Pal content that is 25fps but plays at 23.976 speed

[Stamper]

Hi folks,

So I'm kinda surprised as I find some bonuses on Pal DVD, that are encoded Pal 25fps 50hz, but have the exact same lenght of the same bonuses on the NTSC DVD that are 23.976fps 60hz.

Let say I want to overlay both bonuses to obtain a better looking encode with more detail.

How do I do because when I import the Pal content, and put it in a NTSC timeline, it suddenly stretches to 23.976 and plays slow.

Thank you.

[deleted user]

What software are you using?

It's unlikely to work though, unless you can manage to reverse the framerate conversion perfectly, which can be difficult to do. Though, I'm thinking that with enough thought and a bit of math you could probably do it in AviSynth, if the conversion follows a pattern, but I've never even bothered to attempt that. And with interlacing (which I think you're implying here) it just becomes even more of a pain in the attic.

[Stamper]

I'm on a Mac with FCPX.

It's totally weird.

[deleted user]

Ah, sadly don't have experience with FCPX. I know that in Premiere, you have some settings on how to interpret the footage. But even with that you would have to be very lucky for each frame to land in exactly the right spot. Not to say it's impossible, but I think the chances are low without some manual labor.

[Stamper]

How do NTSC footage end up in Pal at the same lenght in the first place?
There is probably some interlacing at work.

On a note, this happens with the cut scenes, and all the extras of the first Terminator.

Also all the Abyss second disc video in Pal are playing the same, 25fps/50hz but exact same lenght as the NTSC version.

It's cool because you take the subtitles of the european disc, and mux them with the NTSC disc without hassle.

[deleted user]

Really simple - you just do a framerate conversion and end up with videos of the same length.

I have also noticed this about extras sometimes. They do it differently than for feature films, which usually get the speeding-up approach. I think that's likely because it's a quicker process to just convert to a different framerate than to reinterpret the framerate and then having to process the audio as well for the speed up.

Another aspect is that extras aren't actually usually filmed in 24 fps, but rather tend to come in all kinds of forms, often in 60i for example (60fps but interlaced as 30fps). In that case it just makes very little sense to do any speedup or stretching, because you won't be able to perfectly preserve the frames either way. (You could slow down 60fps to 50fps in theory but I think the change in speed would be too extreme to be tolerable)

So let's say there is indeed some extras in 24p ... person likely just doesn't care I wager. They take good care for the feature film of course but when it comes to those extras, they just do the default processing and that's it.

[Stamper]

Framerate conversion? But if I use, say MpegStreamclip, it stretches the running time and speed it up.

[deleted user]

The most simple and banal types of framerate conversion (as named in Adobe Premiere) are:
- Frame Sampling: Every frame in the target framerate is the frame that is closest to it timing-wise in the source. This results in dropped/duplicate frames.
- Frame Blending: Every frame in the target framerate is a blend of the two closest frames from the source, weighed by how close they are.

That's what happens in Premiere when you, for example, drop a 24fps clip in a 25fps timeline. Premiere, by default, always preserves length. So do most video converters/encoders out there that I have worked with. But you can tell Premiere to reinterpret the framerate as any framerate you choose.

Of course it likely varies from software to software, which explains why MPEGStreamclip may do it differently. I used that software once I think, but I don't remember enough to comment on it.

[Stamper]

Oh yes, I see now they have the same options in FCPX.

Curiously, when I remux the Pal titles with the NTSC video, the subs slowly goes out of sync even though the running time of the videos are the same.

[deleted user]

Strange. I'm not 100% sure about this, but I think some subtitle formats might be frame-based. With that said, there are various tools out there to retime/sync subtitles, pretty sure you'll be able to figure it out with those if you play around long enough.