<!DOCTYPE html>
<title>Reference for WebVTT rendering, when media height is 19 or less, font size should be smaller than when it is 20 and above</title>
<style>
.video {
    display: inline-block;
    width: 1280px;
    height: 19px;
    outline: solid;
    position: relative
}
.cue {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    text-align: center
}
.cue > span {
    font-family: Ahem, sans-serif;
    background: rgba(0,0,0,0.8);
    color: green;
    font-size: 0.95px
}
</style>
<div class=video><span class=cue><span>This is a test subtitle</span></span></div>