Media Remoting: Add remoting control logic for encrypted contents.

media/remoting/remoting_source_impl.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 MEDIA_REMOTING_REMOTING_CONTROLLER_H_
-#define MEDIA_REMOTING_REMOTING_CONTROLLER_H_
+#ifndef MEDIA_REMOTING_REMOTING_SOURCE_IMPL_H_
+#define MEDIA_REMOTING_REMOTING_SOURCE_IMPL_H_
 
+#include <vector>
 #include "base/callback.h"
 #include "base/memory/weak_ptr.h"
-#include "media/base/media_observer.h"
+#include "base/threading/thread_checker.h"
 #include "media/mojo/interfaces/remoting.mojom.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
-namespace base {
-class SingleThreadTaskRunner;
-}
-
-// This class does the following:
-// 1) Sends/Receives messages from/to Remoter;
-// 2) Monitors player events as a MediaObserver;
-// 3) May trigger the switch of the media renderer between local playback
-// and remoting.
-//
 namespace media {
 
 namespace remoting {
 class RpcBroker;
 }
 
-class RemotingController final : public MediaObserver,
-                                 public mojom::RemotingSource {
+// State transition diagram:
+//
+// .--> SESSION_UNAVAILABLE
+// |          |      ^
+// |          V      |
+// |     SESSION_CAN_START
+// |          |
+// |          V
+// | .---SESSION_STARTING --.
+// | |        |             |
+// | |        V             |
+// | |   SESSION_STARTED----|
+// | |        |             |
+// | |        V             |
+// | '-> SESSION_STOPPING   |
+// '-----'    |             |
+//            V             V
+//    SESSION_PERMANENTLY_STOPPED
+
+enum RemotingSessionState {
+  // Remoting sink is not available. Can't start remoting.
+  SESSION_UNAVAILABLE,
+  // Remoting sink is available, Can start remoting.
+  SESSION_CAN_START,
+  // Starting a remoting session.
+  SESSION_STARTING,
+  // Remoting session is successively started.
+  SESSION_STARTED,
+  // Stopping the session.
+  SESSION_STOPPING,
+  // Remoting session is permanently stopped. This state indicates that the
+  // video stack cannot continue operation. For example, if a remoting session
+  // involving CDM content was stopped, there is no way to continue playback
+  // because the CDM is required but is no longer available.
+  SESSION_PERMANENTLY_STOPPED,
+};
+
+// Maintains a single remoting session for multiple clients. The session will
+// start remoting when receiving the first request. Once remoting is started,
+// it will be stopped when any of the following happens:
+// 1) Receives the request from any client to stop remoting.
+// 2) Remote sink is gone.
+// 3) Any client requests to permanently terminate the session.
+// 4) All clients are destroyed.
+//
+// This class is ref-counted because, in some cases, an instance will have
+// shared ownership between RemotingRendererController and
+// RemotingCdmController.
+class RemotingSourceImpl final
+    : public mojom::RemotingSource,
+      public base::RefCountedThreadSafe<RemotingSourceImpl> {
  public:
-  RemotingController(mojom::RemotingSourceRequest source_request,
+  class Client {
+   public:
+    // Get notified whether the remoting session is successively started.
+    virtual void OnStarted(bool success) = 0;
+    // Get notified when session state changes.
+    virtual void OnSessionStateChanged() = 0;
+  };
+
+  RemotingSourceImpl(mojom::RemotingSourceRequest source_request,
                      mojom::RemoterPtr remoter);
-  ~RemotingController() override;
+
+  // Get the current session state.
+  RemotingSessionState state() const {
+    DCHECK(thread_checker_.CalledOnValidThread());
+    return state_;
+  }
+
+  // RemotingSource implementations.
+  void OnSinkAvailable() override;
+  void OnSinkGone() override;
+  void OnStarted() override;
+  void OnStartFailed(mojom::RemotingStartFailReason reason) override;
+  void OnMessageFromSink(const std::vector<uint8_t>& message) override;
+  void OnStopped(mojom::RemotingStopReason reason) override;
 
   using DataPipeStartCallback =
       base::Callback<void(mojom::RemotingDataStreamSenderPtrInfo audio,
                           mojom::RemotingDataStreamSenderPtrInfo video,
                           mojo::ScopedDataPipeProducerHandle audio_handle,
                           mojo::ScopedDataPipeProducerHandle video_handle)>;
   void StartDataPipe(std::unique_ptr<mojo::DataPipe> audio_data_pipe,
                      std::unique_ptr<mojo::DataPipe> video_data_pipe,
                      const DataPipeStartCallback& done_callback);
 
-  // RemotingSource implementations.
-  void OnSinkAvailable() override;
-  void OnSinkGone() override;
-  void OnStarted() override;
-  void OnStartFailed(mojom::RemotingStartFailReason reason) override;
-  void OnMessageFromSink(const std::vector<uint8_t>& message) override;
-  void OnStopped(mojom::RemotingStopReason reason) override;
+  // Requests to start remoting. Will try start a remoting session if not
+  // started yet. |client| will get informed whether the session is
+  // successifully started throught OnStarted().
+  void StartRemoting(Client* client);
 
