screen resize slow down the encoding speed?

I always encode DVD(.vob) movie at screen size 512 x 384(4:3), no problem arise; but I heard that screen resize slow down the encoding and take longer time to complete. It that true? I had tried to encode at 640 x 480(guess it is the DVD original), but the encoding was much longer. What is the reason behind:confused: Is that depend on bitrate, not the screen size?(Because when encoding at 640 x 480, I have to use a higher bitrate setting to maintain the video quality) Thanks for advice.

Original resolution is 720x480. Upsizing reduces speed, not downsizing. Downsizing means less blocks to process, so less time to encode (and less resources to decode)

Higher resolution = More pixel to process = More CPU cycles needed = Slower Bye

Thanks all of you, seem my current encoding style is ok.