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Old March 27th, 2007, 06:52 PM   #1
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What, if any, "cues" define 24p, 30p, and 25p?

Quote:
Originally Posted by Chris Medico View Post
On my side of the pond, video shot in 24p plays fine on my HC3.
24p is an interesting mode. We know 2-3 pulldown is the means used to carry the 24p. We know it is "1080i60 carrying 24p" which is why any camcorder can play it.

But, what IF ANY "cues" are in the data stream that define the video to be 24p? Or 25p? Or 30p?

In R50 -- there may be a cue in the data stream that the video is "progressive." I say may because Piotr and Bob both say that after export "the P flag was not set."

Which leads to the question -- how did you guys know the P-flag was set when it came from the camera and was not set after you exported the clip?

In Vegas, it's clearly indicated what the clips actually are. Which means that Vegas does read something in the file.

In R60 -- FCP in no way sees 1080i60/24p and 1080i60/30p as different from plain 1080i60. All are 60i with Upper Field first. All have a frame rate of 29.97. This seems to indicate that whatever cue is present isn't being sensed by FCP.

Complicating the picture more -- there are two modes of 24p. One assumes that there must be cues to tell these apart. Or, one cue to say "progressive" and one cue that says I am "24A" or I am "24."

I say "cue" because while MPEG-2 provides a complete set of flags to do everything -- they are optional.

It's possible that one or more "flags" are embeded in the bit-stream. Flags that pass through un-noticed except if software is written to check them. It's also possible that the TC is used -- for example to indicate A frames in 24A mode.

All this becomes important not at the capture phase, but the export phase. If the cues are MPEG-2 flags, they have to be added by the software that does the encoding. Which means for Premiere and Vegas, another company has to do the job.

However, if bit's need to be set -- it's possible that only the V1 hardware can do the setting. So, exporting a bit-stream identical to what a V1 records would be impossible. (For example, if it's part of the TC -- I don't think the NLE defines that for HDV Assemble Edits. The camera does.
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Last edited by Steve Mullen; March 27th, 2007 at 09:07 PM.
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Old March 28th, 2007, 04:10 AM   #2
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Quote:
Originally Posted by Steve Mullen View Post
In R50 -- there may be a cue in the data stream that the video is "progressive." I say may because Piotr and Bob both say that after export "the P flag was not set."

Which leads to the question -- how did you guys know the P-flag was set when it came from the camera and was not set after you exported the clip?

In Vegas, it's clearly indicated what the clips actually are. Which means that Vegas does read something in the file.
Steve, all I said you have just repeated: something (cue, flag, whaever) must be set by V1, because when captured and read into Vegas, it's recognized as progressive. I say "recognized" because it's only when you click the file in Vegas explorer, this information is displayed in the explorer satatus bar. Other than that, nothing happens - ie. if you set up a project with Upper Field first and import such a progressive clip into time-line, it stays interlaced. You have to manually define your project (timeline) as "Progressive". You are right in saying that other NLE' s don't even "see" the 25PsF clips as progressive - Edius, Premiere, Ulead treat them as plain 1080i, Upper Field first.

As to the export, let's differentiate:

- export to an MPEG-2 file you can do in Vegas as progressive, and the output clip is flagged or cued so; when you click on it in Vegas Explorer, it says "progressive", just like the original

- print to tape you can only do as 1080/50i or 1080/60i; there are no other choices. However, you can print from timeline or from a specified file; when you do the latter, you can as well point to a 25PfS raw clip and it will be printed to tape. Morover, when you capture it back, it's still recognized as progressive by Vegas. However, if you point to an MPEG-2 progressive file, rendered from a 25PsF clip by an NLE - that's another story (see below).

As an interesting side note I can tell you that Edius has a tool called MPEG TS Writer, which also can select a progressive clip for printing to tape, and even will show the progress of printing - however, nothing goes to tape, apart from the time code!

These are the facts. Now go and figure, because I'm lost:)

UPDATE:

1. I have compared the headers of progressive vs interlaced files in WinHex and yes, they are quite different. There certainly is some information there!

