Audio ingress implementation for voip api.

This is based on channel_receive.cc implementation where non-audio
related logics are trimmed off for smaller footprint in size.

Bug: webrtc:11251
Change-Id: I743c9f93f509fa6fcc12981fa73a6f01ce38348c
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/172821
Commit-Queue: Tim Na <natim@webrtc.org>
Reviewed-by: Per Åhgren <peah@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31117}

8 files changed, 634 insertions, 28 deletions

diff --git a/audio/voip/BUILD.gn b/audio/voip/BUILD.gn
index 9d52121144..8ebc3ce4e7 100644
--- a/audio/voip/BUILD.gn
+++ b/audio/voip/BUILD.gn
@@ -8,6 +8,31 @@
 
 import("../../webrtc.gni")
 
+rtc_library("audio_ingress") {
+  sources = [
+    "audio_ingress.cc",
+    "audio_ingress.h",
+  ]
+  deps = [
+    "../../api:array_view",
+    "../../api:rtp_headers",
+    "../../api:scoped_refptr",
+    "../../api:transport_api",
+    "../../api/audio:audio_mixer_api",
+    "../../api/audio_codecs:audio_codecs_api",
+    "../../audio",
+    "../../audio/utility:audio_frame_operations",
+    "../../modules/audio_coding",
+    "../../modules/rtp_rtcp",
+    "../../modules/rtp_rtcp:rtp_rtcp_format",
+    "../../modules/utility",
+    "../../rtc_base:criticalsection",
+    "../../rtc_base:logging",
+    "../../rtc_base:safe_minmax",
+    "../../rtc_base:timeutils",
+  ]
+}
+
 rtc_library("audio_egress") {
   sources = [
     "audio_egress.cc",
diff --git a/audio/voip/audio_egress.cc b/audio/voip/audio_egress.cc
index c145201c00..98f73fa37f 100644
--- a/audio/voip/audio_egress.cc
+++ b/audio/voip/audio_egress.cc
@@ -1,12 +1,12 @@
-//
-//  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.
-//
+/*
+ *  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 "audio/voip/audio_egress.h"
 
diff --git a/audio/voip/audio_egress.h b/audio/voip/audio_egress.h
index fcdafa640b..192d5ff839 100644
--- a/audio/voip/audio_egress.h
+++ b/audio/voip/audio_egress.h
@@ -1,12 +1,12 @@
-//
-//  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.
-//
+/*
+ *  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 AUDIO_VOIP_AUDIO_EGRESS_H_
 #define AUDIO_VOIP_AUDIO_EGRESS_H_
diff --git a/audio/voip/audio_ingress.cc b/audio/voip/audio_ingress.cc
new file mode 100644
index 0000000000..aae684278a
--- /dev/null
+++ b/audio/voip/audio_ingress.cc
@@ -0,0 +1,257 @@
+/*
+ *  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 "audio/voip/audio_ingress.h"
+
+#include <algorithm>
+#include <utility>
+#include <vector>
+
+#include "api/audio_codecs/audio_format.h"
+#include "audio/utility/audio_frame_operations.h"
+#include "modules/audio_coding/include/audio_coding_module.h"
+#include "rtc_base/critical_section.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/numerics/safe_minmax.h"
+
+namespace webrtc {
+
+namespace {
+
+AudioCodingModule::Config CreateAcmConfig(
+    rtc::scoped_refptr<AudioDecoderFactory> decoder_factory) {
+  AudioCodingModule::Config acm_config;
+  acm_config.neteq_config.enable_muted_state = true;
+  acm_config.decoder_factory = decoder_factory;
+  return acm_config;
+}
+
+}  // namespace
+
+AudioIngress::AudioIngress(
+    RtpRtcp* rtp_rtcp,
+    Clock* clock,
+    rtc::scoped_refptr<AudioDecoderFactory> decoder_factory,
+    std::unique_ptr<ReceiveStatistics> receive_statistics)
+    : playing_(false),
+      remote_ssrc_(0),
+      first_rtp_timestamp_(-1),
+      rtp_receive_statistics_(std::move(receive_statistics)),
+      rtp_rtcp_(rtp_rtcp),
+      acm_receiver_(CreateAcmConfig(decoder_factory)),
+      ntp_estimator_(clock) {}
+
+AudioIngress::~AudioIngress() = default;
+
+void AudioIngress::StartPlay() {
+  playing_ = true;
+}
+
+void AudioIngress::StopPlay() {
+  playing_ = false;
+  output_audio_level_.ResetLevelFullRange();
+}
+
+AudioMixer::Source::AudioFrameInfo AudioIngress::GetAudioFrameWithInfo(
+    int sampling_rate,
+    AudioFrame* audio_frame) {
+  audio_frame->sample_rate_hz_ = sampling_rate;
+
+  // Get 10ms raw PCM data from the ACM.
