Ok, check this out. I have a sequence of 2 hour HDV material. MPE with cuda enabled with my GTX 470 card. I don't apply any effects or transitions and render to mpeg2 Blu Ray ( I have made a preset). It take about 1.2 hours to finish rendering.
I open the same project again and apply heavy GPU effects (RGB color curves). I render again with same preset and takes about 44 minutes to finish!!!!.
Something is wrong here. I use the GPU Z utility http://www.techpowerup.com/gpuz/
and monitor the GPU. Without any effects when rendering the gpu load is 0%. With effects the GPU load goes about 88-90%.
So what is going on here? If you don't apply any effects the GPU-Cuda and the so-fuss about Mercury GPU acceleration is not enabled?
Now I have to find a GPU effect to apply which does not affect the original video image just to have faster rendering times!!
It all seems pretty logical to me. Look at the Background Information page here: PPBM5 Benchmark
Your CPU must be a pretty old or slow, your memory must be limited and slow as well, your cache limited to cause these effects, or you are bitten by the lousy DV threading or the MPEG exporter bug.
Core I7 920, Gigabyte X58-UD5, 9 GB Crucial Ballistic @ 1600, Windows 7 x64 Ultimate