[Mjpeg-users] mplex: peak bitrate < average bitrate

[Libor S. <ls...@lo...>]

Hello,
I noticed  that  sometime mplex reports higher average bitrate than peak 
bitrate.
It is strange, isn't it?

I have been using mjpegtools for some time for DV->SVCD and
bitrates were different in usual way: peak ~ average + 20%.
Now I'm trying to create my first dvd, so I changed mpeg2enc and mplex 
options
so it looks like :
lav2yuv x.eli | mpeg2enc -f 8 -q 4  -4 1 -2 1 -b 7500 -s -g 6 -G 15 -B 
240 -o video.m2v
lav2wav x.eli | mp2enc -b 224 .... audio.mp1
mplex -V -f8 -h -o dvd.mpg video.m2v audio.mp1

and mplex reports usually average bitrate near to 7,5Mbit/s
but peak bitrate about 7Mbit/s.

I don't understand what I'm doing wrong.
What is acceptable difference between those bitrates?
I use mjpegtools 1.6.1.92.

Thanks for any hint.

Libor