+  bool muted = false;
+  if (acm_receiver_.GetAudio(sampling_rate, audio_frame, &muted) == -1) {
+    RTC_DLOG(LS_ERROR) << "GetAudio() failed!";
+    // In all likelihood, the audio in this frame is garbage. We return an
+    // error so that the audio mixer module doesn't add it to the mix. As
+    // a result, it won't be played out and the actions skipped here are
+    // irrelevant.
+    return AudioMixer::Source::AudioFrameInfo::kError;
+  }
+
+  if (muted) {
+    AudioFrameOperations::Mute(audio_frame);
+  }
+
+  // Measure audio level.
+  constexpr double kAudioSampleDurationSeconds = 0.01;
+  output_audio_level_.ComputeLevel(*audio_frame, kAudioSampleDurationSeconds);
+
+  // Set first rtp timestamp with first audio frame with valid timestamp.
+  if (first_rtp_timestamp_ < 0 && audio_frame->timestamp_ != 0) {
+    first_rtp_timestamp_ = audio_frame->timestamp_;
+  }
+
+  if (first_rtp_timestamp_ >= 0) {
+    // Compute elapsed and NTP times.
+    int64_t unwrap_timestamp;
+    {
+      rtc::CritScope lock(&lock_);
+      unwrap_timestamp =
+          timestamp_wrap_handler_.Unwrap(audio_frame->timestamp_);
+      audio_frame->ntp_time_ms_ =
+          ntp_estimator_.Estimate(audio_frame->timestamp_);
+    }
+    // For clock rate, default to the playout sampling rate if we haven't
+    // received any packets yet.
+    absl::optional<std::pair<int, SdpAudioFormat>> decoder =
+        acm_receiver_.LastDecoder();
+    int clock_rate = decoder ? decoder->second.clockrate_hz
+                             : acm_receiver_.last_output_sample_rate_hz();
+    RTC_DCHECK_GT(clock_rate, 0);
+    audio_frame->elapsed_time_ms_ =
+        (unwrap_timestamp - first_rtp_timestamp_) / (clock_rate / 1000);
+  }
+
+  return muted ? AudioMixer::Source::AudioFrameInfo::kMuted
+               : AudioMixer::Source::AudioFrameInfo::kNormal;
+}
+
+int AudioIngress::Ssrc() const {
+  return rtc::dchecked_cast<int>(remote_ssrc_.load());
+}
+
+int AudioIngress::PreferredSampleRate() const {
+  // Return the bigger of playout and receive frequency in the ACM. Note that
+  // return 0 means anything higher shouldn't cause any quality loss.
+  return std::max(acm_receiver_.last_packet_sample_rate_hz().value_or(0),
+                  acm_receiver_.last_output_sample_rate_hz());
+}
+
+void AudioIngress::SetReceiveCodecs(
+    const std::map<int, SdpAudioFormat>& codecs) {
+  {
+    rtc::CritScope lock(&lock_);
+    for (const auto& kv : codecs) {
+      receive_codec_info_[kv.first] = kv.second.clockrate_hz;
+    }
+  }
+  acm_receiver_.SetCodecs(codecs);
+}
+
+void AudioIngress::ReceivedRTPPacket(const uint8_t* data, size_t length) {
+  if (!Playing()) {
+    return;
+  }
+
+  RtpPacketReceived rtp_packet;
+  rtp_packet.Parse(data, length);
+
+  // Set payload type's sampling rate before we feed it into ReceiveStatistics.
