Mercer:

there is no such thing as SD PAL 24fps (or any 24 fps in PAL)

There most certainly is.

There are three kinds that I am aware of:

1. 24 frames spread over 25 frames by repeating an entire frame every second

2. 24 frames spread over 50 fields by repeating each 12th field (and reversing field order after that)

3. with modified decks or files running to a slower clock (Apple's Cinema Tools let you convert a 25fps QT movie to 24fps, the DVPAL codec allows for a true 24fps playback rate)

Of course, the latter is by no means legal PAL anymore, and the other two are not generally accepted as broadcast masters. But for offline editorial (and sound mix), they are very common.

Avid has been using the second kind for ages now. It is the way theatrically released movies are being cut in PAL-based countries. Effectively, the footage is 24p INSIDE the Avid (without any duplicated fields or pulldown), and 'PAL pulldown' is added during playback through the video output box (Meridien, DNA, DX).

The downside of the third party hardware so far is that they will not provide an output at all when you have a 24p PAL project (apparently the AJA will play it back, not capture it). Avid hardware has had 24p PAL support for a very long time.

* edited AJA 24p PAL playback *

Job ter Burg:

PsF is not the same as pulldown. Pulldown means adding fields and converting 23.976p to 59.98i. Maybe the AJA supports that (the Matrox does, AFAIK), maybe not. But PsF is just P-in-two-segments. It's the way all HD decks work as well.

Ah -- I see.  I read somewhere that PsF was essentially the same as "23.976 in a 29.97 wrapper" but it looks like that was not correct.

Thanks,

Larry

lalittle:

Ah -- I see.  I read somewhere that PsF was essentially the same as "23.976 in a 29.97 wrapper" but it looks like that was not correct.

The same reason that NTSC is interlaced is why we have PsF.  Take one 1080 progessive frame and split it into two interlaced frames of odd and even scan lines.  Then display them as 1080i.  You save in bandwidth requirements and even though it is not true 1080p it does not suffer from the same issues as 1080i because the odd and even interlaced frames represent the same instant in time.  It works similar to how stripping hard drives improves performance. 

Keith

Job ter Burg:

There are three kinds that I am aware of:

1. 24 frames spread over 25 frames by repeating an entire frame every second

2. 24 frames spread over 50 fields by repeating each 12th field (and reversing field order after that)

3. with modified decks or files running to a slower clock (Apple's Cinema Tools let you convert a 25fps QT movie to 24fps, the DVPAL codec allows for a true 24fps playback rate)

This is how to handle 24fps within a PAL project such as Film Composer used to do and now MC. I am clearly talking about delivery and camera original formats. There is no such thing as a 24fps SD PAL broadcast delivery format (or camera capable of shooting such), there is no way to play and show it. When Avid slows down 25fps to 24fps for film projects it stutters to do so, this would be unacceptable for broadcast. It is an offline workaround for both Apple and Avid (and for any other capable NLE) for film telecined to PAL tapes frame for frame. There is no 720 x 576 tape format that runs at true 24fps. It is becoming less common to offline film originated projects this ways since HD native rates.

Standards conversion is also a completely different matter.

I understand what you are saying about 3rd party limitations on output of these PAL film projects for offline and viewing copy output (i haven't cut a film project this way for some time but I recall always having some limitations). Does this apply to the AJA then over SDI? I could not imagine why it would be different to Mojo and Nitris DX in this respect.

Mercer:

There is no such thing as a 24fps SD PAL broadcast delivery format

Agreed.

Mercer:

It is becoming less common to offline film originated projects this way

However, it's still done a lot. SD telecine is often cheaper than HD telecine (although the difference is becoming marginal).

Mercer:

Does this apply to the AJA then over SDI?

If you look at http://cdn.pinnaclesys.com/SupportFiles/attach/HW-Capabilities_1.2.pdf, then you can see that the Matrox MXO2 Mini does not support 24p PAL projects, and 24.00p NTSC projects. The AJA apparently does play them back, but somehow is specified as not being capable of capturing in 23.976p (SD), 24.00p (SD), 25p (SD) formats.

So folks looking to replace their Adrenalines with an AJA box may run into trouble when they have to embark on a 24p PAL project (with a need to capture) for instance.

Seems weird, though, that the box can't pull it off. ALL Avid boxes (NuVista, ABVB, Meridien, DNA, DX) have always supported it for more than 15 years now. 

