RtpFrameReferenceFinder reference_finder_;
 };

 RtpVideoFrameAssembler::Impl::Impl(
     std::unique_ptr<VideoRtpDepacketizer> depacketizer)
     : depacketizer_(std::move(depacketizer)),
       packet_buffer_(/*start_buffer_size=*/2048, /*max_buffer_size=*/2048) {}

 RtpVideoFrameAssembler::FrameVector RtpVideoFrameAssembler::Impl::InsertPacket(
     const RtpPacketReceived& rtp_packet) {
   if (rtp_packet.payload_size() == 0) {
     ClearOldData(rtp_packet.SequenceNumber());
     return UpdateWithPadding(rtp_packet.SequenceNumber());
   }

   absl::optional<VideoRtpDepacketizer::ParsedRtpPayload> parsed_payload =
       depacketizer_->Parse(rtp_packet.PayloadBuffer());

   if (parsed_payload == absl::nullopt) {
     return {};
   }

   if (rtp_packet.HasExtension<RtpDependencyDescriptorExtension>()) {
     if (!ParseDependenciesDescriptorExtension(rtp_packet,
                                               parsed_payload->video_header)) {
       return {};
     }
   } else if (rtp_packet.HasExtension<RtpGenericFrameDescriptorExtension00>()) {
     if (!ParseGenericDescriptorExtension(rtp_packet,
                                          parsed_payload->video_header)) {
       return {};
     }
   }

   parsed_payload->video_header.is_last_packet_in_frame |= rtp_packet.Marker();

   auto packet = std::make_unique<video_coding::PacketBuffer::Packet>(
       rtp_packet, parsed_payload->video_header);
   packet->video_payload = std::move(parsed_payload->video_payload);

   ClearOldData(rtp_packet.SequenceNumber());
   return FindReferences(
       AssembleFrames(packet_buffer_.InsertPacket(std::move(packet))));
 }

 void RtpVideoFrameAssembler::Impl::ClearOldData(uint16_t incoming_seq_num) {
   constexpr uint16_t kOldSeqNumThreshold = 2000;
   uint16_t old_seq_num = incoming_seq_num - kOldSeqNumThreshold;
   packet_buffer_.ClearTo(old_seq_num);
   reference_finder_.ClearTo(old_seq_num);
 }

 RtpVideoFrameAssembler::Impl::RtpFrameVector
 RtpVideoFrameAssembler::Impl::AssembleFrames(
     video_coding::PacketBuffer::InsertResult insert_result) {
   video_coding::PacketBuffer::Packet* first_packet = nullptr;
   std::vector<rtc::ArrayView<const uint8_t>> payloads;
   RtpFrameVector result;

   for (auto& packet : insert_result.packets) {
     if (packet->is_first_packet_in_frame()) {
       first_packet = packet.get();
       payloads.clear();
     }
     payloads.emplace_back(packet->video_payload);

     if (packet->is_last_packet_in_frame()) {
       rtc::scoped_refptr<EncodedImageBuffer> bitstream =
           depacketizer_->AssembleFrame(payloads);

       if (!bitstream) {
         continue;
       }

       const video_coding::PacketBuffer::Packet& last_packet = *packet;
       result.push_back(std::make_unique<RtpFrameObject>(
           first_packet->seq_num,                  //
           last_packet.seq_num,                    //
           last_packet.marker_bit,                 //
           /*times_nacked=*/0,                     //
           /*first_packet_received_time=*/0,       //
           /*last_packet_received_time=*/0,        //
           first_packet->timestamp,                //
           /*ntp_time_ms=*/0,                      //
           /*timing=*/VideoSendTiming(),           //
           first_packet->payload_type,             //
           first_packet->codec(),                  //
           last_packet.video_header.rotation,      //
           last_packet.video_header.content_type,  //
           first_packet->video_header,             //
           last_packet.video_header.color_space,   //
           /*packet_infos=*/RtpPacketInfos(),      //
           std::move(bitstream)));
     }
   }

   return result;
 }

 RtpVideoFrameAssembler::FrameVector
 RtpVideoFrameAssembler::Impl::FindReferences(RtpFrameVector frames) {
   FrameVector res;
   for (auto& frame : frames) {
     auto complete_frames = reference_finder_.ManageFrame(std::move(frame));
     for (std::unique_ptr<RtpFrameObject>& complete_frame : complete_frames) {
       uint16_t rtp_seq_num_start = complete_frame->first_seq_num();
       uint16_t rtp_seq_num_end = complete_frame->last_seq_num();
       res.emplace_back(rtp_seq_num_start, rtp_seq_num_end,
                        std::move(complete_frame));
     }
   }
   return res;
 }