2. Also in Vegas, when you try to PTT a progressive MPEG-2 file other than a raw 25PsF clip from the V1E, the result differs depending on which NLE produced that file: some start printing, but the camera displays the "Invalid format" error message; some will be reported as unrecognized by Vegas and won't print at all; yet others behave just like described above with the Edius MPEG TS Writer - only the timecode goes to tape.

So it seems like only V1E can set the flag properly, and only Vegas can read (but not set) it properly! A captured 25PsF file is recognized by Vegas as progressive, it can be printed to tape by Vegas as 1080/50i BUT after re-capture, it's still progressive. The rest is mistery to me.
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Last edited by Piotr Wozniacki; March 28th, 2007 at 04:50 AM.
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Old March 28th, 2007, 08:11 AM   #3
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Why all the fuss about flags anyway. If the flags are misssing so what, it's not exactly hard to eyeball the footage to tell if it's progressive or not. On top of that there's plenty of formats that don't have any such flags anyway and we've managed to live without them.
I'd add 16:9 flags as well to the mix of things that regularly don't / can't / get lossed somewhere along the pipeline.
Isn't this why we slate and label tapes?
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Old March 28th, 2007, 03:58 PM   #4
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Quote:
Originally Posted by Bob Grant View Post
Why all the fuss about flags anyway. If the flags are misssing so what, it's not exactly hard to eyeball the footage to tell if it's progressive or not.
I have no doubt one can. That isn't the point.

The question is -- is it possible to write to the V1U, video that is exactly the same as what what the V1 shoots. With all other tape formats, one can record from the camera or an NLE and get the same result on tape. And, you can do this with all other types of HDV -- so it's BS that if it can't be done with the V1U's 24p -- that it is a general HDV limitation.

If Sony has created a 24p format that can only be written by the camera, then this is critical to those that move content via HDV tape -- which is the only low-cost way to move HD.

For example, I can burn to HD DVD, but Sony has only BD players. A good friend needs to send HD to Sony. Sony's solution is to send him an XDCAM deck. Now that's very nice of them. But it is not a general solution.

Remember that HDV is the replacement for DV. Thus, all the ways one works with DV need to be available for HDV. So far with 720p, this has been true. This may not be true of 1080i60/24p.

With only Vegas out -- and with Sony not talking about these details -- one cannot tell if it's an NLE limitation or a format limitation.

Piotr -- thank you for confirming that the V1E behaves just like a V1U. Clearly to be recorded, the V1 needs to receive exactly what it bits it expects. (Just like all systems.) The questions are:

Can an NLE set these bits:

1) are they bits in the data stream or written by the camera. And, is the answer different for the 2 types of 24fps?

2) will the NLE or encoder company need a license from Sony to set these bits?

3) has Sony designed it's 24p system to prevent making perfect copies of 24p video through an NLE?

I'm not the one who raised the latter two possibilities, but they must be considered.
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Old March 28th, 2007, 04:39 PM   #5
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Quote:
Originally Posted by Steve Mullen View Post

If Sony has created a 24p format that can only be written by the camera, then this is critical to those that move content via HDV tape -- which is the only low-cost way to move HD.
Give it up Steve. No one in their right mind would go back to HDV. I bet you could count on you left hand the number of people that actually do that. The low cost way to move HD is on HDD.

A camera is a capture device not a playback device. Sony clearly understand that principle.

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Old March 28th, 2007, 06:02 PM   #6
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Quote:
Originally Posted by Tony Tremble View Post
Give it up Steve. No one in their right mind would go back to HDV. I bet you could count on you left hand the number of people that actually do that. The low cost way to move HD is on HDD.

A camera is a capture device not a playback device. Sony clearly understand that principle.

TT
Couldn't agree more. I've rented HDV decks to many users and own one myself. Neither I or any of of those renting decks have ever recorded HDV on a VCR in the line of fire.
It's also worth keeping in mind that none of the HDV VCRs will encode HDV, that's a more interesting limitation.
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Old March 28th, 2007, 06:14 PM   #7
 
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HDV=Acquisition format. A format used to _aquire_ mages as seen through the camera lens.

HDV==Pseudo editing format. Definitely not ideal for editing, no one genuinely serious about their work is compositing or color correcting with mpeg files; they're converting to AIC, DnX, CineForm, Sheer, or other HDI/editing format. Intraframe just isn't an ideal format for editing, never has been, even though FAST (now Pinnacle) made a pretty good stab at it.

