Beginning Game Development Part X –Direct Sound Part III

Audio audio = new Audio("AudioFileName");

Audio audio = new Audio();

audio.Open("AudioFileName");

audio.Play();

audio.Pause();

audio.Stop();

audio.Dispose();

private void _audio_Ending(object sender, EventArgs e)

{

    audio.Play();

}

audio.Open("//www.audiofile.com/music.mp3");

While playing the audio file you can control the volume and balance of the file.

Volume: Volume is expressed as an integer. Somewhat counterintuitive is that a setting of 0 is full volume. Smaller values decrease the volume up to a setting of -10,000 which is silent.

audio.Volume = 0; // Maximum

audio.Volume = -10000; // Silent

audio.Balance = -10000; // Only Left channel

audio.Balance = 10000; // only Right channel

audio.Balance = 0; // balanced

* While playing the audio class indicates the current position of the stream with the CurrentPosition property.

** The audio class also provides a property, StopPosition, which indicates the position in the audio stream where the file is stopped

You can also use the State property of the Audio class to determine its state. This property returns a StateFlags enumeration with the possible values of: Running, Paused and Stopped.
Also of interest is the SeekingCaps property of the Audio class. This read only property indicates the seeking capabilities of the playback stream. It is represented in the form of the SeekingCaps structure. This structure indicates whether the stream supports the following seek actions:

You should check the capabilities of the stream before calling SeekCurrentPosition, SeekStopPosition or checking the Duration property.

Ok, let's package this simple class into a Jukebox. I want the Jukebox class to pull files from a predetermined location so I can just point it at a media folder within the games directory structure. I also want the Jukebox to either play all the files it finds in order or play a single file in a looping fashion.

Finally I want this class to play a specific file on demand, for example, when I am on the splash screen I want to play the intro tune, while on the main game screen I want some other background music.

NOTE: I am not providing any audio files with the source code. By default the SoundTrack class reads from C:\Documents and Settings\All Users\Documents\My Music\Sample Music where you should have two WMA files on a standard XP machine. If you do not have those files you need to change the directory and point it at a location that has sound files.

Creating the SoundTrack class

The first step is to add a reference to the Microsoft.DirectX.AudioVideoPlayback assembly.
Next we add a new class and call it Soundtrack. At the top of the class we need add the using statement for the AudioVideoPlayback namespace.

using Microsoft.DirectX.AudioVideoPlayback;

public void Dispose()

{

    Dispose(true);

    GC.SuppressFinalize(this);

}

protected virtual void Dispose(bool disposing)

{

    if (!this._disposed)

    {

        if (disposing)

        {

            if (_audio != null)

            _audio.Dispose();

        }

    }

    _disposed = true;

}

// Use C# destructor syntax for finalization code.

~SoundTrack()

{

    // Simply call Dispose(false).

    Dispose(false);

}

private bool _disposed;

public SoundTrack ( string[] songCollection, bool repeat )

{

    _songList = songCollection;

    _isRepeat = repeat;

    if ( _songList.Length == 0 )

        _enabled = false;

    else

        _audio = new Audio ( _songList[ _songCounter ].ToString ( ) );

}

private Audio _audio;

private string[] _songList;

private int _songCounter = 0;

private bool _isRepeat;

private bool _enabled = true;

public void Play()

{

    if ( !_enabled )

        return;

    _audio.Play();

    _audio.Ending += new EventHandler(_audio_Ending);

}

private void _audio_Ending(object sender, EventArgs e)

{

    if ( _isRepeat )

    {

        Stop ( );

        Play ( );

    }

    else

        NextSong ( );

}

public void NextSong ( )

{

    if ( !_enabled )

        return;

    _songCounter++;

    if ( _songCounter == _songList.Length )

        _songCounter = 0;

    if ( _audio.Playing == true )

        _audio.Stop ( );

    _audio.Open ( _songList[ _songCounter ].ToString ( ) );

    _audio.Play ( );

}

The only remaining method we now need is to stop the player

public void Stop ( )

{

    if ( !_enabled )

        return;

    if ( _audio != null )

        _audio.Stop ( );

}

To allow us to control the balance and volume we simply add two properties to the SoundTrack class that expose the identical properties of the Audio class. Since we know the upper and lower bounds of the values, we add a simple check to the property setter to ensure we only pass valid values. This is more efficient than passing an invalid value and having to check for exceptions. In general you should enforce boundaries whenever possible.

   1: public int Volume

   2: {

   3:     get { return _audio.Volume; }

   4:     set 

   5:     {

   6:         if ( value > 0 | value < -10000 )

   7:             return;

   8:         

   9:         _audio.Volume = value; 

  10:     }

  11: }

  12:  

  13: public int Balance

  14: {

  15:     get { return _audio.Balance; }

  16:     set 

  17:     {

  18:         if ( value > 10000 | value < -10000 )

  19:             return;

  20:         

  21:         _audio.Balance = value; 

  22:     }

  23: }

Now we can integrate the new class into the game. First we add a reference to the new class to the GameEngine class.

private SoundTrack _mainSoundTrack;

_mainSoundTrack = new SoundTrack ( Directory.GetFiles ( @"C:\Documents" + 

    "and Settings\All Users\Documents\My Music\Sample Music" ), true );

// Control the Sound

if ( _keyboard.State[ Key.P ] )

    _mainSoundTrack.Play ( );

if ( _keyboard.State[ Key.M ] )

    _mainSoundTrack.Stop ( );

if ( _keyboard.State[ Key.N ] )

    _mainSoundTrack.NextSong ( );

if ( _keyboard.State[ Key.UpArrow ] )

    _mainSoundTrack.Volume += 10;

if ( _keyboard.State[ Key.DownArrow ] )

    _mainSoundTrack.Volume -= 10;

if ( _keyboard.State[ Key.RightArrow ] )

    _mainSoundTrack.Balance += 10;

if ( _keyboard.State[ Key.LeftArrow ] )

    _mainSoundTrack.Balance -= 10; 

Summary

Now we have pretty much completed the pass through the basic functionality of the all the DirectX namespaces. There are many more advanced topics that could cover additional graphics classes such as HLSL (High Level Shader Language), but in the next articles we are going to focus on two non DirectX parts of game development - Artificial Intelligence (AI) and Physics.

Without good AI and Physics, even the best designed games are no fun to play. Nothing shatters the illusion of reality more than predictable enemies or rocks floating in mid air.

Together with game Physics, AI represents a major portion of the game that has no support in DirectX and limited support in other (free) libraries. We are not going to be able to fill that gap and write a fully featured AI engine, but we can cover most of the principles and techniques behind some of the more basic AI problems, such as chasing and evading and path finding.

Until then: Happy coding.

Derek Pierson is a software developer with 12 years experience designing and developing enterprise applications using a variety of programming languages. He is an enthusiastic teacher of the art of programming and believes that elegance and simplicity are defining features of good software.

Filed under: arcade, gaming