DSBCAPS

The DSBCAPS structure specifies the capabilities of a DirectSound buffer object, for use by the IDirectSoundBuffer::GetCaps method.

typedef struct {

DWORD dwSize;

DWORD dwFlags;

DWORD dwBufferBytes;

DWORD dwUnlockTransferRate;

DWORD dwPlayCpuOverhead;

} DSBCAPS, *LPDSBCAPS;

typedef const DSBCAPS *LPCDSBCAPS;

Members

dwSize

Size of the structure, in bytes. This member must be initialized before the structure is used.

dwFlags

Flags that specify buffer-object capabilities.

DSBCAPS_CTRL3D

The buffer is either a primary buffer or a secondary buffer that uses 3-D control. To create a primary buffer, the dwFlags member of the DSBUFFERDESC structure should include the DSBCAPS_PRIMARYBUFFER flag.

DSBCAPS_CTRLFREQUENCY

The buffer must have frequency control capability.

DSBCAPS_CTRLPAN

The buffer must have pan control capability.

DSBCAPS_CTRLVOLUME

The buffer must have volume control capability.

DSBCAPS_GETCURRENTPOSITION2

Indicates that IDirectSoundBuffer::GetCurrentPosition should use the new behavior of the play cursor. In DirectSound in DirectX 1, the play cursor was significantly ahead of the actual playing sound on emulated sound cards; it was directly behind the write cursor. Now, if the DSBCAPS_GETCURRENTPOSITION2 flag is specified, the application can get a more accurate play position. If this flag is not specified, the old behavior is preserved for compatibility. Note that this flag affects only emulated sound cards; if a DirectSound driver is present, the play cursor is accurate for DirectSound in all versions of DirectX.

DSBCAPS_GLOBALFOCUS

The buffer is a global sound buffer. With this flag set, an application using DirectSound can continue to play its buffers if the user switches focus to another application, even if the new application uses DirectSound. The one exception is if you switch focus to a DirectSound application that uses the DSSCL_EXCLUSIVE or DSSCL_WRITEPRIMARY flag for its cooperative level. In this case, the global sounds from other applications will not be audible.

DSBCAPS_LOCHARDWARE

The buffer is in hardware memory and uses hardware mixing.

DSBCAPS_LOCSOFTWARE

The buffer is in software memory and uses software mixing.

DSBCAPS_MUTE3DATMAXDISTANCE

The sound is reduced to silence at the maximum distance. The buffer will stop playing when the maximum distance is exceeded, so that processor time is not wasted.

DSBCAPS_PRIMARYBUFFER

Indicates that the buffer is a primary sound buffer. If this value is not specified, a secondary sound buffer will be created.

DSBCAPS_STATIC

Indicates that the buffer will be used for static sound data. Typically, these buffers are loaded once and played many times. These buffers are candidates for hardware memory.

DSBCAPS_STICKYFOCUS

Changes the focus behavior of the sound buffer. This flag can be specified in an IDirectSound::CreateSoundBuffer call. With this flag set, an application using DirectSound can continue to play its sticky focus buffers if the user switches to another application not using DirectSound. In this situation, the application's normal buffers are muted, but the sticky focus buffers are still audible. This is useful for nongame applications, such as movie playback (DirectShow™), when the user wants to hear the soundtrack while typing in Microsoft Word or Microsoft Excel, for example. However, if the user switches to another DirectSound application, all sound buffers, both normal and sticky focus, in the previous application are muted.

dwBufferBytes

Size of this buffer, in bytes.

dwUnlockTransferRate

Specifies the rate, in kilobytes per second, at which data is transferred to the buffer memory when IDirectSoundBuffer::Unlock is called. High-performance applications can use this value to determine the time required for IDirectSoundBuffer::Unlock to execute. For software buffers located in system memory, the rate will be very high because no processing is required. For hardware buffers, the rate might be slower because the buffer might have to be downloaded to the sound card, which might have a limited transfer rate.

dwPlayCpuOverhead

Specifies the processing overhead as a percentage of main processing cycles needed to mix this sound buffer. For hardware buffers, this member will be 0 because the mixing is performed by the sound device. For software buffers, this member depends on the buffer format and the speed of the system processor.

Remarks

The DSBCAPS structure contains information similar to that found in the DSBUFFERDESC structure passed to the IDirectSound::CreateSoundBuffer method, with some additional information. Additional information includes the location of the buffer (hardware or software) and some cost measures (such as the time to download the buffer if located in hardware, and the processing overhead to play the buffer if it is mixed in software).

Note The dwFlags member of the DSBCAPS structure contains the same flags used by the DSBUFFERDESC structure. The only difference is that in the DSBCAPS structure, either the DSBCAPS_LOCHARDWARE or DSBCAPS_LOCSOFTWARE flag will be specified, according to the location of the buffer memory. In the DSBUFFERDESC structure, these flags are optional and are used to force the buffer to be located in either hardware or software.

See Also

IDirectSound::CreateSoundBuffer, IDirectSoundBuffer::GetCaps