[CaptureService] Let receiver wait for stream info

So recevier doesn't need to get stream info from side channel. And the
delegate of the receiver can directly get the stream info from receiver.

Merge-With: eureka-internal/408117
Bug: internal: 154953397
Test: Unittest.
Change-Id: I5915b297cb3f252b7493b36719670f842a5d8c95
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2352216Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Commit-Queue: Kehuang Li <kehuangli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805513}

chromecast/media/audio/capture_service/capture_service_receiver.cc

@@ -4,6 +4,8 @@
 
 #include "chromecast/media/audio/capture_service/capture_service_receiver.h"
 
+#include <cstdint>
+#include <memory>
 #include <string>
 #include <utility>
 
@@ -42,6 +44,13 @@ class CaptureServiceReceiver::Socket : public SmallMessageSocket::Delegate {
   ~Socket() override;
 
  private:
+  enum class State {
+    kInit,
+    kWaitForAck,
+    kStreaming,
+    kShutdown,
+  };
+
   // SmallMessageSocket::Delegate implementation:
   void OnSendUnblocked() override;
   void OnError(int error) override;
@@ -50,13 +59,17 @@ class CaptureServiceReceiver::Socket : public SmallMessageSocket::Delegate {
 
   bool SendRequest();
   void OnInactivityTimeout();
-  bool HandleAudio(int64_t timestamp);
+  void OnInitialStreamInfo(const capture_service::StreamInfo& stream_info);
+  bool HandleAck(char* data, size_t size);
+  bool HandleAudio(char* data, size_t size);
   void ReportErrorAndStop();
 
   SmallMessageSocket socket_;
+
   const capture_service::StreamInfo request_stream_info_;
   CaptureServiceReceiver::Delegate* const delegate_;
-  bool error_reported_ = false;
+
+  State state_ = State::kInit;
 };
 
 CaptureServiceReceiver::Socket::Socket(
@@ -77,8 +90,9 @@ CaptureServiceReceiver::Socket::Socket(
 CaptureServiceReceiver::Socket::~Socket() = default;
 
 bool CaptureServiceReceiver::Socket::SendRequest() {
+  DCHECK_EQ(state_, State::kInit);
   auto request_buffer = capture_service::MakeMessage(
-      capture_service::PacketInfo{capture_service::MessageType::kRequest,
+      capture_service::PacketInfo{capture_service::MessageType::kHandshake,
                                   request_stream_info_, 0 /* timestamp_us */},
       nullptr /* data */, 0 /* data_size */);
   if (!request_buffer) {
@@ -89,6 +103,7 @@ bool CaptureServiceReceiver::Socket::SendRequest() {
                     "first buffer sent.";
     return false;
   }
+  state_ = State::kWaitForAck;
   return true;
 }
 
@@ -99,9 +114,9 @@ void CaptureServiceReceiver::Socket::OnSendUnblocked() {
 }
 
 void CaptureServiceReceiver::Socket::ReportErrorAndStop() {
-  DCHECK(!error_reported_) << "Error should not be reported more than once.";
+  DCHECK_NE(state_, State::kShutdown);
   delegate_->OnCaptureError();
-  error_reported_ = true;
+  state_ = State::kShutdown;
 }
 
 void CaptureServiceReceiver::Socket::OnError(int error) {
@@ -115,6 +130,45 @@ void CaptureServiceReceiver::Socket::OnEndOfStream() {
 }
 
