Разное качество привью картинок для youtube

есть вот такой список:

<media:thumbnail url='http://i1.ytimg.com/vi/VGazSZUYyf4/default.jpg' height='90' width='120' time='00:15:12.500' yt:name='default'/>
<media:thumbnail url='http://i1.ytimg.com/vi/VGazSZUYyf4/mqdefault.jpg' height='180' width='320' yt:name='mqdefault'/>
<media:thumbnail url='http://i1.ytimg.com/vi/VGazSZUYyf4/hqdefault.jpg' height='360' width='480' yt:name='hqdefault'/>
<media:thumbnail url='http://i1.ytimg.com/vi/VGazSZUYyf4/1.jpg' height='90' width='120' time='00:07:36.250' yt:name='start'/>
<media:thumbnail url='http://i1.ytimg.com/vi/VGazSZUYyf4/2.jpg' height='90' width='120' time='00:15:12.500' yt:name='middle'/>
<media:thumbnail url='http://i1.ytimg.com/vi/VGazSZUYyf4/3.jpg' height='90' width='120' time='00:22:48.750' yt:name='end'/>

обрабатываем так:

<?php

$youtub_id = "VGazSZUYyf4";

$images = json_decode(file_get_contents("http://gdata.youtube.com/feeds/api/videos/".$youtub_id."?v=2&alt=json"), true);
$images = $images['entry']['media$group']['media$thumbnail'];
$image  = $images[count($images)-4]['url'];

$maxurl = "http://i.ytimg.com/vi/".$youtub_id."/maxresdefault.jpg";
$max    = get_headers($maxurl);

if (substr($max[0], 9, 3) !== '404') {
    $image = $maxurl;   
}

echo '<img src="'.$image.'">';

или через функцию:

function fetch_highest_res($videoid)
{

$image_qualities = array('maxresdefault', 'hqdefault', 'mqdefault');
//in the order of preference

    foreach($image_qualities as $image_quality) 
    {
        if(@getimagesize( ('http://i.ytimg.com/vi/'. $videoid. '/'.$image_quality.'.jpg') ) ) 
        {
          $imgurl = "http://i.ytimg.com/vi/$videoid/$image_quality.jpg";
          return $imgurl;
          break; //exiting
        }
    }

}

задаем:

echo fetch_highest_res('Cj6ho1-G6tw').'<br>';
echo fetch_highest_res('VGazSZUYyf4');

и на выводе получаем:

http://i.ytimg.com/vi/Cj6ho1-G6tw/maxresdefault.jpg
http://i.ytimg.com/vi/VGazSZUYyf4/hqdefault.jpg

инфа найдена тут