This determines the speed of event playback. Default is 1.0 for 1x playback speed.
For faster playback, use values greater than one such as 2x, 3x or even 4x. For slower playback, use values between 0 and 1; 0.25 will replay at 1/4th speed. To pause playback, use 0.0
Negative (going backwards), is not supported. Use seekTo to go back in time.