Media Remoting: Data/Control plumbing between renderer and Media Router.

chrome/browser/media/cast_remoting_sender.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/media/cast_remoting_sender.h"
 
+#include <algorithm>
 #include <map>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/lazy_instance.h"
 #include "base/memory/ptr_util.h"
 #include "base/numerics/safe_conversions.h"
+#include "base/stl_util.h"
 #include "base/trace_event/trace_event.h"
 #include "content/public/browser/browser_thread.h"
 #include "media/base/bind_to_current_loop.h"
 #include "media/cast/constants.h"
 
+using content::BrowserThread;
+
 namespace {
 
 // Global map for looking-up CastRemotingSender instances by their
-// |remoting_stream_id_|.
+// |rtp_stream_id|.
 using CastRemotingSenderMap = std::map<int32_t, cast::CastRemotingSender*>;
 base::LazyInstance<CastRemotingSenderMap>::Leaky g_sender_map =
     LAZY_INSTANCE_INITIALIZER;
 
 constexpr base::TimeDelta kMinSchedulingDelay =
     base::TimeDelta::FromMilliseconds(1);
 constexpr base::TimeDelta kMaxAckDelay = base::TimeDelta::FromMilliseconds(800);
-constexpr base::TimeDelta kMinAckDelay = base::TimeDelta::FromMilliseconds(400);
 constexpr base::TimeDelta kReceiverProcessTime =
     base::TimeDelta::FromMilliseconds(250);
 
 }  // namespace
 
 namespace cast {
 
 class CastRemotingSender::RemotingRtcpClient final
     : public media::cast::RtcpObserver {
  public:
@@ skipping 23 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(RemotingRtcpClient);
 };
 
 // Convenience macro used in logging statements throughout this file.
 #define SENDER_SSRC (is_audio_ ? "AUDIO[" : "VIDEO[") << ssrc_ << "] "
 
 CastRemotingSender::CastRemotingSender(
     scoped_refptr<media::cast::CastEnvironment> cast_environment,
     media::cast::CastTransport* transport,
     const media::cast::CastTransportRtpConfig& config)
-    : remoting_stream_id_(config.rtp_stream_id),
+    : rtp_stream_id_(config.rtp_stream_id),
       cast_environment_(std::move(cast_environment)),
       transport_(transport),
       ssrc_(config.ssrc),
       is_audio_(config.rtp_payload_type ==
                 media::cast::RtpPayloadType::REMOTE_AUDIO),
+      binding_(this),
       max_ack_delay_(kMaxAckDelay),
       last_sent_frame_id_(media::cast::FrameId::first() - 1),
       latest_acked_frame_id_(media::cast::FrameId::first() - 1),
       duplicate_ack_counter_(0),
-      last_frame_was_canceled_(false),
+      input_queue_discards_remaining_(0),
+      flow_restart_pending_(true),
       weak_factory_(this) {
+  // Confirm this constructor is running on the IO BrowserThread and the
+  // CastEnvironment::MAIN thread is the same thread.
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
   DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
 
-  CastRemotingSender*& pointer_in_map = g_sender_map.Get()[remoting_stream_id_];
+  CastRemotingSender*& pointer_in_map = g_sender_map.Get()[rtp_stream_id_];
   DCHECK(!pointer_in_map);
   pointer_in_map = this;
+
   transport_->InitializeStream(
       config, base::MakeUnique<RemotingRtcpClient>(weak_factory_.GetWeakPtr()));
 }
 
 CastRemotingSender::~CastRemotingSender() {
-  DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
+  DCHECK_CURRENTLY_ON(BrowserThread::IO);
+  g_sender_map.Pointer()->erase(rtp_stream_id_);
+}
 