+  {
+    rtc::CritScope lock(&lock_);
+    const auto& it = receive_codec_info_.find(rtp_packet.PayloadType());
+    // If sampling rate info is not available in our received codec set, it
+    // would mean that remote media endpoint is sending incorrect payload id
+    // which can't be processed correctly especially on payload type id in
+    // dynamic range.
+    if (it == receive_codec_info_.end()) {
+      RTC_DLOG(LS_WARNING) << "Unexpected payload id received: "
+                           << rtp_packet.PayloadType();
+      return;
+    }
+    rtp_packet.set_payload_type_frequency(it->second);
+  }
+
+  rtp_receive_statistics_->OnRtpPacket(rtp_packet);
+
+  RTPHeader header;
+  rtp_packet.GetHeader(&header);
+
+  size_t packet_length = rtp_packet.size();
+  if (packet_length < header.headerLength ||
+      (packet_length - header.headerLength) < header.paddingLength) {
+    RTC_DLOG(LS_ERROR) << "Packet length(" << packet_length << ") header("
+                       << header.headerLength << ") padding("
+                       << header.paddingLength << ")";
+    return;
+  }
+
+  const uint8_t* payload = rtp_packet.data() + header.headerLength;
+  size_t payload_length = packet_length - header.headerLength;
+  size_t payload_data_length = payload_length - header.paddingLength;
+  auto data_view = rtc::ArrayView<const uint8_t>(payload, payload_data_length);
+
+  // Push the incoming payload (parsed and ready for decoding) into the ACM.
+  if (acm_receiver_.InsertPacket(header, data_view) != 0) {
+    RTC_DLOG(LS_ERROR) << "AudioIngress::ReceivedRTPPacket() unable to "
+                          "push data to the ACM";
+  }
+}
+
+void AudioIngress::ReceivedRTCPPacket(const uint8_t* data, size_t length) {
+  // Deliver RTCP packet to RTP/RTCP module for parsing
+  rtp_rtcp_->IncomingRtcpPacket(data, length);
+
+  int64_t rtt = GetRoundTripTime();
+  if (rtt == -1) {
+    // Waiting for valid RTT.
+    return;
+  }
+
+  uint32_t ntp_secs = 0, ntp_frac = 0, rtp_timestamp = 0;
+  if (rtp_rtcp_->RemoteNTP(&ntp_secs, &ntp_frac, nullptr, nullptr,
+                           &rtp_timestamp) != 0) {
+    // Waiting for RTCP.
+    return;
+  }
+
+  {
+    rtc::CritScope lock(&lock_);
+    ntp_estimator_.UpdateRtcpTimestamp(rtt, ntp_secs, ntp_frac, rtp_timestamp);
+  }
+}
+
+int64_t AudioIngress::GetRoundTripTime() {
+  const std::vector<ReportBlockData>& report_data =
+      rtp_rtcp_->GetLatestReportBlockData();
+
+  // If we do not have report block which means remote RTCP hasn't be received
+  // yet, return -1 as to indicate uninitialized value.
+  if (report_data.empty()) {
+    return -1;
+  }
+
+  // We don't know in advance the remote SSRC used by the other end's receiver
+  // reports, so use the SSRC of the first report block as remote SSRC for now.
+  // TODO(natim@webrtc.org): handle the case where remote end is changing ssrc
+  // and update accordingly here.
