Bad Picture with experience different OS?
Please take it easy I am no expert on this. That is why I have not suggested before.
I had experimented before with creating some IP streaming that then I can see on VLC or Medial Portal. It shows similarity in bad streaming, you know the pixelation you seen above.
In my past experience I see it relates to the heavy loads that lava or any other codec ( in my case was ffmpeg) puts on the PC resources at the time to re-code & render HD movies. I hope I did not confused you guys.
Here is the important part. When you get the pixelation, do [CTRL][ALT][DEL] to get see the active process and CPU Loads. Now you need to identify the process that relates to the Movie Picture Viewing; ALTDVB or any viewer , plugins and the codec mechanism. In my case was easy I selected the MediaPortal Server, VLC and ffmpeg. Then I right Click over each process and in priority I set its value higher than normal. You need to test it for yourself.
Well the issue is that the OS hold process in lower priorities in favor of higher priorities. And if your system is running low the OS will hold. That is why you need to increase those priorities values.
Now be careful you do not want to increase those values to a point where the OS do not have time to do its job. You may end crashing your system.
I suggest to stop complaining about what is best for each OS. Try to find the reason why it happens.