23.976 vs. 30i with Panasonic DVCPRO50 24p Advanced

[Lj Corwin]

I don’t think there is an advantage. I shoot 24pa with the SDX900, work in a 29.97 timeline, output to Digi-Beta and/or IMX and it goes on the air. And it looks great.

The doc editor in the room next to me is headed for a filmout when she’s done with her gig. Also shot 24pa. I guess it makes sense for her to work in 23.976. Unfortunately, she never asked when she set up her project (or rather her assistant didn’t) and instead she is working in a 29.97 project.

No one here wants to tell her because she kills messengers. Also, who knows? Maybe I’m wrong.

Anyone?…. Anyone?….. Bueller?…..

[Chris Bové]

Yo!

Be careful – you should NOT (never ever never) use a 24p or 23.976 project if you shot in 24pA. Only if shot in regular 24p. People told me this, but I didn’t believe them until I frigged it up myself.

24pA converts the 24p footage to 30i inside the camera (pulldown). Thus when any footage shot in 24pA comes out of the camera, it should from then on be considered 30i.

If you try to edit 24pA in a 23.976 project, you’ll see jerky interpolation (especially on moving shots) because the system is trying to undo the pulldown that the camera did for you.

I know this cuz I just finished a 23.976 project that originally had true 24p footage… but then the DP accidentally shot 24pA. There was NO fix. Media, sequences, titles, NOTHING from a 23.976 project is usable in a 30i project. I would have had to print out an EDL and start from scratch.

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\`(=)`/…Pixel Monkey
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[Lj Corwin]

Excellent info. Thanks!

[Casique]

Thanks for the feedback / clarification – I’ll sleep better tonight!

[Oliver Peters]

Unfortunately Pixel Monkey is wrong. The Panasonic cameras shoot with two pulldown modes. 24p (standard pulldown with cadence 2-3-2-3) and 24pA (“advanced” pulldown with cadence 2-3-3-2). BOTH modes record to tape as 30i, just like a film-to-tape transfer. The advantage of 24pA is that the tape signal can be captured as true 24p media over FireWire with the simple removal of the middle frame (a split frame) of a five frame stream. Standard pulldown is more complex to remove.

In fact, certain Avid models will ONLY remove pulldown at the highest resolution over FW if it was recorded as 24pA. It is quite possible that in the example Pixel Monkey gave, the 24pA footage was captured with pulldown removal on a system designed to remove only standard pulldown, such as a Meridien-based Composer, which expects 2-3 cadence, not 2-3-3-2. This means the system would have removed the wrong split frames resulting in a totally screwed up cadence, which sounds like what he described.

Either mode can be used if you intend to work in 24p, but proper removal of the specific pulldown mode used will depend on your system. Generally 24p (standard) should be used if you want a film look but intend the destination to be video and not film or a 24p DVD. If you record 24pA, but cut 29.97, the image will be technically correct, but strobe in odder ways than what you are used to seeing because of the different cadence.

The advantage to cutting it as a 29.97 project is that you will get a film look, but all effects, like credit rolls, DVE moves and transitions will be smoother on interlaced TVs because the movement is field based. If you edit it in a 23.976 project, these effects are progressive (frame-based) and will strobe more on TV, but look better if you went to a film-out or upconvert to 24p HD formats.

Modern compression systems and upconversion systems, like to see consistent and not mixed cadences on 24fps footage, because the image processing required is better when it can be done in a progressive mode. This mode detection is difficult to non-existant on some units when they encounter mixed cadences on a project (shot 24p with pulldown and cut in 29.97). So if you don’t have a lot of video-style effects and all your footage is 24p, they will be a number of advantages to cutting 24fps material in a 23.976 project.

Check out more info on 24p.com.

Sincerely,
Oliver

Oliver Peters
Post-Production & Interactive Media
Orlando, FL
http://www.oliverpeters.com

[Michael Phillips]

Oliver is correct – there are several advantages to working in native 23.976. ADVANCED was meant for easy removal of pulldown over FireWire. But Avid systems can remove both ADVANCED and NORMAL over FireWire if needed (Xpress Pro 5.1 and later) as well as over SDI to any resolution on Adrenaline. Avid does not need the flags to remove ADVANCED or NORMAL (in case they are missing from a dub etc.) and can pick up on any cadence on any timecode. No other system can offer this type of flexibility to cover any issue or problem that might occur before the tapes make into editorial… Yes Virginia, it is not a perfect world (I was feeling a little seasonal with the last remark). It’s called CYA design and implementation… (cover your ass).

Either ADVANCED or NORMAL can go back to film if the pulldown is removed. Once pulldown is removed, there is no difference at all in the resulting media – it is just 23.976 frames per second.

I would argue that if you are planning on mixing footage with 30i material in a 30i project that NORMAL is a better format to shoot since its cadence is more evenly distributed over the 60 fields. I like to use the Morse Code approach –

2:3:2:3 is SHORT | L O N G | SHORT | L O N G | SHORT | L O N G
2:3:3:2 is SHORT | L O N G | L O N G | SHORT | SHORT | L O N G

The pairing of SHORT and LONG in the ADVANCED cadence is more visible to the eye than NORMAL.

So yes, Pixel Monkey, I think you got your facts reversed.

Michael

[Chris Bové]

[MichaelP] “So yes, Pixel Monkey, I think you got your facts reversed.”

Casique – definitely listen to Michael over me on this one – from what I’ve seen on this forum, he’s quite keen on the 24p world.

Michael and Oliver – thanks for your candor. 24p.com does offer up a huge amount of info on the matter, but written word can only go so far. Have you encountered any Avid certified courses, weekend bootcamps or even online courses on the 24p world? As Oliver pointed out, there’s a lot of contingencies with pulldown between Avid systems. Live, interactive instruction would be SO helpful.

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\`(=)`/…Pixel Monkey
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[Michael Phillips]

You can hire Oliver or myseld to host an evening… or user group, etc. And 24p.com is my site… 😉

Michael

[Lj Corwin]

Hmmmm….now I’m more confused than ever.

I have been shooting 24pa footage, capturing component (no SDI available) into a 29.97 project and have been very happy with the results. The reason for the 24pa and not shooting 24p standard was simple; it simply LOOKED better to us. Yes, yes, we know we went against everything ever said and written about 24p vs. 24pa if your not going to a film out or working in a 23.976 project but the deciding factor was that 24p looked “steppy” and 24pa looked “smoother and filmic.”

I am getting a new Adrenaline in a couple few days. My plan was to use the same workflow (24pa into 29.97 project) but capture over SDI. Will going in SDI mess up the footage because of the wrong pulldown cadence? I guess I can run some tests when I get the Adrenaline but I’d love to know technically what, if anything, happens differently to 24p with SDI capture instead of component, Y/C or composite capture.

Please pardon me for my ignorance on this (particularly with my usage of words like “steppy” and filmic”). This is one area that just keeps tripping me up.

Thanks in advance.

LJC

[Michael Phillips]

The same workflow will work just fine on Adrenaline – if you are happy with the look then that’s what counts. SDI will be easier since you won’t have to deal with levels and such on capture.

Michael