I was trying to do this exact same thing earlier this week.
A solution purely from a URL parameter isn't possible. (or if it is,
it's not documentation here:
https://developers.google.com/youtube/player_parameters)
I came accros this JSFiddle by Johan Preynat: http://jsfiddle.net/jpreynat/e11oy0eu/
Worked for me, so hopefully it'll be useful for you too
HTML
<!-- 1. The <iframe> (and video player) will replace this <div> tag. -->
<div id="player"></div>
JavaScript
// 2. This code loads the IFrame Player API code asynchronously.
var tag = document.createElement('script');
tag.src = "https://www.youtube.com/iframe_api";
var firstScriptTag = document.getElementsByTagName('script')[0];
firstScriptTag.parentNode.insertBefore(tag, firstScriptTag);
// 3. This function creates an <iframe> (and YouTube player)
// after the API code downloads.
var player;
function onYouTubeIframeAPIReady() {
player = new YT.Player('player', {
height: '390',
width: '640',
videoId: 'M7lc1UVf-VE',
events: {
'onReady': onPlayerReady
}
});
}
// 4. The API will call this function when the video player is ready.
function onPlayerReady(event) {
player.setPlaybackRate(2);
event.target.playVideo();
}
See also the YouTube documentation on this:
https://developers.google.com/youtube/iframe_api_reference