XAUDIO2_BUFFER structure

Represents an audio data buffer, used with IXAudio2SourceVoice::SubmitSourceBuffer.

Syntax

typedef struct XAUDIO2_BUFFER {
  UINT32     Flags;
  UINT32     AudioBytes;
  const BYTE *pAudioData;
  UINT32     PlayBegin;
  UINT32     PlayLength;
  UINT32     LoopBegin;
  UINT32     LoopLength;
  UINT32     LoopCount;
  void       *pContext;
} XAUDIO2_BUFFER;

Members

Flags

Flags that provide additional information about the audio buffer. May be 0, or the following value.

Value Description
XAUDIO2_END_OF_STREAM Indicates that there cannot be any buffers in the queue after this buffer. The only effect of this flag is to suppress debug output warnings caused by starvation of the buffer queue. 

AudioBytes

Size of the audio data, in bytes. Must be no larger than XAUDIO2_MAX_BUFFER_BYTES (defined in xaudio2.h) for PCM data and no larger than XMA_READBUFFER_MAX_BYTES (defined in xma2defs.h) for XMA data.

Note  XMA buffers submitted to an XAudio2 voice using IXAudio2SourceVoice::SubmitSourceBuffer must contain complete XMA blocks. A complete XMA block must be equal in size to the XMA2WAVEFORMATEX.BytesPerBlock value, except for the last XMA block in a file, which may be shorter but will still be considered complete.
 

pAudioData

Pointer to the audio data.

Xbox 360
The memory allocated for a buffer containing XMA data must have a block alignment of 2048. This is accomplished using XPhysicalAlloc with the ulAlignment argument set to 2048.

PlayBegin

First sample in the buffer that should be played.

For XMA buffers this value must be a multiple of 128 samples.

PlayLength

Length of the region to be played, in samples. A value of zero means to play the entire buffer, and, in this case, PlayBegin must be zero as well. For ADPCM data this value must be a multiple of wSamplesPerBlock in the ADPCMWAVEFORMAT structure that contains this XAUDIO2_BUFFER structure.

LoopBegin

First sample of the region to be looped. The value of LoopBegin must be less than PlayBegin + PlayLength. LoopBegin can be less than PlayBegin. LoopBegin must be 0 if LoopCount is 0.

LoopLength

Length of the loop region, in samples. The value of LoopBegin+LoopLength must be greater than PlayBegin and less than PlayBegin + PlayLength. LoopLength must be zero if LoopCount is 0. If LoopCount is not 0 then a loop length of zero indicates the entire sample should be looped. For ADPCM data this value must be a multiple of wSamplesPerBlock in the ADPCMWAVEFORMAT structure that contains this XAUDIO2_BUFFER structure.

LoopCount

Number of times to loop through the loop region. This value can be between 0 and XAUDIO2_MAX_LOOP_COUNT. If LoopCount is zero no looping is performed and LoopBegin and LoopLength must be 0. To loop forever, set LoopCount to XAUDIO2_LOOP_INFINITE.

pContext

Context value to be passed back in callbacks to the client. This may be NULL.

Remarks

XAudio2 audio data is interleaved, data from each channel is adjacent for a particular sample number. For example if there was a 4 channel wave playing into an XAudio2 source voice, the audio data would be a sample of channel 0, a sample of channel 1, a sample of channel 2, a sample of channel 3, and then the next sample of channels 0, 1, 2, 3, etc.

The AudioBytes and pAudioData members of XAUDIO2_BUFFER correspond to the size in bytes and contents of the 'data' RIFF chunk of the file being played. The contents of the chunk may need to be byte swapped when loading the file on Xbox 360.

Memory allocated to hold a XAUDIO2_BUFFER or XAUDIO2_BUFFER_WMA structure can be freed as soon as the IXAudio2SourceVoice::SubmitSourceBuffer call it is passed to returns. The data the structure points to (pAudioData and pDecodedPacketCumulativeBytes, respectively) can't be freed until the buffer completes (as signaled by the IXAudio2VoiceCallback::OnBufferEnd callback) or the voice is stopped or destroyed.

Platform Requirements

Windows 10 (XAudio2.9); Windows 8, Windows Phone 8 (XAudio 2.8); DirectX SDK (XAudio 2.7)

Requirements

   
Header xaudio2.h

See Also

How to: Build a Basic Audio Processing Graph

IXAudio2SourceVoice::SubmitSourceBuffer

XAudio2 Structures