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The speaker hardware was
typically limited to square waves, which fit the common
nickname of "beeper". The resulting sound was generally
described as a series of beeps and boops. Several companies,
most notably Access Software, developed techniques for
digital sound reproduction over the PC speaker; the
resulting audio, while barely functional, suffered from
distorted output and low volume, and usually required all
other processing to be stopped while sounds were played.
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Other home computer models of the 1980s included hardware
support for digital sound playback, or music synthesis (or
both), leaving the IBM PC at a disadvantage to them when it
came to multimedia applications such as music composition or
gaming.
The Sound Card
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 incorrectly 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 in full-duplex mode, without however any
real-time sound processing capabilities.
Contrary to popular belief, the Sound Blaster didn't
overtake AdLib due to the inclusion of digital sound as a
feature. Support of Sound Blaster's digital sound didn't
occur until a few years later after the release of the Sound
Blaster Pro. In fact, it was the inclusion of a basic game
port that provided the key difference. At the time both the
AdLib card and the Sound Blaster sold for $289. AdLib owners
who also wanted to play games requiring a joystick had to
purchase a separate dedicated game port card that generally
cost about $50. The dedicated game port also came at the
further cost of another precious expansion slot at a time
when many PC clones commonly included only three slots. Once
Creative Labs proved that the Sound Blaster was fully "AdLib
compatible", consumers were left with little reason to
choose the less-functional, but equally priced AdLib card.
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.
Also, for years soundcards had only one or two channels of
digital sound (most notably the Soundblaster series and
their compatibles) with the notable exception of the Gravis
Ultrasound family, which had hardware support for 16 or 32
independent channels of digital audio, and early games and
MOD-players had to fully emulate multiple channels by
software downmixing.
Today, most good quality sound cards have hardware support
for at least 16 channels of digital audio but others, like
cheap Audio codecs, still rely partially or completely on
software, either their drivers or the operating system
itself to perform a software downmix of multiple audio
channels.
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.
As stated before, these "codecs" usually lack the hardware
for direct music synthesis or even multi-channel sound, with
special drivers and software making up for these lacks, at
the expense of CPU speed (e.g. midi reproduction takes away
10-15% CPU time on an Athlon XP 1600+ CPU).
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