 bool CaptureServiceReceiver::Socket::OnMessage(char* data, size_t size) {
+  uint8_t type = 0;
+  if (size < sizeof(type)) {
+    LOG(ERROR) << "Invalid message size: " << size << ".";
+    return false;
+  }
+  memcpy(&type, data, sizeof(type));
+  capture_service::MessageType message_type =
+      static_cast<capture_service::MessageType>(type);
+
+  if (state_ == State::kWaitForAck &&
+      message_type == capture_service::MessageType::kHandshake) {
+    return HandleAck(data, size);
+  }
+
+  if (state_ == State::kStreaming &&
+      (message_type == capture_service::MessageType::kPcmAudio ||
+       message_type == capture_service::MessageType::kOpusAudio)) {
+    return HandleAudio(data, size);
+  }
+
+  LOG(WARNING) << "Receive message with type " << type << " at state "
+               << static_cast<int>(state_) << ", ignored.";
+  return true;
+}
+
+bool CaptureServiceReceiver::Socket::HandleAck(char* data, size_t size) {
+  DCHECK_EQ(state_, State::kWaitForAck);
+  capture_service::PacketInfo info;
+  if (!capture_service::ReadHeader(data, size, &info) ||
+      !delegate_->OnInitialStreamInfo(info.stream_info)) {
+    ReportErrorAndStop();
+    return false;
+  }
+  state_ = State::kStreaming;
+  return true;
+}
+
+bool CaptureServiceReceiver::Socket::HandleAudio(char* data, size_t size) {
+  DCHECK_EQ(state_, State::kStreaming);
   if (!delegate_->OnCaptureData(data, size)) {
     ReportErrorAndStop();
     return false;

chromecast/media/audio/capture_service/capture_service_receiver.h

@@ -32,6 +32,9 @@ class CaptureServiceReceiver {
    public:
     virtual ~Delegate() = default;
 
+    virtual bool OnInitialStreamInfo(
+        const capture_service::StreamInfo& stream_info) = 0;
+
     // Called when more data are received from socket. Return |true| to continue
     // reading messages after OnCaptureData() returns.
     virtual bool OnCaptureData(const char* data, size_t size) = 0;
@@ -75,6 +78,7 @@ class CaptureServiceReceiver {
 
   const capture_service::StreamInfo request_stream_info_;
   Delegate* const delegate_;
+
   // Socket requires IO thread, and low latency input stream requires high
   // thread priority. Therefore, a private thread instead of the IO thread from
   // browser thread pool is necessary so as to make sure input stream won't be

chromecast/media/audio/capture_service/capture_service_receiver_unittest.cc

@@ -34,9 +34,9 @@ constexpr StreamInfo kStreamInfo =
                SampleFormat::PLANAR_FLOAT,
                16000,
                160};
-constexpr PacketHeader kRequestPacketHeader =
+constexpr PacketHeader kHandshakePacketHeader =
     PacketHeader{0,
-                 static_cast<uint8_t>(MessageType::kRequest),
+                 static_cast<uint8_t>(MessageType::kHandshake),
                  static_cast<uint8_t>(kStreamInfo.stream_type),
                  static_cast<uint8_t>(kStreamInfo.audio_codec),
                  kStreamInfo.num_channels,
@@ -71,6 +71,7 @@ class MockCaptureServiceReceiverDelegate
   MockCaptureServiceReceiverDelegate() = default;
   ~MockCaptureServiceReceiverDelegate() override = default;
 
+  MOCK_METHOD(bool, OnInitialStreamInfo, (const StreamInfo&), (override));
   MOCK_METHOD(bool, OnCaptureData, (const char*, size_t), (override));
   MOCK_METHOD(void, OnCaptureError, (), (override));
 };
@@ -93,10 +94,10 @@ class CaptureServiceReceiverTest : public ::testing::Test {
 TEST_F(CaptureServiceReceiverTest, StartStop) {
   auto socket1 = std::make_unique<MockStreamSocket>();
   auto socket2 = std::make_unique<MockStreamSocket>();
-  EXPECT_CALL(*socket1, Connect(_)).WillOnce(Return(net::OK));
-  EXPECT_CALL(*socket1, Write(_, _, _, _)).WillOnce(Return(16));
-  EXPECT_CALL(*socket1, Read(_, _, _)).WillOnce(Return(net::ERR_IO_PENDING));
-  EXPECT_CALL(*socket2, Connect(_)).WillOnce(Return(net::OK));
+  EXPECT_CALL(*socket1, Connect).WillOnce(Return(net::OK));
+  EXPECT_CALL(*socket1, Write).WillOnce(Return(16));
+  EXPECT_CALL(*socket1, Read).WillOnce(Return(net::ERR_IO_PENDING));
+  EXPECT_CALL(*socket2, Connect).WillOnce(Return(net::OK));
 