-  g_sender_map.Pointer()->erase(remoting_stream_id_);
+// static
+void CastRemotingSender::FindAndBind(
+    int32_t rtp_stream_id,
+    mojo::ScopedDataPipeConsumerHandle pipe,
+    media::mojom::RemotingDataStreamSenderRequest request,
+    const base::Closure& error_callback) {
+  // CastRemotingSender lives entirely on the IO thread, so trampoline if
+  // necessary.
+  if (!BrowserThread::CurrentlyOn(BrowserThread::IO)) {
+    BrowserThread::PostTask(
+        BrowserThread::IO, FROM_HERE,
+        base::Bind(&CastRemotingSender::FindAndBind, rtp_stream_id,
+                   base::Passed(&pipe), base::Passed(&request),
+                   // Using media::BindToCurrentLoop() so the |error_callback|
+                   // is trampolined back to the original thread.
+                   media::BindToCurrentLoop(error_callback)));
+    return;
+  }
+
+  DCHECK(!error_callback.is_null());
+
+  // Look-up the CastRemotingSender instance by its |rtp_stream_id|.
+  const auto it = g_sender_map.Pointer()->find(rtp_stream_id);
+  if (it == g_sender_map.Pointer()->end()) {
+    DLOG(ERROR) << "Cannot find CastRemotingSender instance by ID: "
+                << rtp_stream_id;
+    error_callback.Run();
+    return;
+  }
+  CastRemotingSender* const sender = it->second;
+
+  // Confirm that the CastRemotingSender isn't already bound to a message pipe.
+  if (sender->binding_.is_bound()) {
+    DLOG(ERROR) << "Attempt to bind to CastRemotingSender a second time (id="
+                << rtp_stream_id << ")!";
+    error_callback.Run();
+    return;
+  }
+
+  DCHECK(sender->error_callback_.is_null());
+  sender->error_callback_ = error_callback;
+
+  sender->pipe_ = std::move(pipe);
+  sender->pipe_watcher_.Start(
+      sender->pipe_.get(), MOJO_HANDLE_SIGNAL_READABLE,
+      base::Bind(&CastRemotingSender::ProcessInputQueue,
+                 base::Unretained(sender)));
+  sender->binding_.Bind(std::move(request));
+  sender->binding_.set_connection_error_handler(sender->error_callback_);
 }
 
 void CastRemotingSender::OnReceivedRtt(base::TimeDelta round_trip_time) {
   DCHECK_GT(round_trip_time, base::TimeDelta());
   current_round_trip_time_ = round_trip_time;
-  max_ack_delay_ = 2 * current_round_trip_time_ + kReceiverProcessTime;
-  max_ack_delay_ =
-      std::max(std::min(max_ack_delay_, kMaxAckDelay), kMinAckDelay);
+  max_ack_delay_ = 2 * std::max(current_round_trip_time_, base::TimeDelta()) +
+      kReceiverProcessTime;
+  max_ack_delay_ = std::min(max_ack_delay_, kMaxAckDelay);
 }
 
 void CastRemotingSender::ResendCheck() {
   DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
 
   DCHECK(!last_send_time_.is_null());
   const base::TimeDelta time_since_last_send =
       cast_environment_->Clock()->NowTicks() - last_send_time_;
   if (time_since_last_send > max_ack_delay_) {
     if (latest_acked_frame_id_ == last_sent_frame_id_) {
@@ skipping 118 matching lines @@
       frames_to_cancel.push_back(latest_acked_frame_id_);
       // This is a good place to match the trace for frame ids
       // since this ensures we not only track frame ids that are
       // implicitly ACKed, but also handles duplicate ACKs
       TRACE_EVENT_ASYNC_END1(
           "cast.stream", is_audio_ ? "Audio Transport" : "Video Transport",
           latest_acked_frame_id_.lower_32_bits(), "RTT_usecs",
           current_round_trip_time_.InMicroseconds());
     } while (latest_acked_frame_id_ < cast_feedback.ack_frame_id);
     transport_->CancelSendingFrames(ssrc_, frames_to_cancel);
+
+    // One or more frames were canceled. This may allow pending input operations
+    // to complete.
+    ProcessInputQueue(MOJO_RESULT_OK);
   }
 }
 
