Show all videos by tag name

by

Try this.
Use for tag_id in get_posts.

$tax_terms = get_terms('media_category', 'orderby=count&order=DESC&hide_empty=0');

foreach ( $tax_terms as $tax_term ) {

$posts = get_posts(array(
                "meta_key" => 'select', 
                "meta_value" => 1,
                "tag_id" => 5,
                "post_mime_type" => "video",
                "taxonomy" => $tax_term->taxonomy,
                "term" => $tax_term->slug,
                "numberposts" => 100, 
                "posts_per_page" => 100));