Nominal Bitrate vs Bitrate?

[jweaver]

I am a long time user of Hybrid and use it for one function only, which is to reduce the size of my movie collection to a standard video and audio bitrate.

Typically I encode everything at 384kbs AC3 audion, and have 3 video profiles (all 720p):

2200kbs for Low action movies
2500kbs for Medium action
2800kbs for High action.

And these profiles have served me well...

Typically after encoding my movies are of an expected size and Media Info shows:

Bit rate                                : 2 500 Kbps
Width                                    : 1 280 pixels
Height                                  : 696 pixels

But I am trying to encode a movie using my 2500kbs profile, and for a 90min film its just too big (around 2.7GB)... When I check it with MediaInfo I see this:

Bit rate                                : 3 364 Kbps
Nominal bit rate                        : 2 500 Kbps
Width                                    : 1 280 pixels
Height                                  : 534 pixels


Why does this movie have a higher Bitrate than normal but the correct "Nominal Bit Rate"... How can I get around this and force it to 2500kbs like every other movie? What am I overlooking here?

Can you help me understand what I am looking at?

Thanks in advance

Jon