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Old September 5th, 2006, 06:59 AM   #1
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24p and time code

I'm in the middle of a discussion with the folks in the UK

They are saying that most 24p in the US on camcorders etc is in fact 23.98 which I believe is the case, but that the timecode is drop frame. Has anyone else seen this? Why are the camcorders not in tru 24p? so that there can be for instance a frame to frame transfer to film.

With HD broadcast why do we stil need to have 23.98 following the old throwbacks to nstc?
My understanding is that some of the high end hd caeras the Varicam and the HDX900 do in fact use 24p but the rest do not. Is it based on a need to do a 3 2 pull down for ntsc sd broadcast that has been left over into hd?

IF this is the case, then other than sound issues which can be dealt with, if you want to go to 24p are you infact better off starting with 25p and slowing it down? For instance if Canon does not impliment 24p on the hv10, would a better alternative be to get a european 25p camcorder, and then simply import it and slow it down??


I guess even a better question is with hd why are we still sticking with 29.97, is it simply to have an easy way to convert over to SD

I have been suggestion shooting in the us at 24p and then speading it up for 25 p for europe.
The issue raised is that if you move from 24p to 25p you raise a semi tone and the audio sounds fine, but if you raise from 23.98 to 24p the slight variation makes the sound not sound correct, but some decks correct for this but that none of the nle systems do?

Sharyn

Last edited by Sharyn Ferrick; September 5th, 2006 at 09:12 PM.
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Old September 5th, 2006, 07:45 AM   #2
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As you said, it's because of a throwback to NTSC. If you want to show your material on TV, it will need to be 23.976fps. The 23.976fps frame rate is probably a little easier to do production in, since you can monitor the signal and the timecode is hopefully less confusing (I believe 23.976fps is always non-drop frame timecode too, but don't quote me on that).

HD for NTSC land is 29.97fps for backwards compatibility reasons. There is still a lot of legacy material and equipment that runs at 29.97fps, and SD still needs to be broadcast.

24.000 and 23.976fps conversions can be done... as can 23.976 to 25.000fps.
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Old September 5th, 2006, 08:03 AM   #3
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Thanks GLENN

Can anyone confirm or deny if 23.976 the time code is df or not?

In vegas for instance can you import in HD 25 and convert it to 23.976? what will it do with the audio? is there any pitch correction?

With the limited number of 24p hd camcorders, is shooting in 25p and then converting a viable option? I am curious why no one seems to be talking about it or using in? As far as monitoring goes, most semi prof monitors are multi standard all fo the PVS sony monitors we use are for instance if you had to monitor it in pal.

Sharyn
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Old September 5th, 2006, 08:29 AM   #4
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23.976 (Panasonic 24p or Canon 24F) is non-dropframe.
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Old September 5th, 2006, 09:18 AM   #5
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Quote:
Originally Posted by Sharyn Ferrick
Can anyone confirm or deny if 23.976 the time code is df or not?
It can (theoretically) be either, though in practice is likely to be df.

Historically, the reasons go back to NTSC sub carrier frequencies, and it's necessity for that to be an odd harmonic of line frequency. If the frame rate was 30Hz, the subcarrier was then found to interfere with the audio carrier in the transmitted system.

If you were starting from scratch, the easiest thing would have been to slightly move the audio carrier frequency. In practice, that was the thing that could NOT be done, because of all the existing monochrome TVs, and the requirement for backwards compatability. Hence the frame, line and subcarrier frequencies were all moved slightly off, but all still locked in the correct mathematical relationship - the existing TVs were happy with that.

Non-drop frame timecode is perfectly acceptable, with this system if you prefer to have consistency. Every NTSC time code second will have 30 time code frames. BUT, it will run slow compared to real time, be like the VT machine having a watch running slow compared to the studio clock. Hence "drop frame timecode" - a bit like giving your watch a nudge forward every now and then, so over a period it still shows the same time.

All this is based on TV practice. If you are shooting video with the prime motive of transfer to film, then a lot of the legacy arguments don't hold. Start with a clean slate, 24fps exactly, and you want exactly 24 frames each and every second - so ndf timecode.

Any 24fps standard only comes into practice at all as a legacy from early film days, or early sound films to be precise. It wasn't a magical figure - rather a pragmatic compromise between too slow a rate and poor sound, and excessive film consumption.

Rather than now standardising on it as we move to HD, digital projection etc etc, it may be a good time to take the plunge and go for much higher, and 50p may be a suitable figure.
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Old September 5th, 2006, 10:10 AM   #6
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Quote:
Originally Posted by Pete Bauer
23.976 (Panasonic 24p or Canon 24F) is non-dropframe.
Quote:
Originally Posted by David Heath
It can (theoretically) be either, though in practice is likely to be dropframe.
In SD, Pete is correct.
In HD, David is correct.
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Old September 5th, 2006, 12:51 PM   #7
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Quote:
In vegas for instance can you import in HD 25 and convert it to 23.976? what will it do with the audio? is there any pitch correction?

With the limited number of 24p hd camcorders, is shooting in 25p and then converting a viable option? I am curious why no one seems to be talking about it or using in? As far as monitoring goes, most semi prof monitors are multi standard all fo the PVS sony monitors we use are for instance if you had to monitor it in pal.
Shooting in PAL for film-out has been a practice in the past. The workflow wasn't quite as nice, and you needed PAL equipment for the monitor and camera (as you point out, many of the PVMs do PAL and NTSC).

You do need pitch shift correction... Vegas has this feature and does a decent job at it. All the pitch shifting algorithms vary in quality, so you might prefer another algorithm.
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Old September 5th, 2006, 06:00 PM   #8
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Oops...yup, actually Lee is correct, at least on the XL H1 (don't know about other HD cameras). The XL H1's HD 24F Does allow you to choose between NDF and DF, while any SD Panasonic or SD Canon 24p/24F is going to be NDF, using either 2:3 or 2:3:3:2 pulldown.

It is your choice of how to mark the timecode of the frames, which will pass by at 23.976 fps timebase regardless of DF or NDF timecode. That's only 1 part in 1001 different from true 24fps and easily handled by current versions of most any pro editing app.

And yes, it's a pain!
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Old September 5th, 2006, 08:48 PM   #9
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So to continue along a line of reasoning

IF Canon or any of the HD manufactures decide not to offer a 24p version, the HV10 for instance, would it not be a viable option to get the european version that does support 25p and then just alter the frame rate as the "least worst" Option? Since in HD converting from one rate to the other is a temporal conversion vs the usual problems with standards converting in SD?


Sharyn
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Old September 6th, 2006, 06:13 AM   #10
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Quote:
Originally Posted by Lee Alford
In SD, Pete is correct.
In HD, David is correct
My posting was intended as a generalisation, not regarding any specific model (as Petes did). In principle at least, df or ndf could be used with 23.976 (SD or HD), the difference would be that with df, time code would correspond to actual run time, with ndf it wouldn't.

This may or may not matter to an individual user, but we come back to the original reason for the introduction of df tc. It may not matter to a viewer if a programme lasts 1 hour or 1 hour and 4 seconds, but it does to a broadcaster in regards to programme junctions and timings.
Quote:
Originally Posted by Pete Bauer
And yes, it's a pain!.
Exactly! The European frame rates are generally far easier to work with - no 2:3 pulldown issues, no drop frame timecode, etc.
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