Implement AV1 RtpPacketizer class

Bug: webrtc:11042
Change-Id: Id1fc0acfa87a4520344f2636f50cb4d4e7284829
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/160416
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29947}

modules/rtp_rtcp/BUILD.gn

@@ -181,6 +181,8 @@ rtc_library("rtp_rtcp") {
     "source/rtp_header_extension_size.h",
     "source/rtp_packet_history.cc",
     "source/rtp_packet_history.h",
+    "source/rtp_packetizer_av1.cc",
+    "source/rtp_packetizer_av1.h",
     "source/rtp_rtcp_config.h",
     "source/rtp_rtcp_impl.cc",
     "source/rtp_rtcp_impl.h",
@@ -459,6 +461,7 @@ if (rtc_include_tests) {
       "source/rtp_header_extension_size_unittest.cc",
       "source/rtp_packet_history_unittest.cc",
       "source/rtp_packet_unittest.cc",
+      "source/rtp_packetizer_av1_unittest.cc",
       "source/rtp_rtcp_impl_unittest.cc",
       "source/rtp_sender_audio_unittest.cc",
       "source/rtp_sender_unittest.cc",
@@ -489,6 +492,7 @@ if (rtc_include_tests) {
       "../../api/rtc_event_log",
       "../../api/transport:field_trial_based_config",
       "../../api/units:timestamp",
+      "../../api/video:encoded_image",
       "../../api/video:video_bitrate_allocation",
       "../../api/video:video_bitrate_allocator",
       "../../api/video:video_codec_constants",

modules/rtp_rtcp/source/rtp_packetizer_av1.cc

@@ -0,0 +1,425 @@
+/*
+ *  Copyright (c) 2019 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/rtp_rtcp/source/rtp_packetizer_av1.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <algorithm>
+
+#include "api/array_view.h"
+#include "api/video/video_frame_type.h"
+#include "modules/rtp_rtcp/source/rtp_packet_to_send.h"
+#include "rtc_base/byte_buffer.h"
+#include "rtc_base/checks.h"
+#include "rtc_base/logging.h"
+
+namespace webrtc {
+namespace {
+// TODO(danilchap): Some of the helpers/constants are same as in
+// rtp_depacketizer_av1. Move them to common av1 file.
+constexpr int kAggregationHeaderSize = 1;
+// when there are 3 or less OBU (fragments) in a packet, size of the last one
+// can be omited.
+constexpr int kMaxNumObusToOmitSize = 3;
+constexpr uint8_t kObuSizePresentBit = 0b0'0000'010;
+constexpr int kObuTypeSequenceHeader = 1;
+constexpr int kObuTypeTemporalDelimiter = 2;
+constexpr int kObuTypeTileList = 8;
+constexpr int kObuTypePadding = 15;
+
+bool ObuHasExtension(uint8_t obu_header) {
+  return obu_header & 0b0'0000'100;
+}
+
+bool ObuHasSize(uint8_t obu_header) {
+  return obu_header & kObuSizePresentBit;
+}
+
+int ObuType(uint8_t obu_header) {
+  return (obu_header & 0b0'1111'000) >> 3;
+}
+
+int Leb128Size(int value) {
+  RTC_DCHECK_GE(value, 0);
+  int size = 0;
+  while (value >= 0x80) {
+    ++size;
+    value >>= 7;
+  }
+  return size + 1;
+}
+
+// Returns number of bytes consumed.
+int WriteLeb128(uint32_t value, uint8_t* buffer) {
+  int size = 0;
+  while (value >= 0x80) {
+    buffer[size] = 0x80 | (value & 0x7F);
+    ++size;
+    value >>= 7;
+  }
+  buffer[size] = value;
+  ++size;
+  return size;
+}
+
+// Given |remaining_bytes| free bytes left in a packet, returns max size of an
+// OBU fragment that can fit into the packet.
+// i.e. MaxFragmentSize + Leb128Size(MaxFragmentSize) <= remaining_bytes.