+  const ReportBlockData& block_data = report_data[0];
+
+  const uint32_t sender_ssrc = block_data.report_block().sender_ssrc;
+
+  if (sender_ssrc != remote_ssrc_.load()) {
+    remote_ssrc_.store(sender_ssrc);
+    rtp_rtcp_->SetRemoteSSRC(sender_ssrc);
+  }
+
+  return (block_data.has_rtt() ? block_data.last_rtt_ms() : -1);
+}
+
+int AudioIngress::GetSpeechOutputLevelFullRange() const {
+  return output_audio_level_.LevelFullRange();
+}
+
+bool AudioIngress::Playing() const {
+  return playing_;
+}
+
+NetworkStatistics AudioIngress::GetNetworkStatistics() const {
+  NetworkStatistics stats;
+  acm_receiver_.GetNetworkStatistics(&stats);
+  return stats;
+}
+
+AudioDecodingCallStats AudioIngress::GetDecodingStatistics() const {
+  AudioDecodingCallStats stats;
+  acm_receiver_.GetDecodingCallStatistics(&stats);
+  return stats;
+}
+
+}  // namespace webrtc
diff --git a/audio/voip/audio_ingress.h b/audio/voip/audio_ingress.h
new file mode 100644
index 0000000000..f703440d27
--- /dev/null
+++ b/audio/voip/audio_ingress.h
@@ -0,0 +1,125 @@
+/*
+ *  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 AUDIO_VOIP_AUDIO_INGRESS_H_
+#define AUDIO_VOIP_AUDIO_INGRESS_H_
+
+#include <atomic>
+#include <map>
+#include <memory>
+#include <utility>
+
+#include "api/array_view.h"
+#include "api/audio/audio_mixer.h"
+#include "api/rtp_headers.h"
+#include "api/scoped_refptr.h"
+#include "audio/audio_level.h"
+#include "modules/audio_coding/acm2/acm_receiver.h"
+#include "modules/audio_coding/include/audio_coding_module.h"
+#include "modules/rtp_rtcp/include/receive_statistics.h"
+#include "modules/rtp_rtcp/include/remote_ntp_time_estimator.h"
+#include "modules/rtp_rtcp/include/rtp_rtcp.h"
+#include "modules/rtp_rtcp/source/rtp_packet_received.h"
+#include "rtc_base/critical_section.h"
+#include "rtc_base/time_utils.h"
+
+namespace webrtc {
+
+// AudioIngress handles incoming RTP/RTCP packets from the remote
+// media endpoint. Received RTP packets are injected into AcmReceiver and
+// when audio output thread requests for audio samples to play through system
+// output such as speaker device, AudioIngress provides the samples via its
+// implementation on AudioMixer::Source interface.
+//
+// Note that this class is originally based on ChannelReceive in
+// audio/channel_receive.cc with non-audio related logic trimmed as aimed for
+// smaller footprint.
+class AudioIngress : public AudioMixer::Source {
+ public:
+  AudioIngress(RtpRtcp* rtp_rtcp,
+               Clock* clock,
+               rtc::scoped_refptr<AudioDecoderFactory> decoder_factory,
+               std::unique_ptr<ReceiveStatistics> receive_statistics);
+  ~AudioIngress() override;
+
+  // Start or stop receiving operation of AudioIngress.
+  void StartPlay();
+  void StopPlay();
+
+  // Query the state of the AudioIngress.
+  bool Playing() const;
+
+  // Set the decoder formats and payload type for AcmReceiver where the
+  // key type (int) of the map is the payload type of SdpAudioFormat.
+  void SetReceiveCodecs(const std::map<int, SdpAudioFormat>& codecs);
+
+  // APIs to handle received RTP/RTCP packets from caller.
+  void ReceivedRTPPacket(const uint8_t* data, size_t length);
+  void ReceivedRTCPPacket(const uint8_t* data, size_t length);
+
+  // Retrieve highest speech output level in last 100 ms.  Note that
+  // this isn't RMS but absolute raw audio level on int16_t sample unit.
+  // Therefore, the return value will vary between 0 ~ 0xFFFF. This type of
+  // value may be useful to be used for measuring active speaker gauge.
+  int GetSpeechOutputLevelFullRange() const;
+
+  // Returns network round trip time (RTT) measued by RTCP exchange with
+  // remote media endpoint. RTT value -1 indicates that it's not initialized.
+  int64_t GetRoundTripTime();
+
+  NetworkStatistics GetNetworkStatistics() const;
+  AudioDecodingCallStats GetDecodingStatistics() const;
+
+  // Implementation of AudioMixer::Source interface.
+  AudioMixer::Source::AudioFrameInfo GetAudioFrameWithInfo(
+      int sampling_rate,
+      AudioFrame* audio_frame) override;
+  int Ssrc() const override;
+  int PreferredSampleRate() const override;
+
+ private:
+  // Indicate AudioIngress status as caller invokes Start/StopPlaying.
