Libris Britannia 4/science library(b).zip/science library(b)/INFO/PCCDEMO.ZIP/COMP1.EXE/SNDCARD.PRS

Text File | 1993-12-20 | 16KB | 262 lines

                                                   ÆÄöìâ éÇæâÆ?! ╧╧╬╠╬╠╬╠╬╠╡
      σΣα≤⌠±Σ α±≤ΦΓδΣ
                                   │     If you  haven't noticed lately
     ≤τΣ Σ⌡εδ⌠≤Φεφ εσ      ┌─┐     │  (and if you haven't, what Tibetan
┌────┐┌────┐┌─┐┌─┐┌────┐┌──┘ │     │  hillside  have  you  been  living
│  ──┤│ ┌┐ ││ ││ ││ ┌┐ ││ ┌┐ │     │  on?), multimedia is IT - at least
├──  ││ └┘ ││ └┘ ││ ││ ││ └┘ │     │  so the press says.
└────┘└────┘└────┘└─┘└─┘└────┘     │     So what's  a computer  user to
                     ┌─┐           │  do, then? Why,  get a sound card,
┌────┐┌────┐┌────┐┌──┘ │┌────┐     │  of course,  so they  can play all
│ ┌──┘├─── ││ ┌──┘│ ┌┐ ││  ──┤     │  the  latest  game...er multimedia
│ └──┐│ ── ││ │   │ └┘ │├──  │     │  presentations    with    glorious
└────┘└────┘└─┘   └────┘└────┘     │  sound. But  what the  heck is all
                                   │  the blather one hears about sound
       ß√ πα⌡Σ ≤Φ∞εφΣ√             │  cards?
                                   │
                                   │  ≥ε⌠φπ ≤√∩Σ≥
α δεεΩ  α≤  ≤τΣ  πΦσσΣ±Σφ≤ '≥ε⌠φπ  │
≤√∩Σ≥'  ÷τΦΓτ  ≤τΣ  Γ⌠±±Σφ≤ ≥ε⌠φπ  │     Γε∞∩⌠≤Σ± ≥ε⌠φπ≥,  α≤  δΣα≥≤ εφ
ßεα±π≥ α±Σ ßα≥Σπ εφ.               │  ≤τΣ ∩Γ,  Γαφ ßΣ  ß±εΩΣφ πε÷φ Φφ≤ε
                                   │  Θ⌠≥≤   α   σΣ÷   Γα≤Σµε±ΦΣ≥:   ∩Γ
                                   │  ≥∩ΣαΩΣ±, σ∞  ≥√φ≤τΣ≥Φ≥, ÷α⌡Σ≤αßδΣ


≥√φ≤τΣ≥Φ≥,   αφπ   παΓ.   The  PC  │  Adlib card  could actually change
speaker,   lets   just   say   it  │  volume and pitch and had multiple
produces a  reasonably  harsh and  │  voices  (signals)  that  could be
loud sound,  with little relation  │  combined  and   shaped  to  sound
to  real-world   sound  (although  │  something    like    recognizable
programs   using   RealSound  and  │  instruments   or   far-out  space
Digpak do a  credible job -for PC  │  sound effects  (sfx).  The sounds
sound- for  those who  don't wish  │  were created, or 'synthesized' by
to  use  a  sound  card  and want  │  taking  certain   frequencies  or
digitized sound).  Putting the PC  │  groups of frequencies and varying
speaker aside,  let's  spend time  │  (modulating)   them   to   create
talking  about  the  other  three  │  sounds   such   as   a   wavering
types.                             │  trumpet.   Thus   the   frequency
                                   │  modulation (FM) label.
Φφ ≤τΣ ßΣµΦφφΦφµ                   │
                                   │     Another   plus   was,   unlike
   Years ago, a company called Ad  │  digitized   sounds,   the  sounds
Lib revolutionized  the  PC sound  │  themselves weren't  stored in the
market when  it  offered  a sound  │  program;  only  the  commands  to
card  using  FM  synthesis.  This  │  tell the FM synthesis card how to


