Sound Engine Evaluation for Computer Games

1
Sound Engine Evaluation for Computer Games

• Case Study fmod
• Jyun-Ming Chen

2
Typical Game Loop

• Roles of music/sound
• BGM (background music)
• Sound effect

3
Microsoft SDK
Need more sophisticated tools!

• BGM (Midi)
• mciSendCommand ()
• Sound (Wave)
• sndPlaySound
• See msdn for details
• Ex midi_wav.zip on webhd2/game-ex

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Check List

• BGM
• File formats supported mid, mp3, mod,
• Looping
• Early termination
• Volume control
• Sound effects
• File formats supported
• Trigger mechanism
• Reverb and other DSP FX (e.g., room effects)
• Pre-load to avoid delay in first play

• General
• Mixing capability (how many sounds can be mixed
  at one time)
• Spatial sound
• Position 3D vs. panning
• Velocity Doppler supported?
• Occlusion?!
• Sync capability
• sound to action
• Action to sound
• Others
• CPU overhead

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Case Study fmod

• Cross platform audio library (Win32, Linux, mac,
  WinCE, PS2, Xbox, )
• Free unless for commercial use

6
Documentation
FSOUND for sound effect
FMUSIC for bgm
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FSOUND API
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Initialization
Required for both FMUSIC FSOUND
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FSOUND_Sample

• Load, Free
• SetMode LOOP normal bidi off
• Get/SetLoopPoints
• GetLength
• Get/SetMinMaxDistance (min is the distance where
  the sound starts to attenuate)
• increase the min_distance of a sound to make it
  'louder' in a 3d world, and decrease it to make
  it 'quieter' in a 3d world.

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FSOUND_Stream

• If the PCM data (wav) or compressed file (ogg,
  mp3, ) is too big to be read in as a sample, we
  can use stream functions to read it (decompress
  it on-the-fly)
• Certain functionalities are restricted

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Channel Functions

• FSOUND_PlaySound, PlaySoundEx
• FSOUND_FREE Choose a free channel to play in
• Returns the channel selected
• Extended version can play paused (allow
  attributes to be changed, then play)
• FSOUND_SetFrequency (channel, 11025)
• FSOUND_SetVolume(channel, 255)
• FSOUND_SetPan(channel, 255)
• FSOUND_SetPaused(channel, FALSE)
• FSOUND_StopSound

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3d

• FSOUND_Update()
• This updates the 3d sound engine, and should be
  called once a game frame.

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Listener Attributes

• Pos
• Vel (per second)
• Fx, fy, fz (forward orientation vector)
• Tx, ty, tz (top-up orientation vector)
• Fmod uses left-hand coordinate system

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FMUSIC (mid, mod mp3)

• LoadSong
• PlaySong can play more than one music (yes, but
  why?)
• SetPaused
• SetLooping default TRUE
• SetPanSeparation, SetMasterSpeed, SetMasterVolume
• StopSong, StopAllSongs
• FreeSong
• SetReverb (midi only)