Burning mpeg2 to DVD-9 with nero 6

[ictaylor]

Can anyone explain why a 2.7GB mpeg2 file obtained by recording a 3 hour film from Film4+1 digital TV channel at about 2Mbps bitrate needs 6.86GB on a dual layer DVD using Nero 6? Is it because some decompression is taking place during the burning to DVD?
I used DigiTV software to make the recording. It all works OK, it's just that I'm curious about the big change in size from mpeg2 on hard disk to the size on DVD.

[Baldrick]

If the mpg is dvd compliant, see www.videohelp.com/dvd#tech , it should be about the same size after you authored and burned it. But if it's not nero will reconvert it(nero may also reconvert compliant streams), can't you specify the bitrate/output file size in nerovision? Then TRY something else, lots of all-in-one converters out there like TMPGENC DVD Author.