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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 stuffComing soon: cool stuff
Definitions
Frequency: speed of wave oscillationMeasured in Hertz (Hz)
Pitch: a particular constant frequencyHertz (Hz): number of oscillations per
seconddecibels (dB): measure of the degree of
amplitudeNote: a predefined pitch used in music
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?!That’s really high, so who cares?!
Common Sampling Rates
“CD Audio” quality: 16 bit, 44.1 kIP Voice Chat (BattleCom, TeamSpeak):8 – 16 bit, 16k – 24k sample rateBurger King drive-thru: ???High-End sound cards support: 24/96, 24/192
The Tradeoff: Performance vs. QualityThe 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 MechWarrior 2: used hybrid CD for music!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, ReleaseCould define a variety of sound aspects(pitch, volume, rate of repetition)
What would the envelopes look like for:What would the envelopes look like for:• Revving a car engineRevving a car engine• Cymbal crashCymbal crash• John Williams choirJohn Williams choir
Other Sound Parameters
Pan: the “left/right” location of the soundVolume: ratio of amplitude playedPitch/Frequency: can be assigned to
override a sound’s actual pitch3DGS:sound mySound = <gosh.wav>;
snd_tune(mySound, 50, 100, -100);
play mySound at 50% vol, 100% freq, leftplay 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 behindToday: Dolby Surround Sound – 5.1, 6.1, 7.2!
Environmental Effects
Echo: early reflectionsReverberation (reverb): late reflectionsDiffusion: the “breaking up” of a sound
reflecting off of a rough surface (carpet)Obstruction: the blocking of a sound’s
direct path to the earOcclusion: 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: ???Difference in sound: ???
Audio Systems
MIDI: Musical Instrument Digital Interface• file contains sound “instructions”• metaphor: sheet music for a computer• uses preloaded sound banksDigital Audio: actual recording• generally much better sound quality• more “real”• downside: much bigger file sizes
Advanced Audio Programming
• Programmers should not have to Programmers should not have to deal with audio!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 soundLip Synching: matching phonemes to
mouth animationVoice Playback: generating words
using phonemesVoice Recognition: decoding voice
input to understood text of some kind
Dragon Naturally SpeakingDragon Naturally Speaking
Half Life 2: Phoneme Extractor
When you’re Project Lead:
• Create an audio development process
Pre-production: Production:audio engine SFX workflowgame style Music workflowfile 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
•Audio engineers
•Composer
•Voice actors
•Recording equipment
•Audio software
•Audio hardware
•Music gear
•Licenses (sounds, middleware)
•Field Recording
•Hired musicians
•Music composition
•Canned music, SFX, foley
•SFX research
•Sound processors
•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!In short: COMMUNICATE!