1080 @ 24p to NTSC, DVD etc

[drvid]

Hi we are making an animated TV series in 1080 @ 24p.

After our NTSC 29.97 pulldowns, the duration of our show becomes longer; thus we need to cut the timeline to 23:58.16 (in FCP) in order to achieve 24:00:00 at 29.97.

First of all, is this normal? Shouldn't the pulldown keep the duration more or less the same?

Secondly, what percentage of retiming control (in Compressor) should we use to get our 24 to the duration of the 29.97?

Thanks for looking!

[Guest]

First of all, is this normal? Shouldn't the pulldown keep the duration more or less the same? It's not normal. The duration should remain the same because the frame rate is adjusted to account for additional fields/frames.

Probably your pulldown application is assuming that the source is 23.976 instead of 24. If you want to pull 24 down to 29.97, you need a special application, such as DGPulldown (for MPEG2). In other words, applying 3:2 pulldown to 24 fps gives 30 fps, not 29.97 fps, and the difference between 30 and 29.97 accounts for your discrepancy. DGPulldown can pull down 24 fps to 29.97 fps. Other standard pulldown applications cannot do this.

If you leave it as is and just shorten the timeline, you will have AV desync.

What is your video format (VC1, MPEG2, AVC) and how are you applying pulldown?

[deank]

I'll dare to add something i've read sometime ago:


2:3 pulldown

In the United States and other countries with television using 60Hz vertical scanning frequency, video is broadcast at 29.97 frame/s. For the film's motion to be accurately rendered on the video signal, a telecine must use a technique called the 2:3 pulldown (sometimes also called 3:2 pulldown) to convert from 24 to 29.97 frame/s.

The term “pulldown” comes from the mechanical process of “pulling” the film down to advance it from one frame to the next at a repetitive rate (nominally 24 frame/s). This is accomplished in two steps. The first step is to slow down the film motion by 1/1000. This speed change is unnoticeable to the viewer, and makes the film travel at 23.976 frame/s (or 7.2 seconds longer in a 2-hour movie).


Source (http://en.wikipedia.org/wiki/Telecine#Frame_rate_differences)

So, I guess you need to do some advanced pulldown, not just mechanical one.

[Guest]

23.976 versus 24 --> 29.97 versus 30 after pulldown

[drvid]

It's not normal. The duration should remain the same because the frame rate is adjusted to account for additional fields/frames.

Probably your pulldown application is assuming that the source is 23.976 instead of 24.... <snip>

What is your video format (VC1, MPEG2, AVC) and how are you applying pulldown?

Yes I believe when doing 24 to 29.97 its usually recommended to go 23.976 to 29.97 so I think your assumption makes sense. I will do some tests on my footage to see if the duration equalizes at 23.976.

Our footage is all 10 bit uncompressed 1080p (126.7 MBps heh). Using only QuickTime + Final Cut Studio 2 in a purely Mac environment. Pretty heavy stuff... Not sure if the tools you mentioned are useful there without VMWare/Bootcamp etc.

Unfortunately our post facility has so far done the pulldowns from image sequences we deliver. They are the ones who've instructed us to cut the timeline down to 23:58:16 ... In the future we will try to avoid this by doing all conversions here instead.

[Guest]

They are the ones who've instructed us to cut the timeline down to 23:58:16 Which breaks AV sync.

[drvid]

Which breaks AV sync.

Thanks neuron2 ... This is beginning to make sense.

So if they are mixing audio to 29.97 there is no way to sync it to our 24? Sorry if I haven't described the problem well, but this is it.

We can't sync their 24:00:00 audio mix to our 23:58:16 timeline.

[Guest]

You'd have to use an audio processor to time stretch the audio to match the stretched video time.

Can't you make your animations at 23.976? Drop a frame periodically as needed if you have to. It won't be so bad for animation content.

[EuropeanMan]

On the same topic...

I have a bluray @ 24fps
Jodhaa Akbar BluRay (bodega release, france, region B)

IF I want to create a DVD9 from this...what would be the way to make it @ 29.970 then?
Should I NOT apply any deinterlacing in my .avs script to brin 24 to 23.976 and just leave it alone...meaning wait for my mpv file @ 24 & then use DGPulldown to custom 24 --> 29.970?

AND also IF I wanted to rip to .MKV format...what would be the way to bring to 23.976 then? Thanks.

[Guest]

Should I NOT apply any deinterlacing in my .avs script to brin 24 to 23.976 and just leave it alone...meaning wait for my mpv file @ 24 & then use DGPulldown to custom 24 --> 29.970? Yes.

AND also IF I wanted to rip to .MKV format...what would be the way to bring to 23.976 then? Thanks. Can't you put MPEG2 into MKV?

[EuropeanMan]

@ Neuron, I purposely want to get to 23.976...but then I'm sure I'll have to adjust the audio (or not)? As for mpeg2 into MKV - never tried it.

[Guest]

I purposely want to get to 23.976 Then why did you ask if you should use DGPulldown on 24 fps?

but then I'm sure I'll have to adjust the audio (or not)? If you use AssumeFPS() to get to 23.976, then you will have to adjust the audio.

If you use ChangeFPS() to get to 23.976, you will not have to adjust the audio, but you will have a possibly visible video discontinuity about every 42 seconds.

[EuropeanMan]

Then why did you ask if you should use DGPulldown on 24 fps?


I asked about the pulldown on 24fps ONLY for the CCE for DVD9 that I wanted to make...that's all.

As for MKV...I don't know if this is a stupid question or what...as I've always been used to deinterlacing to 23.976 or 25...but IF I keep it @ 24fps, will SAPs like PS3 be able to play those MKV's @ 24fps? I'm clueless on this subject...which is why I was asking about the 24fps to begin with. I know already about NTSC DVD9's @ 29.970...that much I am comfortable with.

On a slightly different subject...lets say I have a DVD9 that is of course @ 29.970 but I must deinterlace to 23.976.

What is the effect IF I add a line that says AssumeFPS(29.970) at the end. I will 'assume' that I won't have to do a pulldown of the .mpv file from CCE to 29.970...but just do a 'no-change' pulldown. This is as opposed to leaving my .mpv file @ 23.976 and pulling it to 29.970...is there any benefit to adding theAssumeFPS(29.970) at the end of my .avs script? IF there is a benefit to this...will it work if my DVD9 deint's to 25fps?

[Guest]

You've hijacked the thread. Start a new one.

[EuropeanMan]

Sorry boss.

[drvid]

Hey thanks again guys for helping me understand 24 vs 23.976!

Turns out the reason I couldn't sync was due to a flawed audio mix, not anything technical in the timeline or pulldowns.

We will try interpreting the 24 fps FLA rendered footage as 23.98 in Final Cut Pro from now on to avoid that weird timing and confusion.