How do you correctly determine the original FPS of video?

[Eldric]

Okay, first off - when I talk about the "original FPS" of a video clip, I know that depending on where you are in the world, televised content is being broadcasted either at 29.970 fps (NTSC regions) or 25 fps (PAL and SECAM regions). However, when you inverse telecine a clip you are in essence, rolling it back from it's broadcasted format - such as 29.970 fps, to the format it was originally filmed in - 23.976 fps. Now, this isn't always successful, as I recently found out when I was testing out my video capturing abilities with a few one-minute captures off of cable tv. While I had success running an Inverse Telecine Avisynth script through Virtualdub with no hitch - I ran into a problem when I was playing with several one-minute long captures of various old "Western" tv shows such as Bonanza and Big Valley, that had those peculiar "technicolor" color palattes. When running the same script I had previously used, instead of a smooth playing film at 23.976 fps, I got a 1 minute long clip that showed jerky movement, especially when the camera panned horizontally while following an actor. Thankfully, another video encoder was able to diagnose the problem as the film being improperly Inverse Telecined - and that it should have been converted to 25 fps, not 23.976.

However, the big question is - is there a method of correctly determining the framerate for some of these "Unusual" clips that exist out there? I know that when you typically deal with IVTC, you're looking for a 5 frame pattern (while an actor or some motion is going on) of 3 frames without interlacing, followed by 2 frames that contain interlacing or that "Combing" effect. As I said, the typical thing to do here is to run an Inverse Telecine script and convert the clip back to it's original fps - 23.976. But that's not always the case. As I found out - some of these clips were shot originally at 25fps, but some others are actually a bit MORE unusual. I've heard of certain anime clips that were shot originally at 27 fps, others at 29 or even 30 fps. Is there a program or script or method to definatively determine the original frames per second of any given clip - be it anime or live action? I know that there are certain sites that describe in detail Inverse Telecining, and how to go about rolling back a clip to it's original fps - two of them being www.100fps.com and www.doom9.org. In both these cases though - the majority of the information deals with the original 23.976 fps assumption. While that's well and good for the majority of the captures out there, how do you deal with that remaining percentage that was shot at an "off the wall" fps? There has to be a successful, SIMPLE way of determining the original clip's Frame Per Second, so an Avisynth script or some other piece of software combination can be used to roll back the film to the original without constant experimenting or guesstimating on what the original fps could be.

So, anybody happen to know how this can be done and is willing to share?

Eldric

[Sefy]

I'm not totaly sure I understand the question, but if you just want to know how to identify the framerate of your movie, you could use GSpot or VirtualDub. They can both provide you with an exact details of your movies, including which compression was used on them and everything.

[Eldric]

It's not that I want to be able to detect the FPS of a video capture - if I capture video off the TV, since I'm in the NTSC region, all my captures are done at 29.970 fps since that is the speed the video is being broadcasted at. What I want to do is correctly identify the original frames per second of any given video capture clip - be it originally shot at 23.976 fps, or one of the more uncommon fps. Like I described in my original post - I naturally assumed that the video I was capturing was initially shot at 23.976 fps. Every time I had previously tried to Inverse Telecine a test clip, the VirtualDub/Avisynth combination gave me a smooth playing clip that was inverse telecined from 29.970 fps -> 23.976 fps. It wasn't until I attempted to IVTC a clip that was (for some reason) shot at 25 fps, that I ran into a problem. Even attempting to have VirtualDub automatically convert the clip using it's adaptive frame rate feature resulted in the 23.976 fps default being chosen (along with the jerky playback). What I'm wondering is if there is a piece of software or a simple, easy to explain procedure to correctly detect the original frames per second speed that a captured video clip was originally filmed at?

[Sefy]

Mmmm... i've afraid you have me stommed there
PS: As far as I know the NTSC being broadcasted on TV is always 29.970 and only in the Cinemas and some DVDs you get the 23.976 fps which is the FILM standard and while being played back on TV it gets converted to 29.970 since that is the standard playback rate.

