Computer Science 1033A/B Study Guide - Final Guide: Musl, Network Layer, Realplayer

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CS 1033B Final Exam Notes Page 1
SOUND: Record process deliver
Rely on sound to enhance multimedia applications: easily capture the attention of users, facilitate easy
learning, set the mood
On the web sound offers: Background music, narration, sound effects, Record testimonials,
educate/presentations webcast, one-way audio offers on-demand radio listening, conferencing
What is sound: pressure waves of air
Visualize the sounds as a series of recurring waves called WAVEFORM
VOLUME: the higher the wave the louder the sound
PITCH/FREQUENCY: the closer the waves the higher the pitch
Sources of sound:
Pre-packaged (come with computer), purchased/borrowed, create own (recording program,
recording studio for higher quality, electronic instruments captured in MIDI)
How is sound recorded
MICROPHONE translates movement into electrical signals (analog) then tape recorder translates
the waveform from an electrical signal on a wire to a magnetic signal on a tape (analog)
Analog-to-digital converter (ADC): ADC captures a snapshot of the electric voltage on an audio
line and represents it as a digital number that can be sent to a computer
SOUND CARD: a device that is responsible for transforming the bits stored in an audio file into
music. Does 3 things:
Transforms digital bits into analog waves when you play back a waveform audio file
Transforms analog waves into digital bits when you make a sound recording
Handles compression and decompression, if necessary
In multimedia application, sound must be in a DIGITAL FORM (string of 1s and 0s)
Sound can be recorded directly in digital form or an analog sound can be converted to a digital sound
To convert analog sounds to digital sounds thousands of SAMPLES are taken of the sound
waves and recorded as bits
Each dot in the sound wave photo (wavy line) represents ONE audio sample
Quality of digital recording depends on:
SAMPLE RATE: rate at which samples are captured, number of times/sec that the
waveform is measured
1000 samples per second = 1KHZ (1000HZ)****
8KHZ voice only, 22KHZ music files, 44.1KHZ used on CD
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CS 1033B Final Exam Notes Page 2
*lower rate file smaller since missing sound
SAMPLE SIZE: resolution or precision that sample was taken (in bits)
CHANNELS: Mono vs Stereo
MONO SIGNAL: one stream of data reproduced equally on both speaker channels,
lose stereo operation
STEREO SIGNAL: consists of two streams of data working together (left and right)
double the size of mono file
CODECS: software programs that greatly REDUCE the audio file size
Use lossy compression: removes redundant data, quality reduced each time
HIGHER sampling rate and LARGER sample size, the more accurately sound can be digitized
Quality of the digitized sound gets better as file size increases
In audacity, settings are in edit>preferences
1 min of recording could end up being 10MB
Sound editing programs characteristics:
Record sounds in different sample size and resolutions
Digitize analog sounds
Create special effects
Save sounds in different file formats
Audacity software: edit the clip, combine it with other sound files, Add transitions and FX
Same for WaveStudio
Once digitized sound is in the computer
Sound editing software
Edits: unwanted noise, pauses, trimming
Fade-ins, fade-outs, background music, special effects
Several found files can be mixed or spliced together
Save the file in a format intended for the audience application
DELIVER: to head through speakers, digital sound is sent through a digital-to-analog converter (DAC)
Delivery method powerpoint, website, CD
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