DSBUFFERDESC

The DSBUFFERDESC type describes the necessary characteristics of a new DirectSoundBuffer object. This type is used by the DirectSound.CreateSoundBuffer method.

Type DSBUFFERDESC
    lBufferBytes As Long 
    lFlags As CONST_DSBCAPSFLAGS 
End Type

Members

lBufferBytes

Size of the new buffer, in bytes. This value must be 0 when creating primary buffers. For secondary buffers, the minimum and maximum sizes allowed are specified by DSBSIZE_MIN and DSBSIZE_MAX, defined in Dsound.h.

lFlags

Identifies the capabilities to include when creating a new DirectSoundBuffer object. Specify one or more of the following constants of the CONST_DSBCAPSFLAGS enumeration:

DSBCAPS_CTRL3D

The buffer is either a primary buffer or a secondary buffer that uses 3-D control.

DSBCAPS_CTRLFREQUENCY

The buffer must have frequency control capability.

DSBCAPS_CTRLPAN

The buffer must have pan control capability.

DSBCAPS_CTRLPOSITIONNOTIFY

The buffer must have position notification capability. On VxD drivers, if a sound buffer is created with DSBCAPS_CTRLPOSITIONNOTIFY, this buffer will always be a software buffer. This is because the VxD driver model doesn't support the notify interface. With WDM drivers, a position notification enabled buffer may be in hardware, if hardware is available. Calling DirectSoundBuffer.Play with the DSBPLAY_LOCHARDWARE flag will fail when playing a buffer created with this flag set.

DSBCAPS_CTRLVOLUME

The buffer must have volume control capability.

DSBCAPS_GETCURRENTPOSITION2

Indicates that DirectSoundBuffer.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_LOCDEFER

The buffer can be assigned to a hardware or software resource during playing. This flag must be set for buffers that will use the new voice allocation and management features of DirectX 7.0.

DSBCAPS_LOCHARDWARE

Forces the buffer to use hardware mixing, even if DSBCAPS_STATIC is not specified. If the device does not support hardware mixing or if the required hardware memory is not available, the call to the DirectSound.CreateSoundBuffer method will fail. The application must ensure that a mixing channel will be available for this buffer; this condition is not guaranteed.

DSBCAPS_LOCSOFTWARE

Forces the buffer to be stored in software memory and use software mixing, even if DSBCAPS_STATIC is specified and hardware resources are available.

DSBCAPS_MUTE3DATMAXDISTANCE

The sound is to be 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 a DirectSound.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.

Remarks

The DSBCAPS_LOCHARDWARE and DSBCAPS_LOCSOFTWARE flags used in the lFlags member are optional and mutually exclusive. DSBCAPS_LOCHARDWARE forces the buffer to reside in memory located in the sound card. DSBCAPS_LOCSOFTWARE forces the buffer to reside in main system memory, if possible.

These flags are also defined for the lFlags member of the DSBCAPS type, and when used there, the specified flag indicates the actual location of the DirectSoundBuffer object.

When creating a primary buffer, applications must set the lBufferBytes member to 0; DirectSound will determine the optimal buffer size for the particular sound device in use. To determine the size of a created primary buffer, call DirectSoundBuffer.GetCaps.

The actual values for 8-bit buffered data is 0 to 256 and -32,000 to 32,000 for 16-bit buffered data.

Note  Sound buffers created with the DSBCAPS_CTRLPOSITIONNOTIFY flag must set a notification event. If you create a sound buffer with the NOTIFY flag, but don't actually set any notifications, the behavior is undefined. You may experience sounds being played back twice. Therefore, applications should not use DSBCAPS_CTRLPOSITIONNOTIFY unless they actually set a notification event.

See Also

DirectSound.CreateSoundBuffer