A different 24pA v.s. 24Pn question

G

Gordon JL

Well-known member
Here's a 24PA question no one seems to answer; they answer questions related to it; and when to use it, but never getting down to the nitty gritty.

IF I can edit in both 24fps AND 30fps timeline; THEN which mode should I shoot in? I can choose since AVID allows both timelines. Which mode would yield best results, if there is such a thing (more filmic, highest quality, best motion, least compression, etc.); assuming that if I shot 24pA I edit in 24p timeline, and if I shoot 24p I edit in 30fps timeline. If I can do both, which should I choose and why? Keep in mind -- I won't be transfering to film (which pretty much means you MUST shoot 24pA).

Another question is; what if I decide to shoot slo-mo as well (meaning 60i + 30p footage will need to be in same timeline). If I mix different FPS's, which mode should I shoot in now?

Thanks in advance (this may settle the 24Pn v.s. 24pA debate more directly).
 
24pa is specifically designed for a digital workflow in a 24 frame timeline right through to output, and pulldown removal is a must. Pulldown removal is much simpler since every third frame is thrown out. During camera capture fields are AA BB BC CC DD. Cadence however is much more noticeable and playback may not look quite as smooth.

24p(n) on the other hand lets you edit in a 60i timeline without doing any pulldown removal or you could still go to a 24fps timeline but pulldown removal is a lot trickier since you have an AA BB BC CD DD field pattern to convert. Playback looks smoother but you can see that because the pulldown for 24p(n) is 2:3 rather than the 2:3:3:2 of 24pa C frame is split across even field of frame 3 and odd field of frame 4 making certain frame accurate cuts a potential issue.

For best film style editing and going all the way through to DVD I prefer 24pa. If I know I'm going out to broadcast but still want the film look and cadence, I'll shoot 24p(n). The mixed frame rates for slow motion question is therefore a misnomer and is like asking which colour makes the sound quality better.
 
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Actually all of Gordon's questions are valid.

Craigbowman is correct that 24pA allows for a smoother digital capture but since you are on Avid, it allows pulldown removal for either NORMAL or ADVANCED directly over FireWire. Purists will insist that ADVANCED is better, and I agree if you never render your footage again. But if you color correct, add effects, etc. all software must decode, apply the effect, render, compress. That is the very definition of a codec (COmpress/DECompress). So in the end, it pretty much is a wash.

Now, the question of which timeline to edit in - Even if not gong out to film, there are still advantages of working native 24. All primetine shows on TV are edited native 24 when shot that way. The reason is that the resulting 30fps broadcast master will have a continuous 2:3:2:3 cadence which allows for smoother MPEG2 encoding resulting in a higher quality show. Progressive television screens for the last couple generations can undo 2:3 to give a better cinematic look to the content, but it cannot do a good a job if the cadence is broken at every cut point. I won't go into the 25 combinations possible of cadence relationships when cutting at 30.

Also native editing at 24 for 30fps broadcast will give you 20% more storage, and will also reduce the time it takes to do certain effects such as roto, etc.

If creating a DVD, you will get advantages such as the 20% reduction in space needed to store the same length program. And the DVD will look better when paused, advancing frame by frame etc.

The last questions on alternate frame rates: if you want slomo from material shot at 30p or 60i, playing them back at 24 will give you the 25% or 2.5x slomo that you wouldn't get in a 29.97 timeline since that is the native rate of what was shot. For example, shoot 30p, set Film settings to have NO PULLDOWN when capturing, all 30p frames come in - hit play and they will play back at 24fps. No rendering, full vertical resolution 25% slomo with no rendering.

Michael
 
Here's the question to ask:

Will you edit in 24p?

If so, shoot 24pA.

If not, shoot 24p standard.

It really is as simple as that. :)

The only time you WOULDN'T want to edit in 24p is if you're mixing it with another frame rate and you don't want to convert that other frame rate to 24p -- if you want to keep the look of the 60i footage, or if you have 30p footage that you're NOT using for slo-mo (30p doesn't make a good conversion to 24p).

(BTW, this question has been asked and answered quite a few times. :) )
 
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David Jimerson said:
(BTW, this question has been asked and answered quite a few times. :) )
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I have read many answers to this question but never grasped the concept between 24p and 24Pa, but this seems to answer it plainly. I have had so many problems with 24Pa with exporting it to 24fps avi. I finally figured out that quicktime is the way to export in 24fps not avi. This is true with Premier Pro 1.5 anyway. However, shooting in 24P(n) is captured and edited on a 60i timeline? I'll have to give that a shot.
 
The last question on slomo is a misnomer because you have to place 60i or 30p footage in a 24 timeline to get slomo. Period. No other combination gives you slomo.
 
That's not true; you can put 60i or 30p in their own timelines and use velocity envelopes or "time warps" or change the playback rate to get slomo. You can also drop 60i on a 30p timeline and slow it to 50% for a good slomo in 30p.

Nothing gives as good a 24p slomo, though, as using those framerates on a 24p timeline and then slowing the 60i to 40% or the 30p to 80%.
 
Kdawg said:
I finally figured out that quicktime is the way to export in 24fps not avi. This is true with Premier Pro 1.5 anyway.
Click to expand...

Depends on what you're exporting FOR. PP does have a few more export limitations than other NLEs, though.
 
make life easier on yourself, shot 60i 30p 24p throw it on 30fps timeline.....but 24p give you best filmic over all.......
 
