Player

Applies to: Skype for Business 2015

The Player class represents an entity that is capable of playing media to one or more media flows, and as such, provides a simple, scalable way to play an audio segment in a Windows Media Audio (WMA) file to multiple listeners. A Player instance renders the media that is represented by an instance of a subclass of the MediaSource abstract base class. The output from a Player instance goes to one or more AudioVideoFlow instances.

A Player acts as a pointer to a MediaSource object, and determines the current position to play in the media.

Modes of operation

The Player class has two modes of operation:

• Automatic (the default)

  In Automatic mode, the behavior of a Player instance depends on the state of the attached AudioVideoFlow instance. If an application calls the Start method on the Player instance, the State property on the Player instance changes to Started, but nothing is played until there is an active AudioVideoFlow instance attached to the Player instance (that is, until the State property on the AudioVideoFlow instance is Active).

  If the last active AudioVideoFlow instance is detached or terminated while a Player instance in Automatic mode is playing, the Player instance stops automatically.

• Manual

  In Manual mode, a Player instance can operate with or without an attached AudioVideoFlow instance, although no one would be able to listen to the file being played if there were no attached AudioVideoFlow instance. If the last active AudioVideoFlow instance is detached or terminated while a Player instance in Manual mode is playing, the Player instance continues playing. In this regard, a Player instance in Manual mode behaves like a CD player whose speakers are disconnected.

Playback speed

The PlaybackSpeed property on the Player class provides the capability to play back a WMA file at a different speed. This property gets or sets the rate at which the Player renders audio. An application can use PlaybackSpeed to develop an interface that gives the user more control in consuming the content. A message can be played back faster or slower depending on the PlaybackSpeed specified by the application.

The values in the PlaybackSpeed enumeration are Half, ThreeQuarters, Normal, OneAndAQuarter, OneAndAHalf, OneAndThreeQuarters, and TwoTimes. The values represent the multiple of normal playback speed. For example, ThreeQuarters represents 75% of normal playback speed.

Player arrangements

The simplest arrangement is a single Player instance with a single attached AudioVideoFlow instance, as shown in the following illustration.

Single player, single AudioVideoFlow instance

Another arrangement is to have a single Player instance that has multiple AudioVideoFlow instances, as shown in the following illustration. In this arrangement, the audio media to be played has a single play position and all attached AudioVideoFlow instances receive exactly the same audio simultaneously. This capability is useful for providing Music on Hold, or for broadcasting audio to multiple listeners.

Single Player, multiple AudioVideoFlow instances

A third arrangement is to have multiple Player instances with multiple attached AudioVideoFlow instances, as shown in the following illustration. Each Player instance determines a different playing point in the media source. The AudioVideoFlow instances attached to a given Player instance (for example, AudioVideoFlow 1 and AudioVideoFlow 2 that are attached to Player 1) receive the same audio at the same time, but AudioVideoFlow instances attached to different Player instances receive different audio segments at any given time (for example, AudioVideoFlow 1 and AudioVideoFlow 3 that are attached, respectively, to Player 1 and Player 2). This capablity is useful for providing Welcome messages to listeners when they arrive at a conference.

Multiple Player instances, multiple AudioVideoFlow instances

The Player class is scalable. In buffered mode, the MediaSource caches encoded versions of media. Given a WmaFileSource object, an application can play audio that was previously cached (MediaSourceOpenMode.Buffered) or from a file on demand in unbuffered mode (MediaSourceOpenMode.Unbuffered). When buffered mode is used, playing the cached stream provides significant performance gains.

Example – using a player

The following code example shows the steps involved in using a Player.

The essential points of creating and using a Player instance are shown in the following steps. Each step is associated with a line of code that is preceded by a comment with a number in it.

1. Create a Player instance, using the constructor for this class.

2. Attach the flow to the player, using the AttachFlow method on the Player class.

3. Register for the player’s StateChanged event.

4. Load the file that is to be played into memory by creating a WmaFileSource instance. The string parameter is the name of the WMA file to be played.

5. Prepare the source file, using the BeginPrepareSource method on the WmaFileSource instance. The caller can specify whether the file is to be opened in Buffered mode or in Unbuffered mode. In the example code, the argument to EndPrepareSource is the return value from BeginPrepareSource.

6. Set the player’s mode, using the SetMode method. In the example, the mode is set to Manual, which means that the player will begin playing only when the State of the attached AutoVideoFlow instance is Active. The Player stops when it reaches the end of the file or when there are no attached AudioVideoFlow instances that are Active. If the mode were set to Manual, the player would start playing immediately.

