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

chrome/browser/media/cast_remoting_sender.h

 // 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.
 
 #ifndef CHROME_BROWSER_MEDIA_CAST_REMOTING_SENDER_H_
 #define CHROME_BROWSER_MEDIA_CAST_REMOTING_SENDER_H_
 
 #include "base/callback_forward.h"
 #include "base/memory/weak_ptr.h"
 #include "base/time/time.h"
 #include "media/cast/cast_config.h"
 #include "media/cast/cast_environment.h"
 #include "media/cast/net/cast_transport.h"
 #include "media/cast/net/rtcp/rtcp_defines.h"
+#include "media/mojo/interfaces/remoting.mojom.h"
+#include "mojo/public/cpp/bindings/binding.h"
 
 namespace cast {
 
 // RTP sender for a single Cast Remoting RTP stream. The client calls Send() to
-// instruct the sender to transmit the data using a CastTransport.
+// instruct the sender to read from a Mojo data pipe and transmit the data using
+// a CastTransport. This entire class executes on the IO BrowserThread.
 //
 // This class is instantiated and owned by CastTransportHostFilter in response
 // to IPC messages from an extension process to create RTP streams for the media
 // remoting use case. CastTransportHostFilter is also responsible for destroying
 // the instance in response to later IPCs.
 //
-// TODO(miu): Mojo service bindings/implementation to read from data pipes will
-// be added in a soon-upcoming change.
-
-class CastRemotingSender {
+// The Media Router provider extension controls the entire set-up process:
+// First, it uses the cast.streaming APIs to create remoting API streams (which
+// instantiates one or more CastRemotingSenders). Then, it sends a message via
+// Media Router to a CastRemotingConnector to indicate the bitstream transport
+// is ready. Finally, CastRemotingConnector calls FindAndBind() to look-up the
+// CastRemotingSender instances and establish the Mojo bindings and data flows.
+class CastRemotingSender : public media::mojom::RemotingDataStreamSender {
  public:
   // |transport| is expected to outlive this class.
-  explicit CastRemotingSender(
+  CastRemotingSender(
       scoped_refptr<media::cast::CastEnvironment> cast_environment,
       media::cast::CastTransport* transport,
       const media::cast::CastTransportRtpConfig& config);
-  ~CastRemotingSender();
+  ~CastRemotingSender() final;
+
+  // Look-up a CastRemotingSender instance by its |rtp_stream_id| and then bind
+  // to the given |request|. The client of the RemotingDataStreamSender will
+  // then instruct this CastRemotingSender when to read from the data |pipe| and
+  // send the data to the Cast Receiver. If the bind fails, or an error occurs
+  // reading from the data pipe during later operation, the |error_callback| is
+  // run.
+  //
+  // Threading note: This function is thread-safe, but its internal
+  // implementation runs on the IO BrowserThread. If |error_callback| is run, it
+  // will execute on the thread that called this function.
+  static void FindAndBind(int32_t rtp_stream_id,
+                          mojo::ScopedDataPipeConsumerHandle pipe,
+                          media::mojom::RemotingDataStreamSenderRequest request,
+                          const base::Closure& error_callback);
 
  private:
   // Friend class for unit tests.
   friend class CastRemotingSenderTest;
 
   class RemotingRtcpClient;
 
-  // Called to send the serialized frame data.
-  void SendFrame();
-
-  // Called to cancel all the in flight frames when seeking happens.
-  void CancelFramesInFlight();
+  // media::mojom::RemotingDataStreamSender implementation.
+  void ConsumeDataChunk(uint32_t offset, uint32_t size,
+                        uint32_t total_payload_size) final;
+  void SendFrame() final;
+  void CancelInFlightData() final;
 
   // These are called to deliver RTCP feedback from the receiver.
   void OnReceivedCastMessage(const media::cast::RtcpCastMessage& cast_feedback);
   void OnReceivedRtt(base::TimeDelta round_trip_time);
 
-  // Returns the number of frames that were sent but not yet acknowledged. This
-  // does not account for frames acknowledged out-of-order, and is always a high
-  // watermark estimate.
+  // Returns the number of frames that were sent to the CastTransport, but not
+  // yet acknowledged. This is always a high watermark estimate, as frames may
+  // have been acknowledged out-of-order. Also, this does not account for any
+  // frames queued-up in input pipeline (i.e., in the Mojo data pipe, nor in
+  // |next_frame_data_|).
   int NumberOfFramesInFlight() const;
 
