Chapter 13: Sound Effects

Overview

Todor Fay

We have talked a bit about how wonderful DirectX Audio is for sound effects work, but we have yet to really focus on anything outside of music making. Although the Loader, Segment, AudioPath, and scripting are all important prerequisites for creating immersive audio environments with DirectX Audio, our examples have primarily focused on musical applications. Now we will spend some time focusing specifically on using DirectX Audio for sound effects.

There are some big reasons why you can benefit dramatically by playing sound effects through AudioPaths instead of the traditional approach of loading and playing sounds directly in DirectSound Buffers:

• There is a performance advantage. 3D spatialization, whether in software or hardware, is significantly more expensive than software mixing of individual sounds on today's CPUs. Even with hardware acceleration, the overhead of shipping the audio data over the bus can be more expensive than a simple CPU mix. The AudioPath mechanism mixes one or more sounds in one or more Segments and sends them all together to one 3D channel on the sound card. In contrast, every single sound in the Buffer approach has its own 3D channel. This approach ultimately costs quite a bit more when sounds are layered, and to add insult to injury, it is more complex to program.

• Using AudioPaths allows for more densely layered sound environments because the limiting factor is not the number of sounds that can play at once, but rather the number of 3D positions that the sounds can play through.

• The AudioPath approach is content driven. The authoring format, with scripting, variation, and more, is much richer than wave files. Therefore, the sound designer can work on complex sound schemes without tying up the programmer.

Naturally, working with AudioPaths is not without its unique challenges. I hope that we will address all of them in this chapter.

Jones is not the greatest place to demonstrate working with 3D sound effects in a game-like environment, so our programming treat this time, called Mingle, is a reproduction of a lively cocktail party with some truly fascinating people milling around. We will start by walking through the essentials of programming sound effects with DirectX Audio and then spend some time with critical issues that can make or break your audio design. Lastly, we will dig into Mingle.