+int MaxFragmentSize(int remaining_bytes) {
+  if (remaining_bytes <= 1) {
+    return 0;
+  }
+  for (int i = 1;; ++i) {
+    if (remaining_bytes < (1 << 7 * i) + i) {
+      return remaining_bytes - i;
+    }
+  }
+}
+
+}  // namespace
+
+RtpPacketizerAv1::RtpPacketizerAv1(rtc::ArrayView<const uint8_t> payload,
+                                   RtpPacketizer::PayloadSizeLimits limits,
+                                   VideoFrameType frame_type)
+    : frame_type_(frame_type),
+      obus_(ParseObus(payload)),
+      packets_(Packetize(obus_, limits)) {}
+
+std::vector<RtpPacketizerAv1::Obu> RtpPacketizerAv1::ParseObus(
+    rtc::ArrayView<const uint8_t> payload) {
+  std::vector<Obu> result;
+  rtc::ByteBufferReader payload_reader(
+      reinterpret_cast<const char*>(payload.data()), payload.size());
+  while (payload_reader.Length() > 0) {
+    Obu obu;
+    payload_reader.ReadUInt8(&obu.header);
+    obu.size = 1;
+    if (ObuHasExtension(obu.header)) {
+      if (payload_reader.Length() == 0) {
+        RTC_DLOG(LS_ERROR) << "Malformed AV1 input: expected extension_header, "
+                              "no more bytes in the buffer. Offset: "
+                           << (payload.size() - payload_reader.Length());
+        return {};
+      }
+      payload_reader.ReadUInt8(&obu.extension_header);
+      ++obu.size;
+    }
+    if (!ObuHasSize(obu.header)) {
+      obu.payload = rtc::MakeArrayView(
+          reinterpret_cast<const uint8_t*>(payload_reader.Data()),
+          payload_reader.Length());
+      payload_reader.Consume(payload_reader.Length());
+    } else {
+      uint64_t size = 0;
+      if (!payload_reader.ReadUVarint(&size) ||
+          size > payload_reader.Length()) {
+        RTC_DLOG(LS_ERROR) << "Malformed AV1 input: declared size " << size
+                           << " is larger than remaining buffer size "
+                           << payload_reader.Length();
+        return {};
+      }
+      obu.payload = rtc::MakeArrayView(
+          reinterpret_cast<const uint8_t*>(payload_reader.Data()), size);
+      payload_reader.Consume(size);
+    }
+    obu.size += obu.payload.size();
+    // Skip obus that shouldn't be transfered over rtp.
+    int obu_type = ObuType(obu.header);
+    if (obu_type != kObuTypeTemporalDelimiter &&  //
+        obu_type != kObuTypeTileList &&           //
+        obu_type != kObuTypePadding) {
+      result.push_back(obu);
+    }
+  }
+  return result;
+}
+
+int RtpPacketizerAv1::AdditionalBytesForPreviousObuElement(
+    const Packet& packet) {
+  if (packet.packet_size == 0) {
+    // Packet is still empty => no last OBU element, no need to reserve space
+    // for it.
+    return 0;
+  }
+  if (packet.num_obu_elements > kMaxNumObusToOmitSize) {
+    // There is so many obu elements in the packet, all of them must be
+    // prepended with the length field. That imply space for the length of the
+    // last obu element is already reserved.
+    return 0;
+  }
+  // No space was reserved for length field of the last OBU element, but that
+  // element becoming non-last, so it now requires explicit length field.
+  // Calculate how many bytes are needed to store the length in leb128 format.
+  return Leb128Size(packet.last_obu_size);
+}
+
+std::vector<RtpPacketizerAv1::Packet> RtpPacketizerAv1::Packetize(
+    rtc::ArrayView<const Obu> obus,
+    PayloadSizeLimits limits) {
+  std::vector<Packet> packets;
+  if (obus.empty()) {
+    return packets;
+  }
+  // Ignore certian edge cases where packets should be very small. They are
+  // inpractical but adds complexity to handle.
+  if (limits.max_payload_len - limits.last_packet_reduction_len < 3 ||
+      limits.max_payload_len - limits.first_packet_reduction_len < 3) {
+    RTC_DLOG(LS_ERROR) << "Failed to packetize AV1 frame: requested packet "
+                          "size is unreasonable small.";
+    return packets;
+  }
+  // Aggregation header is present in all packets.
+  limits.max_payload_len -= kAggregationHeaderSize;
+
+  // Assemble packets. Push to current packet as much as it can hold before
+  // considering next one. That would normally cause uneven distribution across
+  // packets, specifically last one would be generally smaller.
+  packets.emplace_back(/*first_obu_index=*/0);
+  int packet_remaining_bytes =
+      limits.max_payload_len - limits.first_packet_reduction_len;
+  for (size_t obu_index = 0; obu_index < obus.size(); ++obu_index) {
+    const bool is_last_obu = obu_index == obus.size() - 1;
+    const Obu& obu = obus[obu_index];
+
+    // Putting |obu| into the last packet would make last obu element stored in
+    // that packet not last. All not last OBU elements must be prepend with the
+    // element length. AdditionalBytesForPreviousObuElement calculates how many
+    // bytes are needed to store that length.
+    int previous_obu_extra_size =
+        AdditionalBytesForPreviousObuElement(packets.back());
+    int min_required_size =
+        packets.back().num_obu_elements >= kMaxNumObusToOmitSize ? 2 : 1;
+    if (packet_remaining_bytes < previous_obu_extra_size + min_required_size) {
+      // Start a new packet.
+      packets.emplace_back(/*first_obu_index=*/obu_index);
+      packet_remaining_bytes = limits.max_payload_len;
+      previous_obu_extra_size = 0;
+    }
+    Packet& packet = packets.back();
+    // Start inserting current obu into the packet.
+    packet.packet_size += previous_obu_extra_size;
+    packet_remaining_bytes -= previous_obu_extra_size;
+    packet.num_obu_elements++;
+
+    bool must_write_obu_element_size =
+        packet.num_obu_elements > kMaxNumObusToOmitSize;
+    // Can fit all of the obu into the packet?
+    int required_bytes = obu.size;
+    if (must_write_obu_element_size) {
+      required_bytes += Leb128Size(obu.size);
+    }
+    int available_bytes = packet_remaining_bytes;
+    if (is_last_obu) {
+      // If this packet would be the last packet, available size is smaller.
