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Sound CardA sound card is a computer expansion card that can input and output sound under program control. A typical sound card includes a sound chip usually featuring a digital-to-analog converter that converts recorded or generated digital waveforms of sound into an analog format. This signal is led to a (earphone-type) connector where a cable to an amplifier or similar sound destination can be plugged in. Also, a sound card has a "line in" connector where the sound signal from a cassette tape recorder or similar sound source can be connected to. The sound card can digitize this signal and store it (controlled by the corresponding computer software) on the computer's hard disk. The third external connector a typical sound card has, is used to connect a microphone directly. Its sound can be recorded to hard disk or otherwise processed (for example, by speech recognition software or for Voice over IP). One of the first manufacturers of sound cards for the IBM PC was AdLib, who produced a card based on the Yamaha YM3812 sound chip, aka the OPL2. This set the de facto-standard until Creative Labs produced the Sound Blaster card, which had a YM3812 plus a sound coprocessor (presumably an Intel microcontroller) which Creative creatively called a "DSP" which suggested it was a digital signal processor; several years passed before Creative released a card which could even record and playback sound at the same time, without even speaking about applying any real-time processing to it. The Sound Blaster, in tandem with the first cheap CD-ROM drives and evolving video technology, ushered in a new era of computer capabilities, in which they could play back CD audio, add recorded dialogue to computer games, or even play movies (but only short clips and in a very low quality form, incomparable with modern digital video). Early soundcards could not record and play simultaneously. Most soundcards are now full-duplex. In the late 1990s, many computer manufacturers began to replace plug-in soundcards with a "codec" (actually a combined audio AD/DA-converter) integrated into the motherboard. Many of these used Intel's AC97 specification. Others used cheap ACR slots. Driver architecture To use a sound card, a certain operating system typically requires a specific device driver. - Microsoft Windows uses proprietary drivers supplied by sound card manufacturers and supplied to Microsoft for inclusion in the distributions. Sometimes drivers are also supplied by the individual vendors for download and installation.
- The Linux kernel used in the Linux distributions have two different driver architectures, the Open Sound System and ALSA (Advanced Linux Sound Architecture). Both include drivers for most cards by default. Sound card manufacturers seldom produce stand-alone drivers for Linux.
- The USB specification defines a standard interface for sound cards to adhere to, allowing a single driver to work with the various USB sound cards on the market.
See also References External Links
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