Job ter Burg:

So folks looking to replace their Adrenalines with an AJA box may run into trouble when they have to embark on a 24p PAL project (with a need to capture) for instance.

Thanks for the info Job. But that's not how I've ever done a 24fps film project in PAL SD Film Composer or MC. I always received a PAL tape copy of the telecined master frame for frame and captured normally. Then Avid slows the picture down upon playback to match the normally transferred audio takes.

Mercer:

I always received a PAL tape copy of the telecined master frame for frame and captured normally. Then Avid slows the picture down upon playback

Yes, that's how I do it too, TK at 25, capture from 50i source (into a 24p PAL project !!), and so does the rest of the world AFAIK there is no other way, nor has there been. But: you need to be able to open a 24p PAL project and capture.

But look at the spec sheet. It specifically states no capture support in 24 projects (PAL nor NTSC) for the AJA box. And no 23.976 NTSC either. This is precisely what I am talking about.

So apparently, the AJA box does not support this capture-then-slowdown? Which is what strikes me as very odd, as the slowdown - to the best of my knowledge - is done by the software, not the box. Perhaps it makes SOME sense for 23.976, as maybe the box needs to do the pulldown removal?

And again, look at the DX boxes. These are specifically supported for 24p SD projects, the AJA box specifically is listed as NOT supporting those projects.

I can read nothing other into the spec sheet is that if your project is set to 24p PAL, 25p PAL, 23.976p NTSC or 24p NTSC, that your AJA will not allow for capture. And you sure can/could with Meridien, DNA, DX...

Job ter Burg:

But look at the spec sheet. It specifically states no capture support in 24 projects (PAL nor NTSC). And no 23.976 NTSC either.

I see what you're saying now. It does seem odd and not supported on NC with even Mojo or Nitris DX (but then that would maybe make sense because it dispenses with the Film Composer element of MC)

Could you not capture say in a PAL project and import the bin to a 24 project I wonder? It could be an artificial limitation to force high end customers like studios into DX hardware perhaps?

Mercer:

Could you not capture say in a PAL project and import the bin to a 24 project I wonder?

You can, but your footage would carry motion adapters doing a 25-24 conversion (keeping the playback speed the same [so speeded-up!], not slowing it down). Maybe you could remove these, but only in a sequence. So how would you sync up to sound? I don't think it's a viable solution.

Mercer:

It could be an artificial limitation

I'm afraid it might be. Precisely my point...

On the other hand, AJA in the past has forgotten about 24p in the PAL world, for example in their BBGEN (which only does 1080p24 when you set it to NTSC) and I think in earlier versions of the Io there was no 1080p24, only 23.976.

It could also be an incorrect listing in the spec sheet. I'm following up on it.

Job ter Burg:

I'm afraid it might be. Precisely my point...

If this is true some people could stick with Adrenaline HD on 5.5 for now perhaps?

Job ter Burg:

You can, but your footage would carry motion adapters doing a 25-24 conversion (keeping the playback speed the same [so speeded-up!], not slowing it down). Maybe you could remove these, but only in a sequence. So how would you sync up to sound? I don't think it's a viable solution.

You're right of course. You could create slomo clips or you could use the IgnoreQTRate console command for import, but it would be very laborious. Again the AJA limitations don't really make sense since as you mentioned it is an Avid software feature from Film Composer  days and SDI should be SDI, no?

Cagey:

The same reason that NTSC is interlaced is why we have PsF.  Take one 1080 progessive frame and split it into two interlaced frames of odd and even scan lines.  Then display them as 1080i.  You save in bandwidth requirements and even though it is not true 1080p it does not suffer from the same issues as 1080i because the odd and even interlaced frames represent the same instant in time.  It works similar to how stripping hard drives improves performance. 

Keith

I don't understand how this would save any bandwidth.  It's still 23.976 fps of material displayed every second, so isn't the actual amount of image data per second the same?

Thanks,

Larry

NO, it is half because each field is 1/2 of an interlaced frame, that is then put back together as a full progressive frame. Since there is no time delay between fields, you get a progressive frame after re-assembly instead of  torn movement as you have with true interlaced. The benefit is each transmitted field of video uses 1/2 the bandwith of a true progressive frame. Hope that makes sense.

But there are twice as many of them so the  bandwidth is the same....

I too fail to see the difference in overall bandwidth. 24*1*60 equals 48*0.5*60. Total amount of data adds up to the same number.

I vaguely recall that it has to do with how VTRs record the signal, and that storing as PsF was easier to implement.