Dirpy allows to download segments of audio streams from youtube. This is pretty easy since you can download HTTP .FLV streams from youtube, extract MP3 audio tracks from them and then split such tracks. This can be done with freeware command line tools... but of course dirpy allows to simplify the process.

The problem is that dirpy doesn't allow to record video segments neither from youtube, nor from any other site.

You can download or capture pornhub .FLV streams with a Flash stream recorder. Then just use a video editor like freeware AviDemux to cut parts that you don't need.

You can also record video segments from screen using screen video capture software.