setPlaybackRate abstract method

This function sets the suggested playback rate for the current video. If the playback rate changes, it will only change for the video that is already cued or being played. If you set the playback rate for a cued video, that rate will still be in effect when the playVideo function is called or the user initiates playback directly through the player controls. In addition, calling functions to cue or load videos or playlists (cueVideoById, loadVideoById, etc.) will reset the playback rate to 1.

Calling this function does not guarantee that the playback rate will actually change. However, if the playback rate does change, the onPlaybackRateChange event will fire, and your code should respond to the event rather than the fact that it called the setPlaybackRate function.