   // Sync.
   receiver_.StartWithSocket(std::move(socket1));
@@ -111,8 +112,8 @@ TEST_F(CaptureServiceReceiverTest, StartStop) {
 
 TEST_F(CaptureServiceReceiverTest, ConnectFailed) {
   auto socket = std::make_unique<MockStreamSocket>();
-  EXPECT_CALL(*socket, Connect(_)).WillOnce(Return(net::ERR_FAILED));
-  EXPECT_CALL(delegate_, OnCaptureError());
+  EXPECT_CALL(*socket, Connect).WillOnce(Return(net::ERR_FAILED));
+  EXPECT_CALL(delegate_, OnCaptureError);
 
   receiver_.StartWithSocket(std::move(socket));
   task_environment_.RunUntilIdle();
@@ -120,8 +121,8 @@ TEST_F(CaptureServiceReceiverTest, ConnectFailed) {
 
 TEST_F(CaptureServiceReceiverTest, ConnectTimeout) {
   auto socket = std::make_unique<MockStreamSocket>();
-  EXPECT_CALL(*socket, Connect(_)).WillOnce(Return(net::ERR_IO_PENDING));
-  EXPECT_CALL(delegate_, OnCaptureError());
+  EXPECT_CALL(*socket, Connect).WillOnce(Return(net::ERR_IO_PENDING));
+  EXPECT_CALL(delegate_, OnCaptureError);
 
   receiver_.StartWithSocket(std::move(socket));
   task_environment_.FastForwardBy(CaptureServiceReceiver::kConnectTimeout);
@@ -129,8 +130,8 @@ TEST_F(CaptureServiceReceiverTest, ConnectTimeout) {
 
 TEST_F(CaptureServiceReceiverTest, SendRequest) {
   auto socket = std::make_unique<MockStreamSocket>();
-  EXPECT_CALL(*socket, Connect(_)).WillOnce(Return(net::OK));
-  EXPECT_CALL(*socket, Write(_, _, _, _))
+  EXPECT_CALL(*socket, Connect).WillOnce(Return(net::OK));
+  EXPECT_CALL(*socket, Write)
       .WillOnce(Invoke([](net::IOBuffer* buf, int buf_len,
                           net::CompletionOnceCallback,
                           const net::NetworkTrafficAnnotationTag&) {
@@ -140,18 +141,14 @@ TEST_F(CaptureServiceReceiverTest, SendRequest) {
         base::ReadBigEndian(data, &size);
         EXPECT_EQ(size, sizeof(PacketHeader) - sizeof(size));
         PacketHeader header;
-        memcpy(&header, data, sizeof(PacketHeader));
-        EXPECT_EQ(header.message_type, kRequestPacketHeader.message_type);
-        EXPECT_EQ(header.stream_type, kRequestPacketHeader.stream_type);
+        std::memcpy(&header, data, sizeof(PacketHeader));
+        EXPECT_EQ(header.message_type, kHandshakePacketHeader.message_type);
+        EXPECT_EQ(header.stream_type, kHandshakePacketHeader.stream_type);
         EXPECT_EQ(header.codec_or_sample_format,
-                  kRequestPacketHeader.codec_or_sample_format);
-        EXPECT_EQ(header.num_channels, kRequestPacketHeader.num_channels);
-        EXPECT_EQ(header.sample_rate, kRequestPacketHeader.sample_rate);
-        EXPECT_EQ(header.timestamp_or_frames,
-                  kRequestPacketHeader.timestamp_or_frames);
+                  kHandshakePacketHeader.codec_or_sample_format);
         return buf_len;
       }));
-  EXPECT_CALL(*socket, Read(_, _, _)).WillOnce(Return(net::ERR_IO_PENDING));
+  EXPECT_CALL(*socket, Read).WillOnce(Return(net::ERR_IO_PENDING));
 
   receiver_.StartWithSocket(std::move(socket));
   task_environment_.RunUntilIdle();
@@ -163,9 +160,20 @@ TEST_F(CaptureServiceReceiverTest, SendRequest) {
 
