WAVEFORMATEXTENSIBLE

The WAVEFORMATEXTENSIBLE structure defines the format of waveform-audio data for formats having more than two channels.

This structure is part of the Platform SDK and is not declared in Dsound.h. It is documented here for convenience.

Syntax

typedef struct {
  WAVEFORMATEX  Format;
  union {
    WORD  wValidBitsPerSample;
    WORD  wSamplesPerBlock;
    WORD  wReserved;
  } Samples;
  DWORD   dwChannelMask; 
  GUID    SubFormat;
} WAVEFORMATEXTENSIBLE, *PWAVEFORMATEXTENSIBLE;

Members

Format

WAVEFORMATEX structure that specifies the basic format. The wFormatTag member must be WAVE_FORMAT_EXTENSIBLE, defined in Mmreg.h. The cbSize member must be at least 22.

wValidBitsPerSample

How many bits of precision are present in the signal. Usually equal to WAVEFORMATEX.wBitsPerSample.

wSamplesPerBlock

How many samples are contained in one compressed block of audio data. If zero, the number of samples in each block is variable.

wReserved

Set to zero if neither wValidBitsPerSample nor wSamplesPerBlock applies to the format.

dwChannelMask

Bitmask specifying which channels are present. See Remarks.

SubFormat

Subformat of the data. Must be KSDATAFORMAT_SUBTYPE_PCM, defined in Ksmedia.h.

Remarks

The dwChannelMask member indicates which channels are present in the multichannel stream. The least significant bit corresponds with the front left speaker, the next least significant bit corresponds to the front right speaker, and so on. The bits, in order of significance, are defined in Ksmedia.h and Mmreg.h as follows:

SPEAKER_FRONT_LEFT
SPEAKER_FRONT_RIGHT
SPEAKER_FRONT_CENTER
SPEAKER_LOW_FREQUENCY
SPEAKER_BACK_LEFT
SPEAKER_BACK_RIGHT
SPEAKER_FRONT_LEFT_OF_CENTER
SPEAKER_FRONT_RIGHT_OF_CENTER
SPEAKER_BACK_CENTER
SPEAKER_SIDE_LEFT
SPEAKER_SIDE_RIGHT
SPEAKER_TOP_CENTER
SPEAKER_TOP_FRONT_LEFT
SPEAKER_TOP_FRONT_CENTER
SPEAKER_TOP_FRONT_RIGHT
SPEAKER_TOP_BACK_LEFT
SPEAKER_TOP_BACK_CENTER
SPEAKER_TOP_BACK_RIGHT

For more information on this structure, see the document Enhanced Audio Formats for Multi-Channel Configurations and High-Bit Resolution, available at http://www.microsoft.com/hwdev/audio/multichaud.htm.

Requirements

  Header: Declared in Mmreg.h, Ksproxy.h.