create  the  sounds  were needed.  │  you don't support  it, you'll get
Game   companies   embraced  this  │  a  lot  of  raised  eyebrows from
system of sound generation, since  │  vendors   and   end  users....but
it   needed    relatively   small  │  probably not their cash.
amounts of  additional  sound and  │     Although the  Yamaha OPL2 chip
provided an  exponential increase  │  was originally the  basis for the
in the  enjoyability and interest  │  Adlib card, newer  cards use more
in  the  game.   It  also  helped  │  advanced circuits with more sound
convey     emotional     content,  │  features  such  as  the  OPL3 for
something game  designers quickly  │  generating FM synthesized sound.
noted and the  call went out (and  │
is still  out)  for  (good) music  │     Just as  the  address  on your
composers.  Indeed,   even  today  │  mailbox   allows   you   and  the
there  is  a  scarcity  of  well-  │  mailman  to  tranfer  information
rounded  musical   folks  in  the  │  (yes,     evenjunk     mail    is
computer industry.                 │  information)  because   you  both
                                   │  know  where  to  put  or  get the
   The  Adlib  standard  is still  │  mail,  the  Adlib   card  had  an
the de facto music standard today  │  Input/Output  (I/O)   address  to
- if  you're a  game designer and  │  allow the  microprocessor and the


FM    circuitry    to    exchange  │  (ADC)  circuit  on  a  sound (the
information.  This   address  was  │  analog part) to convert it from a
assigned  the  number  330H. Even  │  continuous sound  into  samples -
today, many cards that are Adlib-  │  digital  numbers  that  represent
compatible will  still have their  │  the  value  of  the  sound  at  a
FM synthesis circuitry configured  │  particular point  of  time. These
for address  330H  (they  may not  │  numbers, or bytes,  are stored in
even  mention  it  in  the card's  │  one or more of the program files.
documentations as  most  times it  │  When it comes time for a sound to
isn't user-selectable).            │  play, it must  be sent  to a card
                                   │  with  a  digital-to-analog  (DAC)
   It  was   all  fairly  simple,  │  circuit  to  convert  the samples
really.  It   soon   turned  out,  │  back into  a sound.  This process
however, that  Adlib  sound alone  │  is necessary,  because a computer
wasn't enough for many people.     │  cannot directly store sounds, but
                                   │  must convert  them.  True, CDROMs
πΦµΦ≤ΦⁿΣπ ≥ε⌠φπ≥                   │  will sometimes have true audio on
                                   │  the CDROM, but  it is usually not
   Digitized sound is the process  │  fully integrated into the program
of  using   an  analog-to-digital  │  (i.e the program may play it, but


the   sounds   are   not   really  │  game to  be  played  back  at the
'controllable' by the program).    │  appropriate    moment.   Screams,
                                   │  clangs, embarrassing noises, even
   We're    getting    ahead   of  │  speech could all be designed into
ourselves,   though,   as  CDROMs  │  programs and played back later.
weren't out  yet  - at  least not  │
for  the  masses.  What  did come  │     Like  the   Adlib,  the  Sound
out, after  the  Adlib  card, was  │  Blaster  had   its  FM  synthesis
the Sound  Blaster  from Creative  │  circuitry set  to  an  address of
Labs. This  card had  wisely been  │  330.  One  advancement  that  the
designed to support  the Adlib FM  │  Sound Blaster  made  was  that it
Synthesis (hereafter  just called  │  handled  an  additional  type  of
Adlib)     method     of    music  │  sounds  -  digitized  sounds. The
generation,  but  added  to  that  │  Sound    Blaster     (SB)    used
some   DAC   circuitry   (and   a  │  additional circuits,  with one of
joystick  controller  and  a MIDI  │  six   user-selectable   addresses
port and  an  ADC to  record your  │  around 220H to send commands to a
own  sounds).   Now  sounds,  any  │  DAC. And,  since digitized sounds
sounds, could  be  recorded  by a  │  can be  very  big  (and therefore
game maker  and  inserted  into a  │  take a  long time  to process, at


