Interlaced and Non-interlaced shown w/ DVD2AVI

[Ripper2860]

Just quick question to hopefully better understand what is going on ...

I have been using DVD2AVI to "preview" my VOB rips and determine whether they are INTERLACED or NON-INTERLACED. I've run into a few DVD's where while previewing, the statistics windows for DVD2AVI alternates between INTERLACED AND NON-INTERLACED and NTSC and FILM.

Why is this going on? What does this say about the VOB's? I can see if the TITLE SCREEN or something like that was one thing and the main movie another, but the main movie alternates as well.

Any ideas ??

Thanks in Advance !!

[racer-x]

Run it through BitrateViewer. It will tell you if it is interlaced or progressive. If it is interlaced, it will tell you the Field Order.

[Ripper2860]

Racer-x,

Thanks! A much better tool to accomplish what I needed and provides field order to boot !!

[SLK001]

Well, first off, all DVDs are interlaced. What you need to do is run DVD2AVI with the FORCE FILM option enabled to see if the video was HARD TELECINED, and not just had a 2:3 PULLDOWN applied.

Anyway, both programs only look at the flags in the video stream. These flags may be incorrect (don't know if this is from incompetence at the studio, or from some evil attempt to thwart legitiment backups). I have seen videos with both the field order flags alternating and the pulldown flags in the wrong place in the stream. It was so bad that DVD2AVI could not handle it properly. I had to run the video through an external Inverse Telecine program.

Bitrate Viewer only looks at the first header. It doesn't update itself on field order changes, which can be missleading if you start in the wrong place.

[adam]

Yeah I really don't think BitrateViewer is very useful for determining the interlaced or progressive nature of the source. Almost all DVDs are going to come back as interlaced because the first cells of the movie are going to be the studio logo's, not the actual movie, and the opening logos are almost always interlaced.

If dvd2avi flickers back and forth extremely quickly between interlaced/progressive and NTSC/FILM than most likely it is progressive but the prog_frames flag is incorrectly set to false meaning interlaced. I have seen this on many commercial DVDs, even big ones like Signs and Gladiator. Just turn forced flim on and then load the d2v into something like TMPGenc and preview it. If you don't see any interlacing (horizontal white lines) than just treat it like any other progressive DVD.

When authoring DVDs the prog_seq flag should ALWA"YS be set to interlaced. The prog_seq flag should be set according to the type of pictures you encode with, ie: interlaced or progressive. Apparantly not even commercial studios get this right.

An interesting side effect of incorrectly setting the prog_seq flag is that the top scan line will flicker. Watch the movie Signs really closely and look at the top letterboxing. It will appear to bounce down into the picture every second.

[jbenj01]

adam, (sorry, slight off-topic)

When you say, "When authoring, prog_seq flag should ALWAYS be set to interlaced", where/how in the authoring process (or program, i.e., Maestro) do you set that??

I ask b/c when I reauthor in Maestro, i simply import my re-encoded m2v file and don't recall ever having option to set to either progressive or interlaced.. ??

[SLK001]

I've only seen the PROGRESSIVE_SEQUENCE option available in PULLDOWN.EXE. This should always be set to INTERLACED. However, PROGRESSIVE_FRAMES should always be set to PROGRESSIVE (if you have a FILM source).

I don't know when you would ever set your sequences PROGRESSIVE.

[Ripper2860]

SLK001, Adam, and all ...

Thank you very much for your replies. It seems that this is a much more convoluted process than I thought. However, I have a few questions ...

1.

Well, first off, all DVDs are interlaced. What you need to do is run DVD2AVI with the FORCE FILM option enabled to see if the video was HARD TELECINED, and not just had a 2:3 PULLDOWN applied.

How will I be able to tell whther it's 3:2 or hard telecined? Is this done by the previewing in Once I am able to tell, what should I do then -- encode as interlaced on non-interlaced?

3. I primarily use DVD2SVCD a/ CCE, is it safe to assume that there is a 50/50 chance that the program is detecting this properly?

Sorry if these questions are "simplistic".

Thanks !!

[vhelp]

no effense to anyone here :P

But, in my experience, I've concluded that ALL dvd titles are interelaced,
unless they were pure Progressive to start with.

