1. Chapter 13 DirectSound 로 잡음 만들기

2. 2 History 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

3. 3 Extension of DirectSound and Music DirectSound3D –3D sound support DirectMusic –Playing MIDI files –DLS (Downloadable Sounds) data –Sound can be selected by game users on-the-fly.

4. 4 DirectSound Related components –DirectSound3D –DirectSoundCapture

5. 5 DirectSound Components Run-time.DLL Compile-time library and header (DSOUND.LIB and DSOUND.H)

6. 6 DirectSound Interfaces - 1

7. 7 DirectSound 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 (sound RAM) IDirectSoundCapture –capture (record), ex) record player’s name!, voice recognition IDirectSoundNotify –Send message back to DirectSound

8. 8 Sound Buffer

9. 9 Starting Up DirectSound LPDIRECTSOUND lpds; DirectSoundCreate(NULL, &lpds, NULL); // lpGuid, lpDS, … // lpGuid = NULL : default sound card

10. 10 Understanding 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 buffer: 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.

11. 11 Setting the Cooperation Level if (FAILED(lpds->SetCooperativeLevel(main_window_handle, DSSCL_NORMAL))) { … }

12. 12 Primary 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)

13. 13 Secondary Buffers Can be any size SRAM or System memory? –Sounds on SRAM: low-cost for processing Two Kinds of Secondary Buffers –Static –Streaming

14. 14 Creating Secondary Sound Buffers // After filling the sound buffer description structure here. …. CreateSoundBuffer(LPDSBUFFERDESC lpdsbd, LPDIRECTSOUNDBUFFER lpdsbuffer, NULL);

15. 15 Sound 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

16. 16 WAVEFORMAT 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;

17. 17 Sound 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

18. 18 Sound 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 */ }

19. 19 Writing 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, audio_length_2))) { … }

20. 20 Locking Sound Buffer

21. 21 Rendering Sounds Playing HRESULT Play( DWORD dwReserved1, DWORD dwReserved2, // both 0 DWORD dwFlags); // control flags to play // Example lpdsbuffer->Play(0, 0, DSBPLAY_LOOPING); // or flag=0 (no looping) Stopping lpdsbuffer->Stop( )

22. 22 DEMO: PROG13_2.CPP

23. 23 Controlling Sound - 1 Controlling the Volume lpdsbuffer->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)

24. 24 Controlling Sounds - 4 Frequency –lpdsbuffer->SetFrequency(22050) : 만약 원래가 11025 Hz 라 면 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)

25. 25 Getting Information - 1 Determining the Capability of the H/W –GetCaps(LPDSCAPS lpDSCaps); –DSCAPS structure typedef { DWORD dwSize; … DWORD dwMaxSecondarySampleRate; … } DSCAPS;

26. 26 Getting 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;

27. 27 Getting 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