 TEST_F(CaptureServiceReceiverTest, ReceivePcmAudioMessage) {
   auto socket = std::make_unique<MockStreamSocket>();
-  EXPECT_CALL(*socket, Connect(_)).WillOnce(Return(net::OK));
-  EXPECT_CALL(*socket, Write(_, _, _, _)).WillOnce(Return(16));
-  EXPECT_CALL(*socket, Read(_, _, _))
+  EXPECT_CALL(*socket, Connect).WillOnce(Return(net::OK));
+  EXPECT_CALL(*socket, Write).WillOnce(Return(16));
+  EXPECT_CALL(*socket, Read)
+      // Ack message.
+      .WillOnce(Invoke(
+          [](net::IOBuffer* buf, int buf_len, net::CompletionOnceCallback) {
+            int total_size = sizeof(PacketHeader);
+            EXPECT_GE(buf_len, total_size);
+            uint16_t size = total_size - sizeof(uint16_t);
+            PacketHeader header = kHandshakePacketHeader;
+            FillHeader(buf->data(), size, header);
+            return total_size;
+          }))
+      // Audio message.
       .WillOnce(Invoke([](net::IOBuffer* buf, int buf_len,
                           net::CompletionOnceCallback) {
         int total_size = sizeof(PacketHeader) + DataSizeInBytes(kStreamInfo);
@@ -176,7 +184,8 @@ TEST_F(CaptureServiceReceiverTest, ReceivePcmAudioMessage) {
         return total_size;  // No need to fill audio frames.
       }))
       .WillOnce(Return(net::ERR_IO_PENDING));
-  EXPECT_CALL(delegate_, OnCaptureData(_, _)).WillOnce(Return(true));
+  EXPECT_CALL(delegate_, OnInitialStreamInfo).WillOnce(Return(true));
+  EXPECT_CALL(delegate_, OnCaptureData).WillOnce(Return(true));
 
   receiver_.StartWithSocket(std::move(socket));
   task_environment_.RunUntilIdle();
@@ -186,13 +195,37 @@ TEST_F(CaptureServiceReceiverTest, ReceivePcmAudioMessage) {
   task_environment_.RunUntilIdle();
 }
 
+TEST_F(CaptureServiceReceiverTest, ReceiveMetadataMessage) {
+  auto socket = std::make_unique<MockStreamSocket>();
+  EXPECT_CALL(*socket, Connect).WillOnce(Return(net::OK));
+  EXPECT_CALL(*socket, Write).WillOnce(Return(16));
+  EXPECT_CALL(*socket, Read)
+      .WillOnce(Invoke(
+          [](net::IOBuffer* buf, int buf_len, net::CompletionOnceCallback) {
+            uint16_t size = sizeof(uint8_t) + 1;  // MessageType and 1 byte.
+            int total_size = size + sizeof(size);
+            EXPECT_GE(buf_len, total_size);
+            base::WriteBigEndian(buf->data(), size);
+            uint8_t message_type = static_cast<uint8_t>(MessageType::kMetadata);
+            std::memcpy(buf->data() + sizeof(size), &message_type,
+                        sizeof(message_type));
+            return total_size;  // No need to fill metadata.
+          }))
+      .WillOnce(Return(net::ERR_IO_PENDING));
+  // Neither OnCaptureError nor OnCaptureData will be called.
+  EXPECT_CALL(delegate_, OnCaptureError).Times(0);
+  EXPECT_CALL(delegate_, OnCaptureData).Times(0);
+
+  receiver_.StartWithSocket(std::move(socket));
+  task_environment_.RunUntilIdle();
+}
+
 TEST_F(CaptureServiceReceiverTest, ReceiveError) {
   auto socket = std::make_unique<MockStreamSocket>();
-  EXPECT_CALL(*socket, Connect(_)).WillOnce(Return(net::OK));
-  EXPECT_CALL(*socket, Write(_, _, _, _)).WillOnce(Return(16));
-  EXPECT_CALL(*socket, Read(_, _, _))
-      .WillOnce(Return(net::ERR_CONNECTION_RESET));
-  EXPECT_CALL(delegate_, OnCaptureError());
+  EXPECT_CALL(*socket, Connect).WillOnce(Return(net::OK));
+  EXPECT_CALL(*socket, Write).WillOnce(Return(16));
+  EXPECT_CALL(*socket, Read).WillOnce(Return(net::ERR_CONNECTION_RESET));
+  EXPECT_CALL(delegate_, OnCaptureError);
 
