Capture Buffer Information

[The feature associated with this page, DirectSound, is a legacy feature. It has been superseded by WASAPI and Audio Graphs. Media Casting have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use Media Casting instead of DirectSound, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

You can use the IDirectSoundCaptureBuffer8::GetCaps method to retrieve the size of a capture buffer. Be sure to initialize the dwSize member of the DSCBCAPS structure before passing it as a parameter.

To retrieve information about the format of the data in the buffer, as set when the buffer was created, call IDirectSoundCaptureBuffer8::GetFormat. This method returns the format information in a WAVEFORMATEX structure.

Note that your application can allow for extra format information in the WAVEFORMATEX structure by first calling the GetFormat method with NULL as the lpwfxFormat parameter. In this case the DWORD pointed to by the lpdwSizeWritten parameter receives the size of the structure needed to receive complete format information.

To find out what a capture buffer is currently doing, call the IDirectSoundCaptureBuffer8::GetStatus method. This method fills a DWORD variable with a combination of flags that indicate whether the buffer is busy capturing, and if so, whether it is looping; that is, whether the DSCBSTART_LOOPING flag was set in the last call to IDirectSoundCaptureBuffer8::Start.

The IDirectSoundCaptureBuffer8::GetCurrentPosition method returns the offsets of the read and capture cursors within the buffer. The read cursor is at the end of the data that has been fully captured into the buffer at this point. The capture cursor is at the end of the block of data that is currently being copied from the hardware. You can safely copy data from the buffer only up to the read cursor.