+void CastRemotingSender::ConsumeDataChunk(uint32_t offset, uint32_t size,
+                                          uint32_t total_payload_size) {
+  DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
+  input_queue_.push(
+      base::Bind(&CastRemotingSender::TryConsumeDataChunk,
+                 base::Unretained(this), offset, size, total_payload_size));
+  ProcessInputQueue(MOJO_RESULT_OK);
+}
+
 void CastRemotingSender::SendFrame() {
   DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
+  input_queue_.push(
+      base::Bind(&CastRemotingSender::TrySendFrame, base::Unretained(this)));
+  ProcessInputQueue(MOJO_RESULT_OK);
+}
 
+void CastRemotingSender::ProcessInputQueue(MojoResult result) {
+  DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
+  while (!input_queue_.empty()) {
+    if (!input_queue_.front().Run(input_queue_discards_remaining_ > 0))
+      break;  // Operation must be retried later. Stop processing queue.
+    input_queue_.pop();
+    if (input_queue_discards_remaining_ > 0)
+      --input_queue_discards_remaining_;
+  }
+}
+
+bool CastRemotingSender::TryConsumeDataChunk(uint32_t offset, uint32_t size,
+                                             uint32_t total_payload_size,
+                                             bool discard_data) {
+  DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
+
+  do {
+    if (!pipe_.is_valid()) {
+      VLOG(1) << SENDER_SSRC << "Data pipe handle no longer valid.";
+      break;
+    }
+
+    if (offset + size > total_payload_size) {
+      LOG(ERROR)
+          << SENDER_SSRC << "BUG: offset + size > total_payload_size ("
+          << offset << " + " << size << " > " << total_payload_size << ')';
+      break;
+    }
+
+    // If the data is to be discarded, do a data pipe read with the DISCARD flag
+    // set.
+    if (discard_data) {
+      const MojoResult result = mojo::ReadDataRaw(
+          pipe_.get(), nullptr, &size,
+          MOJO_READ_DATA_FLAG_DISCARD | MOJO_READ_DATA_FLAG_ALL_OR_NONE);
+      if (result == MOJO_RESULT_OK)
+        return true;  // Successfully discarded data.
+      if (result == MOJO_RESULT_OUT_OF_RANGE)
+        return false;  // Retry later.
+      LOG(ERROR) << SENDER_SSRC
+                 << "Unexpcted result when discarding from data pipe ("

[dcheng, 2016/09/23 04:51:07]

Nit: Unexpected

[miu, 2016/09/23 05:52:00]

Done.

+                 << result << ')';
+      break;
+    }
+
+    // If |total_payload_size| has changed, resize the data string. If it has
+    // not changed, the following statement will be a no-op.
+    next_frame_data_.resize(total_payload_size);
+
+    const MojoResult result = mojo::ReadDataRaw(
+        pipe_.get(), base::string_as_array(&next_frame_data_) + offset, &size,
+        MOJO_READ_DATA_FLAG_ALL_OR_NONE);
+    if (result == MOJO_RESULT_OK)
+      return true;  // Successfully consumed data.
+    if (result == MOJO_RESULT_OUT_OF_RANGE)
+      return false;  // Retry later.
+    LOG(ERROR)
+        << SENDER_SSRC << "Read from data pipe failed (" << result << ')';
+  } while (false);
+
+  // If this point is reached, there was a fatal error. Shut things down and run
+  // the error callback.
+  pipe_watcher_.Cancel();
+  pipe_.reset();
+  binding_.Close();
+  error_callback_.Run();
+  return true;
+}
+
+bool CastRemotingSender::TrySendFrame(bool discard_data) {
+  DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
+
+  // If the frame's data is to be discarded, just return immediately.
+  if (discard_data)
+    return true;
+
+  // If there would be too many frames in-flight, do not proceed.
   if (NumberOfFramesInFlight() >= media::cast::kMaxUnackedFrames) {
-    // TODO(xjz): Delay the sending of this frame and stop reading the next
-    // frame data.
-    return;
+    VLOG(1) << SENDER_SSRC
+            << "Cannot send frame now because too many frames are in flight.";
+    return false;
   }
 