   receiver_.StartWithSocket(std::move(socket));
   task_environment_.RunUntilIdle();
@@ -200,10 +233,10 @@ TEST_F(CaptureServiceReceiverTest, ReceiveError) {
 
 TEST_F(CaptureServiceReceiverTest, ReceiveEosMessage) {
   auto socket = std::make_unique<MockStreamSocket>();
-  EXPECT_CALL(*socket, Connect(_)).WillOnce(Return(net::OK));
-  EXPECT_CALL(*socket, Write(_, _, _, _)).WillOnce(Return(16));
-  EXPECT_CALL(*socket, Read(_, _, _)).WillOnce(Return(0));
-  EXPECT_CALL(delegate_, OnCaptureError());
+  EXPECT_CALL(*socket, Connect).WillOnce(Return(net::OK));
+  EXPECT_CALL(*socket, Write).WillOnce(Return(16));
+  EXPECT_CALL(*socket, Read).WillOnce(Return(0));
+  EXPECT_CALL(delegate_, OnCaptureError);
 
   receiver_.StartWithSocket(std::move(socket));
   task_environment_.RunUntilIdle();

chromecast/media/audio/capture_service/constants.h

@@ -54,10 +54,10 @@ enum class AudioCodec : uint8_t {
 };
 
 enum class MessageType : uint8_t {
-  // Request message that has stream header but empty body. It is used by
+  // Handshake message that has stream header but empty body. It is used by
   // receiver notifying the stream it is observing, and sender can confirm the
-  // parameters are all correct.
-  kRequest = 0,
+  // types/codec are supported and send back more detailed parameters.
+  kHandshake = 0,
   // PCM audio message that has stream header and audio data in the message
   // body. The audio data will match the parameters in the header.
   kPcmAudio,
@@ -79,9 +79,9 @@ struct StreamInfo {
 };
 
 // Info describes the message packet. PacketInfo is only for message types that
-// support packet header, i.e., kRequest and kPcmAudio. |timestamp_us| is about
-// when the buffer is captured. If the audio source is from ALSA, i.e., stream
-// type is raw mic, it's the ALSA capture timestamp; otherwise, it may be
+// support packet header, i.e., kHandshake and kPcmAudio. |timestamp_us| is
+// about when the buffer is captured. If the audio source is from ALSA, i.e.,
+// stream type is raw mic, it's the ALSA capture timestamp; otherwise, it may be
 // shifted based on the samples and sample rate upon raw mic input.
 struct PacketInfo {
   MessageType message_type;
@@ -89,6 +89,10 @@ struct PacketInfo {
   int64_t timestamp_us = 0;
 };
 
+// Size of a message header. The header can be parsed into PacketInfo with
+// methods in message_parsing_utils.h
+constexpr size_t kMessageHeaderBytes = 14;
+
 }  // namespace capture_service
 }  // namespace media
 }  // namespace chromecast

chromecast/media/audio/capture_service/message_parsing_utils.cc

@@ -12,6 +12,7 @@
 #include "base/big_endian.h"
 #include "base/logging.h"
 #include "base/notreached.h"
+#include "chromecast/media/audio/capture_service/constants.h"
 #include "chromecast/media/audio/capture_service/packet_header.h"
 #include "media/base/limits.h"
 
