MeGUI: Average bit rate?

[TECK]

Hi guys,

I encode my movies from Bluray with crf 18 mode and sometimes I re-encode the video with ABR, to further lower the bitrate. I noticed that on some videos I get an exact bitrate value and others I get something like:
Bit rate : 4 932 Kbps
Nominal bit rate : 5 195 Kbps

Why the 2 values in certain cases only and how can I avoid this?
Thanks for your help.

[LoRd_MuldeR]

You mean that in ABR or 2-Pass mode x264 doesn't hit the selected target bitrate exactly?

Well, that is because x264 allows a minor derivation of the resulting average bitrate from the target bitrate.

I think you can use the "--ratetol" parameter to control the tolerance, if you really have to...

See also:
http://mewiki.project357.com/wiki/X264_Settings#ratetol