HDV==Not a delivery format. Outside of Japan, there isn't a single broadcaster, replication house, film transfer that will officially accept an HDV cassette that I'm aware of, or can find after many hours of scouring the web.

SD-DVD, HD-DVD=, Blu-ray...all delivery formats for replication and festival
HDD=-Delivery format for broadcast and replication.
HDCAM=-Delivery format for broadcast, festival and replication

The discussion has zero to do with Vegas, and everything to do with what offerings are available, vs real-world needs vs measurebation and "what-ifs". This is not Vegas discussion; it's an HDV discussion.
*NO* NLE offers what you're asking for. As to why, I've heard at least three very different answers. But if it was "easy" then everyone would be doing it.

No one is going to PTT for 24p footage. There is no point in waving this flag.

I'm a partner in a very active production house. Our workflow has become roughly 70% HDV. We deliver to a variety of clients, ranging from very small corporate events to very large international broadcasters. Our footage from the preproduction V1 was the first national and international broadcast from this series. We've never delivered, nor been asked to deliver HDV on an HDV cassette.

We acquire (shoot) in HDV. That's where it ends. Either we capture as component via an AJA card, or we capture as HDV and convert immediately to one of two intermediaries. If we're delivering SD it's either 60i, 30p or 23.97 with pulldown on a DVD, or on a DVCAM master. If we're delivering HD, it's either HDD, or HDCAM. We've had a couple of clients recently inquire about BD, but at the moment, we're not ready to take our BD options into the realm of commercial delivery. Very soon perhaps, but not at this very moment.
We archive to HDD.

We don't at all care about being able print back to the camera.

This is the trend of the future. P2 doesn't "print" back to the camera (I guess you could), nor will HDD or DVD based camcorders. Given that the future is AVCHD, and some format of MPEG 2 on HDD, no one is *ever* going to be concerned about printing to tape in the future. Tape is merely a data container. Once moved from the linear data container to the non-linear HDD, it's just a file that can be manipulated and delivered to any number of industry standard delivery formats.

XDCAM can certainly be file-transferred to, but this is predominantly for archiving in a newsroom situation. The *majority* of XDCAM shooters that aren't ENG are archiving on HDD, and perhaps back to XDCAM. XDCAM discs are convenient, but HDD is more convenient in a properly managed facility.


This seems to be an attempt to create an "issue" where none exists. Data transport is the future, and printing to tape isn't part of that future. Acquiring from tape isn't part of the future either, the current trend of camcorders, and likely what we'll see at NAB in two weeks will bear that out.


XDCAM, Infinity, P2, the proliferation of SD card cams, DVD cams, Firestore and the like, Bella Catapult, and new offerings coming soon demonstrate that no one is considering tape much as anything but an acquisition medium. It's used less and less for archiving, transport, and delivery, and no expectation nor likelihood that it's going to gain ground.
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Old March 28th, 2007, 08:43 PM   #8
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Hey guys,

I just wanted to throw in my 2 cents about HDV, even though we're completely of topic and may have to split this thread.

Anyway, my DP Jon Fordham shot my film 9:04 AM on HDV (HVR-Z1u) in 50i/CF25. Once I'm done editing, I will put the film to tape in 50i mode, then convert it to 24p and output via a less compressed HD format (I'm choosing, in Final Cut Pro, photo - jpeg at 75% quality, 4:2:2 YCbCr.

I'll take it to a post-house for BetaSP output (that's the format the film festival we're premiering in wants it) and HDCAM and probably DVCPro 50. Heck, I'll create my own mini-dv version, too.

The point is, HDV is a viable source and for a few bucks, you can output it to whatever any company, film festival, etc., wants. I wish the film festival supported at least mini-dv, but they request BetaSP. So that's what we'll give it to them on.

As for the 24p info, well, I think of packaging the 24p signal in 60i as a very common place thing to do. The DVX, XL2, etc., all do it. And most NLEs support removing the pulldown, even if you use a workaround. I use the photo - jpeg 75% (again, FCP) before removing it.

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Old March 28th, 2007, 09:01 PM   #9
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Forgive an amateur for popping in here but...