+      if (packets.size() == 1) {
+        available_bytes += limits.first_packet_reduction_len;
+        available_bytes -= limits.single_packet_reduction_len;
+      } else {
+        available_bytes -= limits.last_packet_reduction_len;
+      }
+    }
+    if (required_bytes <= available_bytes) {
+      // Insert the obu into the packet unfragmented.
+      packet.last_obu_size = obu.size;
+      packet.packet_size += required_bytes;
+      packet_remaining_bytes -= required_bytes;
+      continue;
+    }
+
+    // Fragment the obu.
+    int max_first_fragment_size = must_write_obu_element_size
+                                      ? MaxFragmentSize(packet_remaining_bytes)
+                                      : packet_remaining_bytes;
+    // Because available_bytes might be different than
+    // packet_remaining_bytes it might happen that max_first_fragment_size >=
+    // obu.size. Also, since checks above verified |obu| should not be put
+    // completely into the |packet|, leave at least 1 byte for later packet.
+    int first_fragment_size = std::min(obu.size - 1, max_first_fragment_size);
+    if (first_fragment_size == 0) {
+      // Rather than writing 0-size element at the tail of the packet,
+      // 'uninsert' the |obu| from the |packet|.
+      packet.num_obu_elements--;
+      packet.packet_size -= previous_obu_extra_size;
+    } else {
+      packet.packet_size += first_fragment_size;
+      if (must_write_obu_element_size) {
+        packet.packet_size += Leb128Size(first_fragment_size);
+      }
+      packet.last_obu_size = first_fragment_size;
+    }
+
+    // Add middle fragments that occupy all of the packet.
+    // These are easy because
+    // - one obu per packet imply no need to store the size of the obu.
+    // - this packets are nor the first nor the last packets of the frame, so
+    // packet capacity is always limits.max_payload_len.
+    int obu_offset;
+    for (obu_offset = first_fragment_size;
+         obu_offset + limits.max_payload_len < obu.size;
+         obu_offset += limits.max_payload_len) {
+      packets.emplace_back(/*first_obu_index=*/obu_index);
+      Packet& packet = packets.back();
+      packet.num_obu_elements = 1;
+      packet.first_obu_offset = obu_offset;
+      int middle_fragment_size = limits.max_payload_len;
+      packet.last_obu_size = middle_fragment_size;
+      packet.packet_size = middle_fragment_size;
+    }
+
+    // Add the last fragment of the obu.
+    int last_fragment_size = obu.size - obu_offset;
+    // Check for corner case where last fragment of the last obu is too large
+    // to fit into last packet, but may fully fit into semi-last packet.
+    if (is_last_obu &&
+        last_fragment_size >
+            limits.max_payload_len - limits.last_packet_reduction_len) {
+      // Split last fragments into two.
+      RTC_DCHECK_GE(last_fragment_size, 2);
+      // Try to even packet sizes rather than payload sizes across the last
+      // two packets.
+      int semi_last_fragment_size =
+          (last_fragment_size + limits.last_packet_reduction_len) / 2;
+      // But leave at least one payload byte for the last packet to avoid
+      // weird scenarios where size of the fragment is zero and rtp payload has
+      // nothing except for an aggregation header.
+      if (semi_last_fragment_size >= last_fragment_size) {
+        semi_last_fragment_size = last_fragment_size - 1;
+      }
+      last_fragment_size -= semi_last_fragment_size;
+
+      packets.emplace_back(/*first_obu_index=*/obu_index);
+      Packet& packet = packets.back();
+      packet.num_obu_elements = 1;
+      packet.first_obu_offset = obu_offset;
+      packet.last_obu_size = semi_last_fragment_size;
+      packet.packet_size = semi_last_fragment_size;
+      obu_offset += semi_last_fragment_size;
+    }
+    packets.emplace_back(/*first_obu_index=*/obu_index);
+    Packet& last_packet = packets.back();
+    last_packet.num_obu_elements = 1;
+    last_packet.first_obu_offset = obu_offset;
+    last_packet.last_obu_size = last_fragment_size;
+    last_packet.packet_size = last_fragment_size;
+    packet_remaining_bytes = limits.max_payload_len - last_fragment_size;
+  }
+  return packets;
+}
+
+uint8_t RtpPacketizerAv1::AggregationHeader() const {
+  const Packet& packet = packets_[packet_index_];
+  uint8_t aggregation_header = 0;
+
+  // Set Z flag: first obu element is continuation of the previous OBU.
+  bool first_obu_element_is_fragment = packet.first_obu_offset > 0;
+  if (first_obu_element_is_fragment)
+    aggregation_header |= (1 << 7);
+
+  // Set Y flag: last obu element will be continuated in the next packet.
+  int last_obu_offset =
+      packet.num_obu_elements == 1 ? packet.first_obu_offset : 0;
+  bool last_obu_is_fragment =
+      last_obu_offset + packet.last_obu_size <
+      obus_[packet.first_obu + packet.num_obu_elements - 1].size;
+  if (last_obu_is_fragment)
+    aggregation_header |= (1 << 6);
+
+  // Set W field: number of obu elements in the packet (when not too large).
