23.976fps divx movie to (?)fps on DVD - Need some help

[TripACT]

Hi all,

Its my first post in here. I can say for sure that this site is really great and useful and i have read many of the tutorials in here and found them truthfully useful


I need an advice about the best way to convert divx movie to m2v movie.
I have a complete tv series on cds (divx/xvid format) which i want to convert to DVD format for convenient purposes.
In order to do so, i know i have to convert the AVI files (Video content) to M2V format.

Season 1 was divx movie @ 25fps - so i had no problem at all converting the avi file to m2v format using TMPGEnc Plus (which is the ultimate tool for doing so) and just loading the DVD (PAL) template and tweaking small things up to my taste.

Season 2 is divx as well but the framerate is 23.976fps. I know that PAL is 25fps and NTSC is 29.97fps....but what is 23.976fps ? How do i convert the AVI to M2V ? what template to work with in TMPGEnc Plus..there are some settings like 3:2 Pulling and such that i dont know how to use. Improper convertion will cause sharp movments or camera movments in the movie to jitter/distort a bit.

I love this website and found many useful guides. But i havnt found a guide that will tell me exactly how to convet 23.976fps mpeg4 (divx) movie to m2v...
What would be the best way? converting 23.976fps mpeg4 to 23.976fps mpeg2? or converting it to a whole different framrate such as 29.97fps?
Please tell me what to do and of course how (what settings to change in TMPGEnc Plus).


Thanks in Advance,

Gary.

[Abond]

If you can play NTSC DVD's:
1. Convert 23.976 divx to 23.976 m2v selecting "3:2 pulldown during playback". Here is how the settings look like:

If you cannot play NTSC DVD's
1. Convert 23.976 divx to 23.976 m2v, but with pal resolution (720x576)
2. Apply pulldown to the m2v 23.976->25 fps with DGPulldown (it is not preseted, so you are using "custom" typing the framerates.)
Hopefully I didn't typed something wrong. It is quite long ago I used TMPG for the last time.

[TripACT]

Abond,

Thanks for the reply
i think ive been told that NTSC is 29.97 and not 23.976 fps...can you explain to me abit how this is possible to be playable on a capable NTSC DVD?

Secondly, Can you tell what does 3:2 pulldown during playback option mean? ive read in some other places about this option but never qutie understood it all.
And last but not least, Which of the two options is preferable in this case? NTSC or PAL (Assuming the DVD is capable playing both - multizone)


Cheers,
Gary

[Abond]

3:2 pulldown make 23.976 fps to appear as 29.97 but only at playback - so the NTSC DVD compliancy is preserved. The process is called Telecine. Most NTSC DVD's containing movies (but not TV shows!) are made this way.
To explain your fist question you should take in mind as given that TV display fields, but not whole frames. Every frame is constructed from two fields.
Let say we have 24(for convenience think of it as 24 fps) frames per second. The pulldown marks sertain frames with rff (repeat field flag). So the display order at 24 fps would be:
1A-1B, 2A-2B, 3A-3B,4A-4B ...... where A and B are the two field of the frames 1,2,3 and 4 (so one can say it plays at 48 fields per second!).
Now we should get 5 frames constructed from the fields of these 4 frames to achieve 30 fps playback.
1A-1B,2A-2B,2B(field is repeated!)-3A, 3A-3B, 4A-4B... so now we have it at 60 fields per second.
Now you can see the frames 1 and 2 and 5 are progressive (fields match) at playback, and 3 and 4 are interlaced - they are constructed from the fields of originally different frames (fields don't match).
Hmm, I personally prefer pal.

[jagabo]

This might make it a little clearer:

Standard definition NTSC is not 29.97 frames per second. It's 59.94 fields per second. You never see a whole frame at once, you only see one field at a time.

3:2 pulldown alternates between displaying each film frame two and three times. This creates 60 fields out of 24 frames (24 * 2.5). On top of that the fields alternate between top and bottom.

In case you don't know, a field is half a picture, every other scanline, starting with either the topmost scanline, or the next one down. So if you number the scanlines 1,2,3,4...480, the top field is 1,3,5...479, the bottom field is 2,4,6...480.

Logically, starting with film frames numbered:

1 2 3 4 5 6...

first you repeat in a 3:2 sequence

1 1 1 2 2 3 3 3 4 4 5 5 5 6 6...

then you pull out fields to send to the TV:

1T 1B 1T 2B 2T 3B 3T 3B 4T 4B 5T 5B 5T 6B 6T...

