Transcript Game Audio Mark Peskir November 14, 2005 ITCS 5010 Overview • Terms/Fundamentals • Computers and Sound • Parameters, Filters, Effects • Types of Sound Production • Planning For.

Game Audio
Mark Peskir
November 14, 2005
ITCS 5010
Overview
• Terms/Fundamentals
• Computers and Sound
• Parameters, Filters, Effects
• Types of Sound Production
• Planning For Game Audio
Definitions
Sound: compression waves transmitted
through a medium
Wave: cycle of compression and
rarefaction
Amplitude: measure of sound wave
pressure
Coming soon: cool stuff
Definitions
Frequency: speed of wave oscillation
Measured in Hertz (Hz)
Pitch: a particular constant frequency
Hertz (Hz): number of oscillations per
second
decibels (dB): measure of the degree of
amplitude
Note: a predefined pitch used in music
Common Frequency Ranges
Human Hearing: 20Hz – 20kHz
Human Voice: 90 – 300 Hz
Middle C: 261 Hz
Digital Sound
A “unit” of digital sound is called a sample
The sampling rate is the number of
samples taken per second
Bit depth: size of sound sample data
See Figure 5.5.2, pg 598
Nyquist Limit
A sampling rate can only accurately
record sounds of frequencies at half its
value
48 kHz sampling rate:
can record a 24 kHz max frequency
That’s really high, so who cares?!
Common Sampling Rates
“CD Audio” quality: 16 bit, 44.1 k
IP Voice Chat (BattleCom, TeamSpeak):
8 – 16 bit, 16k – 24k sample rate
Burger King drive-thru: ???
High-End sound cards support:
24/96, 24/192
The Tradeoff: Performance vs. Quality
Flow of Tone Production
• Tone is generated
• Amplitude (volume) set
• Filters, effects, etc.
added
• Sound is mixed with
other sounds
• Sound signal sent to
speakers
Sound Formats
Sample: short recording of live sound, with
frequency adjusted to produce other
pitches/notes
Streaming Audio: a full soundtrack or
complete sound effect, loaded into a
buffer and played while the rest of sound
loads
MechWarrior 2: used hybrid CD for music!
Audio Compression
• The Goal: reduce the amount of data
needed to produce quality sound (like
JPEG images)
Two methods:
• Bit reduction: reduce bit depth
• Psychoacoustic Compression: discard
audio not generally heard (MP3)
ADSR Envelope
Attack, Decay, Sustain, Release
Could define a variety of sound aspects
(pitch, volume, rate of repetition)
What would the envelopes look like for:
• Revving a car engine
• Cymbal crash
• John Williams choir
Other Sound Parameters
Pan: the “left/right” location of the sound
Volume: ratio of amplitude played
Pitch/Frequency: can be assigned to override a
sound’s actual pitch
3DGS:
sound mySound = <gosh.wav>;
snd_tune(mySound, 50, 100, -100);
play mySound at 50% vol, 100% freq, left
Pass Filters
Low Pass Filter: only allow sounds below a
certain frequency
High Pass Filter: only allow sounds above
a certain frequency
Band Pass Filter: only allow sounds in a
given frequency range
used for cutting “highs” and/or “lows”
3D Sound Methods
Head Relative Transfer Function (HRTF)
• used in stereo speaker config
• dynamically changes balance for L/R
• reduces high frequencies if behind
Today:
Dolby Surround Sound – 5.1, 6.1, 7.2!
Environmental Effects
Echo: early reflections
Reverberation (reverb): late reflections
Diffusion: the “breaking up” of a sound
reflecting off of a rough surface (carpet)
Obstruction: the blocking of a sound’s direct
path to the ear
Occlusion: high freqs being blocked by a
material, while low freqs pass through
(car bass with windows up, underwater)
Environmental Effects
Two current standards:
• I3DL2: established by the Interactive
Audio Special Interest Group (IASIG)
• EAX: created by Creative Labs for
SoundBlaster audio cards – multiple
versions exist (1.0, 2.0, 3.0)
Difference in sound: ???
Half Life 2: Soundscape DSP
Audio Systems
MIDI: Musical Instrument Digital Interface
• file contains sound “instructions”
• metaphor: sheet music for a computer
• uses preloaded sound banks
Digital Audio: actual recording
• generally much better sound quality
• more “real”
• downside: much bigger file sizes
Audio Systems
MIDI:
Digital Audio:
Advanced Audio Programming
• Programmers should not have to deal
with audio!
• Audio scripts handle production of
sound (HL2 DSP presets)
• Common problems: sound variation,
repetition, looping, ambience
Advanced Music Programming
• HALO 2: Quantum Audio – music has
starts, ends, middles, transitions
• Interactive Music: “musical boxcars”
Voice Interaction
Phoneme: individual voice sound
Lip Synching: matching phonemes to
mouth animation
Voice Playback: generating words using
phonemes
Voice Recognition: decoding voice input to
understood text of some kind
Dragon Naturally Speaking
Half Life 2: Phoneme Extractor
When you’re Project Lead:
• Create an audio development process
Pre-production:
Production:
audio engine
SFX workflow
game style
Music workflow
file system
VO workflow
Foley workflow
When you’re Project Lead:
• Create an audio asset list
“How many sounds can this make?”
“How often will we hear this?”
“How much music can/should we use?”
• Excel spreadsheets are commonly used
When you’re Project Lead:
• Understand audio budget needs
•Audio Designer
•Licenses (sounds, middleware)
•Audio engineers
•Field Recording
•Composer
•Hired musicians
•Voice actors
•Music composition
•Recording equipment
•Canned music, SFX, foley
•Audio software
•SFX research
•Audio hardware
•Sound processors
•Music gear
•Sound file storage
When you’re Project Lead:
• Integrate your audio team
• Audio team works with art
• Audio team works with animation
• Audio team works with design
• Audio team works with story writers
In short: COMMUNICATE!
The End
Thanks for listening