+  if (packet.num_obu_elements <= kMaxNumObusToOmitSize)
+    aggregation_header |= packet.num_obu_elements << 4;
+
+  // Set N flag: beginning of a new coded video sequence.
+  // Encoder may produce key frame without a sequence header, thus double check
+  // incoming frame includes the sequence header. Since Temporal delimiter is
+  // already filtered out, sequence header should be the first obu when present.
+  if (frame_type_ == VideoFrameType::kVideoFrameKey && packet_index_ == 0 &&
+      ObuType(obus_.front().header) == kObuTypeSequenceHeader) {
+    aggregation_header |= (1 << 3);
+  }
+  return aggregation_header;
+}
+
+bool RtpPacketizerAv1::NextPacket(RtpPacketToSend* packet) {
+  if (packet_index_ >= packets_.size()) {
+    return false;
+  }
+  const Packet& next_packet = packets_[packet_index_];
+
+  RTC_DCHECK_GT(next_packet.num_obu_elements, 0);
+  RTC_DCHECK_LT(next_packet.first_obu_offset,
+                obus_[next_packet.first_obu].size);
+  RTC_DCHECK_LE(
+      next_packet.last_obu_size,
+      obus_[next_packet.first_obu + next_packet.num_obu_elements - 1].size);
+
+  uint8_t* const rtp_payload =
+      packet->AllocatePayload(kAggregationHeaderSize + next_packet.packet_size);
+  uint8_t* write_at = rtp_payload;
+
+  *write_at++ = AggregationHeader();
+
+  int obu_offset = next_packet.first_obu_offset;
+  // Store all OBU elements except the last one.
+  for (int i = 0; i < next_packet.num_obu_elements - 1; ++i) {
+    const Obu& obu = obus_[next_packet.first_obu + i];
+    size_t fragment_size = obu.size - obu_offset;
+    write_at += WriteLeb128(fragment_size, write_at);
+    if (obu_offset == 0) {
+      *write_at++ = obu.header & ~kObuSizePresentBit;
+    }
+    if (obu_offset <= 1 && ObuHasExtension(obu.header)) {
+      *write_at++ = obu.extension_header;
+    }
+    int payload_offset =
+        std::max(0, obu_offset - (ObuHasExtension(obu.header) ? 2 : 1));
+    size_t payload_size = obu.payload.size() - payload_offset;
+    memcpy(write_at, obu.payload.data() + payload_offset, payload_size);
+    write_at += payload_size;
+    // All obus are stored from the beginning, except, may be, the first one.
+    obu_offset = 0;
+  }
+  // Store the last OBU element.
+  const Obu& last_obu =
+      obus_[next_packet.first_obu + next_packet.num_obu_elements - 1];
+  int fragment_size = next_packet.last_obu_size;
+  RTC_DCHECK_GT(fragment_size, 0);
+  if (next_packet.num_obu_elements > kMaxNumObusToOmitSize) {
+    write_at += WriteLeb128(fragment_size, write_at);
+  }
+  if (obu_offset == 0 && fragment_size > 0) {
+    *write_at++ = last_obu.header & ~kObuSizePresentBit;
+    --fragment_size;
+  }
+  if (obu_offset <= 1 && ObuHasExtension(last_obu.header) &&
+      fragment_size > 0) {
+    *write_at++ = last_obu.extension_header;
+    --fragment_size;
+  }
+  RTC_DCHECK_EQ(write_at - rtp_payload + fragment_size,
+                kAggregationHeaderSize + next_packet.packet_size);
+  int payload_offset =
+      std::max(0, obu_offset - (ObuHasExtension(last_obu.header) ? 2 : 1));
+  memcpy(write_at, last_obu.payload.data() + payload_offset, fragment_size);
+  write_at += fragment_size;
+
+  RTC_DCHECK_EQ(write_at - rtp_payload,
+                kAggregationHeaderSize + next_packet.packet_size);
+
+  ++packet_index_;
+  if (packet_index_ == packets_.size()) {
+    // TODO(danilchap): To support spatial scalability pass and use information
+    // if this frame is the last in the temporal unit.
+    packet->SetMarker(true);
+  }
+  return true;
+}
+
+}  // namespace webrtc

modules/rtp_rtcp/source/rtp_packetizer_av1.h

@@ -0,0 +1,70 @@
+/*
+ *  Copyright (c) 2019 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 MODULES_RTP_RTCP_SOURCE_RTP_PACKETIZER_AV1_H_
+#define MODULES_RTP_RTCP_SOURCE_RTP_PACKETIZER_AV1_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <vector>
+
+#include "api/array_view.h"
+#include "api/video/video_frame_type.h"
+#include "modules/rtp_rtcp/source/rtp_format.h"
+
+namespace webrtc {
+
+class RtpPacketizerAv1 : public RtpPacketizer {
+ public:
+  RtpPacketizerAv1(rtc::ArrayView<const uint8_t> payload,
+                   PayloadSizeLimits limits,
+                   VideoFrameType frame_type);
+  ~RtpPacketizerAv1() override = default;
+
+  size_t NumPackets() const override { return packets_.size() - packet_index_; }
+  bool NextPacket(RtpPacketToSend* packet) override;
+
+ private:
+  struct Obu {
+    uint8_t header;
+    uint8_t extension_header;  // undefined if (header & kXbit) == 0
+    rtc::ArrayView<const uint8_t> payload;
+    int size;  // size of the header and payload combined.
