Chapter 13Chapter 13

DirectSoundDirectSound 로 잡음 만들기 로 잡음 만들기

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History of Sound ProgrammingHistory of Sound Programming

• Sound programming always gets put off until the end• DOS

– Third party sound libraries: Miles Sound System, Diamondware Sound Toolkit… high price

• Windows– Sound and multimedia support: not for real-time video game– DirectSound and DirectMusic

• free• high performance• Support for million different sound card

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Extension of DirectSound and Extension of DirectSound and MusicMusic• DirectSound3D

– 3D sound support

• DirectMusic– Playing MIDI files– DLS (Downloadable Sounds) data– Sound can be selected by game users on-the-fly.

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DirectSoundDirectSound

• Related components– DirectSound3D– DirectSoundCapture

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DirectSound ComponentsDirectSound Components

• Run-time .DLL• Compile-time library and header (DSOUND.LIB and

DSOUND.H)

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DirectSound Interfaces - 1DirectSound Interfaces - 1

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DirectSound Interfaces - 2DirectSound Interfaces - 2

• IUnknown• IDirectSound

– main COM object, one per a sound card

• IDirectSoundBuffer– primary buffer : currently playing sound– secondary buffer : stored sound, system memory or SRAM (s

ound RAM)

• IDirectSoundCapture– capture (record), ex) record player’s name!, voice recognition

• IDirectSoundNotify– Send message back to DirectSound

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Sound BufferSound Buffer

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Starting Up DirectSoundStarting Up DirectSound

LPDIRECTSOUND lpds;

DirectSoundCreate(NULL, &lpds, NULL); // lpGuid, lpDS, …

// lpGuid = NULL : default sound card

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Understanding Cooperation LevelUnderstanding Cooperation Level

• Normal Cooperation– Play sound for the game application + other applications– Default primary buffer of 22KHz, stereo, 8-bit 가 제공됨

• Priority Cooperation– First access to all the h/w– Only necessary for changing the data format of the primary bu

ffer: ex) 16-bit sample ..

• Exclusive Cooperation– Same as Priority, your application will be audible only when it’

s in the foreground.

• Write-Primary Cooperation– Total control for the primary buffer.

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Setting the Cooperation LevelSetting the Cooperation Level

if (FAILED(lpds->SetCooperativeLevel(main_window_handle, DSSCL_NORMAL))) { … }

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Primary Sound BufferPrimary Sound Buffer

• Mixing h/w (or s/w) on the sound card• Processes all the time • You don’t need to manually control the primary buffer• DirectSound create one primary buffer for you (when

we use DSSCL_NORMAL). • 22 KHZ stereo in 8-bit (default)

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Secondary BuffersSecondary Buffers

• Can be any size• SRAM or System memory?

– Sounds on SRAM: low-cost for processing

• Two Kinds of Secondary Buffers– Static – Streaming

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Creating Secondary Sound BuffersCreating Secondary Sound Buffers

// After filling the sound buffer description structure here. ….

CreateSoundBuffer(LPDSBUFFERDESC lpdsbd,

LPDIRECTSOUNDBUFFER lpdsbuffer,

NULL);

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Sound Buffer DescriptionSound Buffer Description

typedef struct {

DWORD dwSize;

DWORD dwFlags;

DWORD dwBufferBytes; // buffer size in bytes

DWORD dwReserved; // unused

LPWAVEFORMATEX lpwfxFormat; // the wave format

} DSBUFFERDESC;

• Usual Flag Combination– DSBCAPS_CTRLDEFAULT : default control (volume, pan, frequency)– DSBCAPS_STATIC : static (not streaming)– DSBCAPS_LOCSOFTARE : system memory

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WAVEFORMAT structureWAVEFORMAT structure

typedef structure { WORD wFormatTag; // always WAVE_FORMAT_PCM WORD nChannels; // 1 for mono, 2 for stereo DWORD nSamplesPerSec; // Samples per second 11025 or 22050 … DWORD nAvgBytesPerSec; // average data rate (SamplePerSec * nBlockAlign) WORD nBlockAlign; // nchannels * bytespersample WORD wBitsPerSample; // Bits per sample WORD cbSize; // advanced, 0} WAVEFORMATEX;

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Sound Buffer Creation Example - 1Sound Buffer Creation Example - 1

ex) 11 KHz, mono, 8-bit with enough storage for 2 secs

LPDIRECTSOUNDBUFFER lpdsbuffer;