@@ -20,9 +21,8 @@ namespace media {
 namespace capture_service {
 namespace {
 
-// Size in bytes of the total/message header.
-constexpr size_t kTotalHeaderBytes = 16;
-constexpr size_t kMessageHeaderBytes = kTotalHeaderBytes - sizeof(uint16_t);
+// Size in bytes of the total message header.
+constexpr size_t kTotalHeaderBytes = kMessageHeaderBytes + sizeof(uint16_t);
 
 static_assert(sizeof(PacketHeader) == kTotalHeaderBytes,
               "Invalid packet header size.");
@@ -146,7 +146,7 @@ bool HasPacketHeader(MessageType type) {
   // other message type such as kOpusAudio and kMetadata, the packet does not
   // contain the packet header and only contains the message type and serialized
   // data.
-  return type == MessageType::kRequest || type == MessageType::kPcmAudio;
+  return type == MessageType::kHandshake || type == MessageType::kPcmAudio;
 }
 
 }  // namespace
@@ -159,10 +159,10 @@ char* PopulateHeader(char* data, size_t size, const PacketInfo& packet_info) {
   header.stream_type = static_cast<uint8_t>(stream_info.stream_type);
   header.num_channels = stream_info.num_channels;
   header.sample_rate = stream_info.sample_rate;
-  // In request message, the header contains a codec field and a
+  // In request/ack message, the header contains a codec field and a
   // frames_per_buffer field, while in PCM audio message, it instead contains a
   // sample format field and a timestamp field.
-  if (packet_info.message_type == MessageType::kRequest) {
+  if (packet_info.message_type == MessageType::kHandshake) {
     header.codec_or_sample_format =
         static_cast<uint8_t>(stream_info.audio_codec);
     header.timestamp_or_frames = stream_info.frames_per_buffer;
@@ -176,10 +176,7 @@ char* PopulateHeader(char* data, size_t size, const PacketInfo& packet_info) {
   base::WriteBigEndian(  // Deduct the size of |size| itself.
       data, static_cast<uint16_t>(size - sizeof(uint16_t)));
   DCHECK_EQ(sizeof(header), kTotalHeaderBytes);
-  memcpy(data + sizeof(uint16_t),
-         reinterpret_cast<const char*>(&header) +
-             offsetof(struct PacketHeader, message_type),
-         kMessageHeaderBytes);
+  memcpy(data + sizeof(uint16_t), &header.message_type, kMessageHeaderBytes);
   return data + kTotalHeaderBytes;
 }
 
@@ -190,12 +187,10 @@ bool ReadHeader(const char* data, size_t size, PacketInfo* packet_info) {
     return false;
   }
   PacketHeader header;
-  memcpy(reinterpret_cast<char*>(&header) +
-             offsetof(struct PacketHeader, message_type),
-         data, kMessageHeaderBytes);
+  memcpy(&header.message_type, data, kMessageHeaderBytes);
   MessageType message_type = static_cast<MessageType>(header.message_type);
   uint8_t last_codec_or_sample_format =
-      (message_type == MessageType::kRequest)
+      (message_type == MessageType::kHandshake)
           ? static_cast<uint8_t>(AudioCodec::kLastCodec)
           : static_cast<uint8_t>(SampleFormat::LAST_FORMAT);
   if (!HasPacketHeader(message_type) ||
@@ -213,7 +208,7 @@ bool ReadHeader(const char* data, size_t size, PacketInfo* packet_info) {
       static_cast<StreamType>(header.stream_type);
   packet_info->stream_info.num_channels = header.num_channels;
   packet_info->stream_info.sample_rate = header.sample_rate;
-  if (message_type == MessageType::kRequest) {
+  if (message_type == MessageType::kHandshake) {
     packet_info->stream_info.audio_codec =
         static_cast<AudioCodec>(header.codec_or_sample_format);
     packet_info->stream_info.frames_per_buffer = header.timestamp_or_frames;
@@ -231,8 +226,9 @@ scoped_refptr<net::IOBufferWithSize> MakeMessage(const PacketInfo& packet_info,
                                                  const char* data,
                                                  size_t data_size) {
   if (!HasPacketHeader(packet_info.message_type)) {
-    LOG(ERROR) << "Only kRequest and kPcmAudio message have packet header, use "
-                  "MakeSerializedMessage otherwise.";
+    LOG(ERROR)
+        << "Only kHandshake and kPcmAudio message have packet header, use "
+           "MakeSerializedMessage otherwise.";
     return nullptr;
   }
   const size_t total_size = kTotalHeaderBytes + data_size;

