NTSC=29.97fps? FILM=23.97fps? Please clarify ...

[I_AM_CANADIAN]

I use vStrip, DVD2AVI and TMPGEnc Plus in the "Eazy VCD" package (NOT VCD Easy!)

I've found errors in how the program runs, figured them out in PAL format, but NTSC is killing me!

I've noticed vStrip ALWAYS sets my Frame Rate at 29.97, no matter if NTSC or FILM. I've noticed that FILM is usually for movies, while NTSC is used for "lower quality" movies, like porn and television series compilations. Im experiencing audio-sync problems in SVCD format, but when I "trick it to VCD", seems no problems. I think it has to do with vStrip setting all my DVD Rips at 29.97. So the questions:

1) Is NTSC usually 29.97fps?
2) Is NTSC usually interlaced?
3) Is FILM usually 23.97fps?
4) Is FILM usually progressive?
5) Am I suppose to use the 3:2 pulldown option when making SVCD?

Similair problems/questions were posed on my other unanswered post:
https://www.videohelp.com/forum/viewtopic.php?t=218935&highlight=

Anyone can clear this up?

[FulciLives]

1) Is NTSC usually 29.97fps?

From a DVD ... well you already hit the nail on the head. Most DVD Videos from movies shot on film will be progressive and as such will be 23.976fps whereas stuff shot on video will always be 29.970fps BUT some film material will be 29.970fps. Usually DVD2AVI is pretty accurate here in determining which. If you don't know for sure you can always do 29.970fps and be A-OK

2) Is NTSC usually interlaced?

It depends. If it is from a DVD then see above. If it is a capture then it should be interlaced but often people deinterlace say Xvid or DivX files. It is possible to have deinterlaced 29.970fps video.

3) Is FILM usually 23.97fps?

Well FILM on DVD is another way of saying progressive NTSC aka 23.976fps but something shot on film can still be done on DVD as 29.970fps depending on the master that was used. But when we talk about FILM in terms of DVD we usually mean 23.976fps progressive NTSC.

4) Is FILM usually progressive?

Well yes. See above. You can't have 23.976fps video that is interlaced. If you have 23.976fps video then it is progressive.

5) Am I suppose to use the 3:2 pulldown option when making SVCD?

Only if the source is a progressive 23.976fps NTSC video. You don't use 3:2 pulldown when you have 29.970fps be it interlaced or de-interlaced.

In short you can leave any NTSC DVD at 29.970fps and you should not have any sync problems.

However you will get slightly better image quality if you can use the FORCE FILM option in DVD2AVI simply because the "fixed" amount of bits you have to encode go much further with 23.976fps than when spread out over 29.970fps and this is of course a concern when using a low bitrate and the SVCD format qualifies as a low bitrate format.

Yet you can't do the FORCE FILM option with just any NTSC DVD disc. It depends on the disc of course. If you do FORCE FILM on a NTSC DVD that is 29.970fps interlaced then you will screw it up BIG time and such a screw up will probably also introduce audio sync errors.

Wish I could give more advice but I only make DVD videos and only very rarely fooled around with SVCD discs WAY back in the day.

- John "FulciLives" Coleman

[I_AM_CANADIAN]

Fulci,

Thanks for the response, but still have a little unanswered. Thanks for clearing up FILM issue based on response to Questin 3.

As I said, I use vStrip for ripping, and noticed that it ALWAYS rips the movies at 29.97fps, hence why I have the confusion with 23.97 vs 29.97fps.

When I use "Option > Preview" in DVD2AVI, it will tell me its a "29.97fps Progressive" movie if I have left the "Video > Field Operation > None" selected OR a "23.97fps Progressive" movie if the "Video > Field Operation > Force Film" was selected. In other words, depending what was selected at the time, I had a hard time determining what the actual .VOB files were converted into, 23.97 or 29.97 FPS.

What I really dont understand, if most movies on DVD are 23.97 Progressive, why not leave it at this, and make SVCD's this way. Forgive me for my stupidness on this subject, but is this where we come into home DVD players affecting "what you see".

I see all the newer home DVD players advertising "Progressive", so are these the only ones that can play 23.97 Progressive SVCDs? And if the home DVD player does not support Progressive, would this cause huge synch prolems with a SVCD encoded 23.97 Progressive?

