Mixing Sounds

It is easy to mix multiple streams with DirectSound. You simply create secondary sound buffers, obtaining an IDirectSoundBuffer8 interface for each sound. You then play the buffers simultaneously. DirectSound takes care of the mixing in the primary buffer and plays the result.

The DirectSound mixer produces the best sound quality if all your application's sounds use the same wave format and the hardware output format is matched to the format of the sounds. If this is done, the mixer does not need to perform any format conversion.

Your application can change the hardware output format by creating a primary sound buffer object and calling the IDirectSoundBuffer8::SetFormat method. This primary buffer object is for control purposes only; creating it is not the same as obtaining write access to the primary buffer as described under Writing to the Primary Buffer, and you do not need the DSSCL_WRITEPRIMARY cooperative level. However, you do need a cooperative level of DSSCL_PRIORITY or higher in order to call the SetFormat method. DirectSound will restore the hardware format to the format specified in the last call every time the application gains the input focus.

You must set the format of the primary buffer before creating any secondary buffers.

Note   With WDM drivers, setting the primary buffer format has no effect. The format is determined by the kernel mixer. For more information, see DirectSound Driver Models.