/**
 *
 * Get youtube video ID
 *
 * @param  string $url
 * @return true|false
 *
 * @since  1.0.0
 *
 */
function videotube_child_get_youtube_id( $url ){

    preg_match( '/(youtube.com\/watch\?v=|youtu.be\/|youtube.com\/embed\/)(?P<id>.{11})/', $url, $matched );

    if( is_array( $matched ) && array_key_exists( 'id' , $matched ) ){
        return $matched['id'];
    }

    return false;
}

/**
 *
 * Convert youtube link to iframe
 *
 * @param   $output
 * @param  [type] $media_object
 * @since  1.0.0
 *
 */
function videotube_child_filter_player( $output, $media_object ){

    if( "" != $youtubeId = videotube_child_get_youtube_id( $media_object ) ){
        $output = sprintf(
            '<iframe src="https://www.youtube.com/embed/%s?autoplay=1" frameborder="0" allowfullscreen="allowfullscreen"></iframe>',
            $youtubeId
        );
    }

    return $output;

}
add_filter( 'videotube_player', 'videotube_child_filter_player', 100, 2 );