Generally, M=3, N/M=5 is used for NTSC DVD, M=3, N/M=4 for PAL DVD, but when you create a stream for DVD with applying inverse 3:2 pulldown, M=3, N/M=4 should be set. This info was taken from CCE guide and I think that are good settings. About your speed I wouldn't be sure, because I read that on 2xXenon 3.2GHz CCE 2.70 is about 5 times faster then realtime.