Horizontally center video in Bootstrap - html

Question

Researched elsewhere, can't find a solution to horizontally center a video in a Bootstrap div / header section while keeping the video vertically aligned with the top. Div / header section is 100% width with two fixed heights at certain viewport breakpoints.
I've tried removing/renaming the <header> tag in case Bootstrap's styles interfere. Tried <center> tags, specifying the video tag as display:inline and many many other attempts.
The video in this example centers at certain breakpoints but otherwise is left-aligned. I'd like it to be centered throughout all viewport widths, and top aligned as well.
Thanks very much!
HTML:
<header>
<video loop muted autoplay poster="images/3671960.jpg" class="fullscreen-video">
<source src="video/3671960.mp4" type="video/mp4">
</video>
<div class="header-content">
<div class="header-content-inner">
<h1>A bunch of header text.</h1>
</div>
</div>
<div class="launcher">
<div class="launcher-inner">
Button text
</div>
</div>
CSS :
header {
position: relative;
text-align: center;
top: 0;
left: 0;
width:100%;
height: 475px;
color: #fff;
overflow: hidden;
margin: 0 auto;
}
header .fullscreen-video {
position: absolute;
top: 0;
left: 0;
min-width:100%;
min-height:100%;
z-index: -100;
}
#media (min-width: 768px) {
header {
height: 665px;
}
}

Answer 1

HTML
<header>
<video loop muted autoplay poster="images/3671960.jpg" class="fullscreen-video">
<source src="video/3671960.mp4" type="video/mp4">
</video>
<div class="header-content">
<div class="header-content-inner">
<h1>A bunch of header text.</h1>
</div>
</div>
<div class="launcher">
<div class="launcher-inner">
Button text
</div>
</div>
</header>
CSS
header {
position: relative;
text-align: center;
top: 0;
left: 0;
width:100%;
height: 475px;
color: #fff;
overflow: hidden;
margin: 0 auto;
}
header .fullscreen-video {
position: absolute;
left: 50%;
top: 0;
-ms-transform: translateX(-50%);
-webkit-transform: translateX(-50%);
transform: translateX(-50%);
min-width:100%;
min-height:100%;
z-index: -100;
}
#media (min-width: 768px) {
header {
height: 665px;
}
}
Demo Link : https://jsfiddle.net/hellosrini/vwc5hek0/