Large filesize variance--normal?

[ATimson]

Since I'm running low on hard drive space, I decided to start burning DVDs of some of the TV stuff I've been recording with my tuner card as AVIs. I've been using TMPGEnc v2.5 and v3.0 (initially the trial of 2.5, then I bought 3.0) to make 16:9 NTSC VBR DVD-ready files, 6000 k avg, 8000 max. Most of the files--all around 40-45 minutes--have been about 1.7-1.8 GB in size.

There's one, though, that's only 1.4. (1.5 when I reinstalled the trial of 2.5 and encoded it with that, after reencoding it with v3.0 and getting the same result.) I've played it, and it seems to be fine. But it seems like that's a rather large drop in bitrate--and significantly below my average (about 4500), especially since this file is slightly longer than most.

Since it seems to be fine, should I just ignore it? And is there any particular reason why this might've happened?

[Gurm]

Variable Bitrate, my friend. Something about the file made it easier to compress.

[ATimson]

Okay. Didn't think it was supposed to be that variable, but I guess it is. Thanks.

[Gurm]

Well, look at it - does it look ok?

If so, don't sweat it. Every once in a while it happens, and the fact that you can get the same result repeatedly indicates that it's no fluke.