I'm running on a Dell Studio XPS 1640 and this problem has been around as long as I can remember, I just haven't been able to pin it down until now. Whenever an application (e.g. a media player, Youtube in my browser, etc.) tries to play an mp4 file or stream using the default Windows decoder for it, my system freezes up completely (no response to anything other than holding down the power button). This sounds a lot like this other post, but my system isn't nice enough to wake up after some number of seconds, even after I tried manually adding the registry key (TdrDelay) mentioned in one of the links.
I've tried both the latest drivers listed on the Dell website for my system and the ones here on the AMD website, but both suffer from this problem, and I don't know of any others. I do know that this has to be the drivers somehow, because by uninstalling all of them I can prevent these freezes from occurring (though video just refuses to play as a result).
My media player of choice (Zoom Player) is nice enough to display a filter graph for what it's hooked up to, but unfortunately I can't use it to figure out the specific decoder that's causing the problem because of the symptom.
For the time being I have redirected all of my current software away from the default Windows decoders, but I would really like to know how to either disable said decoder on a system level, so it can't be accessed at all, or, even better, get the damned thing to work properly.
Does this happen when a video alone is playing, or does it happen when you are playing a game/3D application and have a video playing as well? Have you installed Sharks codex's? Have you tried setting your browser to use software rendering instead of hardware rendering? Have you used/tried other players like Kodi or MPC-HC ? These are the latest drivers for your graphics > Legacy
This problem is confined exclusively to the one(?) default Windows decoder; if it is accessed, the presence or absence of other 3D applications/games is irrelevant. This issue does not occur when video is playing. This issue and video playback are mutually exclusive. I do not have said codecs installed, but if you are suggesting them as an alternative to the Windows default codecs that is unnecessary; Zoom Player can and will set up its own decoders to bypass the Windows defaults. Disabling hardware rendering in my browser will prevent the freezes, though at the moment Youtube no longer seems to cause them anymore regardless (some Youtube updates fix it and others break it). Other media players will work the same way; if they construct their own filter system without the problematic decoder they will work fine (e.g. MPC-HC), but if they try to use it, my system freezes. Those are the drivers I am currently using (for lack of a working option).
As I said, (almost) all my software currently dodges the problem one way or another, but I really need to get rid of it once and for all (so that new software or new updates don't break things). I say "almost" this time as I have just verified that the Windows Experience Index evaluation tool also suffers from this; it freezes upon reaching the "testing video decoding" stage, and I do not know of a workaround for it.