 RtpVideoFrameAssembler::FrameVector
 RtpVideoFrameAssembler::Impl::UpdateWithPadding(uint16_t seq_num) {
   auto res =
       FindReferences(AssembleFrames(packet_buffer_.InsertPadding(seq_num)));
   auto ref_finder_update = reference_finder_.PaddingReceived(seq_num);

   for (std::unique_ptr<RtpFrameObject>& complete_frame : ref_finder_update) {
     uint16_t rtp_seq_num_start = complete_frame->first_seq_num();
     uint16_t rtp_seq_num_end = complete_frame->last_seq_num();
     res.emplace_back(rtp_seq_num_start, rtp_seq_num_end,
                      std::move(complete_frame));
   }

   return res;
 }

 bool RtpVideoFrameAssembler::Impl::ParseDependenciesDescriptorExtension(
     const RtpPacketReceived& rtp_packet,
     RTPVideoHeader& video_header) {
   webrtc::DependencyDescriptor dependency_descriptor;

   if (!rtp_packet.GetExtension<RtpDependencyDescriptorExtension>(
           video_structure_.get(), &dependency_descriptor)) {
     // Descriptor is either malformed, or the template referenced is not in
     // the `video_structure_` currently being held.
     // TODO(bugs.webrtc.org/10342): Improve packet reordering behavior.
     RTC_LOG(LS_WARNING) << "ssrc: " << rtp_packet.Ssrc()
                         << " Failed to parse dependency descriptor.";
     return false;
   }

   if (dependency_descriptor.attached_structure != nullptr &&
       !dependency_descriptor.first_packet_in_frame) {
     RTC_LOG(LS_WARNING) << "ssrc: " << rtp_packet.Ssrc()
                         << "Invalid dependency descriptor: structure "
                            "attached to non first packet of a frame.";
     return false;
   }

   video_header.is_first_packet_in_frame =
       dependency_descriptor.first_packet_in_frame;
   video_header.is_last_packet_in_frame =
       dependency_descriptor.last_packet_in_frame;

   int64_t frame_id =
       frame_id_unwrapper_.Unwrap(dependency_descriptor.frame_number);
   auto& generic_descriptor_info = video_header.generic.emplace();
   generic_descriptor_info.frame_id = frame_id;
   generic_descriptor_info.spatial_index =
       dependency_descriptor.frame_dependencies.spatial_id;
   generic_descriptor_info.temporal_index =
       dependency_descriptor.frame_dependencies.temporal_id;

   for (int fdiff : dependency_descriptor.frame_dependencies.frame_diffs) {
     generic_descriptor_info.dependencies.push_back(frame_id - fdiff);
   }
   for (int cdiff : dependency_descriptor.frame_dependencies.chain_diffs) {
     generic_descriptor_info.chain_diffs.push_back(frame_id - cdiff);
   }
   generic_descriptor_info.decode_target_indications =
       dependency_descriptor.frame_dependencies.decode_target_indications;
   if (dependency_descriptor.resolution) {
     video_header.width = dependency_descriptor.resolution->Width();
     video_header.height = dependency_descriptor.resolution->Height();
   }
   if (dependency_descriptor.active_decode_targets_bitmask.has_value()) {
     generic_descriptor_info.active_decode_targets =
         *dependency_descriptor.active_decode_targets_bitmask;
   }

   // FrameDependencyStructure is sent in the dependency descriptor of the first
   // packet of a key frame and is required to parse all subsequent packets until
   // the next key frame.
   if (dependency_descriptor.attached_structure) {
     RTC_DCHECK(dependency_descriptor.first_packet_in_frame);
     if (video_structure_frame_id_ > frame_id) {
       RTC_LOG(LS_WARNING)
           << "Arrived key frame with id " << frame_id << " and structure id "
           << dependency_descriptor.attached_structure->structure_id
           << " is older than the latest received key frame with id "
           << *video_structure_frame_id_ << " and structure id "
           << video_structure_->structure_id;
       return false;
     }
     video_structure_ = std::move(dependency_descriptor.attached_structure);
     video_structure_frame_id_ = frame_id;
     video_header.frame_type = VideoFrameType::kVideoFrameKey;
   } else {
     video_header.frame_type = VideoFrameType::kVideoFrameDelta;
   }
   return true;
 }

