FFMPEG MPEG-2 VBR output size not coming out as expected

[DJRumpy]

I'm using FFMPEG on OS X. I'm seeing odd results encoding MPEG-2 for NTSC DVD. I can't seem to get a consistent output size using the following command line:

ffmpeg -i /volumes/backup_win/quantum/00050.track_4113.264 -passlogfile /Private/tmp/ffmpegPass.log -target ntsc-dvd -fs 4340685210 -aspect 16:9 -croptop 140 -cropbottom 140 -bufsize 1835k -maxrate 9000k -b 5308k -s 720x352 -padbottom 64 -padtop 64 -r 23.976 -qmin 1 -qmax 20 -pass 1 -y /Users/Shared/output.m2v

The second pass command is identical except for the -PASS param. When I examine the output file's properties, it also reports itself as CBR, not VBR as I would have expected, with a Video Track Bitrate of 3788 kbps @ 23.976 fps.

The source is Blu-Ray (1080P). I also get an error that the encoding won't require all of the bitrate I've specified. The resulting file is only 3 GB instead of 4 GB.

Is there a trick to getting ABR/VBR output from FFMPEG via the command line with a specific target size?[/video]

[DJRumpy]

Bump...

Anyone? Surely I'm not the first to experience this?