Audio Preparation for Game Engines

   By Lisa F   Categories: GeneralMixing Techniques

Here are a few important workflow concepts to keep in mind when preparing your assets. You must . . .

  • Bounce out your sounds from a DAW or Stereo Editor into individual files and into separate folders. These folders will contain all the music, sound effects and voice-over in the game and will need to be meticulously organized.
  • Tightly trim and edit your files so that they can trigger right away when called by the game engine without skips or delay. We also need to trim the start and end of each sound so they are as size efficient as possible and don’t take up any more space than is necessary. Game audio is all about efficiency.

  • Volume balance all your audio . In some cases you will normalize all your elements as individual groups (meaning for example all voiceover files) to 90 percent of maximum volume to prevent clipping, deliver them, and then let the programmers and integrators set the final mix volumes between these groups. In other situations you will premix the entire soundtrack in your DAW—this means you mix the sounds in your DAW, but bounce out the individual files or layers needed along with any reverb, EQ or effects you require and then deliver these files for insertion into the game. In this case, and with luck, the programmer will simply insert the files into the game with no need to do any additional audio work.
  • Create perfect seamless loops that do not skip . We cannot stress this enough—there is nothing worse than getting audio notes that say “Sorry, but the audio is skipping. Can you please re-edit?” We’ll have a lot more to say on the subject of looping later on in this level.
  • Provide an asset list or asset database management system to properly identify your files so a programmer can help to implement them. Alternately, you would provide prepared audio middleware files or do the implementation yourself! Audio does not magically appear inside a game—it takes planning and elbow grease. If you don’t know how to do it yourself, then you must make sure that at the very least you understand the process and can provide the programmer with the information they need to get the job done in as efficient a manner as possible.

This figure shows what should be pretty obvious by now—a looped file of 1 minute duration played eight times is much smaller in size than an 8 minute long file. This does not mean that all loops have to be short, however: these decisions are individual to the game and the situation at hand. Credit: Jeremy Engels.

JUST SO YOU KNOW. . . .

Triple A console titles and big budget games usually involve the use of audio middleware. When a designer works with a middleware engine, all the audio elements are roughly balanced ahead of time, then the mix is refined in real time while the game is being played. Reverb or other effects can be added, music levels are frequently reduced in volume under voice-over through a process called ducking, and spatial sounds are all dealt with on the fly within the middleware audio engine. This is then output to the game engine itself or possibly to a platform-specific development environment like XCode, Visual Studio, or myriad others, to be compiled along with the graphic and structural game data.

Social and mobile games, like iOS, Android and online games, do not usually use audio middleware. In the case of platforms like these that don’t use dynamic mixing, audio elements must be pre-balanced ahead of time by the sound designer, or balanced out by the programmer or designer within the game environment.

THE IMPORTANCE OF LOOPING IN GAMES

As you’re painfully aware by this point, looping is a HUGE part of creating sound effects or music, primarily because of the open nature of time in gameplay. It is impossible to write a perfectly timed music cue when you have no idea how long a player will stay in a specific area within the game environment. Looping also saves space in the game—for example, having a 1 minute loop play eight times is vastly more efficient than having an 8 minute loop playing once. Do the math—the former only takes up 1 minute of audio data at a given bit and sample rate, with a command to repeat eight times, and the latter lasts for 8 minutes at the same bit and sample rate. In other words, it is eight times larger. The other factor to consider is that even at eight times the size, it may still not fill all the time necessary to fulfill the gameplay requirements. Looping audio in games is a global phenomenon that pertains to sound effects, music, and ambient backgrounds.

Uses for Looping Techniques

Sound Effects: A good example of a looping sound effect is a weapon effect in an FPS game, such as a machine gun. Holding down the appropriate button or firing key triggers the loop to play indefinitely (or perhaps until you run out of bullets), and when you release the button it can either stop, or more interestingly, trigger an ending sound (like a single shot or with shell casings clattering on the ground).

Ambient Backgrounds: Location loops are extremely common in games of all shapes and sizes. Outdoor locations or tailored indoor acoustic environments in general use longer audio clips in order to avoid a sense of repetition. One technique for developing a well-crafted loop might be to have the same audio material at the beginning and end, making it harder if not impossible for the ear to detect the loop point. Another technique is to use a few ambient loops of slightly differing length playing together, so that they overlap each other at different points. In this case, the goal is to try to make the game sound more organic and non-repetitive, while at the same time using smaller and more size-efficient files.

Music Soundtracks: In many games, producers want a lot of music, but just don’t have the audio budget available for one reason or other. In such cases, looping is a necessary evil. We have all at one time or another become aware of a repetitive music score in a game—in fact, parents seem especially sensitive to such things! Repetition is necessary and sometimes it’s even expected— Space Invaders or Asteroids , anyone? Even with today’s sophisticated console games there are a ton of very clever techniques that are used to give the player a feeling that there is more music around then there really is. By cleverly changing or layering the orchestration in musical passages, composers are able to turn 30 minutes of music into stems that can run for over an hour without wearing out their welcome.

In certain styles of games, composers develop quick stinger effects to cover up transitions between gameplay or just to inject an unexpected quality into the game. In all cases, it is important to find out the time durations of the gameplay sections you will be composing for, and seek to provide music loops that will not become overtly repetitive. It also takes a highly skilled composer to know how much melody to include in looping musical passages. Too much and you may drive the listener bonkers, too little and there may not be enough tension or development to hold their attention. Similar to film music, often the best kind of loop is the one you don’t even hear because it’s so well integrated with the game.

Excerpt from The Essential Guide to Game Audio:The Theory and Practice of Sound for Games by Steve Horowitz and Scott R. Looney © 2014 Taylor & Francis Group. All Rights Reserved.

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