IVTC: a "virtual guide" on how to perform IVTC on a general title

[Sir Didymus]

The idea of the present "hypothetical guide" is based on a discussion with manomo (Rebuilder forum) and it is on how to reinsert an IVTC video stream back in a general DVD title before compressing it.

It may be useful in case you (NTSC user) want to explicitely apply some IVTC process to restore a badly authored title before backing up a DVD.

The meaning of "badly authored", here, is that instead of properly using RFF and TFF flags, some redundant fields (20% of the total) are physically present in the MPEG stream, purposely [and wrongly] inserted in order to perform the 24 --> 30 fps telecine operation.

Since I am from PAL land and my brain is running at 25 fps, you may easily understand why this "guide" is hypothetical (at least for myself and for all of the PAL-land people). So, I have no idea if it may even work, since no way to check on my own... anyway some feedback is appreciated...

This could be relevant since it may allow to gain 20% of the title size, for these badly authored titles, even before encoding them...

Want to say again that inspiration was due to a nice discussion with manono (Rebuilder forum), and from the fundamental guide of Malcom: http://forum.doom9.org/showthread.php?s=&threadid=84887

What follows is basically a copy, with some obvious adaptations, of the Malcom guide...

You need the following tools:
- any DVD Ripper
- PgcDemux
- Specific tools (and/or avisynth plugins, dont'k know which ones,...) to perform the basic IVTC process on the video stream
- MuxMan [preferred] of ifoEdit or ReJig
- VobBlanker


It should work for multiple audio tracks, keeping subtitles, chapters and the menus-structure.

It seems it may have some limitations (example, at the time writing, VobBlanker cannot process multiangle DVDs...)


1. Rip the DVD to your harddisk.
2. Open PgcDemux, choose the .ifo file for the main movie on the DVD.
Demux all audio, video + substreams.
Create also the Celltimes.txt + the logfile.
3. Use specific IVTC tools/process to convert the demuxed m2v video
stream to a new IVTC'ed m2v stream, containing 20% less frames...
4. Open MuxMan or ifoEdit or ReJig. All of these programs have the
same functionality to create DVDs. MuxMan is preferred due to the
authoring quality, which is the highest... Author a new DVD,
selecting the IVTC'ed video track, the demuxed audio tracks
(taking care for the right order: 0x80, 0x81,..), the demuxed
substreams. Select the modifyed Celltimes.txt. Create the DVD.
5. Open VobBlanker. Open the original, ripped DVD (NOT the one you
have just created with MuxMan/ifoEdit/ReJig)! Select the main
movie TitleSet + PGC (the one you have demuxed with PgcDemux).
Select 'Replace' and choose the VOB from the DVD you have created
with MuxMan. Hit 'PROCESS!!'
6. Maybe some ifoedit processing is missed...
7. Having processed in such a way the source title, it should have
the 20% higher bitrate than from other methods just based on the
straight compression of the original source... Not bad to start...


It should work..., hopefully...

Of course the biggest thanks are due to jsoto for giving VobBlanker and PgcDemux to the community... They are really beautiful [and very useful!!!] applications...

Cheers,
SD

P.S. Hey Malcom, I basically took your excellent guide, and adapted a little bit... Apart a big thanks to you, hope you don't mind this my little cut and paste exercise...

@all: afraid if some evident mistake is present. Shame on me in this case...

Edit 11.02.2005 - Deleted a part related to modifications of the Chapter Points in the CellTimes.txt file produced by PgcDemux; deleted also some final comments, stating [wrongly] something about encoding of already encoded video - it was simply wrong... thanks manomo!!!

[TheSeeker]

Hey Diddy!! Nice guide, especially considering you have no way of testing it personally. What I really want to know... and im sure this has been answered many times, and each time the answer is a little or a lot, different. What is a good way to determine if you SHOULD be IVTC'ing a title? I mean I know that you can use dvd2avi's preview mode to gather some information, but is there a quick and easy way to look at some information and say... YES this title should be ivtc'd or NO most definately not, this does not need to be ivtc'd. What software and/or what guide should i be looking at to determine this? I do mostly fairly major hollywood titles, but I do alot of anime as well and I just dont know a cut and dry way to tell if I should be ivtc'ing a title.

[Sir Didymus]

Hi mate, :)

Well, the topic is very serious; much better if some master on the subject want to take place, not to talk about I feel the very uncomfortable situation of being in the wrong side of the mirror...

What is a good way to determine if you SHOULD be IVTC'ing a title?

My view is that the process is not trivial and it is worthwile only if the perspective of gaining 20% of the bitrate [in cases where redundant information is actually stored in the source material] may compensate for the time spent in the IVTC process and the associated risks of screwing things up...

So, I would adopt some tools capable of showing if RFF flag is actually used or not in the source m2v stream. For example, using bbvinfo (verbose level 2):
Vob tools of dload doom9 area --> bbtools
you may easily log all necessary information for understanding if you are in situation showed as “Example1” or not in the manono’s post:
http://forum.doom9.org/showthread.php?s=&threadid=88164

If 4 mpeg frames and all the flags are used, leave it as it is, since no redundancy is present.

If you are in situations showed as “Example2” or “Example3” [10 fields or 5 frames per cycle], you should understand (with VirtualDub or DGIndex) if your source is coming from a truly interlaced origin (TV or other, 30 Hz Fields) or from a Motion Picture Telecined.

If it is truly interlaced, with all fields different from each other, then leave your source as it is, since no redundancy is present.

That’s my understanding…, and well, it’s not so easy and not so quick…


What software and/or what guide should i be looking at to determine this?

Again better asking to some really competent people [many are zapping all around]; my readings on the subject have been the following:

1. doom9:
http://www.doom9.org/ivtc-tut.htm
http://www.doom9.org/synch.htm
http://www.doom9.org/decomb.htm
http://www.doom9.org/decomb-params.htm

2. the one, very nice, pointed out by manono @ hometheaterhify.com:
http://www.hometheaterhifi.com/volume_7_4/dvd-benchmark-part-5-progressive-10-2000.html

3. inmatrix.com (very basic concepts...)
http://www.inmatrix.com/articles/ivtcsynth.shtml

Cheers,
SD