DSCAPS

  • Article

This structure specifies the capabilities of a DirectSound device for use by the IDirectSound::GetCaps method.

typedef { 
  DWORD dwSize; 
  DWORD dwFlags;  
  DWORD dwMinSecondarySampleRate; 
  DWORD dwMaxSecondarySampleRate; 
  DWORD dwPrimaryBuffers; 
  DWORD dwMaxHwMixingAllBuffers; 
  DWORD dwMaxHwMixingStaticBuffers; 
  DWORD dwMaxHwMixingStreamingBuffers; 
  DWORD dwFreeHwMixingAllBuffers; 
  DWORD dwFreeHwMixingStaticBuffers; 
  DWORD dwFreeHwMixingStreamingBuffers; 
  DWORD dwMaxHw3DAllBuffers; 
  DWORD dwMaxHw3DStaticBuffers; 
  DWORD dwMaxHw3DStreamingBuffers; 
  DWORD dwFreeHw3DAllBuffers; 
  DWORD dwFreeHw3DStaticBuffers; 
  DWORD dwFreeHw3DStreamingBuffers; 
  DWORD dwTotalHwMemBytes; 
  DWORD dwFreeHwMemBytes; 
  DWORD dwMaxContigFreeHwMemBytes; 
  DWORD dwUnlockTransferRateHwBuffers; 
  DWORD dwPlayCpuOverheadSwBuffers; 
  DWORD dwReserved1; 
  DWORD dwReserved2; 
} DSCAPS, *LPDSCAPS; 
 
typedef const DSCAPS *LPCDSCAPS;

Members

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

  • dwFlags
    Specifies device capabilities. Can be one or more of the following values.

    Flag Description
    DSCAPS_CERTIFIED This driver has been tested and certified by Microsoft.
    DSCAPS_CONTINUOUSRATE The device supports all sample rates between the dwMinSecondarySampleRate and dwMaxSecondarySampleRate member values. Typically, this means that the actual output rate will be within +/- 10 Hertz (Hz) of the requested frequency.
    DSCAPS_EMULDRIVER The device does not have a DirectSound driver installed, so it is being emulated through the waveform-audio functions. Performance degradation should be expected.
    DSCAPS_PRIMARY16BIT The device supports primary sound buffers with 16-bit samples.
    DSCAPS_PRIMARY8BIT The device supports primary buffers with 8-bit samples.
    DSCAPS_PRIMARYMONO The device supports monophonic primary buffers.
    DSCAPS_PRIMARYSTEREO The device supports stereo primary buffers.
    DSCAPS_SECONDARY16BIT The device supports hardware-mixed secondary sound buffers with 16-bit samples.
    DSCAPS_SECONDARY8BIT The device supports hardware-mixed secondary buffers with 8-bit samples.
    DSCAPS_SECONDARYMONO The device supports hardware-mixed monophonic secondary buffers.
    DSCAPS_SECONDARYSTEREO The device supports hardware-mixed stereo secondary buffers.

  • dwMinSecondarySampleRate and dwMaxSecondarySampleRate
    Minimum and maximum sample rate specifications that are supported by this device's hardware secondary sound buffers.

  • dwPrimaryBuffers
    Number of primary buffers supported. This value will always be 1.

  • dwMaxHwMixingAllBuffers
    Specifies the total number of buffers that can be mixed in hardware. This member can be less than the sum of dwMaxHwMixingStaticBuffers and dwMaxHwMixingStreamingBuffers. Resource tradeoffs frequently occur.

  • dwMaxHwMixingStaticBuffers
    Specifies the maximum number of static sound buffers.

  • dwMaxHwMixingStreamingBuffers
    Specifies the maximum number of streaming sound buffer.

  • dwFreeHwMixingAllBuffers, dwFreeHwMixingStaticBuffers, and dwFreeHwMixingStreamingBuffers
    Description of the free, or unallocated, hardware mixing capabilities of the device. An application can use these values to determine whether hardware resources are available for allocation to a secondary sound buffer. Also, by comparing these values to the members that specify maximum mixing capabilities, the resources that are already allocated can be determined.

  • dwMaxHw3DAllBuffers, dwMaxHw3DStaticBuffers, and dwMaxHw3DStreamingBuffers
    Description of the hardware 3-D positional capabilities of the device.

  • dwFreeHw3DAllBuffers, dwFreeHw3DStaticBuffers, and dwFreeHw3DStreamingBuffers
    Description of the free, or unallocated, hardware 3-D positional capabilities of the device.

  • dwTotalHwMemBytes
    Size, in bytes, of the amount of memory on the sound card that stores static sound buffers.

  • dwFreeHwMemBytes
    Size, in bytes, of the free memory on the sound card.

  • dwMaxContigFreeHwMemBytes
    Size, in bytes, of the largest contiguous block of free memory on the sound card.

  • dwUnlockTransferRateHwBuffers
    Description of the rate, in kilobytes per second, at which data can be transferred to hardware static sound buffers. This and the number of bytes transferred determines the duration of a call to the IDirectSoundBuffer::Unlock method.

  • dwPlayCpuOverheadSwBuffers
    Description of the processing overhead, as a percentage of the central processing unit, needed to mix software buffers (those located in main system memory). This varies according to the bus type, the processor type, and the clock speed.

    The unlock transfer rate for software buffers is 0 because the data need not be transferred anywhere. Similarly, the play processing overhead for hardware buffers is 0 because the mixing is done by the sound device.

  • dwReserved1, dwReserved2
    Reserved for future use.

Remarks

Some audio cards may be unable to report accurately the number of available or free hardware buffers. This can happen, for example, when the card can play more sounds at lower sampling rates than at higher rates. In general, a non-zero value in any of the members relating to number of free hardware buffers signifies that at least one hardware resource of the appropriate type is available.

Requirements

OS Versions: Windows CE 2.12 and later. Version 2.12 requires DXPAK 1.0 or later.
Header: Dsound.h.

See Also

IDirectSound::GetCaps | IDirectSoundBuffer::Unlock

 Last updated on Thursday, April 08, 2004

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