Playback with NVidia ION based chipset with mythtv can easily provide 1080p H.264 playback even with low powered CPU´s like Atom.
However, with some content I have noticed heavy pixelation, which increases after keyframes gradually, until next keyframe.
I found that adding these custom filters to TV playback settings made the problem go away:
vdpauskipchroma,vdpaucolorspace=auto,vdpaubuffersize=32
