x264: video bitrate

[rumpumpel1]

I'm shrinking my blu-rays with the following command:

ffmpeg -i BD.m2ts -an -sn -vcodec libx264 -b 14000kb -crf 15 -vpre libx264-hq -threads 0 -f mpegts out.ts

After this audio and subtitles are added with tsMuxeR. The result is ok. The question is: why is the resulting video bitrate so different although I'm using always the same parameters. For Coraline I got a video-bitrate of 16000 kb/s (even more than I specified) whereas for Up I got only 9460 kb/s.

Does this mean the quality is different ? (there is no visible difference)
If so, do I have to adapt everytime the crf-paramter ?

[nurbs]

These two, -b 14000kb -crf 15, are mutually exclusive. The last is used so you encode at CRF 15 (which is a huge waste of space in my opinion). CRF encoding produces more or less constant quality so you'll end up with different bitrates every time depending on the complexity of the source video. Bitrate isn't quality.

[creamyhorror]

To add to what nurbs said, remove "-b 14000kb" and change "-crf 15" to "-crf 20" or something more reasonable. You don't need to mess around with CRF values too much.

[rumpumpel1]

thanks, I'll try it out tonight.