Bypassing Inverse Telecine!

[Trenton_Net]

Hi,

I was wondering if rather than doing an IVTC on a rip source (Since sometimes it dosn't work all that well eg. DVD), if its possible to just rip the movie like nomal and burn it as interlaced? If so, would I simply encode the movie the same, but in Tmpgenc, select "Interaced" rather than pulldown when playback?

Thanks for your time, I really appreciate it.

[adam]

Well first off there is absolutely no reason for you to be IVTC'ing every dvdrip that you do. Almost all dvds store the film as 24fps and use RTF/RFF flags to telecine the movie to 29.97fps. If you simply use the forced film option in dvd2avi then you will preserve the 23.976fps and will essentially get the exact same results as if you had done an IVTC.

You should first preview your vobs in dvd2avi and let it get past the credits. If it says %95 or higher film than forced film will work. If its anything else then uncheck forced film and if you want you can then do an IVTC. If you just want to keep it interlaced then yes, select interlaced rather than 3:2 pulldown while playback and also set the framerate to 29.97fps instead of 23.976fps. Also don't forget to set the correct field order otherwise your encode will be ruined.

To do this go into the advanced tab and double click on the deinterlace tab. Set the method to Even-Odd field (field.) Now scroll through your movie and see if it looks ok. If so then your field order is incorrect. If it seems to play a few frame than jump back a few then your field order is incorrect. Go back to the advanced tab and change it. Don't forget to uncheck the deinterlace filter when your done.

[MITSUI_1]

Hi Adam,

I have a comment on just the last point. Where the DVD is hybrid in a couple of places (e.g., where "FILM" is not 100%) I have frequently seen the "force film" introduce sync problems. As I understand it, "forced film" merely tells DVD2AVI to ignore the pulldown flags in a mpeg2 stream. Where it really is a film stream with such flags, the result is to output perfect 23.96 fps video, since that's what's on the disc. But where a clip is "hybrid" in that it has BOTH 29.97 true interlace NTSC source (i.e., in intro screens, intro credits, or logos) AND 23.96 fps full frame source that includes pulldown, forced film can and will cause a problem.

In my opinion: Hybrid DVD + Forced Film = Garbage + audio desync.

Here's why:

First, imagine the hybrid stream as it comes out WITHOUT forced film turned on. Here, lets make a diagram:

The first row of frames represent the "top" fields. The next row represents the "bottom" fields. The final row represents the actual "output" frame number as seen by the encoder your feeding with DVD2AVI. I've diagramed a clip where a true NTSC souce is spliced to a film source that has had the pulldown flags activated. Again, this is the "output" after the pulldown flags are activated (what you'd see in the DVD2AVI preview screen with forced film "off"), i.e., exactly what your DVD player sends to your 29.97fps NTSC television. The asterixes represent fields duplicated by the pulldown effect.

___________TRUE NTSC SOURCE PART___[splice]__FILM W/ PULLDOWN
=================================== | ===============
1a__2a__3a__4a__5a__6a__7a__8a__9a__10a__11a__11a* _12a__13a__14a
_1b__2b__3b__4b__5b__6b__7b__8b__9b__10b__11b__12b __13b*_13b__14b

__1___2___3___4___5___6___7___8___9___10___11___12 ___13___14___15

Thus, in this roughly 1/2 second video clip, your TV sees 30 fields which, considered two at a time are considered frames 1 through 15, for a total of 15 interlaced frames . The TV displays the T & B fields for a 60th of a second each, in the order I have shown.

Now, ask yourself: What are the source frames for this?

Well, there are only 14 total frames of source material: Frames 1 through 10 of the true NTSC stuff (10 frames), and frames 11 through 14 of the film stuff (4 frames), which becomes oubput frames 11 through 15 through the pulldown which duplicates two fields (see the * marks) to create an extra frame. The DVD player knows to add the extra fields by certain "flags" set in the MPEG stream.

Ok, now here's the kicker. "Forced film" simply causes dvd2avi to skip the repeat field flags in the MPEG2 stream. The program then simply collapses fields together and assumes that it will cause orderly 23.96 fps material to be created since every 5 frames would theoretically become 4 frames (remember that you're telling the program to assume its a "film" source).

But, turning back to our example the 5 to 4 assuption is not entirely true!

It IS true for the "film" portion which collapses from 5 to 4 frames when the pulldown flags are ignored. Thus,

With Pulldown flags considered:

_____11a__11a*_12a__13a__14a
_______11b__12b__13b*_13b__14b
Fr:..........1____2____3____4____5

"Forced film" with pulldown flags ignored:

____9a_ 10a_ 11a_ 12a
____9b_ 10b_ 11b_ 12b
Fr:.....1___2___3___4

By ignoring the pulldown flags in "film" material the program causes 5 original output frames to become 4 "film" frames.