chromecast/media/audio/capture_service/message_parsing_utils.h

@@ -20,16 +20,15 @@ namespace capture_service {
 // The header of the message consists of <uint8_t message_type>
 // <uint8_t stream_type> <uint8_t audio_codec|sample_format> <uint8_t channels>
 // <uint16_t sample_rate> <uint64_t frames_per_buffer|timestamp_us>.
-// If |message_type| is kRequest, it is a request message that has |audio_codec|
-// and |frames_per_buffer|, otherwise if |message_type| is kPcmAudio, it's a PCM
-// audio data message that has |sample_format| and |timestamp_us|.
-// Note it cannot be used to read kOpusAudio or kMetadata messages, which don't
-// have header besides |message_type| bits.
-// Note |packet_info| will be untouched if fails to read header.
-// Note unsigned |timestamp_us| will be converted to signed |timestamp| if
-// valid.
-// Note |data| here has been parsed firstly by SmallMessageSocket, and
-// thus doesn't have <uint16_t size> bits.
+// If |message_type| is kHandshake, it is a handshake message that has
+// |audio_codec| and |frames_per_buffer|, otherwise if |message_type| is
+// kPcmAudio, it's a PCM audio data message that has |sample_format| and
+// |timestamp_us|. Note it cannot be used to read kOpusAudio or kMetadata
+// messages, which don't have header besides |message_type| bits. Note
+// |packet_info| will be untouched if fails to read header. Note unsigned
+// |timestamp_us| will be converted to signed |timestamp| if valid. Note |data|
+// here has been parsed firstly by SmallMessageSocket, and thus doesn't have
+// <uint16_t size> bits.
 bool ReadHeader(const char* data, size_t size, PacketInfo* packet_info);
 
 // Make a IO buffer for stream message. It will populate the header with

chromecast/media/audio/capture_service/message_parsing_utils_unittest.cc

@@ -26,8 +26,8 @@ constexpr StreamInfo kStreamInfo =
                SampleFormat::PLANAR_FLOAT,
                16000,
                kFrames};
-constexpr PacketInfo kRequestPacketInfo = {MessageType::kRequest, kStreamInfo,
-                                           0};
+constexpr PacketInfo kHandshakePacketInfo = {MessageType::kHandshake,
+                                             kStreamInfo, 0};
 constexpr PacketInfo kPcmAudioPacketInfo = {MessageType::kPcmAudio, kStreamInfo,
                                             0};
 
@@ -120,7 +120,7 @@ TEST(MessageParsingUtilsTest, InvalidType) {
   size_t data_size = kTotalHeaderBytes / sizeof(float);
   std::vector<float> data(data_size, 1.0f);
   // Request packet
-  PacketInfo request_packet_info = kRequestPacketInfo;
+  PacketInfo request_packet_info = kHandshakePacketInfo;
   PopulateHeader(reinterpret_cast<char*>(data.data()),
                  data.size() * sizeof(float), request_packet_info);
   *(reinterpret_cast<uint8_t*>(data.data()) +
@@ -147,7 +147,7 @@ TEST(MessageParsingUtilsTest, InvalidType) {
 TEST(MessageParsingUtilsTest, InvalidCodec) {
   size_t data_size = kTotalHeaderBytes / sizeof(float);
   std::vector<float> data(data_size, 1.0f);
-  PacketInfo packet_info = kRequestPacketInfo;
+  PacketInfo packet_info = kHandshakePacketInfo;
   PopulateHeader(reinterpret_cast<char*>(data.data()),
                  data.size() * sizeof(float), packet_info);
   *(reinterpret_cast<uint8_t*>(data.data()) +
@@ -179,7 +179,7 @@ TEST(MessageParsingUtilsTest, InvalidFormat) {
 TEST(MessageParsingUtilsTest, RequestMessage) {
   size_t data_size = kTotalHeaderBytes / sizeof(float);
   std::vector<float> data(data_size, 1.0f);
-  PacketInfo packet_info = kRequestPacketInfo;
+  PacketInfo packet_info = kHandshakePacketInfo;
   PopulateHeader(reinterpret_cast<char*>(data.data()),
                  data.size() * sizeof(float), packet_info);
 
