start parameter of YouTube URLs requires a whole number of seconds. Is there some other way to start play in the middle of a second?
According to the documentation:
start] causes the player to begin playing the video at the given number of seconds from the start of the video. The parameter value is a positive integer. Note that similar to the
seekTofunction, the player will look for the closest keyframe to the time you specify. This means that sometimes the play head may seek to just before the requested time, usually no more than around two seconds.
Even if there was a method to specify half-seconds, it'd still play from the nearest keyframe. So no, what you want to do is not possible.