[MPlayer-users] Using multipass in mencoder, file size differs in every pass - why?

[VJ]

Hi,
  I am using mencoder to encode my MythTV recorded programs with
commercials cut out. I am using multi-pass (more than 2-passes) using
vpass=3 for 3 times on every program that I record(script is at the
end).
  I find that the sizes of the files differs a lot for every pass. Why
doesn't it remain same as I provide the required target bitrate to
mencoder?

The directory listing is shown below:

-rw-r--r--  1 mythtv users 1348263936 Mar 14 02:19 Doctor Zhivago-1.mpg
-rw-r--r--  1 mythtv users 1329709056 Mar 14 05:12 Doctor Zhivago-2.mpg
-rw-r--r--  1 mythtv users 1378562048 Mar 14 08:05 Doctor Zhivago-3.mpg

The last pass is in progress so I am not posting the file size for 4th pass.

Regards from
VJ

*****************************************************
vpass=0
for pass in 1 3 3 3
do

vpass=`expr $vpass + 1`
#frames=" -frames 300 "
rm -f vidout
rm -f audout
nice -n 15 mythtranscode --chanid 1011 --starttime 2005-03-12-13-35-00
--profile auto --honorcutlist --fifodir . 1>/dev/null &
sleep 5
 mencoder $frames -noskip -skiplimit 0 -mc 0 -sws 2 -oac lavc
-lavcopts acodec=mp2:abitrate=128 -ovc lavc -lavcopts
vcodec=mpeg2video:preme=2:mbd=2:vqblur=0:mbqmin=1:vqmin=1:vrc_buf_size=1835:vbitrate=2171:vrc_maxrate=2171:trell=1:aspect=1.3333:keyint=25:vstrict=-1:scplx_mask=0.5:lmin=0.3:vrc_buf_size=1835:intra_matrix=8,9,12,22,26,27,29,34,9,10,14,26,27,29,34,37,12,14,18,27,29,34,37,38,22,26,27,31,36,37,38,40,26,27,29,36,39,38,40,48,27,29,34,37,38,40,48,58,29,34,37,38,40,48,58,69,34,37,38,40,48,58,69,79:inter_matrix=16,18,20,22,24,26,28,30,18,20,22,24,26,28,30,32,20,22,24,26,28,30,32,34,22,24,26,30,32,32,34,36,24,26,28,32,34,34,36,38,26,28,30,32,34,36,38,40,28,30,32,34,36,38,42,42,30,32,34,36,38,40,42,44:vpass=$pass
-of mpeg -mpegopts format=dvd -vf hqdn3d,scale=352:288:0:0:0.00:0.75
-audiofile ./audout -audio-demuxer 20 -rawaudio
rate=48000:channels=2:on -rawvideo fps=25:h=576:w=720:on ./vidout -o
"/myth/tmp/work/Doctor Zhivago-$vpass.mpg"

  killmythtranscode
done

  rm /myth/tmp/work/divx*.log
rm audout
rm vidout
********************************************