[MEncoder-users] incorrect bitrate/filesize when transcoding mkv to mpeg2 pulldown/film2pal

[Andrew McKernan]

I'm an ffmpeg who's just started to use mencoder to transcode the excellent hd 
mkv 23.976fps files for dvd authoring.

Typical batch file is:
mencoder "Heroes S02E08.720p.HDTV.X264-DIMENSION.mkv" -of mpeg -vf 
scale=720:576,harddup -channels 6 -oac lavc -ovc lavc -lavcopts 
acodec=ac3:abitrate=384:vcodec=mpeg2video:vbitrate=8000 -mpegopts 
format=dvd:film2pal:vaspect=16/9 -noskip -srate 48000 -ofps 24000/1001 -
o "Heroes S02E08.mencoder.pal.mpg"

This produces a file which plays very well using a PC DVD player.
However, when I try to load the mpg file into TMPGenc DVD Author 2 I get a 
message like: 
"The video bitrate 104857 Kbps exceeds the MP at ML standard."
Also:
"The DVD-Video standard does not accept MPEG-2 with a VBV buffer size of 278 
KByte"

TMPGEnc MPEG Editor accepts the file as input but tries to create and output 
file 20x bigger than necessary.

TMPGEnc DVD Author 3 accepts the file and reports - picure size: 720x576, 
framerate: 25 fps, highest/average bitrate: 0 Kb/s, VBV buffer size: 278 KB, 
longest GOP: 215 fields, profile and level: MP at H-14(*)
It authprs a good DVD but feels the need to transcode the video stream.

Nero 7 Video seems happy to accept the file but transcodes the video stream 
into PAL - about twice the speed of TMPGEnc.

I get similar problems with any downcoding of mkv files to DVD mpeg - 23.976 
fps NTSC, 25 fps PAL or 29.97 fps NTSC.

Is this a bug in mencoder, ffmpeg, tmpgenc or my batch scripts?
Any advice welcome
Andrew
Cambridge UK