7. Inform the player about the source of the media it will play, using the SetSource method.

8. Start the player, using the player’s Start method.

9. Pause the player, using the player’s Pause method. This step is shown only to demonstrate how to pause the player.

10. Restart the player after it was paused, using the Start method.

11. Stop the player, using the player’s Stop method.

12. Close the source, using the Close method on the WmaFileSource instance. An application must close the source when it is no longer needed. A source that is not closed can result in a memory leak.

13. Detach the flow, using the player’s DetachFlow method.

public void Run()
{
  // Initialize and start the platform.
  ClientPlatformSettings clientPlatformSettings = new ClientPlatformSettings(_applicationName, Microsoft.Rtc.Signaling.SipTransportType.Tls);
  _collabPlatform = new CollaborationPlatform(clientPlatformSettings);
  _collabPlatform.BeginStartup(EndPlatformStartup, _collabPlatform);

  // Sync; wait for the startup to complete.
  // The EndPlatformStartup callback method, not shown in this sample, would call EndStartup
  // to complete platform startup.


  // Initialize and register the endpoint, using the credentials of the user the application will be acting as.
  UserEndpointSettings userEndpointSettings = new UserEndpointSettings(_userURI, _userServer);
  userEndpointSettings.Credential = _credential;
  _userEndpoint = new UserEndpoint(_collabPlatform, userEndpointSettings);
  _userEndpoint.BeginEstablish(EndEndpointEstablish, _userEndpoint);

  // The EndEndpointEstablish callback method, not shown in this sample, would call EndEstablish
  // to complete the establishment of the endpoint.


  // Set up the conversation and place the call.
  ConversationSettings convSettings = new ConversationSettings();
  convSettings.Priority = _conversationPriority;
  convSettings.Subject = _conversationSubject;
  // Conversation represents a collection of modalities in the context of a dialog with one or multiple callees.
  Conversation conversation = new Conversation(_userEndpoint, _calledParty, convSettings);

  _audioVideoCall = new AudioVideoCall(conversation);

  // Call: StateChanged: Only hooked up for logging.
  _audioVideoCall.StateChanged += new EventHandler<CallStateChangedEventArgs>(audioVideoCall_StateChanged);

  // Subscribe to the AudioVideoFlowConfigurationRequested event; the flow will be used to send the media.
  // Ultimately, as a part of the callback, the media will be sent/received.
  _audioVideoCall.AudioVideoFlowConfigurationRequested += new EventHandler<AudioVideoFlowConfigurationRequestedEventArgs>(audioVideoCall_FlowConfigurationRequested);



  // Place the call to the remote party;
  // Note that the EndCallEstablish callback method is not shown in this sample.
  IAsyncResult asyncResult = _audioVideoCall.BeginEstablish(EndCallEstablish, _audioVideoCall);

  // Sync; wait for the call to complete.
  _audioVideoCall.EndEstablish(asyncResult);

  // Sync; wait for the AudioVideoFlow goes Active
  _autoResetAVFlowActiveEvent.WaitOne();

  // 1) Create a Player and attach to AVFlow
  Player player = new Player();
  // 2) Attach the Player to the AVFlow
  player.AttachFlow(_audioVideoFlow);

  // 3) Subscribe to player StateChanged event, including the play completed event. 
  player.StateChanged += new EventHandler<PlayerStateChangedEventArgs>(player_StateChanged);

  // 4) Load the file into memory
    WmaFileSource source = new WmaFileSource("startup.wma");
  
  // 5) Prepare the source for the player.
  source.EndPrepareSource(source.BeginPrepareSource(MediaSourceOpenMode.Buffered, null, null));

  // 6) Set the play mode. In automatic mode, player will start playing only when the flow is in the active state.
  // In manual mode, player will start playing immediately.
  player.SetMode(PlayerMode.Manual);

  // 7) Inform the player about the source.
  player.SetSource(source);

  // 8) Start the player.
    player.Start();

    Thread.Sleep(2000);

  // 9) Pause the player.
    player.Pause();

    Thread.Sleep(2000);

  // 10) Resume playing.
  player.Start();

    Thread.Sleep(5000);

  // 11) Stop the player.
  player.Stop();

  // 12) Source must be closed after it is no longer needed, otherwise memory will not be released even after garbage collection.
  source.Close();

  // 13) Player must be detached from the flow, otherwise if the player is rooted, it will keep the flow in memory.
  player.DetachFlow(_audioVideoFlow);


  _collabPlatform.BeginShutdown(EndPlatformShutdown, _collabPlatform);

  // Wait for shutdown to occur.
  _autoResetShutdownEvent.WaitOne();
}