The Differences between SoundEffect and SoundEffectInstance in XNA

The original article has been posted here.

Introduction/Catalog

If you want to create a game for Windows Phone, then XNA is a choice. Now, I will explore and learn XNA for Windows Phone with you.

In XNA, SoundEffect and SoundEffectInstance are available to play the sound, such as: WAV files. But it is important to note both the SoundEffect or SoundEffectInstance cannot play MP3 files, you need to use the class Song to play the MP3 files.

Shared Resources

You can load a sound file to the SoundEffect class, you can also create a new SoundEffectInstance object from the SoundEffect. And these new SoundEffectInstance objects will share the sound resource contained in the SoundEffect.

The SoundEffect object will keep the resource in the life cycle. Once the SoundEffect is destroyed, the SoundEffectInstance objects which it created will fail, when you call the method Play.

private ContentManager contentManager;
private SoundEffect mySound;
private SoundEffectInstance mySound1;
private SoundEffectInstance mySound2;

protected override void LoadContent ( )
{
 // ...
 spriteBatch = new SpriteBatch ( GraphicsDevice );

 if ( null == this.contentManager )
  this.contentManager = new ContentManager ( Services, "Content" );

 this.mySound = this.contentManager.Load<SoundEffect> ( @"mysound" );
 this.mySound1 = this.mySound.CreateInstance ( );
 this.mySound2 = this.mySound.CreateInstance ( );
 // ...
}

protected override void UnloadContent ( )
{
 // ...
 this.mySound1.Dispose ( );
 this.mySound2.Dispose ( );
 this.mySound.Dispose ( );

 this.contentManager.Unload ( );
 // ...
}

If we release the mySound object in the Update method, there will be an error when you call the Play method of the mySound1 or mySound2.

protected override void Update ( GameTime gameTime )
{
 // ...

 this.mySound.Dispose ( );
 this.mySound1.Play ( );
}

Repeat

Either the SoundEffect or SoundEffectInstance, the sound can't play again before finished. If you call the Play method in the Update method, the sound will only play again until it is finished playing.

protected override void Update ( GameTime gameTime )
{
 // ...

 this.mySound.Play ( );
}

If you want to play the sound again when it's playing, you can define multiple SoundEffectInstance objects.

Total Number of Sounds

On Windows Phone, XNA can play a total of 16 sounds at one time.

Stop Playing

Since the SoundEffect only plays smaller sound file, under normal circumstances, it is not going to stop playing the sound. But sometimes if you're in the loop, may have to use the Stop method. To stop the sound, you need through the SoundEffectInstance class.

protected override void Update ( GameTime gameTime )
{
 // ...

 int seconds = ( int ) gameTime.TotalGameTime.TotalSeconds;

 if ( seconds > 5 )
 {
  if ( this.mySound1.State != SoundState.Stopped )
   this.mySound1.Stop ( );
 }
 else
  if ( this.mySound1.State == SoundState.Stopped )
  {
   this.mySound1.IsLooped = true;
   this.mySound1.Play ( );
  }
}