Setting Up Audio Cards

Advance Technical Repair of Laptops Motherboard

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To start your "quadraphonic wall of sound," you need to have a sound card in your PC. A sound card can be an add-in PCI (or even ISA) card, or it can be integrated on your motherboard. Your card will have a ton of uses — from gaming to audio/video playback. Having a multimedia system just isn't the same without sound.

Fortunately, most modern PCs include a sound card, often of the integrated variety. In the rare case that one isn't included (or the slightly more common case where it isn't supported in Linux), you can add a supported sound card starting for only a few dollars. If you're really pinched, check out eBay, where you probably can get a decent SoundBlaster-compatible card (still the standard) for next to nothing.

I r -[-'-"• - I If you try the procedures in this book but still don't have a working sound card, visit

— www . al sa pro ject. org, home of the Advanced Linux Sound Architecture (ALSA).

Another good resource is the ALSA wiki (http://alsa.opensrc.org).

The following list summarizes the basic features that are included in the popular SoundBlaster family of sound cards:

■ Sound recording and playback — The card can convert analog sound into 8-bit or 16-bit digital numbers. To convert the sound, the board samples the sound in waves from 5 KHz to 48 KHz, or 5,000 to 48,100 times per second. The higher the sampling rate, the better the sound and the larger the output files.

■ Full-duplex support — Full-duplex means that recording and playback occur at the same time. This is particularly useful for bidirectional Internet communication, such as Voice-Over-IP (VOIP) telephony or simultaneous recording and playback.

■ Input/output ports — Several different ports on the board enable you to connect other input/output devices. These ports include:

Line-In (blue) — Connects an external CD player, cassette deck, synthesizer, MiniDisc, or other device for recording or playback. If you have a television card, you might also patch that card's line out to your sound card's line in.

■ Microphone (red) — Connects a microphone for audio recording or communications.

■ Headphone/Line-Out/Speaker Out (green) — Connects speakers, headphones, or a stereo amplifier. (On sound cards I've tested, this is marked as Headphone in mixer utilities.)

Joystick/MIDI (15-pin connector) — Connects a joystick for gaming or MIDI devices. (Some sound cards no longer have these ports because they are now available from most motherboards.)

■ Digital out (orange) — A digital out connector can be used to connect a digital audio tape (DAT) device or CD recordable (CD-R) device.

Rear out (black) — Can be used to deliver audio output to powered speakers or an external amplifier.

Internal CD Audio — This internal port connects the sound card to your computer's internal CD-ROM drive (this port isn't exposed when the board is installed).

Sound drivers provided in Linux come from many sources. Advanced Linux Sound Architecture (ALSA) sound drivers are integrated into the 2.6 kernel. You may find older Open Sound System (OSS) drivers are useful if ALSA does not support your sound card. Commercial support for OSS drivers is available for a small cost from 4Front Technologies (www.opensound.com), which is the company that still maintains OSS.

C a -- Before you install a separate sound driver distribution, check to see if your current distri bution already has a recent driver. Using the driver that came with the kernel is always a safe bet if you are not experiencing a specific driver-related issue.

At times, a sound application will ask you to identify the device from which to access sound on your system. With the introduction of the Udev feature in the 2.6 kernel, some of the device names are different from those used with the 2.4 kernel. The following are audio device nodes that may be of interest to you as you use sound in Linux:

■ /dev/audio, /dev/audio1 — Compatible with Sun workstation audio implementations (audio files with the .au extension). These devices are not recommended for new sound applications.

■ /dev/cdrom — Represents your first CD-ROM drive. /dev/cdrom is usually a symbolic link to the device node, such as /dev/hdc, that corresponds to your CD-ROM drive. Additional CD-ROM drives are located at /dev/cdrom1, /dev/cdrom2, and so on.

■ /dev/dsp, /dev/dsp1 — Digital sampling devices, which many audio applications identify to access your sound card.

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