Brennan

[adam]

The NTSC standard requires 29.97fps but storing video at this framerate is horribly inefficient. With digital formats like SVCD and DVD and even VCD, it is possible to store the video at 23.976fps and allow the DVD decoder to telecine it to 29.97fps on the fly as it plays. This avoids all of the downsides of the telecine process. Most commercial NTSC DVDs do just this, at least for the main features. Most extras are actually shot at 29.97fps and just left that way. If you follow the conversion guides then you shouldn't have any problem with this. Load the vob into dvdavi and set the start point somewhere into the movie. Basically you just want to skip the opening credits which are almost always NTSC (interlaced 29.97fps). Just look at whether dvd2avi reports it as NTSC or Film. If its FILM (it almost always will be) then it is stored at 23.976fps and you should use forced film and then encode at 23.976fps. The dvd player will play it back at 29.97fps. If it says NTSC or any % FILM then forced film won't work. You should either leave it as 29.97fps interlaced or try to perform an inverse telecine. This will get you back to 23.976fps IF it was originally filmed that way. Luckily, with theatrically released movies, the NTSC DVD will almost always be stored at 23.976fps. Seriously, less than probably 1/2 of a % are unsuitable for forced film.

Progressive scan is different. That is just for HDTVs which support progressive display. A progressive scan dvd player basically performs the telecine process differently is all. It essentiall performs the telecine process and then combines the fields in such a way that its like getting 29.97fps progressive frames, whereas on a regular non-HDTV or with a non-progressive scan dvd player you get 29.97fps interlaced fields.

But, encoding your video at 23.976fps and letting the decoder telecine it 29.97fps is beneficial for any kind of playback and should always be done when possible. It is the industry standard and is how NTSC DVDs and SVCDs are really intended to be made.

[I_AM_CANADIAN]

The lightbulb has just clicked and is getting brighter!

Adam, thanks for the info. You mentioned that if my DVD rip was any %FILM, that Force Film was not the best option. Ive found that about 5 of the 10 NTSC DVD's I've done so far all fall in this category (I've just moved back from UK where everything is in PAL which was much more easier!), are 99% FILM, and yes, most of the times its just the opening movie company logo introductions. In other movies, I've seen it jump bak and forth from NTSC (Interlaced) to FILM (Progressive) a few quick times, but again, is 99% Film.

Do you think theres a big problem using Force Film on these? I've only just tested a few so far but havent found any playback problems yet. I hope time will tell ... every night another movie I process (using a 2400+ AMD processor, at 2passVBR, its a 11-12hour affair!)

[Gazorgan]

This helps: There are only 2 valid fps for DVD'; 25 for PAL and 29.97 for NTSC. Period. Try Authoring with 23.97 and see what happens.

Now 3:2 pulldown is a flag the allows hardware to convert to 29.97 on the fly. 3:2 pulldown flag means that the movie is supposed to Telecined up to 29.97 (a valid fps), not that the source is 29.97 itself.

It's a little confusing, but think of it as a post-it note on the header of the video. Telecining is generally done with fields not frames (2 fields = 1 frame), so if you think of a video as 47.92 Fields/sec or 50 fields/sec or 59.94 fileds/sec, you can see where the "extras" come from.

[adam]

I_AM_CANADIAN, if you allow dvd2avi to process the opening credits then it is almost always going to show somewhere between 95% adn 99% film. That's why I always set the input point beyond the opening. This portion of the movie tells you nothing. If you are only looking at teh actual movie, not including the end credits either, and you get ANYTHING less then pure FILM then that means some portions of the movie are hard telecined, aka NTSC. This is usually only done on scene changes but sometimes, very rarely, entire scenes will be NTSC. If you get 99% film then forced film is still a viable option, you just may see interlacing artifacts during scene changes. Usually its not noticable though. If its anything less then 99% film I wouldn't use forced film, I'd perform an IVTC instead. This manually reverses the telecine process and goes through and removes the duplicate fields and reconstructs the progressive 23.976fps frames, as opposed to the forced film option in dvd2avi which prevents the telecing process from occuring in the first place.

If dvd2avi jumps back and forth but still reports pure or almost pure (99%) film then you can still treat it like normal and use forced film. This happens when the stupid studios incorrectly set the prog_frames flag to interlaced when its actually progressive. If you get bored try playing the original DVD on your settop player and look very closely at the top letterbox and you will see it flicker up and down one scan line. (of course only on widescreen movies) Stupid studios. Anyway, just ignore the progressive/interlaced switch in dvd2avi. If you use forced film and encode to 23.976fps progressive in your encoder then the flags will be corrected.