+  };
+  struct Packet {
+    explicit Packet(int first_obu_index) : first_obu(first_obu_index) {}
+    // Indexes into obus_ vector of the first and last obus that should put into
+    // the packet.
+    int first_obu;
+    int num_obu_elements = 0;
+    int first_obu_offset = 0;
+    int last_obu_size;
+    // Total size consumed by the packet.
+    int packet_size = 0;
+  };
+
+  // Parses the payload into serie of OBUs.
+  static std::vector<Obu> ParseObus(rtc::ArrayView<const uint8_t> payload);
+  // Returns the number of additional bytes needed to store the previous OBU
+  // element if an additonal OBU element is added to the packet.
+  static int AdditionalBytesForPreviousObuElement(const Packet& packet);
+  static std::vector<Packet> Packetize(rtc::ArrayView<const Obu> obus,
+                                       PayloadSizeLimits limits);
+  uint8_t AggregationHeader() const;
+
+  const VideoFrameType frame_type_;
+  const std::vector<Obu> obus_;
+  const std::vector<Packet> packets_;
+  size_t packet_index_ = 0;
+};
+
+}  // namespace webrtc
+#endif  // MODULES_RTP_RTCP_SOURCE_RTP_PACKETIZER_AV1_H_

modules/rtp_rtcp/source/rtp_packetizer_av1_unittest.cc

@@ -0,0 +1,365 @@
+/*
+ *  Copyright (c) 2019 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/rtp_rtcp/source/rtp_packetizer_av1.h"
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <initializer_list>
+#include <utility>
+#include <vector>
+
+#include "api/array_view.h"
+#include "api/scoped_refptr.h"
+#include "api/video/encoded_image.h"
+#include "modules/rtp_rtcp/source/rtp_depacketizer_av1.h"
+#include "modules/rtp_rtcp/source/rtp_packet_to_send.h"
+#include "test/gmock.h"
+#include "test/gtest.h"
+
+namespace webrtc {
+namespace {
+
+using ::testing::Each;
+using ::testing::ElementsAre;
+using ::testing::ElementsAreArray;
+using ::testing::Le;
+using ::testing::SizeIs;
+
+constexpr uint8_t kNewCodedVideoSequenceBit = 0b00'00'1000;
+// All obu types offset by 3 to take correct position in the obu_header.
+constexpr uint8_t kObuTypeSequenceHeader = 1 << 3;
+constexpr uint8_t kObuTypeTemporalDelimiter = 2 << 3;
+constexpr uint8_t kObuTypeFrameHeader = 3 << 3;
+constexpr uint8_t kObuTypeTileGroup = 4 << 3;
+constexpr uint8_t kObuTypeMetadata = 5 << 3;
+constexpr uint8_t kObuTypeFrame = 6 << 3;
+constexpr uint8_t kObuTypeTileList = 8 << 3;
+constexpr uint8_t kObuExtensionPresentBit = 0b0'0000'100;
+constexpr uint8_t kObuSizePresentBit = 0b0'0000'010;
+constexpr uint8_t kObuExtensionS1T1 = 0b001'01'000;
+
+// Wrapper around rtp_packet to make it look like container of payload bytes.
+struct RtpPayload {
+  using value_type = rtc::ArrayView<const uint8_t>::value_type;
+  using const_iterator = rtc::ArrayView<const uint8_t>::const_iterator;
+
+  RtpPayload() : rtp_packet(/*extensions=*/nullptr) {}
+  RtpPayload& operator=(RtpPayload&&) = default;
+  RtpPayload(RtpPayload&&) = default;
+
+  const_iterator begin() const { return rtp_packet.payload().begin(); }
+  const_iterator end() const { return rtp_packet.payload().end(); }
+  const uint8_t* data() const { return rtp_packet.payload().data(); }
+  size_t size() const { return rtp_packet.payload().size(); }
+
+  uint8_t aggregation_header() const { return rtp_packet.payload()[0]; }
+
+  RtpPacketToSend rtp_packet;
+};
+
+// Wrapper around frame pointer to make it look like container of bytes with
+// nullptr frame look like empty container.
+class Av1Frame {
+ public:
+  using value_type = uint8_t;
+  using const_iterator = const uint8_t*;
+
+  explicit Av1Frame(rtc::scoped_refptr<EncodedImageBuffer> frame)
+      : frame_(std::move(frame)) {}
+
+  const_iterator begin() const { return frame_ ? frame_->data() : nullptr; }
+  const_iterator end() const {
+    return frame_ ? (frame_->data() + frame_->size()) : nullptr;
+  }
+
+ private:
+  rtc::scoped_refptr<EncodedImageBuffer> frame_;
+};
+
+std::vector<RtpPayload> Packetize(
+    rtc::ArrayView<const uint8_t> payload,
+    RtpPacketizer::PayloadSizeLimits limits,
+    VideoFrameType frame_type = VideoFrameType::kVideoFrameDelta) {
+  // Run code under test.
