Just fyi here. Nothing major and probably has been done before.

I had a hd-dvd that I made into a mkv last year. I'm 99% sure I used ripbot to do so. It was 720p with 5.1 ac3 (regular ac3).

I have recently been converting a lot of my blurays to dvd and wanted to do the same to my small hd-dvd collection. However my hddvd 360 drive was in storage and I didn't want to lug it out again to rip a disc. So I bumped into my mkv file on dvd dl. I copied it and had the file ready to go - avc 720p video fyi.

I loaded it into avs to dvd and it recognized it no problem. So I went ahead and converted it to 720x480 with the 5.1 intact. It turned out beautifully. THere wasn't any noticeable degradation from using a downscaled copy instead of the original 1080p hd-dvd.

Of course I played it through my ps3 which was connected via hdmi and set to upconvert so it was being "enhanced" more so. But it looked great and best yet it stayed in SYNCH! That I liked.

So I went from:

1080p hd-dvd

720p avc mkv file

720x480 mpeg2 dvd

The final dvd looked and sounded just like a normal dvd. Even at the single layer output I set it to it still looked as good or slightly better than a standard store bought dvd.

So just saying that yes I should have started over with the original hd-dvd this intermediate source still worked out rather nicely.

Plus it saved me the hour or so it takes to rip a hd-dvd with my xbox 360 hd-dvd usb drive.

EDIT - to any who ask - YES OF COURSE I STILL HAVE MY ORIGINAL HD-DVD OF THIS MOVIE. Otherwise that would be against forum rules for discussing and wrong to do so.