Sound and Multi-Media
Those of you with a sound card and a recent browser will be now hearing your PC's sound card in action. It will be playing a Midi File, canyon.mid, which ships with Windows 2000! Sound is now an integral part to PC's, especially on the Internet. Understanding sound and sound cards is an invaluable skill in PC Repair, for upgrading systems, and configuring systems so the sound works properly!
Understand these terms and concepts about Sound Cards and
First Sound was PC Speaker: On or Off, Beep or no beep, short vs long beeps, etc.
Used Primarily as Diagnostic.
Beep meant PC had power.
2 Beeps meant a memory or video problem, etc. depending on Mother Board Mfr.
The advent of Games brought about a desire for real sound,
enter ADLib, Roland, Creative Labs and their proprietary sound cards…
Note there was no sound standard till the Sound Blaster became a “de facto standard”. The AdLib was close but no cigar! If you bought a card it might not work with the game you bought, unless it said Sound Blaster Compatible.
As with many add on devices it came with bundled software goodies to apply this new technology It came with a text reader—Star Wars Technology at the Time! Music Sound Playing/Recording ability Synthesizer Capability.
IrQ’s went up to as much as 3 for some ISA sound cards!
With only 14 total in the PC this created problems. Not to mention
problems re their DMA (usually 2 required) and memory address problems!
What is a typical sound card:
Creates/Records and/or Plays digital Sound (we don't hear it as being digital, and the environment may change it as to not be digital when released)
Requires the correct software
Plays “Wave Files”, Midi Files and other types of sound files
Can be 8, 16, or 32 bit.
Has jacks and control circuitry etc. for
a.) Speakers/H eadset Out (right voltage, amplitude, etc for speakers 4-8 watts)
b.) Microphone Input
c.) Audio Input (Optional-From Stereos, etc.)
d.) Audio Output (Non Amplified For Stereo System Input-optional)
f.) Midi Port
(see drawing p 1067)
Adaptors may be necessary for mini pin to RCA, to plug output into a stereo. Beware of stereo vs Monaural Connecters (3 Leads vs two)
Game Port requires an adaptor to plug to standard Midi Devices.
Can be ISA, PCI, or on MB Can be 16 or 32 bit (early
cards were 8 bit) and have FM or Wave Table with 4 or more voices (the more the
better). Distortion, and software included sometimes are important.
Must have the correct drivers to work with our OS! Software must work with
it (usually if the OS has the driver it will work in Win 9X).
Electronics Note: Output and Input must be matched in Impedance & Voltage! Be careful what you hook to what!
Some speakers are amplified, since the sound card does not throw a lot of power this is good!
Multi-Media Standards (Nearly all PC's built today are OK.. It is just a matter of speed of CD ROM, DVD ROM or not, CD Read Write or Not, etc.)
To play audio required adequate storage (.wav files were large) and processing power.
Early PC’s were limited in both. As a result the Multi-Media Standards were introduced:
MPC Level 1,2,3. This way you were sure of getting an adequate PC to play sound and “Multi-Media”, which was sound and video.
Video was itself an issue, and still is. Motion Pictures require about 32 frames each second. The bigger the frame at a given resolution the more memory and speed is required. Not until 200 MHZ MMX Pentiums and faster, with 4 Megs of Video RAM or more, and or special video processors, were PC’s and Their Video Circuitry Fast Enough to Display Full Frame, Full Motion Video. Current PC’s can even play DVD’s. However, DVD’s use video and audio compression. This means the PC must be fast enough to decompress and display.
Most Web Video is limited by the speed of the Internet Connection. If the user has DSL or faster connection he can see full motion video from the web if his PC and Video are fast enough. Otherwise people see a small window with jerky video. To see video you need special decoding and playing software, such as Real Video, or Windows Media Player.
Sizes of Different Types of Sound Files (wav, voc, au, aiff):
This means a wave file 10 seconds in length can be from 100 Kb to over 1 Meg!
Because of this Compressed File Formats such as the MP3 are commonly used.
A 5 minute song which is about 50 MB as a Wave file converts to less than 4 MB as MP3.
MIDI Files are not really sound files they are programs… code to tell how to create a sound, not the actual sound.
To play MIDI files your sound card must have a Sound Synthesizer, which has samples of the different sounds (violins, etc.) and plays them as demanded
How Sounds are Created in the Sound Card
FM Synthesis, vs Wave Table synthesis, which is much better
(sounds like a real violin, piano, etc.)
Uses of Sounds
Sounds used in presentations such as Powerpoint.
Recording Sounds using a microphone plugged into your sound card and recording software on the PC.
Annotating or Inserting Sounds in Documents.
A wav File:
DVD’s… Hear Sample…
Voice Recognition, or Speech to Text: Using the sound card, a microphone, and Voice Recognition software, the PC can convert speech to text. Current Software requires at least a Pentium 500 and minimum of 48 Megs of RAM, preferably 64 MB or more, a good sound card, and a proper microphone.
Voice Command Software: Software which recognizes a limited vocabulary to control the PC and software, E.G. OPEN WORD, Close File, Print File, etc.
Voice Dictation Software, with vocabularies from 5,000 to 50,000 words, and different vocabularies this software in many situations is ready for prime time.
Conferencing, Voice and Video. Telephone Internet, Proofreading, Audio CD Playing, Sound Mixers, Composing and Playing Music, ….
Frequency: 12HZ to 20KHz, Human Hearing.
Amplitude: Analog Waves? vs Digital Wave