I report this bug on bugs wizard, but still has not been repaired.
Playwire HTML5 player not working in Opera.
http://www.playwire.com/html5-video-player/
http://www.okgoals.com/match-highlights-1456593572---43
still see the loading animation icon, but nothing happens.

The extension Magic Actions does this for YouTube. I don't know about other websites.

Yes I know. I know this extension , I use it from Opera 15 (on 12.50 ExtendTube )
The problem is on the other sites.

Is it possible, is it any way?

Not that i know of. There are some
extensions that can do that for some specific pages.

Just as I suspected, html5 is a step backwards.

Autoplay is one of the worst thing of user experience on internet!

I have to agree too.

Edit * it stop autoplay but on some sites I can not start video

Is it possible, is it any way? I found UserJS to disable HTML5 AutoPlay ( https://greasyfork.org/pl/scripts/388-html5-video-auto-pause/code ), it stop autoplay but I can not start video... I can not find anything to disable automatic preload/buffer.
How to change preload="auto|metadata" to preload="none", is possible to inject some html or css or something else to stop this &^%# preload ;)?