There rae two type of Interlace dvd's:

* Pure Interlace (that every frame (or field) is interlaced) or,
* Telecined (that's 3:2 ie, PPP:II PPP:II PPP:II PPP:II PPP:II PPP:II)

DVD2AVI only inserts (or parses) out the pattern so that all you see is
progressive frame when your .d2v your dvd's. Actually, all it does is use a
pointer to a given frame.. that's all your .d2v file is. One big library of
of pointers, actually pointing to your HD's (VOB data) areas and storing them
in he .d2v as reference numbers

As ben indicated above, dvd2avi can fale things up - - take for instance,
the dvd tile, "Just Visiting" (w/ Christina Applegate) run this through your
dvd2avi, and I guarentee it will give you Interlaced hickups (or ~80% under
dvd2avi)
After foiling w/ this for the last year, and doing verious tests (as I always
do) I have concluded that the BEST way to handle a dvd rip/convert/encode/author
and burn w/ success, is to first rip w/ Field Operation: None
and code your .avs script w/ the following, for a PERFECT Flawless encode:

* pulldown(0,2)

I tell you, the above works perfectly. You just gotta STOP using dvd2avi's
window, because it just isn't accurate. If you just ignore that process, and
just rip w/ true Telecine on (set to None) you'll get a perfect 3:2 source,
that means, Progressive Progressive Progresive : Interlace Interlace ...
And, the * pulldown(0,2) will process this Pure Telecine perfectly !!
One thing, remember to run your .d2v source starting frame as the first
Progressive (ie, PPP:II) (not, P:II PPP:II, or II:PPP) as this is incorrect a
pattern sequence for pulldown(0,2) to parse.

Do the above, and you will have PERFECT rips every time. I've never had
an issue w/ any rips I've done (though mostly test for this process)
.
.
I know its hard to say no, but you just gotta do it. Do it, and you won't
regret it. It WILL become second nature to you. It will :P

From the Video Workstation of,
-vhelp 2336

[SLK001]

1) I use Virtualdub to step through the material to see if the FORCE FILM gave me true progressive frames (3 PROGRESSIVE frames, then 2 TELECINED frames). If so, then I know that the video has been HARD TELECINED, so I run a IVTC filter in my AVISYNTH script.

2) There is no question #2.

3) I guess that the odds of getting it correct with a guess is 50-50 as you say. The problem with these "do-it-all" programs is that they are never as intelligent as the human at the keyboard.

[adam]

Yes I was referring to the progressive sequence flag, which should always be set to interlaced for DVD. So in this sense, yes all DVDs are interlaced. You can change this flag in pulldown or something like DVD Patcher probably, other than that I don't even know how this flag would ever be set to anything other than interlaced...like it should be.

The frames themselves, however, can be either frame or field type. Basically they are still made up of two fields but if encoded as a frame picture both fields are displayed simultaneously, effectively giving you a progressive frame. Of course if you are using pulldown flags than some of these fields will be repeated and will be used to create new frames which are in effect field type for just these frames. But if you take the actual source, it will be nothing but progressive frames. That is why if you decode an NTSC vob and parse the RFF/TFF flags you will typically see 3 progressive and then 2 interlaced frames. The source itself is entirely progressive, but it is creating new interlaced frames on the fly. Run it through dvd2avi with forced film on and it simply ignores the RFF/TFF (pulldown) flags and skips the on the fly telecine process, so it exports the frames exactly as they are stored on the DVD...as 23.976fps progressive frames. Of course this only works if the DVD is in fact stored as FILM, but luckily this applies to almost all theatrically released NTSC DVDs.

vhelp that is not at all how dvd2avi or d2v works. The vast majority of DVDs are in fact progressive frames. The interlaced frames are created on the fly by the DECODER. DVD2avi is not just selectively passing the progressive ones on, there are no interlaced fields at all because it is simply ignoring the command to create them. There is really nothing being decided by dvd2avi at all. It is simply parsing the field frame type for each frame and reporting what it is. Assuming all frames are flagged correctly, then if you have any field type pictures than your source is not proper for forced film. Forced film only works on FILM (progressive frame sources.) If you get jerky playback or visible interlacing it is because you used forced film incorrectly. To prove this take an NTSC vob which dvd2avi reports as film. Demux and run pulldown on it and set it to remove the 2:3 pulldown flag. Now play this back in anything that will decode it and you will see nothing but progressive frames. This proves that the film itself is stored as frame pictures and dvd2avi simply bypasses the pulldown flags so as to get the unaltered source before the telecine occurs.