least as  far  as  a  computer is  │  such  as  serial  cards,  printer
concerned),  the  sound  data was  │  cards,  video  cards,  disk drive
put  on   a   DMA   channel  that  │  controllers,  and  timers. Unless
transfers data  faster because it  │  specificly designed  for  it, IRQ
doesn't have  to bother  the CPU.  │  lines cannot be shared.
The  DMA  channel   acts  like  a  │     Therefore,  one  device  - one
superhighway,  allowing  the data  │  IRQ line. Break the rule and some
to travel  straight to  the sound  │  very  odd   things   (though  not
card, without detours at the CPU.  │  damaging)  can   happen  on  your
                                   │  computer.
   What  really  made  the  Sound  │
Blaster  stand  out  was  that it  │     A mouse takes  an IRQ, a modem
used an IRQ totell the CPU it was  │  another,   a   hard   drive   yet
ready for more.  An IRQ is simply  │  another.  An  ISA  bus  (the most
a way  for  the card  to  get the  │  common type,  also called  the AT
CPU's   attention   (not   unlike  │  bus) typically  has several cards
waving   twenty   dollars   at  a  │  plugged into it that use up IRQs,
waiter).                           │  and there are  only 16 available.
   Several things in the computer  │  In fact,  at  least six  IRQs are
can activate  IRQ lines  - things  │  used by  the motherboard circuit-


ry, so  it isn't  a good  idea to  │  IRQ line to use has always been a
try and  use those.  If you're an  │  pain.
average computer user, you've got  │     Fortunately,  some  I/O  cards
two serial  ports  and  a printer  │  are   made   for   sharing;  many
port, using  up a  total of three  │  printer  cards  are  designed  to
IRQs. Well then,  now you're down  │  share  IRQ7  -  at  least  if the
to seven IRQs you can use....best  │  printer is off-line.
hope  at  least  one  of  them is  │
available on your sound card.      │     Even with all that hassle, the
                                   │  enhancement    in    sound    was
   When PCs  came out  there were  │  considered worth it  by many. The
plenty of IBM  XTs and its clones  │  Sound   Blaster   digital   sound
out there, with only 8 IRQ lines.  │  configuration  became  another PC
So, cards were  designed with the  │  industry  standard.   Other  card
assumption of  8  lines.  The IBM  │  manufacturers  began  to  emerge,
AT's ISA bus  added an additional  │  most  touting   Adlib  and  Sound
8 IRQ  lines, which  are only now  │  Blaster  compatibility.... though
being  supported  from  both card  │  not  always  100%  compatibility.
manufacturers and  sound software  │  Today,   there   is   a   growing
developers. Finding  an available  │  multitude of  Adlib/DAC cards out


there, most  Adlib compatible and  │  called     synthesizers.    These
some  Sound  Blaster  compatible,  │  'samples' were  digitized record-
some  partially   compatible  and  │  ings of  instruments  or whatever
some having  gone their  own way.  │  that could be strung together and
The  options  for  IRQs  and  DMA  │  modified not unlike FM synthesis.
channels   and   addresses   have  │  But,  unlike   FM   synthesis,  a
increased,  as  have  the options  │  french horn  would  sound  like a
for digitized  sound quality...at  │  french horn -  if the french horn
the  expense   of   larger  sound  │  samples were used, of course ( we
files.                             │  won't go  into what  would happen
   Sometimes,    the    circuitry  │  if you used, say, the barking dog
provides additional  features, at  │  samples instead ). Also developed
the cost  of  true  Sound Blaster  │  was the Musical Instrument Device
compatibility.                     │  Interface,  or  MIDI.  MIDI would
                                   │  allow  a  computer  to  act  as a
∞ΦπΦ ∞⌠≥ΦΓ                         │  controller, recording music input
                                   │  by a  musician  and  then control
   The  music  industry  had, for  │  the synthesizer. So, the musician
years,  used  small  fragments of  │  could define the bassoon notes to
sound,  in   the   music  devices  │  be played and  the computer would