I asked whether it was possible to export 1080/24P with pulldown as 60i to tape in Vegas in a post in January (http://www.dvinfo.net/conf/showthread.php?t=85159) and learned that I could not.

But, I asked this from the perspective of an amateur trying to do things on the cheap.

I would find it surprising that any professional (who by definition requires higher standards with regard to his/her work) would ever be concerned with going back to tape. Like I said, I was interested because I wanted to do things cheaply and "good enough" for an amateur (I have since changed my mind in this regard, however).

Considering the investment that many of you make to work in your profession, why would you ever want to go back to HDV? As the Cineform website clearly says in one of their HDV quality analyses: "Clamping the image to the original 25Mb/s forces data loss". I know I've seen it. I would think that any pro would want their footage left in a format that maintains image integrity.

If it really is important, two inexpensive (for a professional, at least) options exist:

DVFilm Maker: "Maker will add either 3:2 or 2:3:3:2 pulldown to HD and uses the correct field dominance (upper field first). You would then have to encode to HDV using Vegas for recording back to tape."

Cineform AspectHD HDLink: "Once you have completed your 24p production, some may wish to archive back to HDV tape. The CineForm M2T export with Aspect HD and Prospect HD will support 24p encoding into a 60i stream, by simply adding the 3:2 pulldown back."
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Old March 28th, 2007, 09:18 PM   #10
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You also have www.nattress.com as well.

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Old March 28th, 2007, 09:19 PM   #11
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Originally Posted by Heath McKnight View Post
The point is, HDV is a viable source and for a few bucks, you can output it to whatever any company, film festival, etc., wants. I wish the film festival supported at least mini-dv, but they request BetaSP. So that's what we'll give it to them on.

As for the 24p info, well, I think of packaging the 24p signal in 60i as a very common place thing to do. The DVX, XL2, etc., all do it. And most NLEs support removing the pulldown, even if you use a workaround.

heath
Exactly. I'll bet more places will have an HDV camcorder or VTR than will have a BD player. If they don't, you can carry your camcorder to them and make a dub via analog component. I doubt many posters here have either an XDCAM HD or an HDCAM VTR sitting on their desk. And, why should you rent a VTR when you can use your HDV camcorder. It's the DV way of getting the job done cheap. That point keeps getting lost. And, this site is dvinfo.net -- not HD.net.
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Old March 28th, 2007, 09:28 PM   #12
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But keep in mind, Steve, my final 24p output, which was a converted 50i HDV movie, won't be HDV. Only the 50i is going to HDV.

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Old March 28th, 2007, 09:57 PM   #13
 
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Quote:
Originally Posted by John McManimie View Post

Considering the investment that many of you make to work in your profession, why would you ever want to go back to HDV? As the Cineform website clearly says in one of their HDV quality analyses: "Clamping the image to the original 25Mb/s forces data loss". I know I've seen it. I would think that any pro would want their footage left in a format that maintains image integrity.

Well said, John.

Quote:
As for the 24p info, well, I think of packaging the 24p signal in 60i as a very common place thing to do. The DVX, XL2, etc., all do it. And most NLEs support removing the pulldown, even if you use a workaround.
DVX, XL2 are not interframe technologies.
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Old March 28th, 2007, 10:03 PM   #14
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Spot,

The DVX and XL2 package the 24p signal in a 60i stream--I need to clarify that, sorry for any confusion. I was just comparing how camera manufacturers do this.

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Old March 28th, 2007, 11:42 PM   #15
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Quote:
Originally Posted by John McManimie View Post
Considering the investment that many of you make to work in your profession, why would you ever want to go back to HDV? As the Cineform website clearly says in one of their HDV quality analyses: "Clamping the image to the original 25Mb/s forces data loss".
Of course the CineForm folks say this. But, it is very minor -- at least with FCP. One decode and one re-encode. Really nothing to worry about, because the big hit is in the first encode.

In any case, you are not going to deliver CFHD to anyone. So there's no point in talking about it here.

You have to live with there being no HD deliverable that is not inter-frame 4:2:0 MPEG-2, VC-1, or AVC. Moreover, the fact is that HDV, XDCAM HD, and both HD DVD and BD are all brand names for exactly the same MPEG-2 codec.
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