Most movies are encoded at 23.976 frames per second and the MPEG stream contains instructions telling the DVD player how to produce the 59.94 fields from the 23.976 frames.

[Abond]

So if you number the scanlines 1,2,3,4...480, the top field is 1,3,5...479, the bottom field is 2,4,6...480.

Erm, kha, sorry it is not exactly. The top field is 0,2,4,6,8,.... That is why is callen "even field". The bottom is 1,3,5,7... so "odd field".

[jagabo]

So if you number the scanlines 1,2,3,4...480, the top field is 1,3,5...479, the bottom field is 2,4,6...480.

Erm, kha, sorry it is not exactly. The top field is 0,2,4,6,8,.... That is why is callen "even field". The bottom is 1,3,5,7... so "odd field".

That's why I said "if you number the scanlines 1,2,3..." As a computer programmer I start counting with 0. But normal people like to start with 1.

[Abond]

Poor normal people!

[TripACT]

Hehe

Thanks alot for the info...you ppl rock
This should help...i think i'll just make m2v @ 23.976fps with 3:2 pulldown during playback. My DVD is multizone so no problems playing either PAL or NTSC.

Love ya ppl :P

Too bad they invented PAL vs. NTSC...should've been one standard and thats it...just like the DVD-R versus DVD+R standards...stupidity

[macnab]

The problem is not NTSC vs PAL - that only applies to TV broadcasts. The problem is that frame/field rate is based on mains frequency - 60Hz in USA and 50Hz in Europe.

[TripACT]

Cool

I have some more questions and would be happy if you'll answer them as well...

1.
The program i'm using to author a dvd is DVD-LAB...which is really neat.
I want to author the movie with a subtitle.

The DivX movie is originally 23.976 fps and so the subtitle file is 23.976 fps... when enocoding with TMPGEnc the DivX movie to .m2v file @ 23.976 fps with "3:2 pulldown during playback" option, should i manually convert the subtitle file to 29.97 fps before importing it in the DVD-LAB subtitle section?

To pull some light on... DVD-LAB can let me have a PAL project or a NTSC project.
When working in NTSC project, in the subtitle section where i can import .srt file, it lets you choose which timecode to use 29.97 fps (Drop Frame/Realtime) or 30 fps (Non-Drop Frame).
Obviously i'll choose 29.97 fps, but the real question is... which version of the .srt subtitle file should i import?
The original 23.976 srt file (which worked well with the 23.976 fps divx movie) or... should i first convert the 23.976 fps .srt file to 29.97 fps and only then import the subtitle?

I'd convert the 23.976 .srt file to 29.97 fps before importing since you said that 23.976 is being converted in realtime at playback to 29.97fps when encoding with 3:2 pulldown setting...But you guys will know better than i do..so..any advice is welcomed

2.
Does the video quality suffer when encoding using 3:2 pulldown setting? i mean...If you compare an origial video filmed at 29.97 fps
and the same video filmed at 23.976 fps but encoded with 3:2 pulldown at playback setting (so both version will be played back @ 29.97 fps) ?

3.
Why are there 23.976fps and 29.97fps timecodes? What do you mean by "TV Shows" or "Films"... Why is there a difference at all?
Is it becase tv shows are played back on TVs (that can mostly support PAL - 25fps or NTSC - 29.97fps) and films are played back in cinema screens (Non-TV screens) at 23.976fps?
Why did they make it difference at the first place? Is there a significant difference qualitywise?




Thanks alot in advance,

Gary.

[guns1inger]

1. Keep the subtitles timed at 23.976, and select realtime (29.976) in DVD Lab Pro. Let the player do the hard work of playing back at the required rate.

2. In most cases, the original was either 24 fps (film) or 23.976 progressive video. If the source was DVD then it will generally be 23.976. If it was shot at 29.976, then there is a high chance the avi will be 29.976. That said, you generally get much higher quality (less jerking, smoother playback) if you let the hardware do what it was designed to do. If you convert to 29.976 fps then you will be trusting the encoder to put in the extra frames/fields. IMO this is a bad move, and always results in poor quality, jerky playback.

