Sound Engine Evaluation for Computer Games

Case Study: fmod

Jyun-Ming Chen

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Typical Game Loop

Roles of music/soundBGM (background music)Sound effect

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Microsoft SDK

BGM (Midi) mciSendCommand (…)

Sound (Wave) sndPlaySound

See msdn for details

Ex: midi_wav.zip on webhd2/game-ex

Need more sophisticated tools!

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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

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DocumentationFSOUND: for sound

effect

FMUSIC: for bgm

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FSOUND API

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InitializationRequired for

both FMUSIC & FSOUND

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FSOUND_Sample

Load, FreeSetMode: LOOP normal | bidi | offGet/SetLoopPointsGetLengthGet/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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FMUSIC (mid, mod; mp3)

LoadSongPlaySong: can play more than one music (yes, but why?)SetPausedSetLooping: default TRUESetPanSeparation, SetMasterSpeed, SetMasterVolumeStopSong, StopAllSongsFreeSongSetReverb (midi only)

OpenGL Tests

Webhd2/game-ex/fmod_opengl_tests

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Basics

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BgmusicFMUSIC PLAYS S3M AND MID; NOT MP3 (sequenced file, not PCM-type)

OK for mod files

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Stream

Works for mp3, ogg, wavOnly wav can store cue point (for sync)

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3dsound

FSOUND_Update():

This updates the 3d sound engine, and should be called whether sound source or listener changes position

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Listener Attributes

Float *posFloat *Vel (per second) NULL to ignore

Fx, fy, fz (forward orientation unit vector)Tx, ty, tz (top-up orientation unit vector)

x

y

z

Global Axes in Fmod

Left-handed

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Doppler FSOUND_3D_SetDopplerFactor (4.0);

Commonly Used APIs

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Init and Close

Load and Free sample

Sound API

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