tell the synth to play it...again  │  musician have  access to  all the
and again,  if desired.  In early  │  sounds   desired,   yet   without
synths, cables (patch cords) were  │  having  to   pay  the  exorbitant
run  from  the  output  of signal  │  amount  of  money  such  a  synth
sources  to   inputs  of  signal-  │  would  cost  if  it  had  all the
modifying   devices,    and   the  │  potential  sounds   the  musician
outputs  of  these  to  inputs to  │  might want in  it. Storage memory
other    devices,    etc.   These  │  is still precious, even today.
connections, used  to create each  │
unique sound,  were  written down  │     Problem is,  this  setup works
and referred to as 'patches'.      │  fine for  a  musician  working by
                                   │  themselves but can be a real pain
   Another  thing  this  type  of  │  for computer  users who  can play
setup could do was keep a library  │  MIDI-devised music.
of sounds and  transfer them from  │     Downloading  takes  time, time
the computer  to the synthesizer.  │  added  to  that  of  the  program
This   'downloading'   of  sounds  │  loading  from  disk.  And  if you
allowed  the   musician  and  the  │  don't download,  how do  you know
synthesizer designer  a  lot more  │  the bassoon  will be  at location
flexibility   by    letting   the  │  #156 where the musician put it in


his/her  machine.  After  all, it  │  music.  The  MT-32  is  no longer
was   just   a   randomly  chosen  │  being  made,  though  games still
location.   So,    you're   stuck  │  support it and other vendors have
downloading sounds.                │  cards  that  emulate  it. Another
   And, you  can't  just download  │  potential  standard  has emerged,
the  files  once,  and  leave it;  │  called General  MIDI  or GenMIDI.
what  happens  when   you  run  a  │  It  is   system-independent,  and
different program  and bypass the  │  defines where  a particular sound
downloading stage?                 │  can be found  on any machine that
                                   │  supports GenMIDI.
   One answer to this was to come  │
up with standards. With computers  │   ÷α⌡Σ ≤αßδΣ≥
and   standards    basically   an  │
oxymoron, it's  amazing  that one  │     Anyway,  back  to  storage and
did  emerge.  Roland  put  out  a  │  time. Instead of downloading most
device called the MT-32, a device  │  of the  sounds, which  are always
seized upon  by high-end computer  │  going to  be needed  (snare drum,
music   lovers.   Supporting   it  │  piano,  steel-string  guitar,  et
became  prevalent  among programs  │  al), why not  put all these sound
wanting   to   support   high-end  │  waveforms  in  a  ROM  chip  on a


board, so they're always there.    │  tables   are   basically  'patch'
   No    downloading   necessary,  │  files, consisting  of information
unless    the    program    needs  │  on which  sound  location  to use
additional    sounds     to    be  │  and   what   longevity,   volume,
generated....but  even  then  the  │  effects and  wave-shaping options
download time will  be less. This  │  to use on the sound.
is what a wavetable is all about.  │
It  has   the   digitized  sounds  │     Wave tables  are usually MIDI-
burned  into  a   ROM  (which  is  │  compatible and  some  are General
accessed by specifying  a row and  │  MIDI  compliant.   As   might  be
column, in  what would  look kind  │  suspected,  wave  tables  are not
of like  the multiplication table  │  good   for    playing   digitized
if drawn  out on  paper) which is  │  speech. Speech is too complex and
mounted on the wavetable card.     │  varying,    and    wave    tables
   One  can  usually  assume that  │  typically don't  have  enough RAM
the  larger  the  amount  of  ROM  │  in them to store much speech. So,
storage  used,   the  better.  In  │  if  your  plans  include programs
addition, there  is  usually some  │  with speech  or digitized speech,
RAM   for    storing   downloaded  │  you'll still  need a  sound board
sounds. The sound  files for wave  │  with  a  DAC  on  it.  Since most


cards have at  least FM synthesis  │
on them, if you're not particular  │
about the  music then  maybe wave  │
tables are a luxury.               │
                                   │
   Sound    is    becoming   more  │
prevalent  in  software.  In  the  │
case of some  computer games, the  │
lack of sound  can be detrimental  │
to one's successfully completing.  │
Even  productivity   software  is  │
emerging with  sounds  built into  │
programs,  a  far  cry  from  the  │
'blip!' of just a year ago. Now's  │
the time to decide: will you soar  │
in the sky  with your sound card?  │
Or run silent, run deep? ñ         │