 bool RtpVideoFrameAssembler::Impl::ParseGenericDescriptorExtension(
     const RtpPacketReceived& rtp_packet,
     RTPVideoHeader& video_header) {
   RtpGenericFrameDescriptor generic_frame_descriptor;
   if (!rtp_packet.GetExtension<RtpGenericFrameDescriptorExtension00>(
           &generic_frame_descriptor)) {
     return false;
   }

   video_header.is_first_packet_in_frame =
       generic_frame_descriptor.FirstPacketInSubFrame();
   video_header.is_last_packet_in_frame =
       generic_frame_descriptor.LastPacketInSubFrame();

   if (generic_frame_descriptor.FirstPacketInSubFrame()) {
     video_header.frame_type =
         generic_frame_descriptor.FrameDependenciesDiffs().empty()
             ? VideoFrameType::kVideoFrameKey
             : VideoFrameType::kVideoFrameDelta;

     auto& generic_descriptor_info = video_header.generic.emplace();
     int64_t frame_id =
         frame_id_unwrapper_.Unwrap(generic_frame_descriptor.FrameId());
     generic_descriptor_info.frame_id = frame_id;
     generic_descriptor_info.spatial_index =
         generic_frame_descriptor.SpatialLayer();
     generic_descriptor_info.temporal_index =
         generic_frame_descriptor.TemporalLayer();
     for (uint16_t fdiff : generic_frame_descriptor.FrameDependenciesDiffs()) {
       generic_descriptor_info.dependencies.push_back(frame_id - fdiff);
     }
   }
   video_header.width = generic_frame_descriptor.Width();
   video_header.height = generic_frame_descriptor.Height();
   return true;
 }

 RtpVideoFrameAssembler::RtpVideoFrameAssembler(PayloadFormat payload_format)
     : impl_(std::make_unique<Impl>(CreateDepacketizer(payload_format))) {}

 RtpVideoFrameAssembler::~RtpVideoFrameAssembler() = default;

 RtpVideoFrameAssembler::FrameVector RtpVideoFrameAssembler::InsertPacket(
     const RtpPacketReceived& packet) {
   return impl_->InsertPacket(packet);
 }

 }  // namespace webrtc
	/*
	* Copyright (c) 2021 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/video/rtp_video_frame_assembler.h"

	#include <algorithm>
	#include <cstdint>
	#include <map>
	#include <memory>
	#include <utility>
	#include <vector>

	#include "absl/container/inlined_vector.h"
	#include "absl/types/optional.h"
	#include "modules/rtp_rtcp/source/frame_object.h"
	#include "modules/rtp_rtcp/source/rtp_dependency_descriptor_extension.h"
	#include "modules/rtp_rtcp/source/rtp_generic_frame_descriptor_extension.h"
	#include "modules/rtp_rtcp/source/rtp_packet_received.h"
	#include "modules/rtp_rtcp/source/video_rtp_depacketizer_av1.h"
	#include "modules/rtp_rtcp/source/video_rtp_depacketizer_generic.h"
	#include "modules/rtp_rtcp/source/video_rtp_depacketizer_h264.h"
	#include "modules/rtp_rtcp/source/video_rtp_depacketizer_raw.h"
	#include "modules/rtp_rtcp/source/video_rtp_depacketizer_vp8.h"
	#include "modules/rtp_rtcp/source/video_rtp_depacketizer_vp9.h"
	#include "modules/video_coding/packet_buffer.h"
	#include "modules/video_coding/rtp_frame_reference_finder.h"
	#include "rtc_base/logging.h"
	#include "rtc_base/numerics/sequence_number_unwrapper.h"