DSBUFFERDESC dsbd; // description

WAVEFORMATEX pcmwf; // format description

// WAVEFORMAT Creation

memset(&pcmwf, 0, sizeof(WAVEFORMATEX));

pcmwf.wFormatTag = WAVE_FORMAT_PCM; // always

pcmwf.nChannels = 1; // Mono

pcmwf.nSamplesPerSec = 11025; // 11 kHz sampling

pcmwf.nBlockAlign = 1; // 1 channel * 1 bytes / sample

pcmwf.nAvgBytesPerSec = pcmwf.nSamplesPerSec * pcmwf.nBlockAlign;

pcmwf.wBitsPerSample = 8; // 8bits / sample

pcmwf.cbSize = 0; // always 0

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Sound Buffer Creation Example - 2Sound Buffer Creation Example - 2

// Create DSBUFFERDESC

memset(dsbd, 0, sizeof(DSBUFFERDESC));

dsbd.dwSize = sizeof(DSBUFFERDESC);

dsbd.dwFlags = DSBCAPS_CTRLDEFAULT | DSBCAPS_STATIC | DSBCAPS_LOCSOFTARE;

dsbd.dwBufferBytes = 22050; // for 2 seconds with 11 kHz

dsbd.lpwfxFormat = &pcmwf;

// Create the buffer

if (FAILED(lpds->CreateSoundBuffer(&dsbd, &lpdsbuffer, NULL)))

{ /* error */ }

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Writing Data to Secondary BuffersWriting Data to Secondary Buffers

• Lock the buffer• Fill the buffer• Unlock the buffer

UCHAR *audio_ptr_1, *audio_ptr_2; int audio_length_1, audio_length_2;

if (FAILED(lpdsbuffer->Lock(0, 1000, (void **)audio_ptr_1, &audio_length_1, (void **)audio_ptr_2, &audio_length_2, DSBLOCK_ENTIREBUFFER))) {…}…. if (FAILED(lpdsbuffer->Unlock(audio_ptr_1, audio_length_1, audio_ptr_2, au

dio_length_2))) { … }

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Locking Sound BufferLocking Sound Buffer

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Rendering SoundsRendering Sounds

• Playing

HRESULT Play(

DWORD dwReserved1, DWORD dwReserved2, // both 0

DWORD dwFlags); // control flags to play

// Examplelpdsbuffer->Play(0, 0, DSBPLAY_LOOPING); // or flag=0 (no looping)

• Stopping

lpdsbuffer->Stop( )

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DEMO: PROG13_2.CPPDEMO: PROG13_2.CPP

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Controlling Sound - 1Controlling Sound - 1

• Controlling the Volumelpdsbuffer->SetVolume(LONG lVolume)lVolume = 0 : max sound (0 dB)lVolume = -10000 : no sound (-100 dB)

• Volume control macro (0 ~ 100)#define DSVOLUME_TO_DB(volume) ((DWORD)(-30*(100-volume)))lpdsbuffer->SetVolume(DSVOLUME_TO_DB(50)); // 50% volume// -30 * (100 – 50) = -1500 (50%)// -30 * (100 – 100) = 0 (maximum)// -30 * (100 – 0) = -30 * 100 = -3000 (minimum)

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Controlling Sounds - 4Controlling Sounds - 4

• Frequency– lpdsbuffer->SetFrequency(22050) : 만약 원래가 11025 Hz

라면 속도가 2 배로 된다 .

• Panning– lpdsbuffer->SetPan(0) : center– lpdsbuffer->SetPan(-10000) : right channel = -100dB– lpdsbuffer->SetPan(10000) : left channel = -100dB– lpdsbuffer->SetPan(-500) : right channel = -5 dB (more sound

to left channel)

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Getting Information - 1Getting Information - 1

• Determining the Capability of the H/W– GetCaps(LPDSCAPS lpDSCaps); – DSCAPS structure

typedef {

DWORD dwSize;

…

DWORD dwMaxSecondarySampleRate;

…

} DSCAPS;

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Getting Information - 2Getting Information - 2

• Determining the Info of Buffer GetCaps(LPDSBCAPS lpDSBCaps);

typdef struct {

…

DWORD dwBufferBytes;

DWORD UnlockTransferRate; // Sample rate

DWORD dwPlayCpuOverhead; // % of processor to mix this sound …

} DSBCAPS;

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Getting Information - 3Getting Information - 3

• Determining the Status of Sound Play– lpdsbuffer->GetStatus(&status); – Status

• DSBSTATUS_BUFFERLOST : something wrong!

• DSBSTATUS_LOOPING : looped mode

• DSBSTATUS_PLAYING : sound is now playing

• Other Information– Retrieve volume, pan, frequency setting etc.. – See DirectSound documents