As long as you don't mind seeing some possible interlacing during opening and closing credits, which are usually interlaced, dvdavi's forced film will always work perfectly on a pure FILM source, which most DVDs are. Of course you can accomplish the same thing via an inverse telecine, but it takes twice as long at least.

So now on to field type pictures, they are just created by displaying each field one after the other rather than at the same time. You see this alot with extras on DVDs because that is how they are shot. But you will rarely ever see this on a theatrically released DVD for the main movie.

So if you encode with frame pictures than you must set the prog_frames flag in the video stream to true, and if you encode with field picture you must set it to false. These flags are typically set by the encoder. Look for an option to encode as interlaced or progressive. If you mix and match than you may get anomolies during playback, and if you preview the vobs in dvd2avi it will flicker back and forth between interlaced and progressive.

[vhelp]

Hi Adam,

I don't mind being corrected :P when I'm wrong.. zats how I learn, right ?
anyways..

I gotta question then. Is there a direct VOB reader, that will read in a VOB
file (after ripping (ie, using smartripper)) and allow me to walk through each
frame so that I can verify what I see against what you described ??

I asked this, cause no matter how I bring in a VOB (dvd2avi, or vdubMOD)
I will various Interlace frames (ie, "Just Visiting") has this all over the place.
I'm verifitying it now. And, no matter how I do it, I see Interlace, However.
If I run it through my process I described above, perfect progressive frames :P

Hope you (or soneome here) has a suggestion for a good app to use in
these trying projects. Thanks in advanced,

-vhelp

[FOO]

I have seen several movies on DVD that were mixed
Telecined Film and straight 30 fps. Usually with
"made for TV" movies or episodic movies. They are hell to edit.
My last one switched modes about every 10 minutes for no
apparent reason.

FYI The MPEG2 spec reqires that the Progressive flag be set to
enable the Pulldown. That doesn't make much sense because
pulldown is inherently field based. There is another separate 2 bit field that specifies frame or field based pictures.

An easy way to observe this is to generate a D2V file with DVD2AVI and
open it with Notepad. The file consists mostly of numbers representimg
the Tff/RFF flags
00000000 is Bottom field first 30 fps
22222222 is Top field first 30 fps
01230123 is Telecined 24 fps

Also I have NEVER seen a DVD that wasn't STORED progressive
as opposed to 2 fields in a row , which MPEG2 allows

[vhelp]

I U/L'ed a small VOB file (use winRAR v2.90 b2)

The only purpose is to demonstrate the Interlace that I
described above, w/ respect to why I use the method above,
for all my DVD processes :P

The process to VOB: ...

* The VOB is based on Smartriper v2.27, ripped only chp #2
* Open VOB inside MPEG2Cut v1.15 (by jakei/symbiose/Dark Avenger)
...to cut out a small section (71 frames is enough)

You can't miss the Interlace lines, but the rest is Progressive, though
throughout the movie it alternates.

My thought on DVD processes (via Hollywood/Commerical/Professionals)
is that some are just "domb" poorly, or produced on purpose this way,
or some other "domb" reason

My finding in "Just Visiting" (though nice quality) is:
* 2:35.1 aspect ratio
* nice color space quality
* The reason for the switching back and forth Int/Prog is partly due
...to the fact that when the frame shifts up then down, this is throwing
...off the pattern, or the flags or whatever. This is why I wanted
...or asked for a pure VOB reader, so there would be no sign of tainting
...the source VOB for analigy (Interlace or Progressive frame findings)


** pic is a copy from vdubMOD, resized to 512x218 (keeping aspect ratio)

Grab the VOB here:

* just_visiting.interlace.rar

-vhelp

[adam]

vhelp I don't know of ANY program that will allow you to view the vob's source frames and selectively ignore certain flags in the stream. The flags tell the decoder what the frame is, the decoder needs this type of information in order to display them. You can't just load a vob into Vdubmod. It will parse the pulldown flags..everything will. You are always going to see the product the telecine this way, which will always be interlaced. That is the job of the decoder, to do what the flags in the stream tell it to do, and that includes performing a 2:3 telecine.

