Custom youtube shortcode that uses $content

Shortcode functions accept a second parameter which contains the value in between the shortcode opening and closing tags:

function youtube( $atts, $value="http://" ) {
    extract( shortcode_atts( array(
        "width" => '620',
        "height" => '350',
        "name"=> 'movie',
        "allowFullScreen" => 'true',
        "allowScriptAccess"=>'always',
    ), $atts ) );
    return '<object style="height: '.$height.'px; width: '.$width.'px"><param name="'.$name.'" value="'.$value.'"><param name="allowFullScreen" value="'.$allowFullScreen.'"></param><param name="allowScriptAccess" value="'.$allowScriptAccess.'"></param><embed src="'.$value.'" type="application/x-shockwave-flash" allowfullscreen="'.$allowFullScreen.'" allowScriptAccess="'.$allowScriptAccess.'" width="'.$width.'" height="'.$height.'"></embed></object>';
}
add_shortcode( 'yt', 'youtube' );