   VLOG(2) << SENDER_SSRC
           << "About to send another frame: last_sent=" << last_sent_frame_id_
           << ", latest_acked=" << latest_acked_frame_id_;
 
   const media::cast::FrameId frame_id = last_sent_frame_id_ + 1;
   const bool is_first_frame_to_be_sent = last_send_time_.is_null();
 
   base::TimeTicks last_frame_reference_time = last_send_time_;
   last_send_time_ = cast_environment_->Clock()->NowTicks();
   last_sent_frame_id_ = frame_id;
   // If this is the first frame about to be sent, fake the value of
   // |latest_acked_frame_id_| to indicate the receiver starts out all caught up.
   // Also, schedule the periodic frame re-send checks.
   if (is_first_frame_to_be_sent)
     ScheduleNextResendCheck();
 
   DVLOG(3) << "Sending remoting frame, id = " << frame_id;
 
   media::cast::EncodedFrame remoting_frame;
   remoting_frame.frame_id = frame_id;
-  remoting_frame.dependency =
-      (is_first_frame_to_be_sent || last_frame_was_canceled_)
-          ? media::cast::EncodedFrame::KEY
-          : media::cast::EncodedFrame::DEPENDENT;
+  if (flow_restart_pending_) {
+    remoting_frame.dependency = media::cast::EncodedFrame::KEY;
+    flow_restart_pending_ = false;
+  } else {
+    DCHECK(!is_first_frame_to_be_sent);
+    remoting_frame.dependency = media::cast::EncodedFrame::DEPENDENT;
+  }
   remoting_frame.referenced_frame_id =
       remoting_frame.dependency == media::cast::EncodedFrame::KEY
           ? frame_id
           : frame_id - 1;
   remoting_frame.reference_time = last_send_time_;
   media::cast::RtpTimeTicks last_frame_rtp_timestamp;
   if (is_first_frame_to_be_sent) {
     last_frame_reference_time = remoting_frame.reference_time;
     last_frame_rtp_timestamp =
         media::cast::RtpTimeTicks() - media::cast::RtpTimeDelta::FromTicks(1);
@@ skipping 18 matching lines @@
   remoting_event->media_type =
       is_audio_ ? media::cast::AUDIO_EVENT : media::cast::VIDEO_EVENT;
   remoting_event->rtp_timestamp = remoting_frame.rtp_timestamp;
   remoting_event->frame_id = frame_id;
   remoting_event->size = remoting_frame.data.length();
   remoting_event->key_frame =
       remoting_frame.dependency == media::cast::EncodedFrame::KEY;
   cast_environment_->logger()->DispatchFrameEvent(std::move(remoting_event));
 
   RecordLatestFrameTimestamps(frame_id, remoting_frame.rtp_timestamp);
-  last_frame_was_canceled_ = false;
 
   transport_->InsertFrame(ssrc_, remoting_frame);
+
+  return true;
 }
 
-void CastRemotingSender::CancelFramesInFlight() {
+void CastRemotingSender::CancelInFlightData() {
   DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
 
   base::STLClearObject(&next_frame_data_);
 
+  // TODO(miu): The following code is something we want to do as an
+  // optimization. However, as-is, it's not quite correct. We can only cancel
+  // frames where no packets have actually hit the network yet. Said another
+  // way, we can only cancel frames the receiver has definitely not seen any
+  // part of (including kickstarting!). http://crbug.com/647423
+#if 0
   if (latest_acked_frame_id_ < last_sent_frame_id_) {
     std::vector<media::cast::FrameId> frames_to_cancel;
     do {
       ++latest_acked_frame_id_;
       frames_to_cancel.push_back(latest_acked_frame_id_);
     } while (latest_acked_frame_id_ < last_sent_frame_id_);
     transport_->CancelSendingFrames(ssrc_, frames_to_cancel);
   }
+#endif
 
-  last_frame_was_canceled_ = true;
+  // Flag that all pending input operations should discard data.
+  input_queue_discards_remaining_ = input_queue_.size();
+
+  flow_restart_pending_ = true;
+  VLOG(1) << SENDER_SSRC
+          << "Now restarting because in-flight data was just canceled.";
 }
 
 }  // namespace cast