src.html
<!DOCTYPE html>
<html lang="ja">
<head>
<meta charset="utf-8">
<title>sample</title>
<script>
//A再生
function PlayA(){
vp = document.getElementById("videoplay");
vp.src = "./a.mp4";
vp.play();
}
//D一時停止
function PlayD(){
vp = document.getElementById("videoplay");
vp.src = "./d.mp4";
vp.play();
}
</script>
</head>
<body>
<video id="videoplay" width="500" height="300" >
<source src="./d.mp4" type="video/mp4">
</video>
<br />
<button onclick="PlayA()">a.mp4を再生</button>
<button onclick="PlayD()">d.mp4を再生</button>
</body>
</html>