decomb Decimate: which mode do you recommend for my purpose?

[JohnMK]

Hello,

I'm ripping/encoding Star Trek - The Next Generation DVDs, and would like some advice as to how I should go about reducing to 23.976 fps. The source material is 29.970fps NTSC, of which DVD2AVI reports 77% as FILM, 23% as NTSC, or so. If I Force FILM in DVD2AVI I get pretty good output, except in the NTSC portions. Do you think these portions (credits/special effects scenes) were originally shot at native 29.970 fps interlaced? I'm hoping I'm not completely blind, but Forced FILM looks good for most the show, (I'm guessing those parts were indeed originally 24fps telecined -> 29.970fps) but I'm not happy with that. I need a solution that looks exceptional for the entire episode, and I'm getting closer if I use decomb.

So far I've found the following is an improvement for the interlaced portions. Since I'm not a specialist, I can't really tell, but the FILM portions still look pretty good too, but I'm not certain of that:

Telecide()
Decimate(mode=0,qualitiy=3) (I'm using the beta 4 version)

What I'm after is your opinion on the different modes. Is this the mode I need, or would mode 2 work better for me? Do I need to mess with thresholds or 3:2 pulldown or other stuffs? I'm really at a loss, and your advice would be so appreciated. I've read so much already, and learned a lot, but not enough to be absolutely sure I'm doing things correctly yet, so please be tolerant. :D

I know I'll learn a lot from your comments. Thank you very much.

[manono]

Hi-

Hybrid material, such as ST:THG is tailor-made for Decomb's Decimate(Mode=1). It will preserve most of the progressive frames and deinterlace the video material allowing it to play smoothly. So, you might try:

Telecide()
Decimate(Mode=1,Threshold=50)

There may be a couple of drawbacks. One is that it will remain at 29.97fps and so you'll need a larger file size for the same quality when compared to 23.976fps. The other and minor one is that the original film material may play slightly jerky in pans and scrolls. You can find more information in the Decomb Help file (which you've already spent some time studying, I think).

[JohnMK]

I was afraid you might suggest mode=1. That is less than preferable. Cutting the framerate down to 23.976 (which is native for almost 80% of it) is rather important IMO. With that goal in mind, what do you recommend? Like I said, Telecide() Decimate(mode=0,quality=3) produces decent results while eliminating the combing interlaced artifacts. Can you recommend anything better? Please? :D Like threshold and guidance settings and stuff.

Thank you for your help.

[asifanwar]

I have so far done all the TNG discs out there (well I am at Season 4 disc 3 done and witing for the rest to arrive)
I have been playing around with TONS of settings and up until recently they were compromises.

A HUGE thanks goes out to Donald Graft who has come out with decomb beta 4. I used that for Season4 Disc 3 and it looked by far the best.

Here is what works for me:

Rip each episode (ie each PGC) using DVDdecryptor IFO mode.
DVD2AVI at 29.97 but with swapfield ON (not sure why, but seems to be smoother to me)
frameserve with AVIsynth using decomb4.0b using
telecide(guide=1) & decimate(quality=3)
encode in CCE2.5 using 3 pass VBR @ 2750
Pulldown afterwards and drop into Scenarist. Recreate the chapter points and drop the 4 PGCs into Title1 and then author.
Then I rename them VOBs to VTS2 and do the IFOupdate thingy (having already gotten rid of the copyright bit)

I am left with all four episodes VERY nicely encoded with all the orignal menus all coming to 4.25Gb. I found the space scenes to be pretty smooth with no compromise on the people which I HAD to have smooth.

Sorry this got so long, but maybe it helps somebody else too.
I would be happy to hear from you if you come across any new discovery in the ST:TNG arena, BTW! I dont pretend this way is the ONLY way to do it and I would be keen to keep improving.

Good luck

Asif

[JohnMK]

How does one determine if it's 3:2 pulldown material? :D

[asifanwar]

The original is mixed as you correctly diagnosed using DVD2AVI. It hovers between FILM & NTSC and never settles enough on either.
If it settled on FILM you could use the ForceFILM mode, and if it settled on NTSC then a simple deinterlace would likely work, but the middle-zone is where an good IVTC does the job.

By doing a proper IVTC you are taking the 29.97 and creating your new 23.97 encoded stream. This is why you then apply the 3:2 pulldown flag on it so your DVD player plays it OK. If you change your AVIsynth so that your DVD software takes the file without a pulldown, then you havent completely IVTC'd it back down to 23.97 (that is not to say it doesnt look OK)

23.97 is good too cos then you get the most out of your encode bits as there are less fps during the encode.

[JohnMK]

Thanks for your advice but everything aside from your avisynth script suggestions are pretty much irrelevant to my goals. :D

I'm going for 262MB/episode within the ogg media (.ogm) container w/ Ogg Vorbis --quality 2 audio for playback on PCs. :)

[asifanwar]

oh well.
Hope you find the AVIsynth of some use, and I would be interested to hear of any improvements you discover.

Good luck with your project!
Kind regards.

[jimbokoz]

Hello... your description of the Star Trek DVD's is similar to a DVD I've always had trouble with. (Stargate R1, Artisan). It has approximately 90% film and 10% NTSC. It's also got a really screwy telecine pattern, sometimes the fields get reversed when played on a soft DVD player, or when Force film is turned on.

Decomb appears to work very well - here's the script I used...

LoadPlugin("C:\PROGRA~1\DivX\GordianKnot\mpeg2dec.dll")
LoadPlugin("C:\PROGRA~1\DivX\GordianKnot\decomb.dll")
LoadPlugin("C:\PROGRA~1\DivX\GordianKnot\Convolution3D.dll")
mpeg2source("D:\Movies\Stargate\Stargate.d2v")
Telecide(guide=1,firstlast=true,gthresh=10,post=true)
Decimate(mode=2,cycle=5,quality=3,threshold2=2.0)
crop(3,104,712,270)
BicubicResize(640,272,0,0.5)
Convolution3d(1,8,8,8,8,3,0)

A couple of notes:

1. Using Decomb latest version (i think)

2. Telecide is using pattern guidance - it appears to help with the screwed up telecine. i've set the threshold's lower as the movie has several dark sections it seems to struggle with.

3. I'm using Decimate mode 2, which does a good job of sorting out what the best frames to drop are. It decodes the film sections very well, and seems to work well on the NTSC portions as well. 2 problems though - it's slow, and it sometimes gets jerky in dark scenes (seems to have trouble with the pattern guidance).

4. Convolution3d is used as the source material is fairly noisy...

hopefully this helps... decimate mode 2 will do the mode 1 sort of processing, but actually give u 23.976 fps..

jk

btw - can anyone improve on the script above?