+  RtpPacketizerAv1 packetizer(payload, limits, frame_type);
+  // Convert result into structure that is easier to run expectation against.
+  std::vector<RtpPayload> result(packetizer.NumPackets());
+  for (RtpPayload& rtp_payload : result) {
+    EXPECT_TRUE(packetizer.NextPacket(&rtp_payload.rtp_packet));
+  }
+  return result;
+}
+
+Av1Frame ReassembleFrame(rtc::ArrayView<const RtpPayload> rtp_payloads) {
+  std::vector<rtc::ArrayView<const uint8_t>> payloads(rtp_payloads.size());
+  for (size_t i = 0; i < rtp_payloads.size(); ++i) {
+    payloads[i] = rtp_payloads[i];
+  }
+  return Av1Frame(RtpDepacketizerAv1::AssembleFrame(payloads));
+}
+
+class Obu {
+ public:
+  explicit Obu(uint8_t obu_type) : header_(obu_type | kObuSizePresentBit) {
+    EXPECT_EQ(obu_type & 0b0'1111'000, obu_type);
+  }
+
+  Obu& WithExtension(uint8_t extension) {
+    extension_ = extension;
+    header_ |= kObuExtensionPresentBit;
+    return *this;
+  }
+  Obu& WithoutSize() {
+    header_ &= ~kObuSizePresentBit;
+    return *this;
+  }
+  Obu& WithPayload(std::vector<uint8_t> payload) {
+    payload_ = std::move(payload);
+    return *this;
+  }
+
+ private:
+  friend std::vector<uint8_t> BuildAv1Frame(std::initializer_list<Obu> obus);
+  uint8_t header_;
+  uint8_t extension_ = 0;
+  std::vector<uint8_t> payload_;
+};
+
+std::vector<uint8_t> BuildAv1Frame(std::initializer_list<Obu> obus) {
+  std::vector<uint8_t> raw;
+  for (const Obu& obu : obus) {
+    raw.push_back(obu.header_);
+    if (obu.header_ & kObuExtensionPresentBit) {
+      raw.push_back(obu.extension_);
+    }
+    if (obu.header_ & kObuSizePresentBit) {
+      // write size in leb128 format.
+      size_t payload_size = obu.payload_.size();
+      while (payload_size >= 0x80) {
+        raw.push_back(0x80 | (payload_size & 0x7F));
+        payload_size >>= 7;
+      }
+      raw.push_back(payload_size);
+    }
+    raw.insert(raw.end(), obu.payload_.begin(), obu.payload_.end());
+  }
+  return raw;
+}
+
+TEST(RtpPacketizerAv1Test, PacketizeOneObuWithoutSizeAndExtension) {
+  auto kFrame = BuildAv1Frame(
+      {Obu(kObuTypeFrame).WithoutSize().WithPayload({1, 2, 3, 4, 5, 6, 7})});
+  EXPECT_THAT(Packetize(kFrame, {}),
+              ElementsAre(ElementsAre(0b00'01'0000,  // aggregation header
+                                      kObuTypeFrame, 1, 2, 3, 4, 5, 6, 7)));
+}
+
+TEST(RtpPacketizerAv1Test, PacketizeOneObuWithoutSizeWithExtension) {
+  auto kFrame = BuildAv1Frame({Obu(kObuTypeFrame)
+                                   .WithoutSize()
+                                   .WithExtension(kObuExtensionS1T1)
+                                   .WithPayload({2, 3, 4, 5, 6, 7})});
+  EXPECT_THAT(Packetize(kFrame, {}),
+              ElementsAre(ElementsAre(0b00'01'0000,  // aggregation header
+                                      kObuTypeFrame | kObuExtensionPresentBit,
+                                      kObuExtensionS1T1, 2, 3, 4, 5, 6, 7)));
+}
+
+TEST(RtpPacketizerAv1Test, RemovesObuSizeFieldWithoutExtension) {
+  auto kFrame = BuildAv1Frame(
+      {Obu(kObuTypeFrame).WithPayload({11, 12, 13, 14, 15, 16, 17})});
+  EXPECT_THAT(
+      Packetize(kFrame, {}),
+      ElementsAre(ElementsAre(0b00'01'0000,  // aggregation header
+                              kObuTypeFrame, 11, 12, 13, 14, 15, 16, 17)));
+}
+
+TEST(RtpPacketizerAv1Test, RemovesObuSizeFieldWithExtension) {
+  auto kFrame = BuildAv1Frame({Obu(kObuTypeFrame)
+                                   .WithExtension(kObuExtensionS1T1)
+                                   .WithPayload({1, 2, 3, 4, 5, 6, 7})});
+  EXPECT_THAT(Packetize(kFrame, {}),
+              ElementsAre(ElementsAre(0b00'01'0000,  // aggregation header
+                                      kObuTypeFrame | kObuExtensionPresentBit,
+                                      kObuExtensionS1T1, 1, 2, 3, 4, 5, 6, 7)));
+}
+
+TEST(RtpPacketizerAv1Test, OmitsSizeForLastObuWhenThreeObusFitsIntoThePacket) {
+  auto kFrame = BuildAv1Frame(
+      {Obu(kObuTypeSequenceHeader).WithPayload({1, 2, 3, 4, 5, 6}),
+       Obu(kObuTypeMetadata).WithPayload({11, 12, 13, 14}),
+       Obu(kObuTypeFrame).WithPayload({21, 22, 23, 24, 25, 26})});
+  EXPECT_THAT(
+      Packetize(kFrame, {}),
+      ElementsAre(ElementsAre(0b00'11'0000,  // aggregation header
