True cbr for MPEG 1

Hello,

I need to create MPEG 1 video that is flagged and truly 1500 cbr. I have tried many things. I can submit settings but I wanted to ensure first that cbr is truly still supported. 

For instance, Format 1 which is VCD comes up variable. Or If I set it to format 0 and use - -cbr alone it will still remain variable. The list goes on...

Any help is gracefully appreciated,
Drew