I just have this small question because I have seen videos in PAL and plenty of DVD's in NTSC format but have never come across something that is in NTSC Film format. When is it used? And more importantly, how can one differentiate between NTSC and NTSC Film? What I mean is, if I have a DVD, how can I tell whether it is NTSC Film (so that I can tell DVD2AVI to Force Film) or just regular NTSC?
Mike
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Ntscfilm is really an intermediate format. Film is shot at 24fps and in the case of ntsc, is telecined to 29.976fps. Well you do the math, if you add 6 frames every sec to your 24 than you get 30fps which is slightly too fast so the first step in the telecining process is to slow down the film by %.03, which causes no noticable visual change. This now brings your framerate down to 23.976fps which is referred to as ntscfilm.
From here the film is split into fields and is undergone what is called a 2:3 sequence which results in a 29.97fps interlaced video. For a more thorough explanation read here http://www.doom9.org/synch.htm.
Anyway, the vast majority of ntsc dvds store their content at 23.976fps and use RFF/TFF to telecine the video as it plays. The benefit of this is that you have %20 less frames to encode so you end up with %20 more bitrate to work with. This is the point of forced film, it preserves the 23.976fps and allows you to encode in either the vcd format or the svcd format with the 3:2 pulldown, saving you that exra %20 of your bitrate.
Now the way to determine whether your dvd is stored as 23.976fps (ntscfilm) with RFF/TFF flags or at 29.97fps interlaced (ntsc,) is to preview your vobs in dvd2avi. Let it get past the openeing credits and into the movie. If dvd2avi reads the movie as %95 or higher film than your movie is stored as ntscfilm and forced film will work. If it is recognized as pure ntsc than you must uncheck forced film and you have the option of doing an inverse telecine to get back to 23.976fps. Some dvds are actually a hybrid of progressive and interlaced and as a result it may be impossible to regain the original 23.976 framerate. -
Why must I use 3:2 pulldown with SVCD? Doesn't SVCD have an NTSC Film template?
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The ntscfilm template in TMPGenc includes the pulldown, just open it up and look at it, it says "3:2 pulldown while playback."
If your not using the template and encoding mpeg2 at 23.976fps than you must set the pulldown flag manually in TMPGenc.
If you are using any other mpeg2 encoder than you must run your encoded video stream through pulldown.exe to insert the flags.
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