BUT... the ten frames of "true" NTSC stuff at the beginning does not have HAVE any pulldown flags to ignore, because it is true NTSC stuff. It was recorded at 29.97 frames and thus it is on the DVD simply as alternating fields with now duplicate field flags. Therefore, when "force film" ignores such flags for frames 1 through 10 it gets the same thing that was there before:

____1a_ 2a_ 3a_ 4a_ 5a_ 6a_ 7a_ 8a_ 9a_ 10a
____1b_ 2b_ 3b_ 4b_ 5b_ 6b_ 7b_ 8b_ 9b_ 10b
Fr:....1__ 2__ 3__ 4__ 5__ 6__ 7__ 8__ 9__ 10

There are still ten frames there!

While the total stream (had it been "pure" film) SHOULD have collapsed down from 15 to 12 frames when the pulldown flags were ignored, it actually only collapes down to 14 frames.

What effect? Well, because of the hybrid stream, there are audio sync problems. Distinct noises and mouth-voice coordination will not jive with what you are seeing. Not good.

Therefore, I never use "forced film" unless I scan the ENTIRE movie with preview in DVD2AVI and get 100% FILM.

If it's anything less than 100% film (and most are), I uncheck "forced film" and simply use AVISYNTH and decomb.dll to inverse telecine and decimate the film to a true 23.96 fps which I know will then stay in sync when re-encoded.

This has resulted in VERY GOOD SVCDs with perfect sync whereas experiments on some of the same discs using "forced film" resulted in major sync problems.

So I don't really disagree that forced film saves the need for an IVTC step, but I would simply point out that too many people simply "assume" that they should check "forced film" without understanding what it really means. I'd rather have to do some IVTC ('specially since decomb.dll is so amazing at it) than have a crappy out of sync SVCD.

[adam]

Ok, now here's the kicker. "Forced film" simply causes dvd2avi to skip the repeat field flags in the MPEG2 stream. The program then simply collapses fields together and assumes that it will cause orderly 23.96 fps material to be created since every 5 frames would theoretically become 4 frames (remember that you're telling the program to assume its a "film" source).

Your logic is correct except that, that is not how dvd2avi's forced film works. Your right that forced film skips the repeat field flag but that does not cause the fields to be collapsed. Remember a true film source is stored as progressive frames, it is only separated into fields during playback while it is being telecined. For the x% of your movie that is stored as film it will be output exactly as it is stored, 23.976fps progressive frames.

Now as for the x% that is not stored as film, dvd2avi does not treat this the same as the % stored as film and it does not collapse the fields. In these instances dvd2avi decimates frames to maintain 23.976fps. This does often result in visible interlacing but if your dvd shows %95 or higher film than it is fairly safe to say that the %5 or less that is stored at 29.97fps is only on the credits, logos, etc...where its not that noticable or important.

I really don't see how forced film could possibly cause desync. You have the same number of total frames being played at the speed as the dvd. I can also tell you from personal experience that as long as the dvd shows %95 or higher film, than forced film maintains sync perfectly, at least it has on the 300+ dvds I have used it on. I would hazard a guess that your sync problems are caused by bugs in dvd2avi itself. Using dvd2avi to decode my audio I get sync problems about 1/3 of the time. Simply using azid to decode my audio instead sync is always maintained.

I stand by my statement that when making a dvdrip, IVTC is only needed if the dvd has less than %95 film.

[homerpez]

Would now be a bad place to mention... that if you make an SVCD, you can simply leave all video as "Interlaced" and it's supported and it works? No IVTC?

I suppose that would be too easy.

P.S. - despite the long speech on why "Forced FILM" doesn't work right, I have never EVER had it fail me yet. 99.9% of all feature-films (shown in a theater) are FILM rate, and play just fine when you choose "Forced FILM". I have even done "Forced FILM" rate on some Anime movies, which are clearly not exactly FILM telecined to 29.97... and it works for those too!

And, when you go to SVCD, you no longer have to worry about Interlace artifacts at all... just always use "Interlace" mode encoding output, and be amazed.

[N0SoopForU]

Would now be a bad place to mention... that if you make an SVCD, you can simply leave all video as "Interlaced" and it's supported and it works? No IVTC?

Yes, you can just leave it interlaced @ 29.97, but there are quality benefits to inverse telecining and encoding at 23.976 progressive.

[adam]

And those quality improvements are massive. Preserving the original framerate as opposed to encoding at 29.97fps interlaced is the single most significant thing you can do to increase the quality of your encodes.
With a max bitrate of 2.6Mbits the extra %20 bitrate you gain goes a long way.

[Trenton_Net]

How do I do a true 100% inverse Telecine? I know you can use AVISYNTH, but I don't even know where to begin using a scripting thing like that. And Tmpgenc's IVTC dosn't work very well, and I can't seem to find a IVTC plugin filter for virtual dub.

Does anyone know how I could get a flawless IVTC done?

[kwag]

How do I do a true 100% inverse Telecine? I know you can use AVISYNTH, but I don't even know where to begin using a scripting thing like that. And Tmpgenc's IVTC dosn't work very well, and I can't seem to find a IVTC plugin filter for virtual dub.

