Adding CastRemotingSender for media remoting.

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 <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/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"
+
+namespace {
+
+// Global map for looking-up CastRemotingSender instances by their
+// |remoting_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:
+  explicit RemotingRtcpClient(base::WeakPtr<CastRemotingSender> remoting_sender)
+      : remoting_sender_(remoting_sender) {}
+
+  ~RemotingRtcpClient() final {}
+
+  void OnReceivedCastMessage(
+      const media::cast::RtcpCastMessage& cast_message) final {
+    if (remoting_sender_)
+      remoting_sender_->OnReceivedCastMessage(cast_message);
+  }
+
+  void OnReceivedRtt(base::TimeDelta round_trip_time) final {
+    if (remoting_sender_)
+      remoting_sender_->OnReceivedRtt(round_trip_time);
+  }
+
+  void OnReceivedPli() final {
+    // Receiving PLI messages on remoting streams is ignored.
+  }
+
+ private:
+  const base::WeakPtr<CastRemotingSender> remoting_sender_;
+
+  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),
+      cast_environment_(std::move(cast_environment)),
+      transport_(transport),
+      ssrc_(config.ssrc),
+      is_audio_(config.rtp_payload_type ==
+                media::cast::RtpPayloadType::REMOTE_AUDIO),
+      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),
+      weak_factory_(this) {
+  DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
+
+  CastRemotingSender*& pointer_in_map = g_sender_map.Get()[remoting_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));
+
+  g_sender_map.Pointer()->erase(remoting_stream_id_);
+}
+
+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);
+}
+
+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_) {
+      // Last frame acked, no point in doing anything.
+    } else {
+      VLOG(1) << SENDER_SSRC
+              << "ACK timeout; last acked frame: " << latest_acked_frame_id_;
+      ResendForKickstart();
+    }
+  }
+  ScheduleNextResendCheck();
+}
+
+void CastRemotingSender::ScheduleNextResendCheck() {
+  DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
+
+  DCHECK(!last_send_time_.is_null());
+  base::TimeDelta time_to_next =
+      last_send_time_ - cast_environment_->Clock()->NowTicks() + max_ack_delay_;
+  time_to_next = std::max(time_to_next, kMinSchedulingDelay);
+  cast_environment_->PostDelayedTask(
+      media::cast::CastEnvironment::MAIN, FROM_HERE,
+      base::Bind(&CastRemotingSender::ResendCheck, weak_factory_.GetWeakPtr()),
+      time_to_next);
+}
+
+void CastRemotingSender::ResendForKickstart() {
+  DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
+
+  DCHECK(!last_send_time_.is_null());
+  VLOG(1) << SENDER_SSRC << "Resending last packet of frame "
+          << last_sent_frame_id_ << " to kick-start.";
+  last_send_time_ = cast_environment_->Clock()->NowTicks();
+  transport_->ResendFrameForKickstart(ssrc_, last_sent_frame_id_);
+}
+
+// TODO(xjz): We may need to count in the frames acknowledged in
+// RtcpCastMessage::received_later_frames for more accurate calculation on
+// available bandwidth. Same logic should apply on
+// media::cast::FrameSender::GetUnacknowledgedFrameCount().
+int CastRemotingSender::NumberOfFramesInFlight() const {
+  if (last_send_time_.is_null())
+    return 0;
+  const int count = last_sent_frame_id_ - latest_acked_frame_id_;
+  DCHECK_GE(count, 0);
+  return count;
+}
+
+void CastRemotingSender::RecordLatestFrameTimestamps(
+    media::cast::FrameId frame_id,
+    media::cast::RtpTimeTicks rtp_timestamp) {
+  frame_rtp_timestamps_[frame_id.lower_8_bits()] = rtp_timestamp;
+}
+
+media::cast::RtpTimeTicks CastRemotingSender::GetRecordedRtpTimestamp(
+    media::cast::FrameId frame_id) const {
+  return frame_rtp_timestamps_[frame_id.lower_8_bits()];
+}
+
+void CastRemotingSender::OnReceivedCastMessage(
+    const media::cast::RtcpCastMessage& cast_feedback) {
+  DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
+
+  if (last_send_time_.is_null())
+    return;  // Cannot get an ACK without having first sent a frame.
+
+  if (cast_feedback.missing_frames_and_packets.empty() &&
+      cast_feedback.received_later_frames.empty()) {
+    if (latest_acked_frame_id_ == cast_feedback.ack_frame_id) {