+  // If not playing, incoming RTP data processing is skipped, thus
+  // producing no data to output device.
+  std::atomic<bool> playing_;
+
+  // Currently active remote ssrc from remote media endpoint.
+  std::atomic<uint32_t> remote_ssrc_;
+
+  // The first rtp timestamp of the output audio frame that is used to
+  // calculate elasped time for subsequent audio frames.
+  std::atomic<int64_t> first_rtp_timestamp_;
+
+  // Synchronizaton is handled internally by ReceiveStatistics.
+  const std::unique_ptr<ReceiveStatistics> rtp_receive_statistics_;
+
+  // Synchronizaton is handled internally by RtpRtcp.
+  RtpRtcp* const rtp_rtcp_;
+
+  // Synchronizaton is handled internally by acm2::AcmReceiver.
+  acm2::AcmReceiver acm_receiver_;
+
+  // Synchronizaton is handled internally by voe::AudioLevel.
+  voe::AudioLevel output_audio_level_;
+
+  rtc::CriticalSection lock_;
+
+  RemoteNtpTimeEstimator ntp_estimator_ RTC_GUARDED_BY(lock_);
+
+  // For receiving RTP statistics, this tracks the sampling rate value
+  // per payload type set when caller set via SetReceiveCodecs.
+  std::map<int, int> receive_codec_info_ RTC_GUARDED_BY(lock_);
+
+  rtc::TimestampWrapAroundHandler timestamp_wrap_handler_ RTC_GUARDED_BY(lock_);
+};
+
+}  // namespace webrtc
+
+#endif  // AUDIO_VOIP_AUDIO_INGRESS_H_
diff --git a/audio/voip/test/BUILD.gn b/audio/voip/test/BUILD.gn
index e0aedf673e..0decdb2886 100644
--- a/audio/voip/test/BUILD.gn
+++ b/audio/voip/test/BUILD.gn
@@ -9,13 +9,30 @@
 import("../../../webrtc.gni")
 
 if (rtc_include_tests) {
+  rtc_library("audio_ingress_unittests") {
+    testonly = true
+    sources = [ "audio_ingress_unittest.cc" ]
+    deps = [
+      "..:audio_egress",
+      "..:audio_ingress",
+      "../../../api:transport_api",
+      "../../../api/audio_codecs:builtin_audio_decoder_factory",
+      "../../../api/audio_codecs:builtin_audio_encoder_factory",
+      "../../../api/task_queue:default_task_queue_factory",
+      "../../../modules/audio_mixer:audio_mixer_test_utils",
+      "../../../rtc_base:logging",
+      "../../../rtc_base:rtc_event",
+      "../../../test:mock_transport",
+      "../../../test:test_support",
+    ]
+  }
+
   rtc_library("audio_egress_unittests") {
     testonly = true
     sources = [ "audio_egress_unittest.cc" ]
     deps = [
       "..:audio_egress",
       "../../../api:transport_api",
-      "../../../api/audio_codecs:builtin_audio_decoder_factory",
       "../../../api/audio_codecs:builtin_audio_encoder_factory",
       "../../../api/task_queue:default_task_queue_factory",
       "../../../modules/audio_mixer:audio_mixer_test_utils",
diff --git a/audio/voip/test/audio_egress_unittest.cc b/audio/voip/test/audio_egress_unittest.cc
index 23c4e45b0c..a7e3d65eab 100644
--- a/audio/voip/test/audio_egress_unittest.cc
+++ b/audio/voip/test/audio_egress_unittest.cc
@@ -1,12 +1,12 @@
-//
-//  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.