[Eldric]

That's the problem. As far as I know - whenever you deal with film (such as a mainstream movie) the DVD will automatically playback the film in the original FPS it was shot in. That's where you get the setting NTSC-Film (which is 23.976) which can be seen in such programs such as TMPEGENC. When a TV program or film is played back either in NTSC or PAL/SECAM format, it is speeded up and extra frames are created to compensate - which is why we get these interlaced or combed frames.

In the original frames per second, you got frames that go A -> B
However, when this is sped up for broadcast, you get extra frames that are created, so you now have A -> C -> B
Frame C is a pseudo frame, created from the merging of Frames A and B. It didn't really exist in the original film, but was captured by whatever program you used to capture video from a TV broadcast. Please understand, I'm not 100% sure about any of this, I'm still somewhat of a newbie when it comes to the whole FPS issue, so please grant me some leeway (especially if I get something wrong) with my explination. These pseudo frames are apparent when you see the combing effect on the 2 frames, in the 5 frame pattern that I mentioned in my first post on this thread. When you Inverse Telecine, what the program is doing is supposedly de-interlacing the frames, and then cutting, or "Decimating" every 5th (or Nth) frame, in order to once again get the video clip back down to it's original format. The main issue is that for whatever reason, the standard 23.976 fps length just won't work. In my case with some of the problem clips I had, I ended up with orphaned fields which when played back resulted in the jerky motion in the clip. *shrugs* Just how we can correctly determine the original fps is out of my league - I don't have the technical knowhow to understand just how it can be accomplished. Hopefully, someone has either figured that out and will be kind enough to post, or if this thread goes unanswered, some coder might take it upon themselves to eventually realize that there's a need for a program that'll identify the original FPS of a program, and code it as a freeware or shareware project. One can only hope.

[Sefy]

I Think (not 100% sure) that it doesn't really matter what was the "original" frame rate, because once you did the capture at a certain fps, then that IS the "original" fps of your movie, whatever you do to it, those "added" frames are part of the movie if you like it or not.

Atleast that is what I think, lets hope SatStorm gets here, he is the pro when it comes to those kind of topics

[Eldric]

Ah, finally found it - just in case anybody wanted to see just how "Strange" some of the FPS can be with some certain programs, this webpage lists just a few of the FPS that show up with Anime (very bottom of the page).

http://arbor.ee.ntu.edu.tw/~jackei/dvd2avi/ivtc/

For those that don't feel like clicking on the link, here's the info in a nutshell:

"Another trouble of Anime is that they are not always pure 24fps. It may be...

* pure 30fps: ToHeart OP, Lain ED, Sakura War OVA2
* pure 60fps: Silent Mobius OP
* hybrid 30/60fps: Dual OP, SolBianca
* hybrid 24/30fps: Lain OP, Kurumi OP, Angel Links OP "

Wheither it's due to video quality or simply how it was filmed in that part of the world, these programs have fps that don't follow the "Norm". For those of you not familiar with Anime - MST3K (Mystery Science Theater 3000), was another hybrid - where the live-action shots were shot at one speed, while the shots containing the filmed segments were shot at another.

[Sefy]

One day I hope will never have to worry about resolution and frames and all that mombo jumbo, I honestly don't see the point to all that. Have a one nice good standard and get it over with

[Eldric]

I agree - unfortunately, until that time - you're stuck with Inverse Telecining a clip if you want to convert it from NTSC -> PAL/SECAM or vice versa. It's how conversion companies can get away with charging 50 bucks (US) to convert a VHS tape from PAL to NTSC. Unfortunately, it's not only the conversion companies making $$$ off of this. By seperating the different regions into NTSC/SECAM/PAL, the video companies can limit the release of certain DVDs/Tapes and also further make money by selling specialized video equipment such as converters to ensure that your TV or VCR can read and playback a signal format that is from outside of your region. Not sure if all that made sense, but the bottom line is - diversity = more money for the electronics and media companies.

[Sefy]

Well, it is obvious someone is making money over this, thankfuly where I live I have no problem, cause all the VHS and DVD Players are MultiZone and Multi Region and just about play everything from everywhere, since no one knows how to categorize Israel on the map