How to handle "Uncaught (in promise) DOMException: play() failed because the user didn't interact with the document first." on Desktop with Chrome 66?

To make the autoplay on html 5 elements work after the chrome 66 update you just need to add the muted property to the video element.

So your current video HTML

<video
    title="Advertisement"
    webkit-playsinline="true"
    playsinline="true"
    style="background-color: rgb(0, 0, 0); position: absolute; width: 640px; height: 360px;"
    src="http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.mp4"
    autoplay=""></video>

Just needs muted="muted"

<video
    title="Advertisement"
    style="background-color: rgb(0, 0, 0); position: absolute; width: 640px; height: 360px;"
    src="http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.mp4"
    autoplay="true"
    muted="muted"></video>

I believe the chrome 66 update is trying to stop tabs creating random noise on the users tabs. That's why the muted property make the autoplay work again.

For me (in Angular project) this code helped:

In HTML you should add autoplay muted

In JS/TS

playVideo() {
    const media = this.videoplayer.nativeElement;
    media.muted = true; // without this line it's not working although I have "muted" in HTML
    media.play();
}

Try to use mousemove event listener

var audio = document.createElement("AUDIO")
document.body.appendChild(audio);
audio.src = "./audio/rain.m4a"

document.body.addEventListener("mousemove", function () {
    audio.play()
})

The best solution i found out is to mute the video

HTML

<video loop muted autoplay id="videomain">
  <source src="videoname.mp4" type="video/mp4">
</video>

Answering the question at hand...
No it's not enough to have these attributes, to be able to autoplay a media with audio you need to have an user-gesture registered on your document.

But, this limitation is very weak: if you did receive this user-gesture on the parent document, and your video got loaded from an iframe, then you could play it...

So take for instance this fiddle, which is only

<video src="myvidwithsound.webm" autoplay=""></video>

At first load, and if you don't click anywhere, it will not run, because we don't have any event registered yet.
But once you click the "Run" button, then the parent document (jsfiddle.net) did receive an user-gesture, and now the video plays, even though it is technically loaded in a different document.

But the following snippet, since it requires you to actually click the Run code snippet button, will autoplay.

<video src="https://upload.wikimedia.org/wikipedia/commons/transcoded/2/22/Volcano_Lava_Sample.webm/Volcano_Lava_Sample.webm.360p.webm" autoplay=""></video>

This means that your ad was probably able to play because you did provide an user-gesture to the main page.

Now, note that Safari and Mobile Chrome have stricter rules than that, and will require you to actually trigger at least once the play() method programmatically on the <video> or <audio> element from the user-event handler itself.

btn.onclick = e => {
  // mark our MediaElement as user-approved
  vid.play().then(()=>vid.pause());
  // now we can do whatever we want at any time with this MediaElement
  setTimeout(()=> vid.play(), 3000);
};

<button id="btn">play in 3s</button>
<video
  src="https://upload.wikimedia.org/wikipedia/commons/transcoded/2/22/Volcano_Lava_Sample.webm/Volcano_Lava_Sample.webm.360p.webm" id="vid"></video>

And if you don't need the audio, then simply don't attach it to your media, a video with only a video track is also allowed to autoplay, and will reduce your user's bandwidth usage.