-//
+/*
+ *  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 "audio/voip/audio_egress.h"
 #include "api/audio_codecs/builtin_audio_encoder_factory.h"
diff --git a/audio/voip/test/audio_ingress_unittest.cc b/audio/voip/test/audio_ingress_unittest.cc
new file mode 100644
index 0000000000..752c06c749
--- /dev/null
+++ b/audio/voip/test/audio_ingress_unittest.cc
@@ -0,0 +1,182 @@
+/*
+ *  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 "audio/voip/audio_ingress.h"
+#include "api/audio_codecs/builtin_audio_decoder_factory.h"
+#include "api/audio_codecs/builtin_audio_encoder_factory.h"
+#include "api/call/transport.h"
+#include "api/task_queue/default_task_queue_factory.h"
+#include "audio/voip/audio_egress.h"
+#include "modules/audio_mixer/sine_wave_generator.h"
+#include "rtc_base/event.h"
+#include "rtc_base/logging.h"
+#include "test/gmock.h"
+#include "test/gtest.h"
+#include "test/mock_transport.h"
+
+namespace webrtc {
+namespace {
+
+using ::testing::Invoke;
+using ::testing::NiceMock;
+using ::testing::Unused;
+
+constexpr int16_t kAudioLevel = 3004;  // Used for sine wave level.
+
+std::unique_ptr<RtpRtcp> CreateRtpStack(Clock* clock, Transport* transport) {
+  RtpRtcp::Configuration rtp_config;
+  rtp_config.clock = clock;
+  rtp_config.audio = true;
+  rtp_config.rtcp_report_interval_ms = 5000;
+  rtp_config.outgoing_transport = transport;
+  rtp_config.local_media_ssrc = 0xdeadc0de;
+  auto rtp_rtcp = RtpRtcp::Create(rtp_config);
+  rtp_rtcp->SetSendingMediaStatus(false);
+  rtp_rtcp->SetRTCPStatus(RtcpMode::kCompound);
+  return rtp_rtcp;
+}
+
+class AudioIngressTest : public ::testing::Test {
+ public:
+  const SdpAudioFormat kPcmuFormat = {"pcmu", 8000, 1};
+
+  AudioIngressTest()
+      : fake_clock_(123456789), wave_generator_(1000.0, kAudioLevel) {
+    rtp_rtcp_ = CreateRtpStack(&fake_clock_, &transport_);
+    task_queue_factory_ = CreateDefaultTaskQueueFactory();
+    encoder_factory_ = CreateBuiltinAudioEncoderFactory();
+    decoder_factory_ = CreateBuiltinAudioDecoderFactory();
+  }
+
+  void SetUp() override {
+    constexpr int kPcmuPayload = 0;
+    ingress_ = std::make_unique<AudioIngress>(
+        rtp_rtcp_.get(), &fake_clock_, decoder_factory_,
+        ReceiveStatistics::Create(&fake_clock_));
+    ingress_->SetReceiveCodecs({{kPcmuPayload, kPcmuFormat}});
+
+    egress_ = std::make_unique<AudioEgress>(rtp_rtcp_.get(), &fake_clock_,
+                                            task_queue_factory_.get());
+    egress_->SetEncoder(kPcmuPayload, kPcmuFormat,
+                        encoder_factory_->MakeAudioEncoder(
+                            kPcmuPayload, kPcmuFormat, absl::nullopt));
+    egress_->StartSend();
+    ingress_->StartPlay();
+    rtp_rtcp_->SetSendingStatus(true);
+  }
+
+  void TearDown() override {
+    rtp_rtcp_->SetSendingStatus(false);
+    ingress_->StopPlay();
+    egress_->StopSend();
+  }
+
+  std::unique_ptr<AudioFrame> GetAudioFrame(int order) {
+    auto frame = std::make_unique<AudioFrame>();
+    frame->sample_rate_hz_ = kPcmuFormat.clockrate_hz;
+    frame->samples_per_channel_ = kPcmuFormat.clockrate_hz / 100;  // 10 ms.
+    frame->num_channels_ = kPcmuFormat.num_channels;
+    frame->timestamp_ = frame->samples_per_channel_ * order;
+    wave_generator_.GenerateNextFrame(frame.get());
+    return frame;
+  }
+
+  SimulatedClock fake_clock_;
+  SineWaveGenerator wave_generator_;
+  NiceMock<MockTransport> transport_;
+  std::unique_ptr<AudioIngress> ingress_;
+  rtc::scoped_refptr<AudioDecoderFactory> decoder_factory_;
+  // Members used to drive the input to ingress.