David Jimerson said:
Unless you have a very very good reason not to, it's always best to match your timeline to your footage.
Click to expand...

Whoa, this thread grew since my posting. Thanks a lot for the responses so far.

So I guess the verdict is, shoot 24PA and edit on a 24fps timeline, unless you can't (in a nutshell), even when doing slow-motion effects.

But David, I remember reading in Barry's book that while one may give better motion, the other actually gives less compression (so there is a tradeoff); one isn't strictly better than the other. I just don't remember which is which. I may be misreading what Barry said, but are you sure 24pa would yield best quality, or does 24pn in 30p timeline have its own benefits as well?

I have another question: when shooting 24PA, you pretty much have to remove the pulldown after you're done with your editing right? (Unless it's AVID, which does it for you as you're capturing). Well, what if you are mixing in 30p and 60i Slo-mo footage in the timeline as well; the footage will be converted to 24fps; but do I still have to worry about pulldown removal for these particular clips/scenes in my timeline; or should I remove the pulldown from the 24pa footage separately (because I don't want to remove pulldown from the 30 and 60 fps footage when it's not necessary -- it may degrade the motion or whatnot). I'm confused on how this all works when it comes to pulldown removal.

MichaelP; you mentioned something about AVID removing pulldown for you in AVID as you're capturing footage, and that this is sometimes considered bad if you want to add in effects, or CC, or do some grading, etc. And for me, I ALWAYS want to do CC and grading for my footage; so this option (let's call it auto-pulldown-remove) in AVID is ALWAYS bad one for me -- is there a way to turn it off? And when I do, can I remove pulldown as I export instead, that way all my CC'ing and effects will already be done first?

Someone mentioned something about exporting to Quicktime if you shoot 24PA -- is this an issue with AVID? I often times will also edit my projects with Adobe Premiere Pro 1.5; so does that mean I should stick to exporting in Quicktime, or can this issue be fixed? I don't like being stuck with Quicktime formats (I mean, what if I want to burn the stuff on a DVD? Don't DVDs only accept MPEG2?)
 
You might be referring to a couple of things Barry was talking about in his book.

One of the differences between 24pA and 24p standard is that 24pA uses frame-based compression and 24p standard uses field-based compression. Because of that, 24pA may be slightly higher-quality than 24p standard. But in reality, the difference is too negligible to notice. Standard definition is so low-resolution . . .

As for compression cycles, he also mentioned (I believe) how it takes extra effort to extract the original 24p frames from 24p standard footage, because the way the frames are split up into the 60i stream, the third 24p frame has to be reconstructed in a more difficult way, as opposed to 24pA, where it involves simply fusing a "natural" field pairing. This can result in higher quality as well, but see my caveat above.

So, in terms of absolute potential quality, 24pA is better.

As for the benegits of 24p on a 30p timeline, there are none that I'm aware of, and it's a net detriment, because the 24p will have to be resampled to 30p and it's an awkward resampling; there isn't enough difference in the frame count between the two to make for an efficient resample. This is also why you never want to convert 30p to 24p unless you're using it for slo-mo.

As for removing pulldown, you do that BEFORE you edit. If you use Vegas or Premiere, that's done automatically on the timeline. If you use FCP or Avid, it's done during capture. Either way, it's done before you edit.

And you want it that way -- you want to work with the original 24p frame, not all these extra fields which are thrown in simply because of the limitations of DV and interlaced television.

As for the slo-mo -- what you'll do with 60i or 30p is put it on a 24p timeline and then slow it down -- to 40% for 60i, and to 80% for 30p. What this does is line up each time sample (60 per second with 60i; 30 per second with 30p) of the footage with a 24p frame, resulting in the smoothest slo-mo you can get. That's a general guideline; the exact method of how to do that in Avid -- MichaelP can answer that. But there's definitely no pulldown to remove at all. The only reason pulldown exists is so that 24 frames-per-second material can be shown on a 60 fields-per-second TV screen, or recorded in a field stream intended for TV (like NTSC DV).

Removing pulldown is NEVER bad for color correction or any other effects. In fact, it's better, because it gets rid of interlacing and lets you work with the full, native progressive frames.

When you edit in 24p, you can export to any format you want -- AVI, Quicktime, MPEG, Windows Media -- anything. You're not limited to anything specific.
 
I am interested in converting 24p standard footage to 24pA so that I can use it on a 24p timeline with other 24pA material. I could just use the 24pA footage on a 29.97 timeline with the 24p standard footage (the 24pA footage is interview talking heads, so there's not a lot of movement in the frame), but I'd like to be able to output to a 24p DVD so I'd prefer converting the other way around. Also, my hope is to minimize interlacing artifacts as much as possible. I have found solutions for converting the 24pA to 24pN with Graeme Nattress' conversion tools, but I have not found the details for how to convert 24pN (SD) to 24pA in Compressor. Any word on this issue?

I've heard that cinema tools can sometimes accomplish this, but not ideally because it does not read the changes in cadence that happen with different clips on the same tape. I understand that it is possible to do it in Compressor if you get the custom settings right and that Compressor will actually read the changes in cadence and change the pulldown pattern accordingly and more continuously than Cinema Tools. Does anyone know how to create this custom filter in Compressor and what the right settings are?
 
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