If you want to verify that the vob itself only has progressive frames then do what I said in my original post. Manually remove the flag. You can use pulldown.exe or DVD Patcher. Then view the vob in anything and you will see that the frames of the movie are entirely progressive and the framerate will be about 24fps (slightly higher because the credits are 29.97fps). You will not see any interlacing at all except possibly during the opening or closing credits. This will apply to about 99% of all theatrically released DVDs. There are the occasional ones (Jay and Silent Bob) that differ from the norm and may have an actual mix between interlaced and progressive material in the movie. This is extremely rare though. Out of maybe 1000 NTSC DVDs I have looked at, the aforementioned one is the only one I have ever seen like this.

The only time you really can't use forced film is on material that was shot in NTSC or with video that has undergone very strange editing or conversions such as Anime. Other than that, DVDs almost always use progressive frames. Its a vastly more efficient method of storing the information, its much easier to produce, and possibly most importantly it is the very reason why we have progressive scan televisions now. The whole point of progressive scan televisions is so you can keep the progressive nature of the source rather than have to deinterlace it.

BTW: The DVD Demystified FAQ talks alot about this subject.

[vhelp]

thanks adam,

for your continue explanations.

I did some reading up at various websites after numerous digging and searching
and I'm pretty beat. But, so far, everything that I've read, seems to support
your responses :P

Hay, I did say I don't mind being corrected when I'm wrong.

But, I'm still confused becuase of the way dvd2avi will act w/ various dvd
titles, as in my "Just Visiting" did, were it switches back and forth w/
* NTSC/Film
* Progressive/Interlace

This tells me that the actual VOB source is messed up or processed poorly
at the studios. So, either somewhere along the line, dvd2avi can't make
up it's mind, or the VOBs are just poorly flaged or some Frames in the MPEG-2
got screwed up. (After my carefl analiysis of some frames that act up, by
shifting up/down, could throw off the flags or dvd2avi) even if the MPEG-2
is in perfect shape, maybe some frames were left along for some other
reason

However, given my long experience w/ my method above, I will continue
to main that process, as it gives me perfect encodes :P even if the above
discussions say otherwise.

Thanks again, it was an interesting topic.
-vhelp 2340

[adam]

If dvd2avi jumps between NTSC and FILM during its preview than that means the movie is a mix between film and telecined material. Yes the actual data on the DVD is partly progressive, and is being telecined during playback, and other frames are physically stored interlaced, and will just be played as is. This is extremely rare for the main movie but is common for extras, but apparantly you have just found a movie that happens to be like this. The studios have their reasons for doing this. I suppose it could just be incompetance but sometimes certain types of special effects or film processing may require them to telecine the movie first...I honestly don't know why it happens but it definitely happens. Forced Film won't work on these DVDs, so you have to do an inverse telecine.

This is why I always check my vobs before running forced film on them. Set the start point somewhere in the movie and preview it. Then move the slider to a couple different spots in the stream and do the same. If it reports FILM each time than you should have no problem using forced film. Sure an inverse telecine will always work, but I don't know about you but my encoding speed gets cut in 3rds by doing this and for the vast majority of DVDs the end result is identical whether you IVTC or use forced film.

[SLK001]

I had a theatrical released movie that actually did jump from FILM to NTSC all throughout the movie (on the DVD). This was because the PULLDOWN FLAGS were not properly placed (don't ask me how they did this, either). Being a theatrical release, I know that the movie was a 24fps source. I had to run DVD2AVI with NONE for the FIELD OPERATION, then run DG's DECOMB filter on the result. The DECOMB filter worked perfectly, and gave me back the original film material.

The movie was STARGATE.

This movie also alternated between TOP FIELD FIRST and BOTTOM FIELD FIRST. I ignored this flag and just selected TFF. This also worked.

[adam]

That is what we are talking about SLK001. They encoded with frame pictures but set the flag to field pictures. It happens all the time. If you stick that DVD in your dvd player (the original) you will probably see the jumping top pixel problem I mentioned earlier.

These DVDs really do not call for any special attention. Just use forced film as normal and treat it like any other DVD. It doesn't matter what the frames are flagged as. If you know they are progressive than you can just treat them as such, and ensure that you set the flag correctly in your own video stream.

[lordsmurf]

Just to add to this conversation, you can use RESTREAM to change it back and forth just fine.

The jumping pixels can also be INSIDE the image. I've got to re-encode 13 files now because I had it set wrong, wasn't paying attention.