	namespace webrtc {
	namespace {
	std::unique_ptr<VideoRtpDepacketizer> CreateDepacketizer(
	RtpVideoFrameAssembler::PayloadFormat payload_format) {
	switch (payload_format) {
	case RtpVideoFrameAssembler::kRaw:
	return std::make_unique<VideoRtpDepacketizerRaw>();
	case RtpVideoFrameAssembler::kH264:
	return std::make_unique<VideoRtpDepacketizerH264>();
	case RtpVideoFrameAssembler::kVp8:
	return std::make_unique<VideoRtpDepacketizerVp8>();
	case RtpVideoFrameAssembler::kVp9:
	return std::make_unique<VideoRtpDepacketizerVp9>();
	case RtpVideoFrameAssembler::kAv1:
	return std::make_unique<VideoRtpDepacketizerAv1>();
	case RtpVideoFrameAssembler::kGeneric:
	return std::make_unique<VideoRtpDepacketizerGeneric>();
	case RtpVideoFrameAssembler::kH265:
	// TODO(bugs.webrtc.org/13485): Implement VideoRtpDepacketizerH265
	RTC_DCHECK_NOTREACHED();
	return nullptr;
	}
	RTC_DCHECK_NOTREACHED();
	return nullptr;
	}
	} // namespace

	class RtpVideoFrameAssembler::Impl {
	public:
	explicit Impl(std::unique_ptr<VideoRtpDepacketizer> depacketizer);
	~Impl() = default;

	FrameVector InsertPacket(const RtpPacketReceived& packet);

	private:
	using RtpFrameVector =
	absl::InlinedVector<std::unique_ptr<RtpFrameObject>, 3>;

	RtpFrameVector AssembleFrames(
	video_coding::PacketBuffer::InsertResult insert_result);
	FrameVector FindReferences(RtpFrameVector frames);
	FrameVector UpdateWithPadding(uint16_t seq_num);
	bool ParseDependenciesDescriptorExtension(const RtpPacketReceived& rtp_packet,
	RTPVideoHeader& video_header);
	bool ParseGenericDescriptorExtension(const RtpPacketReceived& rtp_packet,
	RTPVideoHeader& video_header);
	void ClearOldData(uint16_t incoming_seq_num);

	std::unique_ptr<FrameDependencyStructure> video_structure_;
	SeqNumUnwrapper<uint16_t> frame_id_unwrapper_;
	absl::optional<int64_t> video_structure_frame_id_;
	std::unique_ptr<VideoRtpDepacketizer> depacketizer_;
	video_coding::PacketBuffer packet_buffer_;
	RtpFrameReferenceFinder reference_finder_;
	};

	RtpVideoFrameAssembler::Impl::Impl(
	std::unique_ptr<VideoRtpDepacketizer> depacketizer)
	: depacketizer_(std::move(depacketizer)),
	packet_buffer_(/start_buffer_size=/2048, /max_buffer_size=/2048) {}

	RtpVideoFrameAssembler::FrameVector RtpVideoFrameAssembler::Impl::InsertPacket(
	const RtpPacketReceived& rtp_packet) {
	if (rtp_packet.payload_size() == 0) {
	ClearOldData(rtp_packet.SequenceNumber());
	return UpdateWithPadding(rtp_packet.SequenceNumber());
	}

	absl::optional<VideoRtpDepacketizer::ParsedRtpPayload> parsed_payload =
	depacketizer_->Parse(rtp_packet.PayloadBuffer());

	if (parsed_payload == absl::nullopt) {
	return {};
	}

	if (rtp_packet.HasExtension<RtpDependencyDescriptorExtension>()) {
	if (!ParseDependenciesDescriptorExtension(rtp_packet,
	parsed_payload->video_header)) {
	return {};
	}
	} else if (rtp_packet.HasExtension<RtpGenericFrameDescriptorExtension00>()) {
	if (!ParseGenericDescriptorExtension(rtp_packet,
	parsed_payload->video_header)) {
	return {};
	}
	}

	parsed_payload->video_header.is_last_packet_in_frame \|= rtp_packet.Marker();

	auto packet = std::make_unique<video_coding::PacketBuffer::Packet>(
	rtp_packet, parsed_payload->video_header);
	packet->video_payload = std::move(parsed_payload->video_payload);

	ClearOldData(rtp_packet.SequenceNumber());
	return FindReferences(
	AssembleFrames(packet_buffer_.InsertPacket(std::move(packet))));
	}

	void RtpVideoFrameAssembler::Impl::ClearOldData(uint16_t incoming_seq_num) {
	constexpr uint16_t kOldSeqNumThreshold = 2000;
	uint16_t old_seq_num = incoming_seq_num - kOldSeqNumThreshold;
	packet_buffer_.ClearTo(old_seq_num);
	reference_finder_.ClearTo(old_seq_num);
	}

