CompTIA A_ Certification All-In-One Exam Guide, Seventh Edition - Michael Meyers [350]
Figure 20-10 Typical 2.1 speakers
Going beyond standard two-channel (stereo) sound has been a goal in the sound world since the 1970s. However, it wasn’t until the advent of Dolby Laboratory’s Dolby Digital sound standard in the early 1990s that surround sound began to take off. The Dolby Digital sound standard is designed to support five channels of sound: front-left, front-right, front-center, rear-left, and rear-right. Dolby Digital also supports a subwoofer—thus, the term 5.1. Another company, Digital Theatre Systems (DTS), created a competing standard that also supported a 5.1 speaker system. When DVDs were introduced, they included both Dolby Digital and DTS 5.1 standards, making 5.1 speakers an overnight requirement for home theater. If you want to enjoy your DVDs in full surround sound on your PC, you must purchase a full 5.1 speaker system. A number of 5.1 speaker systems are available for PCs. The choice you make is usually determined by what sounds best to you.
Many sound cards also come with a special Sony/Philips digital interface (S/PDIF) connector that enables you to connect your sound card directly to a 5.1 speaker system or receiver (Figure 20-11). Using a single S/PDIF instead of a tangle of separate wires for each speaker greatly simplifies your sound setup. S/PIDF connections come in two types, optical and coaxial. The optical variety looks like a square with a small door (at right in Figure 20-11). The coaxial is a standard RCA connector (at left), the same type used to connect a CD player to your stereo. It doesn’t matter which one you use; just make sure you have an open spot on your receiver or speakers.
Figure 20-11 S/PDIF connectors
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NOTE Only a few 5.1 PC speaker sets come with S/PDIF. In most cases, you’ll have to use the regular audio outputs on the sound card. You’ll find the connector more common on 6.1 and 7.1 sets.
Games can also take advantage of 5.1, 6.1, and 7.1 speakers, but they use the DirectX standard. DirectX offers numerous commands, also known as APIs, that issue instructions such as “make a sound on the right speaker” or “play music in both the right and left channels.” DirectX simplifies the programming needed to create sound and video: rather than having to program sounds in different ways for each sound card option, games can talk DirectX. The hardware manufacturers simply have to ensure that their sound cards are DirectX compatible.
DirectX version 3 introduced DirectSound3D (DS3D), which offered a range of commands to place a sound anywhere in 3-D space. Known as positional audio, it fundamentally changed the way most PC games were played. DS3D could not handle all sound information, but it supported extensions to its instructions for more advanced sound features. This challenged the sound card designers to develop more fully the concept of positional audio. Creative Labs responded by rolling out environmental audio extensions (EAX), a set of audio presets that gave developers the capability to create a convincing sense of environment in entertainment titles and a realistic sense of distance between the player and audio events. Figure 20-12 shows an EAX setup screen.
Figure 20-12 EAX setup screen
In late 2000, a number of EAX effects were incorporated into the DirectX audio component of DirectX 8.0. This signaled the acceptance of EAX as the standard for audio effects in gaming. Shortly afterward, Creative Labs started releasing audio cards that were Dolby 5.1 compatible out of the box. This let you plug a 5.1 speaker system directly into your sound card. The sound card automatically decoded the Dolby/DTS sound track when you played a DVD and the EAX effects when you played a game that supports it.