Two pass encoding time savings

Hello,

I've done a two pass encoding using mplayer, the first pass created the
xvid-twopass.stats file  and approx 1.2GB avi file.  This is my command:

mencoder dvd://2 -ovc xvid -xvidencopts
aspect=1.777778:bitrate=1200:pass=1 -oac mp3lame -lameopts vbr=3 -ss 15
-o output1200.avi;mencoder dvd://2 -ovc xvid -xvidencopts
aspect=1.777778:bitrate=1200:pass=2 -oac mp3lame -lameopts vbr=3 -ss 15
-o output1200.avi


The resulting output1200.avi is about 240MB.

My query is if it is possible to create an approximation of the stats
file? (Not creating a perfect stats file, which takes 6 hours in my
case.)  For instance only processing a one quarter size image of each
frame would likely produce near identical overall statistics for the
actual encode in pass2.  Obviously the stats would need to be scaled to
apply the data to the full size stream in pass2, but this approximation
would save a great deal off the pass1 time.

Maybe this feature is already present?  I could not spot it.  I would be
interested to know what people think of my idea for saving time on the
profiling of the stream to generate the graph.

Regards

JG