Mixing 24p and 30p Footage

[overnighttolondon]

Ok. This is a bit of a non-standard situation, but hopefully someone knows.

I have a project that's mostly 24p, and I want to use a 24p timeline. When I capture (or import an .avi captured some other time, both of which were shot 24pa 2:3:3:2), Premiere is analyzing my 60i footage (everything on NTSC tape is technically 60i) and reversing the 2:3:3:2 pulldown to give me full-frame 24p footage. (correct me if I'm wrong).

What I want to do though is import some 30p footage as well, but I want one frame of 30p footage to be one frame on my 24p timeline - that is, I want my 30p footage to play slower than normal, at 80% (24/30) of its normal speed. I do NOT want it to try to pull down to 24fps so that it plays realtime on my 24p timeline, I want a slight slow motion effect.

My worry is that since I'm in a 24p timeline, Premiere is going to try to interpret my 30p footage (which, of course, on tape is just 60i) as 24p footage and try to extract full frames by reversing the (non-existent) pull-down. How does Premiere know whether the footage on the tape is 60i, 30p, 24p, or 24pa? Does this get stored in the User Bit area of the tape? Or is there something I'm misunderstanding about the whole 24p process?

Thanks

[Sumfun]

Premiere looks at the first frame in a clip to determine if it's 24p, 24pa or 60i. (30p is considered 60i). So you can trick Premiere into thinking that your 30p footage is 24p simply by contatinating 1 (or more) 24p frame to the beginning of your 30p footage, save it as an avi, then importing it back in. You can then edit out the first frame.

However, Premiere will still reverse the pulldown on the footage, and you will not get what you want.

Here's my suggestion to getting your effect (without losing any frames):

1. Edit the 30p footage in a 30fps timeline.
2. Change the speed to 80%.
3. Concatinate some 24p footage to the front of your clip.
4. Save the clip as avi.
5. Import in into your 24p timeline.

I haven't done this myself, but I think it should work. If you try it, please let me know.

[Ralph Oshiro]

Sumfun:

So, if in my case, if I wanted to include both 60i footage and 24p footage within the same 24p timeline, but I want the 60i footage to play at "normal" speed, I would follow the same methodology, sans the 80% speed reduction?

Example:

I want to shoot a short film using an SDX900 in 24PA mode. I will also acquire 60i footage with various other video cameras (BVW400A, VX2000, etc.) to simulate "news" footage. I'll shoot the principal photography with the 24PA SDX900, then intercut full-frame 60i footage into the 24PA timeline (after following your concatenation procedure and saving as .AVI).

Another question is, how do I shoot 60i monitors with a camera shooting in 24PA mode without getting roll bars? Would I be able to synch the SDX900 with the 60i playback using merely the shutter or would I have to actually acquire the playback video at 24PA (does that solve the problem)? If this doesn't work, is my only solution for shooting 60i playback (or whatever) to use LCD or plasma displays rather than CRTs? Thanks!

[Sumfun]

NBCShooter,

First I want to say that I usually shoot 30p now in order to avoid the headache of combining 24p with 60i in Premiere. Also, you can avoid this problem by using FCP, Avid, or Vegas. But if you insist on using Premiere, then what I posted earlier is valid. The only drawback is that once you export, you lose the original timecode of each clip. But on a final project, it doesn't really matter.

Another work around is to trick premiere into thinking that your 24p clip is actually 60i during capture. To do this, simply start the capture on 60i video (such as color bars), and just capture the whole tape.

Depending on what your final output is, you may want to try the inverse of this on a 24fps timeline. For instance, if your final output is a 24fps DVD, then a 24fps timeline may be more appropriate.

Not sure how to synchronize 24p with a 60i monitor. Maybe Barry Green has a suggestion? I remember reading something about synchro scan in his DVX book, but I don't remember the details. But playing back 24p video on the monitor will not do it because the monitor still scans at 60 fields per second. Now if you shoot 30p, you will not get scroll bars. I also tried shooting 30p and then switching to 24p while the tape is running (by turning the "F" dial on the dvx), and I did not get any scroll bars. But I can't be sure that the camera was recording 24p either.

My best advice is for you to do some testing to find out what works best for your needs.

[Ralph Oshiro]

Thanks, Sumfun. Guess I'll try some experimenting. If I figure anything out, I'll post results here.

[seejay1031]

Can't you just import 30p onto a 24p timeline and then adjust speed to 80%. That's what it says to do in Barry's Book.

[egproductions]

what sumfun said seems to be correct it is a fine way of doing what you want to get done. I think there might be an easier way and that would be to highlight the 30p footage in the 24p project and then go to file--->interpuret footage and just change the fram rate to the proper setting. However i am pretty sure thatit doesnt matter what project settings you have when you capture footage that is 30p premiere will already see it at 29.97 and it up to you if you want to keep it progressive depending on what project settings you have.

[Sumfun]

Can't you just import 30p onto a 24p timeline and then adjust speed to 80%. That's what it says to do in Barry's Book.

Yes, you can do it, but I think Overnighttolondon was concerned about losing some of the frames from his 30p footage. I'm not sure about this, but my guess is that when you import 30p footage into a 24fps timeline, Premiere will perform a reverse pull down, and just use 24 of the 30 frames (per second). When you adjust the speed to 80%, it will repeat some of those 24 frames. Thus your motion is a little jerkier than if you had all 30 frames to play with.

[overnighttolondon]

Been a while since I've posted about this, but in the meantime I've figured out a solution that works great for me. It's a little rough on your storage space, but it gets the job done while maintaining the best possible quality and all 30 frames.

Take the 30p footage into a 60i project in Premiere (actually, I used After Effects, but Premiere will work). Then, export your footage out of Premiere as an image sequence (I used PNG because of its lossless compression). Since an image sequence has no extra information in it (like framerate), you can just import that PNG sequence into your 24p timeline. Each frame from your 30p footage will map to a frame on your 24p timeline. You're still 100% progressive, you haven't lost a generation of compression (PNG is lossless), and that slight slow-motion effect is achieved.

Oh, I also read something above about displaying 24p on an NTSC (60i) output monitor - not a problem at all; Premiere automatically performs the same 2:3:3:2 pulldown as the DVX does when outputting footage to an external monitor (even though your timeline is still true 24p)