WordPress テーマカスタマイザーで動画を追加して出力（ver 4.7以降の場合） ref: http://qiita.com/gatespace/items/760533f0c90095cc6571

file2.html

<button type="button" id="wp-custom-header-video-button" class="wp-custom-header-video-button wp-custom-header-video-play">Pause</button>

file3.html

<button type="button" id="wp-custom-header-video-button" class="wp-custom-header-video-button wp-custom-header-video-pause">Play</button>

the_custom_header_markup.php

<?php the_custom_header_markup(); ?>

themename_custom_header_setup

<?php
function themename_custom_header_setup() {
    $args = array(
        'default-image'      => get_template_directory_uri() . 'img/default-image.jpg',
        'default-text-color' => '000',
        'width'              => 1000,
        'height'             => 250,
        'flex-width'         => true,
        'flex-height'        => true,
        'video'              => true,
    )
    add_theme_support( 'custom-header', $args );
}
add_action( 'after_setup_theme', 'themename_custom_header_setup' );

wp-custom-header.css

.wp-custom-header iframe,
.wp-custom-header img,
.wp-custom-header video {
    display: block;
    height: auto;
    max-width: 100%;
}