| DirectX SDK |
Performance is affected when you change the pan, volume, or frequency on a secondary buffer. To prevent interruptions in sound output, the DirectSound mixer must mix ahead from 20 to 100 or more milliseconds. Whenever you make a control change, the mixer has to flush its mix-ahead buffer and remix with the changed sound.
It's a good idea to minimize the number of control changes you send. Try reducing the frequency of calls to routines that use the IDirectSoundBuffer::SetVolume, IDirectSoundBuffer::SetPan, and IDirectSoundBuffer::SetFrequency methods. For example, if you have a routine that moves a sound from the left to the right speaker in synchronization with animation frames, try calling the SetPan method only every second or third frame.
It's a good idea to minimize the number of control changes you send. Try reducing the frequency of calls to routines that use the DirectSoundBuffer.SetVolume, DirectSoundBuffer.SetPan, and DirectSoundBuffer.SetFrequency methods. For example, if you have a routine that moves a sound from the left to the right speaker in synchronization with animation frames, try calling the SetPan method only every second or third frame.
Note 3-D control changes (orientation, position, velocity, Doppler factor, and so on) also cause DirectSound to remix its mix-ahead buffer. However, you can group a number of 3-D control changes together and cause only a single remix. See Deferred Settings.