See the difference between the HD TV3 feed (nearly going 100% CPU) and the SD C4 feed. TV3 looks by no means perfect, but it's not overly stuttery.
Core 2 Duo E6300
Radeon 9600XT 256MB
MediaPortal SVN Build 2008-03-26
Windows XP SP2
Using FFDShow video filter (build rev1920_20080328_sse)
Comment by sbiddle, on 1-Apr-2008 19:48
That is why a video card with H.264 acceleration is essential for DVB-T in New Zealand. Using PowerDVD Ultra's H.264 codec with hardware acceleration with a supported video card and that will drop down to around 5% - 10% CPU usage on all channels.