Sound functionality can also be integrated onto the motherboard, using basically the same components as a plug-in card. The best plug-in cards, which use better and more expensive components, can achieve higher quality than integrated sound. The integrated sound system is often still referred to as a "sound card".
| Color | Function | Connector | symbol | |
|---|---|---|---|---|
| Pink | Analog microphone audio input. | 3.5 mmminijack | A microphone | |
| Light blue | Analog line level audio input. | 3.5 mmminijack | An arrow going into a circle | |
| Lime green | Analog line level audio output for the main stereo signal (front speakers or headphones). | 3.5 mmminijack | Arrow going out one side of a circle into a wave | |
| Orange | Analog line level audio output for center channel speaker and subwoofer. | 3.5 mmminijack | ||
| Black | Analog line level audio output for surround speakers, typically rear stereo. | 3.5 mmminijack | ||
| Silver/Grey | Analog line level audio output for surround optional side channels. | 3.5 mmminijack | ||
| Brown/Dark | Analog line level audio output for a special panning, 'Right-to-left speaker'. | 3.5 mmminijack | ||
| Gold/Grey | Game port / MIDI | 15 pin D | Arrow going out both sides into waves | |
The main function of a sound card is to play audio, usually music, with varying formats (monophonic, stereophonic, various multiple speaker setups) and degrees of control. The source may be a CD or DVD, a file, streamed audio, or any external source connected to a sound card input.
Audio may be recorded. Sometimes sound card hardware and drivers do not support recording a source that is being played.
A card can also be used, in conjunction with software, to generate arbitrary wave forms, acting as an audio-frequency function generator. Free and commercial software is available for this purpose.there are also online services that generate audio files for any desired wave forms, playable through a sound card.
A card can be used, again in conjunction with free or commercial software, to analyse input waveforms. For example, a very-low-distortion sinewave oscillator can be used as input to equipment under test; the output is sent to a sound card's line input and run through Fourier transform software to find the amplitude of each harmonic of the added distortion. Alternatively, a less pure signal source may be used, with circuitry to subtract the input from the output, attenuated and phase-corrected; the result is distortion and noise only, which can be analysed.
There are programs which allow a sound card to be used as an audio-frequency oscilloscope.
For all measurement purposes a sound card must be chosen with good audio properties. It must itself contribute as little distortion and noise as possible, and attention must be paid to bandwidth and sampling. A typical integrated sound card, the Realtek ALC887, according to its data sheet has distortion of about 80dB below the fundamental; cards are available with distortion better than -100dB.
Driver architecture
To use a sound card, the operating system (OS) typically requires a specific device driver, a low-level program that handles the data connections between the physical hardware and the operating system. Some operating systems include the drivers for many cards; for cards not so supported, drivers are supplied with the card, or available for download.
•DOS programs for the IBM PC often had to use universal middleware driver libraries (such as the HMI Sound Operating System, the Miles Audio Interface Libraries (AIL), the Miles Sound System etc.) which had drivers for most common sound cards, since DOS itself had no real concept of a sound card. Some card manufacturers provided (sometimes inefficient) middleware TSR-based drivers for their products. Often the driver is a Sound Blaster and AdLib emulator designed to allow their products to emulate a Sound Blaster and AdLib, and to allow games that could only use SoundBlaster or AdLib sound to work with the card. Finally, some programs simply had driver/middleware source code incorporated into the program itself for the sound cards that were supported.
•Microsoft Windows uses drivers generally written by the sound card manufacturers. Many device manufacturers supply the drivers on their own discs or to Microsoft for inclusion on Windows installation disc. Sometimes drivers are also supplied by the individual vendors for download and installation. Bug fixes and other improvements are likely to be available faster via downloading, since CDs cannot be updated as frequently as a web or FTP site. USB audio device class support is present from Windows 98 SE onwards. Since Microsoft's Universal Audio Architecture (UAA) initiative which supports the HD Audio, FireWire andUSB audio device class standards, a universal class driver by Microsoft can be used. The driver is included with Windows Vista. For Windows XP, Windows 2000or Windows Server 2003, the driver can be obtained by contacting Microsoft support.[15] Almost all manufacturer-supplied drivers for such devices also include this class driver.
•A number of versions of UNIX make use of the portable Open Sound System (OSS). Drivers are seldom produced by the card manufacturer.
•Most present day Linux distributions make use of the Advanced Linux Sound Architecture (ALSA). Up until Linux kernel 2.4, OSS was the standard sound architecture for Linux, although ALSA can be downloaded, compiled and installed separately for kernels 2.2 or higher. But from kernel 2.5 onwards, ALSA was integrated into the kernel and the OSS native drivers were deprecated. Backwards compatibility with OSS-based software is maintained, however, by the use of the ALSA-OSS compatibility API and the OSS-emulation kernel modules.
•Mockingboard support on the Apple II is usually incorporated into the programs itself as many programs for the Apple II boot directly from disk. However a TSR is shipped on a disk that adds instructions to Apple Basic so users can create programs that use the card, provided that the TSR is loaded first
No comments:
Post a Comment