How do you get quality video from the K5

I see all these cool videos, many in low light that were taken with the K5, but even in decent light (indoors with daylight coming through windows) my videos are grainy and/or washed out. In low light, the video is utterly unusable. Outdoors in bright sunlight seem to be useable, but I would not say quality is as high and sharp and vibrant as I've seen elsewhere.

Are these videos made by someone with mystical powers or are they post-processed with some high end software that does noise reduction on video?
Most likely I'm doing something wrong, but I've heard other people mention the same thing with regards to getting quality video results.

I'm using HD mode with high quality settings, and importing at full resolution.
I've tried with auto and manual aperture.

Just not sure where to begin looking for how to get clearer, less grainy video even in decent light.
Any suggestions?

Although I don't use the video on my K5 I do know the following areas will help reduce grain and give your video more impact:

The choice of lens you use will play a big part, so use the best glass you have.

Try various combinations in terms of White Balance and Scene mode settings, as this will help you get better colour rendition

ISO, although very good on the K5 don't abuse it, the lower the better.

Finally editing in Adobe Premiere and Adobe after Effects will make your film pop, just like editing photos in Photoshop.

Just like everything in life you have to practice, experiment and with time and effort things will develop and improve.

Hope this provides some areas to explore.

Does the ISO you start at make a difference? I get the impression the camera just boosts 'ISO' to get the correct exposure, and the only control you have is your aperture.