|Microsoft DirectX 9.0|
The PlayBackwards method starts backward playback from the current location at the specified speed.
Specifies the speed at which to play as a number. This number is a multiplier1.0 is normal playback speed; 2.0 is double speed, 0.5 is half speed, and so on. When nSpeed does not equal 1.0, audio is muted and the subpicture is turned off.
No return value.