25P to 24P

MovieSwede

MovieSwede

Well-known member
I have tested a couple of different methods to achive 23,976P from 25P source.

First of all it seems harder to go 25P-23,976 direct due to you can only change speed 1,000 0,999 0,998 etc.

So if I first makes a 25P-24P conversion (0,960) and after that render ill make a 24P-23,976 conversion (0,999)

But the question will be what method generates true 25P-23,976P

As i found 3 different take and not sure what will simulate and what really makes a perfect conversion.

1. Change time code of event? (25fps-24fps-23,976)

2. Change playback rate? (1,000-0,960-0,999)

3. Change undersample rate (1,000-0,960-0,999)

And then of course what would be the best of the 3 (smart/force/disable).

Done some test but would be nice to discuss the theory.
 
First it was mear to test how 24P stream would be handled by my projector, but other than that im more interested in how to achive it. Now when it seems that 24P is being standard for HD DVD and Blueray even i Europe. So its time to start learning the procedure.

So I want to learn the best way to get the clean conversion with no blending of different frames.
 
Well, in theory, I would think putting it on a 24p timeline and slowing the playback rate down to 0.959 would be the best way. Then, Smart Resample.

I don't have any 25p footage to play with, though.
 
I have tried sooooo many ways to convert 25p to 24p, unsuccessfully! Even if all the mathematics are ok, finally the result is a little jump on every second. This is especially when the footage is shot with moving camera. That's because of every 25th frame lost, obviously. So, whatever you do, you CANT convert 25 -> 24, even if you use pulldown or whatever you wnat. Actually 25 is not divisible (or multiple) by 24, and these two numbers don't have joint aliqout.
 
Actually what you do is slow down the movie. So your 25P represent 24+1 frame in the 24fps timeline.

So 0:00:25 = 0:01:01

Just start a 24P project (not 23,976) import the 25P clip. Right click - properties. change playback rate = 0,960 and the clip will be true 24P. If you want a 23,976. Start a new project 23,976. Import the 24P clip(not the 25P) slow down clip to 0,999 and you will have a 23,976 clip on the timeline.

You cant go 25P to 23,976 in one step but you can do it in 2 (unless someone has a bether method)
 
I have done a lot of testing in the past with 25P PAL conversion to NTSC. I had to do it again with Vegas 7 for the Drama Fest. of Dvxuser. Then I discovered something very simple that seems to work nicely (I did a playback of the footage on a lcd computer screen and on a high end Loewe lcd-tv (with a procinema dvd-player and component cables and for my eyes the conversion looked good enough):
1. import your DV PAL AVI 25P file onto a NTSC 30P timeline
2. change the project settings: choose for the 'none' option at the frame blending/interpolate fields selection list.
3. render to a MPEG2 (for dvd) as a 30P file (not 24P), make sure choosing for the quality setting Best and 2-Pass rendering for the most accurate conversion.

I don't have any scientific explanation for this and I found out about it yesterday, but it seems to work good enough.
 
I found out that this works great, it might be same as mentioned above, but this is how I do it:

-24p or 25p project setting:
-Add velocity envelope and slow down 4% (so its 96%)
-Clips properties -> Disable resample (it removes ghosts)
-Render as 24p

It looks smooth and works great :)
 
Be careful -- a velocity envelope will not slow the sound down with the video. It may be passable for short clips, but over the course of a longer program, the synch will drift considerably.
 
Would it be 4.1% (rounding 4.096%) for 23.976 fps?

I see in the CineForm HDLink converter, it refers to 4.1%, not sure what math they are using under the preferences display, if it is actually 4.096%.

Some time ago, I recall having some 1080p30 stock footage I needed to place in a 24p timeline, and found the simplest method to remove the image stutter, flicker and frame interpolation issues in my failed conversion attempts within the editing application I was using, was to export the clip as, say, a targa sequence from the 1080p30 timeline, then re-import the targa sequence into the 24p sequence. In this case, there was no audio sync, as it was an ariel fly over and the timing change did not appear to affect the clip. If there was relevant audio linked to the clip, we would have had to taken it into Pro Tools and slowed it down, which you can input fractions greater than one decimal point, from memory, and pitch shifted the audio a fraction of a semi-tone, which we had to do in another project to make it sound right.

One global standard sure would be nice and make things easier sometimes...
 
Christopher Barry said:
Some time ago, I recall having some 1080p30 stock footage I needed to place in a 24p timeline, and found the simplest method to remove the image stutter, flicker and frame interpolation issues in my failed conversion attempts within the editing application I was using, was to export the clip as, say, a targa sequence from the 1080p30 timeline, then re-import the targa sequence into the 24p sequence. In this case, there was no audio sync, as it was an ariel fly over and the timing change did not appear to affect the clip. If there was relevant audio linked to the clip, we would have had to taken it into Pro Tools and slowed it down, which you can input fractions greater than one decimal point, from memory, and pitch shifted the audio a fraction of a semi-tone, which we had to do in another project to make it sound right.
Click to expand...
Interesting. 30p is almost impossible to convert into good 24p, because there just aren't enough motion samples to make a good conversion.

If you imported it as a targa sequence into a 24p timeline, you should have gotten a 20% slowdown, or 80% slomo. On something like a an arial flyover, you might not have noticed the slowdown (because they usually look like slomo anyway).

But you already knew that (obviously). Just trying to make it clear for anyone reading who's never tried . . . :)
 
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