The value of this property is a multiple of the media resource’s intrinsic speed. If set to 0.0, a NOT_SUPPORTED_ERR DOM exception is raised. The default value is 1.0. Use this property to create custom controls for playback rate. Values greater than 1.0 fast-forward media and values less than 0.0 rewind. This property can not be set for HTML5 audio/video elements on iOS.