CSE 380 – Computer Game Programming
Audio Engineering
Audio Engineering
• For games:
– Sound Effects and Music
• Sometimes overlooked
• If not done right, can ruin a game
• If done right, enhances
experience
– seamless with gameplay
– not too obvious
What do you need sound effects for?
• Discernable Game Events
– Collisions
• tied to collision response
– Movement
• footfalls, rockets,
• tied to sprite state
– Ambiance
• background noise
• tied to game state
– Gameplay Events
• tied to victory, area triggers, power-ups, death, etc
• to help give your game meaningful play
Recording & Exporting Sounds
• Lots of tools to use
• Recommendation: Audacity
– free
– easy to learn to use
– exports to many formats
• Ex: mp3
– easy to mix sounds
• to make complex sound effects
– http://audacity.sourceforge.net/
Sound Properties
• Frequency
– measures speed of sound vibrations
– measured in cycles per second (Hz)
– audible range for human ear: 20Hz – 20,000Hz
• Intensity
– amount of air molecules pushed around by sound
– pressure applied by sound wave
– measured in decibels (dB), a log scale
• sound of whispering 5ft. Away: 20 dB
• sound of thunder: 120dB
Sound File Formats
• WAV
– stores raw sound data, is the largest format
– easy on CPU
• MP3/M4A, OGG, & WMA
– compressed formats
~10:1 compression over WAV
– negligible quality difference from WAV
– decompression CPU hit
• MIDI
– programmed sound
Long vs. Short sound files
• For short sound effects:
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store as MP3/OGG/etc.
decompress data in memory at load time
play as needed in decompressed format
heavy on memory, light on CPU
• For long sound effects or music:
– store as MP3/OGG/etc.
– play in compressed format
– again, heavy on CPU usage, light on memory
Music
• What role does music play?
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emotion
recognition
themes
fill the void
• Sound & Music:
– should compliment the gameplay, not overwhelm it
For the programmer
• Lots of libraries
• Keep game code platform independent
• Options:
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FMod and tools (FMod Designer, etc.)
DirectSound (deprecated)
XAudio/XACT (soon to be deprecated
XAudio2/XACT3 (soon part of Windows)
• See DirectX Documentation for C++
– lots of other libraries as well (Miles, WWise, etc.)
Microsoft Audio Technologies
For us?
• XACT3
– designer controlled content
– easy audio tweaking
• XAudio2
– API to build sound engine
What’s so great about that?
• The audio designer can focus on audio
• Easy to:
– test many different sound effects & songs
– choose the right sounds & music
– alter/improve sounds & music
• All without having to bother a programmer
• 3 CPU cores
XBox 360
– each with 2 hardware threads
– Common approach:
• run XAudio2 and XACT on their own threads
• Has real-time XMA decoder hardware
– XMA is XBox format for WMA
– Windows uses ADPCM
• Windows is more complicated
– How many cores?
• GetLogicalProcessorInformation
XAudio Tools/APIs
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XACT
XACT Command-Line Tool
AdpcmEncode
Wave Merge Tool
XMA Command-Line Encoder
XMA2 Command-Line Encoder
xWMA Command-Line Encoder
X3DAudio
XAPO
XAPOFX
XMAEncoder
My Recommendation
• Each team pick an audio engineer for Benchmark 3
• That person will become the XACT3/XAudio2 expert
– start with the DirectX Audio manual
• The other team members can continue to concentrate on
gameplay
• Go to DirectX install directory
• Go to Samples/
XACT Terminology
• Start by reading about:
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wave
wave bank
sound
sound bank
track
events
cues
IXAudio2
• Core of the engine
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enumerate available audio devices
configure properties
create & destroy voices
monitor performance
• It’s a COM object
– create after CoInitializeEx
• One can create multiple instances
– each operates in own thread
Voices
• Used to process, manipulate, and play audio data
– Source Voices
• used to stream audio data
– Submix Voices
• manipulate audio data
– Mastering Voices
• send data to audio hardware
Audio Graph
• A collection of voices
To Play a Sound
1. Initialize XAudio2
2. Load Audio Data
– init a WAVEFORMATEX & XAUDIO2_BUFFER
3. Create a Source Voice
4. Pass data to the voice
5. Start the voice
For the Designer
• Determine all the sound effects for your game
• Produce such a list right now
• This is a to-do list of recordings to make
A very good reference to start with
http://www.ultimategameprogramming.com/BeginningDirectX11%5C58958_App_B_rev01_lores.pdf
References
• Programming with DirectX : Sound in DirectX – XAudio 2
– http://programming4.us/multimedia/3830.aspx
• Game Coding Complete, 4th Edition
– McShaffry/Graham
• DirectX Software Development Kit Documentation