@@ -188,7 +188,7 @@ TEST(MessageParsingUtilsTest, RequestMessage) {
       ReadHeader(reinterpret_cast<char*>(data.data()) + sizeof(uint16_t),
                  data_size * sizeof(float) - sizeof(uint16_t), &info);
   EXPECT_TRUE(success);
-  EXPECT_EQ(info.message_type, kRequestPacketInfo.message_type);
+  EXPECT_EQ(info.message_type, kHandshakePacketInfo.message_type);
   EXPECT_EQ(info.stream_info.stream_type, kStreamInfo.stream_type);
   EXPECT_EQ(info.stream_info.audio_codec, kStreamInfo.audio_codec);
   EXPECT_EQ(info.stream_info.num_channels, kStreamInfo.num_channels);

chromecast/media/audio/capture_service/packet_header.h

@@ -16,7 +16,7 @@ namespace capture_service {
 // packet header structure, however, the |size| bits are in big-endian order,
 // and thus is only for padding purpose in this struct, when all bytes after it
 // represent a message header.
-struct PacketHeader {
+struct __attribute__((__packed__)) PacketHeader {
   uint16_t size;
   uint8_t message_type;
   uint8_t stream_type;

chromecast/media/audio/cast_audio_input_stream.cc

@@ -114,6 +114,25 @@ void CastAudioInputStream::SetOutputDeviceForAec(
   // Not supported. Do nothing.
 }
 
+bool CastAudioInputStream::OnInitialStreamInfo(
+    const capture_service::StreamInfo& stream_info) {
+  const bool is_params_match =
+      stream_info.stream_type ==
+          capture_service::StreamType::kSoftwareEchoCancelled &&
+      stream_info.audio_codec == capture_service::AudioCodec::kPcm &&
+      stream_info.num_channels == audio_params_.channels() &&
+      stream_info.sample_rate == audio_params_.sample_rate() &&
+      stream_info.frames_per_buffer == audio_params_.frames_per_buffer();
+  LOG_IF(ERROR, !is_params_match)
+      << "Got different parameters from sender, sample_rate: "
+      << audio_params_.sample_rate() << " Hz -> " << stream_info.sample_rate
+      << " Hz, num_channels: " << audio_params_.channels() << " -> "
+      << stream_info.num_channels
+      << ", frames_per_buffer: " << audio_params_.frames_per_buffer() << " -> "
+      << stream_info.frames_per_buffer << ".";
+  return is_params_match;
+}
+
 bool CastAudioInputStream::OnCaptureData(const char* data, size_t size) {
   capture_service::PacketInfo info;
   if (!capture_service::ReadPcmAudioMessage(data, size, &info,

chromecast/media/audio/cast_audio_input_stream.h

@@ -48,6 +48,8 @@ class CastAudioInputStream : public ::media::AudioInputStream,
   void SetOutputDeviceForAec(const std::string& output_device_id) override;
 
   // CaptureServiceReceiver::Delegate implementation:
+  bool OnInitialStreamInfo(
+      const capture_service::StreamInfo& stream_info) override;
   bool OnCaptureData(const char* data, size_t size) override;
   void OnCaptureError() override;