Well that's the point. You can fit 2hrs of video on a 4.7 GB disk or a 8.5 GB disk depending on the bit rate set for video & audio format & bit rate. You can fit up to about 4 hrs on a 4.7 GB disk (but not such great quality!) Certainly the earlier (& still many now) dvd's use very low video bit rates such as around 4 Mbps. Whereas the dvd format allows up to 9.8 Mbps inclusive of video & audio. But many players on the market cannot play above 9 or 9.5 Mbps.

So in many ways it depend upon what quality setting the video is set at. For standard video a setting of about 8 for video gives a size of about 55 MB/minute, whereas a setting of about 4 Mbps is about 35 MB/min depending upon the particular video in question (yes this can vary!)

For HD ... well there's more than one HD format. But for the one you mentioned, I don't know! lol Never had the experience to date. The uncompressed size is about 20 times the size of standard video roughly AFAIK.