+      VLOG(1) << SENDER_SSRC << "Received duplicate ACK for frame "
+              << latest_acked_frame_id_;
+      TRACE_EVENT_INSTANT2(
+          "cast.stream", "Duplicate ACK", TRACE_EVENT_SCOPE_THREAD,
+          "ack_frame_id", cast_feedback.ack_frame_id.lower_32_bits(),
+          "last_sent_frame_id", last_sent_frame_id_.lower_32_bits());
+    }
+    // We only count duplicate ACKs when we have sent newer frames.
+    if (latest_acked_frame_id_ == cast_feedback.ack_frame_id &&
+        latest_acked_frame_id_ != last_sent_frame_id_) {
+      duplicate_ack_counter_++;
+    } else {
+      duplicate_ack_counter_ = 0;
+    }
+    // TODO(miu): The values "2" and "3" should be derived from configuration.
+    if (duplicate_ack_counter_ >= 2 && duplicate_ack_counter_ % 3 == 2) {
+      ResendForKickstart();
+    }
+  } else {
+    // Only count duplicated ACKs if there is no NACK request in between.
+    // This is to avoid aggressive resend.
+    duplicate_ack_counter_ = 0;
+  }
+
+  base::TimeTicks now = cast_environment_->Clock()->NowTicks();
+  auto ack_event = base::MakeUnique<media::cast::FrameEvent>();
+  ack_event->timestamp = now;
+  ack_event->type = media::cast::FRAME_ACK_RECEIVED;
+  ack_event->media_type =
+      is_audio_ ? media::cast::AUDIO_EVENT : media::cast::VIDEO_EVENT;
+  ack_event->rtp_timestamp =
+      GetRecordedRtpTimestamp(cast_feedback.ack_frame_id);
+  ack_event->frame_id = cast_feedback.ack_frame_id;
+  cast_environment_->logger()->DispatchFrameEvent(std::move(ack_event));
+
+  const bool is_acked_out_of_order =
+      cast_feedback.ack_frame_id < latest_acked_frame_id_;
+  VLOG(2) << SENDER_SSRC << "Received ACK"
+          << (is_acked_out_of_order ? " out-of-order" : "") << " for frame "
+          << cast_feedback.ack_frame_id;
+  if (is_acked_out_of_order) {
+    TRACE_EVENT_INSTANT2(
+        "cast.stream", "ACK out of order", TRACE_EVENT_SCOPE_THREAD,
+        "ack_frame_id", cast_feedback.ack_frame_id.lower_32_bits(),
+        "latest_acked_frame_id", latest_acked_frame_id_.lower_32_bits());
+  } else if (latest_acked_frame_id_ < cast_feedback.ack_frame_id) {
+    // Cancel resends of acked frames.
+    std::vector<media::cast::FrameId> frames_to_cancel;
+    frames_to_cancel.reserve(cast_feedback.ack_frame_id -
+                             latest_acked_frame_id_);
+    do {
+      ++latest_acked_frame_id_;
+      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);
+  }
+}
+
+void CastRemotingSender::SendFrame() {
+  DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
+
+  if (NumberOfFramesInFlight() >= media::cast::kMaxUnackedFrames) {
+    // TODO(xjz): Delay the sending of this frame and stop reading the next
+    // frame data.
+    return;
+  }
+
+  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;
+  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);
+  } else {
+    last_frame_rtp_timestamp = GetRecordedRtpTimestamp(frame_id - 1);
+  }
+  // Ensure each successive frame's RTP timestamp is unique, but otherwise just
+  // base it on the reference time.
+  remoting_frame.rtp_timestamp =
+      last_frame_rtp_timestamp +
+      std::max(media::cast::RtpTimeDelta::FromTicks(1),
+               media::cast::RtpTimeDelta::FromTimeDelta(
+                   remoting_frame.reference_time - last_frame_reference_time,
+                   media::cast::kRemotingRtpTimebase));
+  remoting_frame.data.swap(next_frame_data_);
+
+  std::unique_ptr<media::cast::FrameEvent> remoting_event(
+      new media::cast::FrameEvent());
+  remoting_event->timestamp = remoting_frame.reference_time;
+  // TODO(xjz): Use a new event type for remoting.
+  remoting_event->type = media::cast::FRAME_ENCODED;
+  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);
+}
+
+void CastRemotingSender::CancelFramesInFlight() {
+  DCHECK(cast_environment_->CurrentlyOn(media::cast::CastEnvironment::MAIN));
+
+  // Force to clear internal memory.

[dcheng, 2016/09/13 01:22:20]

Nit: remove this comment, since I think STLClearObject() should make that clear.

[xjz, 2016/09/13 17:06:10]

Done.

+  base::STLClearObject(&next_frame_data_);
+
+  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);
+  }
+
+  last_frame_was_canceled_ = true;
+}
+
+}  // namespace cast