[MEncoder-users] US OTA-HD scripts or flags?

[Robert Current]

I'm wondering if someone can suggest some scripts, or even flags, to
convert/downsample files correctly.

I have a MythTV system that records ATSC (American standard) Over the
Air High Definition (OTA-HD), and the files are HUGE and to big to
play on my computer.  Recording is fine, playback is not working.

There are basically two down conversions I'm trying to do, convert the
captured mpeg2 1920x1080 to an mp4 1280x720 @30fps if it's actually an
HD broadcast.

The second one is to take the mpeg2 1920x1080 and convert it down to a
NTSC SD like 720x480 @30fps.

I've borrowed someone elses command line, and it only get's me as far
as a smaller mpeg2, and I'm pretty sure I'm using some of the flags
wrong...

Anyway, here's I'm currently using:
mencoder -vf \
kerndeint,softskip,scale=1280:720,harddup \
-ofps 30000/1001 -aspect 1.7777 -ovc lavc -lavcopts \
vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9600:\
vbitrate=4771000:keyint=18:turbo:trell:dc=10:autoaspect=1 \
-oac lavc -lavcopts acodec=ac3:abitrate=192 -of mpeg \
-o "$1" "$2"

and

mencoder -vf \
kerndeint,softskip,crop=960:720:160:0,scale=720:480,harddup \
-ofps 30000/1001 -aspect 1.7777 -ovc lavc -lavcopts \
vcodec=mpeg2video:vrc_buf_size=1835:vrc_maxrate=9600:\
vbitrate=4771000:keyint=18:turbo:trell:dc=10:autoaspect=1 \
-oac lavc -lavcopts acodec=ac3:abitrate=192 -of mpeg \
-o "$1" "$2"

Can someone point me to a better way to do this?

Thanks,
Rob C.