encoders in High priority. Depending on the setup of your rips, the encoder itself will calculate the encoding speed and changing the priority won't
speed up the rip, all that happens is needless stress on the RAM and CPU. You should realize that setting up an encoding of any video requires that the encoder has a lot
of knowledge about the video, so setting the encoder to a lower priority is actually more efficient because it allows more time for the encoder to scan every aspect of the video and calculate exactly how it should be compressed: B-frames, reference frames, frame structure, motion prediction, motion estimation, color, amount of blocking and deblocking it should use, amount of noise and denoising it should use, and one of the most important things: are the frames interlaced and how, also which is the best way to deinterlace those frames.
Try free Format Factory for the conversions ( Format Factory - Free media file format converter ). It never gave me a problem and does an excellent job in terms of speed and quality.
Never use a software that doesn't allow you to set up at least some of these options no matter how free or cheap it is and no matter how much other people tell you it's good; the resulting quality of the video will never be as good as with programs that allow these settings to be tweaked and optimized to your liking.
Handbrake is my best choice, but I'm sidestepping the answer here. Just lower the priority of the encoder, you don't need and shouldn't change it... ever!