Multichannel Wave Formats

On WDM drivers, DirectSound buffers support wave formats that have more than two output channels, for speaker configurations such as 5.1, which has speakers at the front left, front center, front right, back left, and back right, plus a low-frequency enhancer.

The WAVEFORMATEXTENSIBLE structure describes a multichannel wave format. This structure is an extension of WAVEFORMATEX that configures the extra bytes already supported by the cbSize member of WAVEFORMATEX. A WAVEFORMATEXTENSIBLE structure can be cast as WAVEFORMATEX wherever the latter is expected, as for example in the DSBUFFERDESC structure.

If there are fewer physical speakers than the number of channels specified in a multichannel wave file, the audio data is mixed appropriately and output to the existing speakers.

DirectSound does not support effects or 3-D processing on buffers in a multichannel format. An attempt to create a buffer with the DSBCAPS_CTRL3D or DSBCAPS_CTRLFX flag and a multichannel wave format will fail.

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