Creating video DVD from MP4 (1,7 GB) takes ages on MacBook 13" 2,16 GHz / 3 GB RAM
I'm not a MacOS user, but this wouldn't be an abnormal amount of time on a Windows PC - it needs to fully recode the video and audio into the correct format.

There's no real way to speed it up, with the exceptions of upgrading the PC or downloading the video in a different format or Standard Definition.