[quote="SansGrip"] Judging by my copies of Highlander and 'Blackadder' these so called compressionists can't come up with anything better than a standard KVCD LBR!

This is starting to get hairy now , like the case of the chicken and the egg. Which came first The CQ_VBR or the GOP size

-kwag

Sounds to me more like a software "Phase Locked Loop" algo

-kwag

I think we make a sample strip and determine a good CQ_VBR the standard way. Then perhaps do an analysis of the MPEG as suggested above to determine the best GOP structure, then adjust CQ_VBR accordingly. Hopefully a small-ish change in CQ_VBR to match desired target size won't change the optimal GOP structure...

Ah, but then you get something like LOTR...

... Because if the changes are to great, we fall into a "positive feedback" type situation where a change in CQ_VBR throws off the GOP, and then it's like a never ending loop. And that's going to be a pain

-kwag

Or how about this: We figure out manually how big a change, on average, we get from optimizing the GOP for a given CQ_VBR. Then we deliberately miss the target with our file size prediction by that amount, then adjust the GOP...

Thinking Thinking ....... Thinking .....

-kwag

Got something
This is what I'm doing manually, and it seems to work correctly.
Start your encode with regular file size prediction. Say at CQ_VBR=25 and a GOP of 1-18-3-1-18. ( Half way between 1-36-3-1-36 )
Keep encoding as usual to target your wanted predicted file size. Then after you're done, go into TMPEG and select a 5 second range. Take something in the beginning of your 100 second window. We still haven't removed the file prediction script, so your range will be within 100 seconds. Now encode this 5 second clip. Take a look at file size. Now change your GOP and encode again. See if file size is larger or smaller, and adjust GOP up or down a couple of MAX P's accordingly.
The 5 second sample clip is very fast to encode, so you can play up and down pretty fast until you find the optimal max number of frames. Now after you're done, remove the frame range in TMPEG and go back to regular file prediction once more. After one or two runs, you should have your target again, with a slightly higher CQ_VBR value, but not that high to make a difference for a new GOP calculation. Hopefully this is what needs to be automated

Edit: I'm doing this right now, as I want to compare the original predicted file size with bit rate viewer, and then the new optimized mpeg. Because both file sizes will be about the same, I want to examine both mpegs to determine if the optimized mpeg has a lower Q factor meaning higher quality. Maybe not visually, but mathematically. If this is true, then we have achieved a GOP optimizing method. If the quality is the same, then CQ_VBR is playing a trick on us, and what we're doing is not worth it.

-kwag

I'm also encoding The Cannonball Run for the second time. The first one had 8 frames/GOP and this one 15. The first one is a couple of megabytes short of a full CD, let's hope that this other one is as well. Then I could check the files both visually and with Bitrate Viewer. Hopefully this will provide some extra information.

And what comes to bad compressionists, nothing can beat Future Film's remasters of Time Bandits and Monty Python's Life of Brian.. they both look more like a really bad XVCD than a DVD to me. The only good thing about them is that they were cheap.

Sansgrip

On the LOTR subject. I just watched the region 4 PAL Special Edition which has the movie on two discs.
It looks as if it needs a bit of blockbuster to me.!!!
For 2 discs it should look WAAAY better.

Beauty and the Beast looked a bit dodgy in places! - and that cost me a fortune!

What makes me laugh is these people have over 8 gigs to play with.

Let me know if it works, and I'll try duplicating here. If it works for me too I'll start figuring out how to add it to KVCDP .

I can only speak of the region 1 "normal edition" of it, full-screen at that (my wife picked it up and forgot to check which version it was, grr ).

I've not looked very closely at it, but from my regular viewings with family etc. it looks pretty darn good.

It's because they try to jam so many BS "extras" on there too. If they used the whole 8gb for video (aka SuperBit discs) the quality should be superb. Usually is, sometimes isn't.

What gets me is that I don't believe I've ever watched one of those "extras" more than once. Most of the discs I've bought, I've not even watched them at all. Very annoying.

Quick... quick!!

And the veredict is......... NOT WORTH IT.
The tighter the GOP, the more visible artifacts on low bit rates. So the higher GOP shines on smoothing artifacts. So the 1-36-3-1-36 is good enough to provide descent quality vs. file size. The smaller file sizes with different GOPs drop the overall quality too. I noticed it on a specific scene on "Red Planet" and after playing it over and over, I finally see that the longer GOP helps A LOT. So CQ_VBR is playing tricks on us as we change the GOP size. One more thing that should be tried is to find how long can we go in the GOP before we loose quality. In the original KVCD templates, this size was 48, and it caused problems with some DVD players. The "flashing" effect. With a GOP size of 36, I don't see anyone complaining. Could we jack this up more? How much more? Or is 36 good enough for what we are getting now?

-kwag

Booooo!

My biggest concern is, of course, retaining compatibility with as many standalones as possible. Anything over 18 (for NTSC) is non-standard and might cause problems.

:P

For DVD, yes 18 is definitively a must. For VCD playback, some will take long GOPs and others won't. Maybe 36 is good enough, or maybe there's not that much diffence between 18 and 36 and we can drop back to 18 for more compatibility I'll make a couple of tests at 18 and 36. If there's not that much difference, I'll fall back the templates to 18 with a note that if your player supports longer GOP, then crank it up at your own risk

-kwag

352x480 cq 20 the movie was 112 minutes in length

-Christopher

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Christopher
Linux is the body, Unix is its soul