HD-DVD compliant AVC/h.264 using x264

[miamicanes]

Does anybody (with access to the details and willingness to share them) actually know what hard limits need to be observed when encoding video (ultimately destined for HD-DVD) using x264? Particularly, with regard to things like maximum GOP length, restrictions on B-pyramid size/distance, etc?

The source video is DV captured from VHS. My goal is to preserve as much DV quality as possible, while taking advantage of every minimally-lossy compression strategy possible, with a target average bitrate of 8mbps if I can get away with it, 10-12mbps if worthwhile, 16mbps if necessary. I have a nagging suspicion that if I try to max out x264's GOP, max reference, and max distance parameters, I'm going to be in for a rude shock 1-3 years from now when I finally go to author my first real HD-DVD...

Put another way, how much of a quality-penalty is there for re-encoding tightly-packed AVC/h.264 into HD-DVD-compliance if the re-encoded file is allowed to be ~25% larger than the original, non-compliant file?

The first is encoded with 8mbit/sec avg, 9mbit/sec max using every optimization supported by x264... 240+ frame GOPs, insane B-frame pyramids with 30+ reference frames, the works. When the day finally comes to put it on a HD-DVD, I grudgingly re-encode it into compliant AVC/h.264 with target bitrate of 12-16mbit/sec avg, 20mbit/sec max.

The second is encoded into HD-DVD compliant AVC/h.264 with 10-12 mbit/sec avg, 20mbit/sec max bitrate. Assuming I can actually find anyone who can tell me what "compliant" specifically means in the context of HD-DVD.

Which of the two files is likely to look better when viewed from HD-DVD? The one that was tightly-packed like a Chinese wood puzzle and fluffed up prior to burning, or the one that was encoded to be compliant in the first place, using a bitrate that's about 20% more than the tightly-packed noncompliant bitrate, but ~75% the size of what that tightly-packed video would have been allowed to grow to when re-encoded?

[jman98]

If you don't get a helpful answer here (sorry, but this is pretty bleeding edge stuff for a lot of us here), you can go over to the forums at http://www.doom9.net and post there. They definitely have people who can answer your questions. Do note that HD-DVD has specific fps requirements that you need to be aware of. Basically everything below 1920x1080 MUST be 60 fps. Only 1920x1080 content is allowed to be 24 or 29.97 fps.

[miamicanes]

Hmmm. Are you sure that's a HARDWARE/CODEC constraint, and not just a content-labeling/logo requirement? I can see the DVD Forum telling content producers, "You can't slap ${HD DVD logo #1} on your box and advertise it as 'HD' if it's really 6-24 hours of 480i60/59.94 shovelware burned onto a HD-DVD-disc", but it blows my mind that they'd completely foreclose the possibility of doing it at all. OK, I could probably see SONY doing something like that with Blu-Ray just because they're Sony & inherently pathological by nature, but I can't see Microsoft EVER going along with an arbitrary restriction like that without putting up a major fight (unless VC-1 can do 480i60/59.94, and it's only AVC/h.264 that can't...).