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Music and sound

Sound and music are an essential part of any gameplay experience, and AGS 3.2 and higher provides a re-written audio system giving you full control over your game audio.

File formats

AGS is able to play the following types of audio file: OGG, MP3, MIDI, WAV (uncompressed), MOD, XM, IT, S3M and VOC.

The only limitation to this is that AGS is only able to play one MIDI file at a time. If you attempt to play two simulataneous MIDI music files, the first one will be cut off when the second one starts playing.

If you haven't heard of OGG before, it's a digital music format, similar to MP3, but achieving better compression and higher quality. More importantly, it is a totally free format so no royalty payments or licenses are required to use it. For more information and programs to encode your music to OGG, see http://www.vorbis.org/

Audio in the Editor

Look under the "Audio" branch in the project tree. Here you'll find sub-nodes called "Speech", "Types" and two default folders called "Music" and "Sounds".

Speech

At the moment, voice speech files are not setup within the editor. See the Speech help page to find out more about adding speech to your game.

Audio Types

Audio Types allow you to group together similar types of audio files. The standard distinction here is between Sound and Music, whereby you usually only want one Music file to be playing at any one time; whereas you might have several simultaneous sound effects.

Double-click on an Audio Type and it will open up; you can see its properties in the Property Grid. Here, the "MaxChannels" setting allows you to specify how many audio clips of this type are allowed to play at the same time. The "VolumeReductionWhenSpeechPlaying" setting allows you to have AGS automatically reduce the volume of these audio clips while speech is playing, to make it easier for the player to hear the speech over the background music.

You'll probably find that the default settings here are fine, and in many games you won't need to change them.

Importing audio files

Now let's get on to the important question -- how do you add sound and music to your game? Well, if you right-click on the "Sound" or "Music" folders (or any other folders that you create yourself), you'll see an option called "Add Audio Files".

Select this option, and you'll be given a dialog box to find the audio files that you want to import. Once imported, they'll be assigned script names automatically.

Double-click an audio file in the project tree to open a window where you can preview it, as well as change its properties in the Property Grid.

Playing audio in the game

The script to play an audio clip in the game is very simple. For example:

aExplosion.Play();
plays the audio clip called aExplosion.

Priorities and channels

AGS currently has an 8-channel audio system, which means that up to 8 sounds can be playing at the same time. With the default Audio Types settings, one channel is reserved for speech, one for music and one for ambient sounds; thus leaving 5 available for sound effects.

If you try to play an audio clip and there are no channels available, then an existing one will be stopped and the new one will take its place. However, this will only happen if the new audio clip has an equal or higher priority than one of the currently playing sounds.

Thus, the priority allows you to decide which audio clips are more important than others. For example, you might set a footstep sound as low priority, and a door opening as high priority. This can be configured at the folder level in the editor, and also by changing the properties of an individual audio clip (by default they will inherit from their containing folder).

Sometimes you might not want the priority of the sound to be fixed in the editor -- you might want to decide it at run-time in the script. For this reason the Play command has an optional parameter which allows you to explicity specify the priority when you play it, for example:

aExplosion.Play(eAudioPriorityLow);
Seeking and changing volume

So, how do you change a sound once it is playing? Well, there are no methods on the Audio Clip to do this, because you might be playing two copies of the same sound at once, and then AGS wouldn't know which one you wanted to access. That's where Audio Channels come to the rescue.

When you use the Play() command, AGS returns to you an AudioChannel* instance representing the channel on which the sound is playing. You can store this to a global variable and access it later on. For example:

AudioChannel* chan = aExplosion.Play();
chan.Volume = 20;
This will start the aExplosion audio clip playing, and then change its volume to 20%.

Using Audio Channels

Supposing you want to start playing a sound now, and then change its volume or panning later on. How would you do that? Well, you'd need to keep the AudioChannel around, so that you can access it later. The easiest way to do that is to make it a Global Variable; if you open the Global Variables editor, you can create a new AudioChannel* variable (let's call it longWindedSound). Then when you play the sound you set it like this:

longWindedSound = aExplosion.Play();

later on, elsewhere in the script, you can change the volume by doing:

if (longWindedSound != null)
{
  longWindedSound.Volume = 20;
}
Note the check for null here -- this makes sure that your game won't crash if the sound isn't playing (it might have finished, or not have been started yet).

Overall system volume

There is a property called System.Volume that controls the overall game volume, which you can use with some sort of volume control slider for the player. All individual sound volumes work within the overall system volume.

Conclusion

The new audio system in AGS gives you much more control over your game audio. Please see the following sections for a complete list of the supported commands:

AudioClip reference, AudioChannel reference

Voice speech
The AudioCache folder


Voice speech

With AGS you can link a line of dialog to a speech file, to enable "talkie"- style games. Suppose you have a dialog script with the following:
ego: "Hi! How are you?"
michael: "I'm fine."
Normally this would display the words in the speech text above the characters heads. However, you can add the special character '&' to symbolise that a voice file should also be played.

The file name has format XXXXY.EXT, where XXXX is made of up to first four letters of the character's script name (except the leading 'c'), the Y is the speech file number (with no leading or trailing zeroes or padding of any kind), and EXT is the file extension.

For example, if you have dialog script:

ego: &10 "Hi! How are you?"
michael: &7 "I'm fine."
or common script using Say script function:
cEgo.Say("&10 Hi! How are you?");
cMichael.Say("&7 I'm fine.");
Both of those examples would play EGO10.WAV with the first line, and MICH7.WAV with the second. When a line of text has a voice linked to it, the text on the screen will not be removed until the voice file has finished playing. If the player interrupts it by clicking the mouse or pressing a key, the text and voice will be stopped. Voice files must be placed in the "Speech" sub-directory of the game folder.

NOTE: WAV, OGG and MP3 format files can be used for speech.

NOTE: You cannot use speech file numbers above 9999. That is, you can have EGO1.OGG all the way up to EGO9999.OGG, but not EGO10000.OGG or higher.

Speech is compiled into a file called SPEECH.VOX and is separate from the rest of your game data so that you can offer it as an optional extra download to the player. The game will function correctly if the file is not present.

SeeAlso: Speech.VoiceMode


The AudioCache folder

When you import audio files into AGS, you'll probably notice that a folder inside your game folder, called AudioCache, starts to fill up with files. What is it and why is it there?

Well, when you import audio into AGS, you might be importing it from anywhere -- it could be off your hard drive, but it might also be off a USB stick or a CD. AGS can't rely on the audio files always being there because you might remove the USB stick or delete the files on it.

Therefore, when you import audio into AGS it makes a copy of the file in the AudioCache folder. AGS also remembers where the file came from, and when you compile your game it will check if the file has been updated in its original location -- if so it will copy the latest version to the AudioCache.

But if the source file no longer exists, your game will continue to build just fine because AGS has its own copy of the file.

This allows AGS to stick to one of its core principles, that all the files you need to build your game are within the game's folder. That way, you have complete security in knowing that by backing up your game folder, your game will be safe if the worst happens.

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