Does anyone know how I could get a flawless IVTC done?

Follow this guide for an excelent IVTC explanation with AviSynth.
http://www.inmatrix.com/articles/ivtcsynth.shtml

kwag

[Trenton_Net]

Hi,

I used their sample script to try an IVTC, but the output picture looks very odd, or "screen door" transparency effect look. You can see hazes of colors expecialy during pictures of the sun ect. Im not sure why the color output is like that. Maybe someone has a script they use for DVDs?

[kwag]

Hi,

I used their sample script to try an IVTC, but the output picture looks very odd, or "screen door" transparency effect look. You can see hazes of colors expecialy during pictures of the sun ect. Im not sure why the color output is like that. Maybe someone has a script they use for DVDs?

Hi Trenton_Net:

Lower the value of the Temporal filter.

kwag

[Trenton_Net]

What the heck is a temporal filter? I don't even think I use one of those in my script. All I have is the Dcomb.dll being used, and I needed to add GRB2YUV or something to get it to work.

Maybe it would be better if someone posted a script that just IVTC's a DVD source but leaves all else the same.

[kwag]

What the heck is a temporal filter? I don't even think I use one of those in my script. All I have is the Dcomb.dll being used, and I needed to add GRB2YUV or something to get it to work.

Maybe it would be better if someone posted a script that just IVTC's a DVD source but leaves all else the same.

Here' an example of what I use:

LoadPlugin("C:\encoding\MPEG2DEC.dll")
LoadPlugin("c:\encoding\decomb.dll")
mpeg2source("F:\THE_MATRIX_16X9LB_N_AMERICA\VIDEO_ TS\matrix.d2v")
Telecide(reverse=false,swap=false,firstlast=false, post=true,threshold=15,dthreshold=9,blend=true,chr oma=false,y0=0,y1=0)
Decimate(cycle=5,mode=0,threshold=0)
BilinearResize(352,352,0,0,720,480)
TemporalSmoother(2,2)
AddBorders(0,64,0,64)

On this example, I have used DVD2AVI on the VOB's WITHOUT "Forced Film" and I let the decomb filter do the IVTC automatically in real-time while encoding with TMPEG.

This works perfectly. Of course the Bilinear Resize will vary, depending on the movie and what you want for output. In this case is for the KVCD template at 352x480.

kwag

[Trenton_Net]

That seems very logical to do. However, where would I be able to obtain "MPEG2DEC.dll" to parse MPEG Files?

[N0SoopForU]

If you are ripping a DVD, especially a non-animation DVD, then I would highly recommend not using any kind of noise filtering. Most DVD's are clean enough and by adding noise filtering you are just spoiling the image (i.e the screen door effect you mentioned).

mpeg2dec.dll can be found at http://www.doom9.org in the Download section.

[kwag]

The sample of "The Matrix" is up.
It's the second file in the site.

It's 30 seconds and about 4 MB.
Made with the template at CQ=74.

It was done with the script I posted here before, without modifications.

@N0SoopForU:

Most DVD are not clean enough. I have a HDTV and I can even see blocks on some DVD's. A good example is "Air Force One". The shots when the plane is in the clouds, looks completely artificial, because the clouds look like hanging pieces of cotton!.

If you increase the temporal filter too much, then you will get a "ghosting" effect.

But the default value of 2,2 does a good job.

kwag

[N0SoopForU]

I'm aware a lot of DVD's exhibit "blockiness", but I personally feel it is better to leave the source as it is. Noise filtering just spoils the image, especially with live-action films.

But, hey, if it works for you, then go for it.

[Trenton_Net]

I did everything, and now it says I have an "Unrecognized exception!" on the "mpeg2source" line. I don't know what is wrong.

[kwag]

I'm aware a lot of DVD's exhibit "blockiness", but I personally feel it is better to leave the source as it is. Noise filtering just spoils the image, especially with live-action films.

But, hey, if it works for you, then go for it.

Yes. I agree with you that they spoil the image, but only if a high value is used.
The problem is that when encoding ( or transcoding ) to MPEG, any small bits of noise translate to viewable macroblocks on the final product ( VCD, xVCD, etc. ).

Specially if you're doing a capture via S-Video, you have to use a small amount of temporal noise reduction. If not, the result is worse that that of a DVD rip.

Have you tried AviSynth with TemporalSmoother(2,2) filter function?.
Look at any sample in the link in my signature. They all had the filter turned on. Specially "Mummy Returns" and "Patriot Games". These are good action scenes. Also "The Matrix".

kwag

[N0SoopForU]

Don't get me wrong, I do believe in noise reduction and am aware of the benefits, especially a reduction in macroblock noise like you mentioned. I use it almost all the time with my TV caps, which tend to be primarily animation. But, I still haven't seen the need to use noise reduction in a DVD rip. Maybe my television isn't large enough to see what you are seeing, but all the DVD rips I have done look much better without noise reduction. Like I said, if it works for you then thats what counts.

Nice samples, by the way.