NTSCFilm vs NTSC

[PPJSmith]

OK I uses dvddecrypter to rip a dvd to harddrive. Then I used dvd2avi to get d2v file. I had force film on (to convert to 23.976 fps). Then I loaded TMPGEnc and loaded NTSCFILM template with no filters and converted to mpeg2. I also did the same thing with the NTSC template. But for some reason my files were the same size and also when I loaded them into nero it said that they were both 29.9? fps. Isn't NTSCFILM suppost to keep it at 23.976? They both played fine in my dvd player just read that 23.976 fps will give a better quality and smaller file size. Anyone know why the NTSCFILM still produced a 29.9 fps mpg? Also does force film even bring the fps down to 23fps? If not what does it do because it did clean up the interlacing problem I was having.

[Kdiddy]

First make sure when you enocde that the FPS is set to appropiate setting in your output, might want to load the "unlock" template...As far as the size, the same clip at same bitrate should ALWAYS be the same size, fps does not affect size, ONLY bitrate does, same amount of info at same speed...the difference with the NTSCfilm setting is that you get to allocate more bits per frame than you do in regular NTSC which produces the better quality, but NOT smaller file size... using the forcefilm option basically peforming inverse telecine, which why you didnt get any interlacing problems.

[stanwebber]

if you loaded the ntscfilm template the video was soft-telecined(3:2 pulldown) after encoding. the video is encoded 23.976fps, but the playback rate is 29.97fps. otherwise it would not be ntsc svcd compliant and nero would not accept it

<font size=-1>[ This Message was edited by: stanwebber on 2001-11-10 15:41:07 ]</font>

[PPJSmith]

Ok. Ok what if I'm not able to do forcefilm (film is less than 90%). So the movie stays at 29.9 fps, but now I have a interlace problem. If I load the NTSCFILM template will it drop the rate down to 23.9 then raise it back to 29.9 and fix the interlace problem, or will i have to run the inverse telecine filter. And if I do this, will it still automatically bring it back to 29.9 fps to make it NTSC compatiable, or will I have to also do the 3:2 pulldown filter. And if I do the IVTC filter is it ok to do it while encoding (option in newer version).

[Kdiddy]

well first, I would not recommend trying to lower 29.97 to 23.97...I would always encode at the same fps as the source...while yes in THEORY 23 fps video get more bits per frame which produces better quality.....the overall PERCEPTUAL quality gain tween the 2 is minimal.. from there go over to http://www.doom9.net and see his IVTC guides which are very good

[stanwebber]

either forced film or ivtc is mandatory with the ntscfilm template. auto-ivtc will work during encoding in tmpgenc; however, it will not work if you frameserve to an external encoder

[adam]

kdiddy I can tell you from experience that the quality gain from going from ntsc to ntscfilm is much more than just theoretical. It really does make a huge difference since your bitrate is literally increased by %20. This is most apparant in vcds where the extra bitrate is especially needed.

[Kdiddy]

Ok maybe I did not phrase properly....I meant it more along the lines of do not expect you quality gain to be that of say going from VCD->SVCD or SVCD->DVD...sort of a quantum leap in quality, 20% ok, maybe minimal was a poor choice of words, more like marginal....but again, as previously discussed in these forums before, quality is relative to the person viewing, I sure hope people could detect a 20% gain, but some may not...did I see it, yes, and thus do NTSCfilm whenever possible, but that gain for me wasnt enough to "raise the roof" over.

[stanwebber]

forget about 20% more theoretical quality. how about 20% more cdr capacity at comparable quality levels? commenting that 20% of anything is only marginal is laughable

[Kdiddy]

" how about 20% more cdr capacity at comparable quality levels? "

Im not sure if you are trying to relate this to the NTSCfile or NSTC option, but neither has any effect on the resulting filesize. I didnt say "20% of anything", lets stick to the subject shall we. Im only referring to the differencde between these 2 options. Of course in certain situations a 20% gain is a big deal, but in others it is not.

[adam]

If encoding in 1-pass vbr then yes, converting to ntscfilm will decrease the filesize by %20. If encoding in cbr or 2-pass vbr then the filesize does not change but the quality increases by %20. Of course you could always decrease your bitrate by %20 and still have the same quality, so either way converting to ntscfilm can lower your filesize by %20.

<font size=-1>[ This Message was edited by: adam on 2001-11-13 10:01:33 ]</font>

[PPJSmith]

Question! If FORCEFILM drops it to 24fps, but if get put back to 30 fps so it can be svcd compliant, wouldn't the quality be the same as the original 30 fps andnot better because the output is still 30 fps? I understand that if it was left at 24 fps the quality would be better because more bits per frame, but it has to go back to 30fps???

[adam]

The file is encoded in ~24fps, so you get more bits per frame each second resulting in higher quality. Svcds and dvds have a 3:2 pulldown which tells the dvd player to telecine it back to ~30fps as it plays. The dvd player is doing all the work here, it doesnt require any extra bitrate. If your file in encoded at 24fps and played back at 30ps, your bitrate is still only being used by the 24fps.

[N0SoopForU]

So, are you guys saying I can get a slight increase in quality if I capture at 29.97fps and encode at 24fps with a 3:2 pulldown? Does this apply only to DVD ripping or does it also apply to SVCD's made from television captures?

[Vejita-sama]

First, take a look at

http://toolbox.sgi.com/TasteOfDT/documents/video/lurker/fields/fields.html

for more info. But here's the short verison.

TV is shot at 29.97fps interlaced. By interlaced I meant that each frame is actually made of two fields (odd and even). Each as 1/2 the lines (ie. 240 lines each, this is way capturing at ???x240 removes interlacing). You're TV set is designed to only show 29.97fps interlaced source (aka 60 fields/s).

Moveis are shot at 23.976fps progressive. Progressive in that each frame is a complete still, and they are shown one right after the other.

In order to play that 23.976fps progressive source on your 29.97 interlace TV, you need to convert the video to that format. This is done by a process called telecine (aka 3:2 pulldown).

Please read the above url for info on telecining and inverse telecining (aka IVTC), cause I don't want to right all that out

Anyway, let's say that we are encoding a video at 1800kbit/s:

23.976fps @ 1800kbit/s = 75.1kbit/frame
29.97fps @ 1800kbit/s = 60.1kbit/frame

So at the same runtime I get a 25% increase in bitrate! Pretty nice (notice that the increase is depend on the bitrate used).

HOWEVER, you can't just take a 29.97fps source and force it to be 23.976fps, or you'll get skips, jumps, etc. So if you source is 29.97 interlace (ie. TV show or from VHS) then just leave it at 29.97, and use the NTSC template.

If it's 29.97 telecined source, convert it to 23.976fps (either dvd2avi force film or IVTC), encode at 23.976fps. And use TMPGencs NTSC_film template.

That's as short as I can make this post, sorry Read the above url it really does a great job explaining all this.