	RtpVideoFrameAssembler::Impl::RtpFrameVector
	RtpVideoFrameAssembler::Impl::AssembleFrames(
	video_coding::PacketBuffer::InsertResult insert_result) {
	video_coding::PacketBuffer::Packet* first_packet = nullptr;
	std::vector<rtc::ArrayView<const uint8_t>> payloads;
	RtpFrameVector result;

	for (auto& packet : insert_result.packets) {
	if (packet->is_first_packet_in_frame()) {
	first_packet = packet.get();
	payloads.clear();
	}
	payloads.emplace_back(packet->video_payload);

	if (packet->is_last_packet_in_frame()) {
	rtc::scoped_refptr<EncodedImageBuffer> bitstream =
	depacketizer_->AssembleFrame(payloads);

	if (!bitstream) {
	continue;
	}

	const video_coding::PacketBuffer::Packet& last_packet = *packet;
	result.push_back(std::make_unique<RtpFrameObject>(
	first_packet->seq_num, //
	last_packet.seq_num, //
	last_packet.marker_bit, //
	/times_nacked=/0, //
	/first_packet_received_time=/0, //
	/last_packet_received_time=/0, //
	first_packet->timestamp, //
	/ntp_time_ms=/0, //
	/timing=/VideoSendTiming(), //
	first_packet->payload_type, //
	first_packet->codec(), //
	last_packet.video_header.rotation, //
	last_packet.video_header.content_type, //
	first_packet->video_header, //
	last_packet.video_header.color_space, //
	/packet_infos=/RtpPacketInfos(), //
	std::move(bitstream)));
	}
	}

	return result;
	}

	RtpVideoFrameAssembler::FrameVector
	RtpVideoFrameAssembler::Impl::FindReferences(RtpFrameVector frames) {
	FrameVector res;
	for (auto& frame : frames) {
	auto complete_frames = reference_finder_.ManageFrame(std::move(frame));
	for (std::unique_ptr<RtpFrameObject>& complete_frame : complete_frames) {
	uint16_t rtp_seq_num_start = complete_frame->first_seq_num();
	uint16_t rtp_seq_num_end = complete_frame->last_seq_num();
	res.emplace_back(rtp_seq_num_start, rtp_seq_num_end,
	std::move(complete_frame));
	}
	}
	return res;
	}

	RtpVideoFrameAssembler::FrameVector
	RtpVideoFrameAssembler::Impl::UpdateWithPadding(uint16_t seq_num) {
	auto res =
	FindReferences(AssembleFrames(packet_buffer_.InsertPadding(seq_num)));
	auto ref_finder_update = reference_finder_.PaddingReceived(seq_num);

	for (std::unique_ptr<RtpFrameObject>& complete_frame : ref_finder_update) {
	uint16_t rtp_seq_num_start = complete_frame->first_seq_num();
	uint16_t rtp_seq_num_end = complete_frame->last_seq_num();
	res.emplace_back(rtp_seq_num_start, rtp_seq_num_end,
	std::move(complete_frame));
	}

	return res;
	}

	bool RtpVideoFrameAssembler::Impl::ParseDependenciesDescriptorExtension(
	const RtpPacketReceived& rtp_packet,
	RTPVideoHeader& video_header) {
	webrtc::DependencyDescriptor dependency_descriptor;

	if (!rtp_packet.GetExtension<RtpDependencyDescriptorExtension>(
	video_structure_.get(), &dependency_descriptor)) {
	// Descriptor is either malformed, or the template referenced is not in
	// the `video_structure_` currently being held.
	// TODO(bugs.webrtc.org/10342): Improve packet reordering behavior.
	RTC_LOG(LS_WARNING) << "ssrc: " << rtp_packet.Ssrc()
	<< " Failed to parse dependency descriptor.";
	return false;
	}

	if (dependency_descriptor.attached_structure != nullptr &&
	!dependency_descriptor.first_packet_in_frame) {
	RTC_LOG(LS_WARNING) << "ssrc: " << rtp_packet.Ssrc()
	<< "Invalid dependency descriptor: structure "
	"attached to non first packet of a frame.";
	return false;
	}

	video_header.is_first_packet_in_frame =
	dependency_descriptor.first_packet_in_frame;
	video_header.is_last_packet_in_frame =
	dependency_descriptor.last_packet_in_frame;

