The WAVEFORMATEX structure defines the format of waveform-audio data. Only format information common to all waveform-audio data formats is included in this structure. For formats that require additional information, this structure is included as the first member in another structure, along with the additional information.
typedef struct WAVEFORMATEX {
WORD wFormatTag;
WORD nChannels;
DWORD nSamplesPerSec;
DWORD nAvgBytesPerSec;
WORD nBlockAlign;
WORD wBitsPerSample;
WORD cbSize;
} WAVEFORMATEX;
wFormatTag
Waveform-audio format type.
For XMA2 this should always be set to WAVE_FORMAT_XMA2.
Format tags are registered with Microsoft Corporation for many compression algorithms. A complete list of format tags can be found in the Mmreg.h header file. For one- or two-channel Pulse Code Modulation (PCM) data, this value should be WAVE_FORMAT_PCM.
Before reinterpreting a WAVEFORMATEX structure as one of these extended structures, verify that the actual structure size is sufficiently large and that the cbSize member indicates a valid size.
nChannels
Number of channels in the waveform-audio data. Monaural data uses one channel and stereo data uses two channels.
nSamplesPerSec
Sample rate, in samples per second (hertz). If wFormatTag is WAVE_FORMAT_PCM, then common values for nSamplesPerSec are 8.0 kHz, 11.025 kHz, 22.05 kHz, and 44.1 kHz. For non-PCM formats, this member must be computed according to the manufacturer’s specification of the format tag.
nAvgBytesPerSec
If the format is WAVE_FORMAT_XMA2 this value is only used internally by the XMA encoder.
Required average data-transfer rate, in bytes per second, for the format tag. If wFormatTag is WAVE_FORMAT_PCM, nAvgBytesPerSec must equal nSamplesPerSec × nBlockAlign. For non-PCM formats, this member must be computed according to the manufacturer’s specification of the format tag.
nBlockAlign
Block alignment, in bytes. The block alignment is the minimum atomic unit of data for the wFormatTag format type. If wFormatTag is WAVE_FORMAT_XMA2 or WAVE_FORMAT_PCM, nBlockAlign must equal (nChannels × wBitsPerSample) / 8. For non-PCM formats, this member must be computed according to the manufacturer’s specification of the format tag.
Software must process a multiple of nBlockAlign bytes of data at a time. Data written to and read from a device must always start at the beginning of a block. For example, it is illegal to start playback of PCM data in the middle of a sample (that is, on a non-block-aligned boundary).
wBitsPerSample
Bits per sample for the wFormatTag format type. If wFormatTag is WAVE_FORMAT_XMA2 this value is always 16. If wFormatTag is WAVE_FORMAT_PCM, then wBitsPerSample should be equal to 8 or 16. For non-PCM formats, this member must be set according to the manufacturer’s specification of the format tag. If wFormatTag is WAVE_FORMAT_EXTENSIBLE, this value can be any integer multiple of 8.
Some compression schemes do not define a value for wBitsPerSample, so this member can be zero.
cbSize
Size, in bytes, of extra format information appended to the end of the WAVEFORMATEX structure. If wFormatTag is WAVE_FORMAT_XMA2 this value is 34. This information can be used by non-PCM formats to store extra attributes for the wFormatTag. If no extra information is required by the wFormatTag, this member must be set to zero. For WAVE_FORMAT_PCM formats (and only WAVE_FORMAT_PCM formats), this member is ignored. However it is still recommended to set the value.
Header: Declared in audioclient.h.
Library: Use d3d11.lib.