+  std::unique_ptr<AudioEgress> egress_;
+  std::unique_ptr<TaskQueueFactory> task_queue_factory_;
+  std::shared_ptr<RtpRtcp> rtp_rtcp_;
+  rtc::scoped_refptr<AudioEncoderFactory> encoder_factory_;
+};
+
+TEST_F(AudioIngressTest, PlayingAfterStartAndStop) {
+  EXPECT_EQ(ingress_->Playing(), true);
+  ingress_->StopPlay();
+  EXPECT_EQ(ingress_->Playing(), false);
+}
+
+TEST_F(AudioIngressTest, GetAudioFrameAfterRtpReceived) {
+  rtc::Event event;
+  auto handle_rtp = [&](const uint8_t* packet, size_t length, Unused) {
+    ingress_->ReceivedRTPPacket(packet, length);
+    event.Set();
+    return true;
+  };
+  EXPECT_CALL(transport_, SendRtp).WillRepeatedly(Invoke(handle_rtp));
+  egress_->SendAudioData(GetAudioFrame(0));
+  egress_->SendAudioData(GetAudioFrame(1));
+  event.Wait(/*ms=*/1000);
+
+  AudioFrame audio_frame;
+  EXPECT_EQ(
+      ingress_->GetAudioFrameWithInfo(kPcmuFormat.clockrate_hz, &audio_frame),
+      AudioMixer::Source::AudioFrameInfo::kNormal);
+  EXPECT_FALSE(audio_frame.muted());
+  EXPECT_EQ(audio_frame.num_channels_, 1u);
+  EXPECT_EQ(audio_frame.samples_per_channel_,
+            static_cast<size_t>(kPcmuFormat.clockrate_hz / 100));
+  EXPECT_EQ(audio_frame.sample_rate_hz_, kPcmuFormat.clockrate_hz);
+  EXPECT_NE(audio_frame.timestamp_, 0u);
+  EXPECT_EQ(audio_frame.elapsed_time_ms_, 0);
+}
+
+TEST_F(AudioIngressTest, GetSpeechOutputLevelFullRange) {
+  // Per audio_level's kUpdateFrequency, we need 11 RTP to get audio level.
+  constexpr int kNumRtp = 11;
+  int rtp_count = 0;
+  rtc::Event event;
+  auto handle_rtp = [&](const uint8_t* packet, size_t length, Unused) {
+    ingress_->ReceivedRTPPacket(packet, length);
+    if (++rtp_count == kNumRtp) {
+      event.Set();
+    }
+    return true;
+  };
+  EXPECT_CALL(transport_, SendRtp).WillRepeatedly(Invoke(handle_rtp));
+  for (int i = 0; i < kNumRtp * 2; i++) {
+    egress_->SendAudioData(GetAudioFrame(i));
+    fake_clock_.AdvanceTimeMilliseconds(10);
+  }
+  event.Wait(/*ms=*/1000);
+
+  for (int i = 0; i < kNumRtp; ++i) {
+    AudioFrame audio_frame;
+    EXPECT_EQ(
+        ingress_->GetAudioFrameWithInfo(kPcmuFormat.clockrate_hz, &audio_frame),
+        AudioMixer::Source::AudioFrameInfo::kNormal);
+  }
+  EXPECT_EQ(ingress_->GetSpeechOutputLevelFullRange(), kAudioLevel);
+}
+
+TEST_F(AudioIngressTest, PreferredSampleRate) {
+  rtc::Event event;
+  auto handle_rtp = [&](const uint8_t* packet, size_t length, Unused) {
+    ingress_->ReceivedRTPPacket(packet, length);
+    event.Set();
+    return true;
+  };
+  EXPECT_CALL(transport_, SendRtp).WillRepeatedly(Invoke(handle_rtp));
+  egress_->SendAudioData(GetAudioFrame(0));
+  egress_->SendAudioData(GetAudioFrame(1));
+  event.Wait(/*ms=*/1000);
+
+  AudioFrame audio_frame;
+  EXPECT_EQ(
+      ingress_->GetAudioFrameWithInfo(kPcmuFormat.clockrate_hz, &audio_frame),
+      AudioMixer::Source::AudioFrameInfo::kNormal);
+  EXPECT_EQ(ingress_->PreferredSampleRate(), kPcmuFormat.clockrate_hz);
+}
+
+}  // namespace
+}  // namespace webrtc