video shortcode autoplay and player size in WP3.6

How do I turn on the autoplay for the new video player in WP3.6?
I use wp_video_shortcode(); in my custom theme and I tried autoplay=”true” but nothing happens. Also I set the width="583" height="328" but the player gets rather adjusted to the surrounding div.
Here is the code in my theme (I use WPML):

$shortcode = '[video autoplay="true" width="583" height="328" mp4="';
$id = icl_object_id($post->ID, 'playing', false, 'en');
$args = array(
'numberposts' => null,
'post_mime_type' => 'video',
'post_parent' => $id,
'post_status' => null,
'post_type' => 'attachment',
'suppress_filters' => false,
);
$video_attachments = get_posts($args);
$movie_url = wp_get_attachment_url( $video_attachments[0]->ID );
$shortcode .= $movie_url.'"][/video]';
echo wp_video_shortcode("$shortcode");

Or is there even a simpler way of implementing this in a custom theme? ??
I’d be thankful for any hint.