-  // MediaObserver implementations.
-  // This is called when the video element or its ancestor enters full screen.
-  // We currently use this as an indicator for immersive playback. May add other
-  // criteria (e.g. the actual display width/height of the video element) in
-  // future.
-  void OnEnteredFullscreen() override;
-  void OnExitedFullscreen() override;
-  void OnSetCdm(CdmContext* cdm_context) override;
-  void OnMetadataChanged(const PipelineMetadata& metadata) override;
+  // Requests to stop the current remoting session if started. When the session
+  // is stopping, all clients will get notified.
+  void StopRemoting(Client* client);
 
-  using SwitchRendererCallback = base::Callback<void()>;
-  void SetSwitchRendererCallback(const SwitchRendererCallback& cb);
+  // Permanently terminates the current remoting session.
+  void Shutdown();
 
-  // Tells which renderer should be used.
-  bool is_remoting() const {
-    DCHECK(task_runner_->BelongsToCurrentThread());
-    return is_remoting_;
-  }
-
-  base::WeakPtr<RemotingController> GetWeakPtr() {
-    return weak_factory_.GetWeakPtr();
-  }
+  // Add/remove a client to/from |clients_|.
+  // Note: Clients can only added/removed through these methods.
+  // Remoting session will be stopped if all clients are gone.
+  void AddClient(Client* client);
+  void RemoveClient(Client* client);
 
   base::WeakPtr<remoting::RpcBroker> GetRpcBroker() const;

[miu, 2016/11/05 04:05:16]

WeakPtrs are not necessary. Just return a raw pointer here. See comment below.

[xjz, 2016/11/07 19:03:55]

Done.

 
  private:
-  bool IsVideoCodecSupported();
-  bool IsAudioCodecSupported();
+  friend class base::RefCountedThreadSafe<RemotingSourceImpl>;
+  ~RemotingSourceImpl() override;
 
-  // Helper to decide whether to enter or leave Remoting mode.
-  bool ShouldBeRemoting();
-
-  // Determines whether to enter or leave Remoting mode and switches if
-  // necessary.
-  void UpdateAndMaybeSwitch();
+  // Updates the current session state and notifies all the clients if state
+  // changes.
+  void UpdateAndNotifyState(RemotingSessionState state);
 
   // Callback from RpcBroker when sending message to remote sink.
   void OnSendMessageToSink(std::unique_ptr<std::vector<uint8_t>> message);
 
   // Handle incomging and outgoing RPC message.
   std::unique_ptr<remoting::RpcBroker> rpc_broker_;

[miu, 2016/11/05 04:05:16]

Don't use a pointer to a heap-allocated object here. You can just compose the
RpcBroker as a direct member of this RemotingSourceImpl:

  remoting::RpcBroker rpc_broker_;

...and this is why I mentioned that, in a future CL the RpcBroker should
probably be merged into RemotingSourceImpl.

[xjz, 2016/11/07 19:03:55]

Done.

 
-  // Indicates if this media element or its ancestor enters full screen.
-  bool is_fullscreen_ = false;
+  const mojo::Binding<mojom::RemotingSource> binding_;
+  const mojom::RemoterPtr remoter_;
 
-  // Indicates the remoting sink availablity.
-  bool is_sink_available_ = false;
+  // The current state.
+  RemotingSessionState state_ = RemotingSessionState::SESSION_UNAVAILABLE;
 
-  // Indicates if remoting is started.
-  bool is_remoting_ = false;
+  // Clients are added/removed to/from this list by calling Add/RemoveClient().
+  // All the clients are not belong to this class. They are supposed to call
+  // RemoveClient() before they are gone.
+  std::vector<Client*> clients_;
 
-  // Indicates whether audio or video is encrypted.
-  bool is_encrypted_ = false;
-
-  // Current audio/video config.
-  VideoDecoderConfig video_decoder_config_;
-  AudioDecoderConfig audio_decoder_config_;
-  bool has_audio_ = false;
-  bool has_video_ = false;
-
-  // The callback to switch the media renderer.
-  SwitchRendererCallback switch_renderer_cb_;
-
-  mojo::Binding<mojom::RemotingSource> binding_;
-  mojom::RemoterPtr remoter_;
-
-  // TODO(xjz): Add a media thread task runner for the received RPC messages for
-  // remoting media renderer in the up-coming change.
-  const scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
-
-  base::WeakPtrFactory<RemotingController> weak_factory_;
-
-  DISALLOW_COPY_AND_ASSIGN(RemotingController);
+  // This is used to check all the methods are called on the current thread in
+  // debug builds.
+  base::ThreadChecker thread_checker_;
 };
 
 }  // namespace media
 
-#endif  // MEDIA_REMOTING_REMOTING_CONTROLLER_H_
+#endif  // MEDIA_REMOTING_REMOTING_SOURCE_IMPL_H_