+                              7, kObuTypeSequenceHeader, 1, 2, 3, 4, 5, 6,  //
+                              5, kObuTypeMetadata, 11, 12, 13, 14,          //
+                              kObuTypeFrame, 21, 22, 23, 24, 25, 26)));
+}
+
+TEST(RtpPacketizerAv1Test, UseSizeForAllObusWhenFourObusFitsIntoThePacket) {
+  auto kFrame = BuildAv1Frame(
+      {Obu(kObuTypeSequenceHeader).WithPayload({1, 2, 3, 4, 5, 6}),
+       Obu(kObuTypeMetadata).WithPayload({11, 12, 13, 14}),
+       Obu(kObuTypeFrameHeader).WithPayload({21, 22, 23}),
+       Obu(kObuTypeTileGroup).WithPayload({31, 32, 33, 34, 35, 36})});
+  EXPECT_THAT(
+      Packetize(kFrame, {}),
+      ElementsAre(ElementsAre(0b00'00'0000,  // aggregation header
+                              7, kObuTypeSequenceHeader, 1, 2, 3, 4, 5, 6,  //
+                              5, kObuTypeMetadata, 11, 12, 13, 14,          //
+                              4, kObuTypeFrameHeader, 21, 22, 23,           //
+                              7, kObuTypeTileGroup, 31, 32, 33, 34, 35, 36)));
+}
+
+TEST(RtpPacketizerAv1Test, DiscardsTemporalDelimiterAndTileListObu) {
+  auto kFrame = BuildAv1Frame(
+      {Obu(kObuTypeTemporalDelimiter), Obu(kObuTypeMetadata),
+       Obu(kObuTypeTileList).WithPayload({1, 2, 3, 4, 5, 6}),
+       Obu(kObuTypeFrameHeader).WithPayload({21, 22, 23}),
+       Obu(kObuTypeTileGroup).WithPayload({31, 32, 33, 34, 35, 36})});
+
+  EXPECT_THAT(
+      Packetize(kFrame, {}),
+      ElementsAre(ElementsAre(0b00'11'0000,  // aggregation header
+                              1,
+                              kObuTypeMetadata,  //
+                              4, kObuTypeFrameHeader, 21, 22,
+                              23,  //
+                              kObuTypeTileGroup, 31, 32, 33, 34, 35, 36)));
+}
+
+TEST(RtpPacketizerAv1Test, SplitTwoObusIntoTwoPacketForceSplitObuHeader) {
+  // Craft expected payloads so that there is only one way to split original
+  // frame into two packets.
+  const uint8_t kExpectPayload1[6] = {
+      0b01'10'0000,  // aggregation_header
+      3,
+      kObuTypeFrameHeader | kObuExtensionPresentBit,
+      kObuExtensionS1T1,
+      21,  //
+      kObuTypeTileGroup | kObuExtensionPresentBit};
+  const uint8_t kExpectPayload2[6] = {0b10'01'0000,  // aggregation_header
+                                      kObuExtensionS1T1, 11, 12, 13, 14};
+  auto kFrame = BuildAv1Frame({Obu(kObuTypeFrameHeader)
+                                   .WithExtension(kObuExtensionS1T1)
+                                   .WithPayload({21}),
+                               Obu(kObuTypeTileGroup)
+                                   .WithExtension(kObuExtensionS1T1)
+                                   .WithPayload({11, 12, 13, 14})});
+
+  RtpPacketizer::PayloadSizeLimits limits;
+  limits.max_payload_len = 6;
+  auto payloads = Packetize(kFrame, limits);
+  EXPECT_THAT(payloads, ElementsAre(ElementsAreArray(kExpectPayload1),
+                                    ElementsAreArray(kExpectPayload2)));
+}
+
+TEST(RtpPacketizerAv1Test,
+     SetsNbitAtTheFirstPacketOfAKeyFrameWithSequenceHeader) {
+  auto kFrame = BuildAv1Frame(
+      {Obu(kObuTypeSequenceHeader).WithPayload({1, 2, 3, 4, 5, 6, 7})});
+  RtpPacketizer::PayloadSizeLimits limits;
+  limits.max_payload_len = 6;
+  auto packets = Packetize(kFrame, limits, VideoFrameType::kVideoFrameKey);
+  ASSERT_THAT(packets, SizeIs(2));
+  EXPECT_TRUE(packets[0].aggregation_header() & kNewCodedVideoSequenceBit);
+  EXPECT_FALSE(packets[1].aggregation_header() & kNewCodedVideoSequenceBit);
+}
+
+TEST(RtpPacketizerAv1Test,
+     DoesntSetNbitAtThePacketsOfAKeyFrameWithoutSequenceHeader) {
+  auto kFrame =
+      BuildAv1Frame({Obu(kObuTypeFrame).WithPayload({1, 2, 3, 4, 5, 6, 7})});
+  RtpPacketizer::PayloadSizeLimits limits;
+  limits.max_payload_len = 6;
+  auto packets = Packetize(kFrame, limits, VideoFrameType::kVideoFrameKey);
+  ASSERT_THAT(packets, SizeIs(2));
+  EXPECT_FALSE(packets[0].aggregation_header() & kNewCodedVideoSequenceBit);
+  EXPECT_FALSE(packets[1].aggregation_header() & kNewCodedVideoSequenceBit);
+}
+
+TEST(RtpPacketizerAv1Test, DoesntSetNbitAtThePacketsOfADeltaFrame) {
+  // Even when that delta frame starts with a (redundant) sequence header.
