media/mojo/interfaces/remoting.mojom

// 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.

module media.mojom;

interface RemoterFactory {
  // Create a new Remoter associated with the given RemotingSource and bind it
  // to the given interface request. The RemotingSource will be notified when
  // the Remoter becomes available for use (or becomes unavailable).
  Create(RemotingSource source, Remoter& remoter);
};

// Interface used by the source to control when media bitstream data is read
// from a data pipe and then sent to the remote endpoint. There is one
// RemotingDataStreamSender per data pipe.
interface RemotingDataStreamSender {
  // Consumes |size| bytes of data from the data pipe, which is a chunk of the
  // next frame's data payload starting at the given byte |offset|.
  // |total_payload_size| indicates the size of the entire data payload for the
  // frame. Before this is called, |size| bytes of data must have been written
  // into the data pipe.
  //
  // Normally, a frame's entire data payload can be pushed through the data pipe
  // in one chunk. However, there can be situations where the size of the
  // payload exceeds the capacity of the data pipe; and so this API supports
  // feeding the frame data through the pipe in multiple chunks.
  ConsumeDataChunk(uint32 offset, uint32 size, uint32 total_payload_size);

  // Enqueues another frame for transmission to the remote endpoint. Before this
  // is called, ConsumeDataChunk() must have been called one or more times to
  // provide all of the frame's data.
  SendFrame();

  // Cancel the transmission of all in-flight data to the remote, up to and
  // including the last SendFrame() call; and also discard any data chunks
  // that were consumed from the data pipe for the next frame. This is used to
  // optimize seeking, when it is known that any in-flight data is no longer
  // needed by the remote. There is no guarantee as to how much of the in-flight
  // data will actually reach the remote before the cancellation takes effect.
  CancelInFlightData();
};

enum RemotingStopReason {
  ROUTE_TERMINATED,  // User-initiated disconnect, etc.
  LOCAL_PLAYBACK,  // Media switched back to local playback.
  SOURCE_GONE,  // RemotingSource has been destroyed.
  MESSAGE_SEND_FAILED,  // Failed to send a message to the sink.
  DATA_SEND_FAILED,  // Failed to consume from a data pipe or send to the sink.
  UNEXPECTED_FAILURE,  // Unexpected failure or inconsistent state encountered.
};

// Interface used by the source to start/stop remoting and send data to the
// sink.
interface Remoter {
  // Start a remoting session (once the sink has been reported to be available;
  // see RemotingSource). Either RemotingSource.OnStarted() or OnStartFailed()
  // will be called to indicate success or failure. Once OnStarted() has been
  // invoked, the source may then make calls to SendMessageToSink() and expect
  // messages from the remote via RemotingSource.OnMessageFromSink().
  Start();

  // Start remoting the media data streams. This is called after Start() to
  // provide data pipes from which the audio/video bitstream data is consumed
  // and then transported to the remote device. RemotingDataStreamSenders are
  // used by the source to control when data should be consumed from the data
  // pipes and sent. One or both pipes (and their corresponding
  // RemotingDataStreamSender interface requests) must be provided.
  StartDataStreams(handle<data_pipe_consumer>? audio_pipe,
                   handle<data_pipe_consumer>? video_pipe,
                   RemotingDataStreamSender&? audio_sender,
                   RemotingDataStreamSender&? video_sender);

  // Stop remoting media. Messages in both directions will be dropped after this
  // point as well as any pending or in-transit media bitstream data.
  Stop(RemotingStopReason reason);

  // Send |message| to the sink. |message| is a serialized protobuf from
  // src/media/remoting/proto.
  SendMessageToSink(array<uint8> message);
};

enum RemotingSinkCapabilities {
  NONE,
  RENDERING_ONLY,
  CONTENT_DECRYPTION_AND_RENDERING,
};

enum RemotingStartFailReason {
  CANNOT_START_MULTIPLE,  // Remoting was already active.
  ROUTE_TERMINATED,  // User-initated disconnect while starting remoting.
};

// Interface used for sending notifications back to the local source's control
// logic, and to pass messages from the sink back to the local media pipeline.
interface RemotingSource {
  // Notify the source that the sink is now available to start remoting. It is
  // up to the source's control logic to decide whether/when to start remoting.
  //
  // TODO(miu): In a later change, pass detailed information about the sink's
  // capabilities (e.g., codec support, DRM keysystem support, etc.).
  OnSinkAvailable(RemotingSinkCapabilities capabilities);

  // Notify the source that the sink is no longer available for remoting. This
  // may happen, for example, because the sink has been shut down, or because
  // another source has started remoting.
  OnSinkGone();

  // One of these is called after the source attempts to start remoting. If
  // OnStarted() is called, messages may begin flowing; and this will continue
  // until OnStopped() is called. On the other hand, if OnStartFailed() is
  // called, then no messages are being passed between source and sink and
  // remoting is not taking place.
  OnStarted();
  OnStartFailed(RemotingStartFailReason reason);

  // Pass a |message| from the sink back to the source. The |message| consists
  // of a serialized protobuf from src/media/remoting/proto. This will only be
  // called after OnStarted() and before OnStopped().
  OnMessageFromSink(array<uint8> message);

  // Notify the source that remoting has terminated. This may or may not be in
  // response to a Remoter.Stop() call, as other events (possibly external) may
  // have caused remoting to end.
  OnStopped(RemotingStopReason reason);
};