   // Schedule and execute periodic checks for re-sending packets.  If no
   // acknowledgements have been received for "too long," CastRemotingSender will
   // speculatively re-send certain packets of an unacked frame to kick-start
   // re-transmission.  This is a last resort tactic to prevent the session from
   // getting stuck after a long outage.
   void ScheduleNextResendCheck();
   void ResendCheck();
   void ResendForKickstart();
 
   void RecordLatestFrameTimestamps(media::cast::FrameId frame_id,
                                    media::cast::RtpTimeTicks rtp_timestamp);
   media::cast::RtpTimeTicks GetRecordedRtpTimestamp(
       media::cast::FrameId frame_id) const;
 
   // Unique identifier for the RTP stream and this CastRemotingSender.
-  const int32_t remoting_stream_id_;
+  const int32_t rtp_stream_id_;
 
   const scoped_refptr<media::cast::CastEnvironment> cast_environment_;
 
   // Sends encoded frames over the configured transport (e.g., UDP). It outlives
   // this class.
   media::cast::CastTransport* const transport_;
 
   const uint32_t ssrc_;
 
   const bool is_audio_;
 
+  // Callback that is run to notify when a fatal error occurs.
+  base::Closure error_callback_;
+
+  // Mojo data pipe from which to consume data.
+  mojo::ScopedDataPipeConsumerHandle pipe_;
+
+  // Mojo binding for this instance. Implementation at the other end of the
+  // message pipe uses the RemotingDataStreamSender interface to control when
+  // this CastRemotingSender consumes from |pipe_|.
+  mojo::Binding<RemotingDataStreamSender> binding_;
+
   // This is the maximum delay that the sender should get ack from receiver.
   // Otherwise, sender will call ResendForKickstart().
   base::TimeDelta max_ack_delay_;
 
   // This is "null" until the first frame is sent.  Thereafter, this tracks the
   // last time any frame was sent or re-sent.
   base::TimeTicks last_send_time_;
 
   // The ID of the last frame sent.  This member is invalid until
   // |!last_send_time_.is_null()|.
   media::cast::FrameId last_sent_frame_id_;
 
   // The ID of the latest (not necessarily the last) frame that has been
   // acknowledged.  This member is invalid until |!last_send_time_.is_null()|.
   media::cast::FrameId latest_acked_frame_id_;
 
   // Counts the number of duplicate ACK that are being received.  When this
   // number reaches a threshold, the sender will take this as a sign that the
   // receiver hasn't yet received the first packet of the next frame.  In this
   // case, CastRemotingSender will trigger a re-send of the next frame.
   int duplicate_ack_counter_;
 
   // The most recently measured round trip time.
   base::TimeDelta current_round_trip_time_;
 
   // The next frame's payload data. Populated by one or more calls to
   // ConsumeDataChunk().
-  // TODO(miu): To be implemented in soon upcoming change.
   std::string next_frame_data_;
 
   // Ring buffer to keep track of recent frame RTP timestamps. This should
   // only be accessed through the Record/GetXX() methods. The index into this
   // ring buffer is the lower 8 bits of the FrameId.
   media::cast::RtpTimeTicks frame_rtp_timestamps_[256];
 
-  // This flag indicates whether CancelFramesInFlight() was called.
-  bool last_frame_was_canceled_;
+  // Current flow control state.
+  enum {
+    RESTARTING,      // Starting new, or restarting after CancelInFlightData().

[xjz, 2016/09/15 18:01:49]

nit: How about just STARTING? Actually this status seems indicating both
starting and restarting. So maybe either one is good.

[miu, 2016/09/16 16:39:28]

Done.

+    CONSUMING,       // Reading from Mojo data pipes.
+    CONSUME_PAUSED,  // Too many frames in-flight; paused Mojo input.
+  } flow_control_state_;
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<CastRemotingSender> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(CastRemotingSender);
 };
 
 }  // namespace cast
 
 #endif  // CHROME_BROWSER_MEDIA_CAST_REMOTING_SENDER_H_