+  auto kFrame = BuildAv1Frame(
+      {Obu(kObuTypeSequenceHeader).WithPayload({1, 2, 3, 4, 5, 6, 7})});
+  RtpPacketizer::PayloadSizeLimits limits;
+  limits.max_payload_len = 6;
+  auto packets = Packetize(kFrame, limits, VideoFrameType::kVideoFrameDelta);
+  ASSERT_THAT(packets, SizeIs(2));
+  EXPECT_FALSE(packets[0].aggregation_header() & kNewCodedVideoSequenceBit);
+  EXPECT_FALSE(packets[1].aggregation_header() & kNewCodedVideoSequenceBit);
+}
+
+// There are multiple valid reasonable ways to split payload into multiple
+// packets, do not validate current choice, instead use RtpDepacketizer
+// to validate frame is reconstracted to the same one. Note: since
+// RtpDepacketizer always inserts obu_size fields in the output, use frame where
+// each obu has obu_size fields for more streight forward validation.
+TEST(RtpPacketizerAv1Test, SplitSingleObuIntoTwoPackets) {
+  auto kFrame = BuildAv1Frame(
+      {Obu(kObuTypeFrame).WithPayload({11, 12, 13, 14, 15, 16, 17, 18, 19})});
+
+  RtpPacketizer::PayloadSizeLimits limits;
+  limits.max_payload_len = 8;
+  auto payloads = Packetize(kFrame, limits);
+  EXPECT_THAT(payloads, ElementsAre(SizeIs(Le(8u)), SizeIs(Le(8u))));
+
+  // Use RtpDepacketizer to validate the split.
+  EXPECT_THAT(ReassembleFrame(payloads), ElementsAreArray(kFrame));
+}
+
+TEST(RtpPacketizerAv1Test, SplitSingleObuIntoManyPackets) {
+  auto kFrame = BuildAv1Frame(
+      {Obu(kObuTypeFrame).WithPayload(std::vector<uint8_t>(1200, 27))});
+
+  RtpPacketizer::PayloadSizeLimits limits;
+  limits.max_payload_len = 100;
+  auto payloads = Packetize(kFrame, limits);
+  EXPECT_THAT(payloads, SizeIs(13u));
+  EXPECT_THAT(payloads, Each(SizeIs(Le(100u))));
+
+  // Use RtpDepacketizer to validate the split.
+  EXPECT_THAT(ReassembleFrame(payloads), ElementsAreArray(kFrame));
+}
+
+TEST(RtpPacketizerAv1Test, SplitTwoObusIntoTwoPackets) {
+  // 2nd OBU is too large to fit into one packet, so its head would be in the
+  // same packet as the 1st OBU.
+  auto kFrame = BuildAv1Frame(
+      {Obu(kObuTypeSequenceHeader).WithPayload({11, 12}),
+       Obu(kObuTypeFrame).WithPayload({1, 2, 3, 4, 5, 6, 7, 8, 9})});
+
+  RtpPacketizer::PayloadSizeLimits limits;
+  limits.max_payload_len = 8;
+  auto payloads = Packetize(kFrame, limits);
+  EXPECT_THAT(payloads, ElementsAre(SizeIs(Le(8u)), SizeIs(Le(8u))));
+
+  // Use RtpDepacketizer to validate the split.
+  EXPECT_THAT(ReassembleFrame(payloads), ElementsAreArray(kFrame));
+}
+
+TEST(RtpPacketizerAv1Test,
+     SplitSingleObuIntoTwoPacketsBecauseOfSinglePacketLimit) {
+  auto kFrame = BuildAv1Frame(
+      {Obu(kObuTypeFrame).WithPayload({11, 12, 13, 14, 15, 16, 17, 18, 19})});
+  RtpPacketizer::PayloadSizeLimits limits;
+  limits.max_payload_len = 10;
+  limits.single_packet_reduction_len = 8;
+  auto payloads = Packetize(kFrame, limits);
+  EXPECT_THAT(payloads, ElementsAre(SizeIs(Le(10u)), SizeIs(Le(10u))));
+
+  EXPECT_THAT(ReassembleFrame(payloads), ElementsAreArray(kFrame));
+}
+
+}  // namespace
+}  // namespace webrtc