	int64_t frame_id =
	frame_id_unwrapper_.Unwrap(dependency_descriptor.frame_number);
	auto& generic_descriptor_info = video_header.generic.emplace();
	generic_descriptor_info.frame_id = frame_id;
	generic_descriptor_info.spatial_index =
	dependency_descriptor.frame_dependencies.spatial_id;
	generic_descriptor_info.temporal_index =
	dependency_descriptor.frame_dependencies.temporal_id;

	for (int fdiff : dependency_descriptor.frame_dependencies.frame_diffs) {
	generic_descriptor_info.dependencies.push_back(frame_id - fdiff);
	}
	for (int cdiff : dependency_descriptor.frame_dependencies.chain_diffs) {
	generic_descriptor_info.chain_diffs.push_back(frame_id - cdiff);
	}
	generic_descriptor_info.decode_target_indications =
	dependency_descriptor.frame_dependencies.decode_target_indications;
	if (dependency_descriptor.resolution) {
	video_header.width = dependency_descriptor.resolution->Width();
	video_header.height = dependency_descriptor.resolution->Height();
	}
	if (dependency_descriptor.active_decode_targets_bitmask.has_value()) {
	generic_descriptor_info.active_decode_targets =
	*dependency_descriptor.active_decode_targets_bitmask;
	}

	// FrameDependencyStructure is sent in the dependency descriptor of the first
	// packet of a key frame and is required to parse all subsequent packets until
	// the next key frame.
	if (dependency_descriptor.attached_structure) {
	RTC_DCHECK(dependency_descriptor.first_packet_in_frame);
	if (video_structure_frame_id_ > frame_id) {
	RTC_LOG(LS_WARNING)
	<< "Arrived key frame with id " << frame_id << " and structure id "
	<< dependency_descriptor.attached_structure->structure_id
	<< " is older than the latest received key frame with id "
	<< *video_structure_frame_id_ << " and structure id "
	<< video_structure_->structure_id;
	return false;
	}
	video_structure_ = std::move(dependency_descriptor.attached_structure);
	video_structure_frame_id_ = frame_id;
	video_header.frame_type = VideoFrameType::kVideoFrameKey;
	} else {
	video_header.frame_type = VideoFrameType::kVideoFrameDelta;
	}
	return true;
	}

	bool RtpVideoFrameAssembler::Impl::ParseGenericDescriptorExtension(
	const RtpPacketReceived& rtp_packet,
	RTPVideoHeader& video_header) {
	RtpGenericFrameDescriptor generic_frame_descriptor;
	if (!rtp_packet.GetExtension<RtpGenericFrameDescriptorExtension00>(
	&generic_frame_descriptor)) {
	return false;
	}

	video_header.is_first_packet_in_frame =
	generic_frame_descriptor.FirstPacketInSubFrame();
	video_header.is_last_packet_in_frame =
	generic_frame_descriptor.LastPacketInSubFrame();

	if (generic_frame_descriptor.FirstPacketInSubFrame()) {
	video_header.frame_type =
	generic_frame_descriptor.FrameDependenciesDiffs().empty()
	? VideoFrameType::kVideoFrameKey
	: VideoFrameType::kVideoFrameDelta;

	auto& generic_descriptor_info = video_header.generic.emplace();
	int64_t frame_id =
	frame_id_unwrapper_.Unwrap(generic_frame_descriptor.FrameId());
	generic_descriptor_info.frame_id = frame_id;
	generic_descriptor_info.spatial_index =
	generic_frame_descriptor.SpatialLayer();
	generic_descriptor_info.temporal_index =
	generic_frame_descriptor.TemporalLayer();
	for (uint16_t fdiff : generic_frame_descriptor.FrameDependenciesDiffs()) {
	generic_descriptor_info.dependencies.push_back(frame_id - fdiff);
	}
	}
	video_header.width = generic_frame_descriptor.Width();
	video_header.height = generic_frame_descriptor.Height();
	return true;
	}

	RtpVideoFrameAssembler::RtpVideoFrameAssembler(PayloadFormat payload_format)
	: impl_(std::make_unique<Impl>(CreateDepacketizer(payload_format))) {}

	RtpVideoFrameAssembler::~RtpVideoFrameAssembler() = default;

	RtpVideoFrameAssembler::FrameVector RtpVideoFrameAssembler::InsertPacket(
	const RtpPacketReceived& packet) {
	return impl_->InsertPacket(packet);
	}

	} // namespace webrtc