3. Basically, the difference is exactly that. 29.976 is the frame rate for NTSC video/TV broadcast. 23.976 closely matches film (24fps). The 3:2 pulldown process allows film source to be played back on NTSC video/TV with minial quality disruption through the conversion process. PAL runs at 25 fps, so for the most part film source is increased in speed approx 4% and played back at 25 fps. Film has been a round a lot longer than video, and was, for a very long time, a mechanical process. 24 fps was universal. Video, on the otherhand, is in part based on the frequency of main power supply, as well as inherently political decisions (we can't use that because they do)

To summerise; There are multiple formats (FILM, NTSC, PAL). NTSC is a confused mess. If the source is 23.976, keep it that way and apply pulldown when encoding (or post encoding with DGPulldown). If the wourse is 29.976, keep it 29.976 and don't apply pulldown. If it is PAL, keep it PAL.

[TripACT]

guns1inger, Thansk man

How can you tell that the DVD player will play the subtitle @ 29.97?
Okay so the movie itself will be converted in realtime but is it the as for same subtitle? I ask that because its said that when encoding with 3:2 pulldown setting the MPEG file has also insturctions for the dvd player how to do the converstion. But there's no such info in .srt text based file..isnt it?
BTW, did you ever do that with DVDLAB?

[guns1inger]

I have just done two of these, both NTSC 23.976, both with subtitles. In both cases the subs were 23.976. I used the settings I described above, and both seem to work out OK. I say seem too only because one of them is in Manderin with English subs, so I can only judge by the progress of the film, rather than direct translation. The other film is in English with English subs, and the subs are timed perfectly.

If in doabt, you can always test on an RW first.

[adam]

When DVD players convert 23.976fps to 29.97fps they do so through a process called a telecine that repeats certain fields to effectively increase the fps. Since the increase is done by creating new frames, as opposed to actually speeding up the playback of the existing ones, the runtime stays the same and basically everything syncs identically so there is no need to adjust the audio or the subs.

Subtitles are overlayed accoring to time ( 1:00:00-1:00:05) not frame, so if new frames are created in between during the telecine process, they will get the sub too.

[guns1inger]

Thanks, Adam. As these were my first attempts at subs, I wasn't entirely sure why the process worked, other than it seemed to make sense at the time.

[TripACT]

guns1inger - cool glad it worked

adam - wow..thanks alot for the professional info.

I know that the subtitle files (such as SRT or SUB) are synced according to the AVI (divx/xvid) video framerate... (23.976/25/29.97)
So how can you say that subtitles are overlayerd according to time?

[manono]

Just open them in Notepad and you'll see the start and end times for each. Those are the same times when they'll start and finish in the DVD.

[TripACT]

Correct, but those times are written according to a given timecode.
How do you explain the fact you can actually change the fps timecode with program such as Subtitle Workshop..etc.. to make the subtitle suitable to the divx/xvid movie ?

[adam]

I know that the subtitle files (such as SRT or SUB) are synced according to the AVI (divx/xvid) video framerate... (23.976/25/29.97)
So how can you say that subtitles are overlayerd according to time?

Going from 23.976fps (internal) or 29.97fps to 25fps requires and actual speedup in playback speed, unlike the 2:3 pulldown method of going from 23.976fps to 29.97fps. So yes, you must adjust your subtimes according to the fps used when changing fps, but its still the subtimes that determine the location (in time) and duration of each sub. Avis are also independant of any regional format so they can be whatever framerate you want so you are not bound, or I'd say guided , by the typical framerate changing methods. When DVD is the ultimate goal, film sources telecined at playback (23.976fps) and pure interlaced or telecined sources (29.97fps) will always sync identically for audio and subs and PAL will always run 4% faster than either, with audio and subs adjusted accordingly.

When using the avi container both 23.976fps and 29.97fps are supported and so that's why you can choose either as your output fps, even though a proper conversion between the two would yield identical subtimes.

I know that in my DVD authoring software (Sonic Scenarist) it allows for custom subtitle syncing for fine adjustments, but the only presets are NTSC and PAL because that's all that matters for DVD.

[TripACT]

adam - thanks alot..that clears it all pretty much

I luv this forum

This forum is like the bible of the video/dvd/svcd/vcd ...

Once again,
Thanks alot

[macnab]

Wouldn't life be wonderful if NTSC was 60 fields per second. The maths would be so much easier.