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Downconverting NTSC HD to PAL SD


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#1 Clay Walker

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Posted 01 September 2008 - 12:48 PM

I am curious what technical/playback issues would occur if I were to shoot in 1080/60i NTSC and then place that footage scaled down into a PAL standard def timeline in Final Cut Pro. ?

I would ultimately be going back to PAL dv tape or PAL DVD with the material to play back on a projector.

I've tried a couple of tests and haven't noticed anything too apparent.

Thanks.
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#2 Phil Connolly

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Posted 02 September 2008 - 02:09 AM

The main problem you can encounter when converting from 60i to 50i, is motion artifacts - most noticeable on pans - they would look jerky.

In a basic standards conversion such as the FCP one your basically throwing frames away to get from 60i - to 50i, these missing frames can make your footage look jumpy.

Expensive standards converters such as the Snell and Willcox Alchemist can fix this issue, as the conversion is motion compensated and does lots of clever things to make up for the missing frames and re-time the motion, resulting in a very good standards conversion - but its expensive.

You might get away with conversions in FCP if your footage doesnt have much movement.

If your final delivery is PAL its better to try and shoot in that format to avoid conversions. But if you have no choice:
I would try and shoot in 24p - as its compatible with NTSC kit with a 3:2 pull down and easily converted to PAL by speeding the 24fps to 25fps - resulting in smooth motion but you would need to have the audio pitch dropped by 4%
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#3 Phil Rhodes

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Posted 02 September 2008 - 06:58 AM

Hi,

You can do motion compensated speed changes on a desktop computer, although it's quite a longwinded process. Look into retimer, twixtor, or motionperfect.

P
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#4 Clay Walker

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Posted 16 September 2008 - 04:48 AM

Thanks everyone. I guess the other variable for my shooting at this point would be that I am going to be using the HPX170 which does shoot 25 FPS with audio, but I am told it is not PAL 25 fps, which I am not sure what that means. It sounds like the frame rate should be very close though.
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#5 Michael Nash

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Posted 18 September 2008 - 03:14 PM

Thanks everyone. I guess the other variable for my shooting at this point would be that I am going to be using the HPX170 which does shoot 25 FPS with audio, but I am told it is not PAL 25 fps, which I am not sure what that means. It sounds like the frame rate should be very close though.


HD is neither NTSC nor PAL -- those are standard def designations. There are however different HD frequencies and frame rates in order to be compatible with those two SD standards.

25 fps in the 50 Hz. "PAL" world is recorded and displayed as 25.00 discreet frames per second. 25 fps in the 60Hz. "NTSC" world will be recorded as 24.98 fps. How your edit system may deal with that footage is a post question.
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#6 Clay Walker

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Posted 01 October 2008 - 12:46 PM

thank you for the information!

I have a SD PAL shoot in Italy next week and I have rented an EX1 to shoot PAL there. But, I am still kicking around the idea that I might be able to pull a useable image from my HPX170 that I just received and use it instead.

In attempt to "fake" some PAL footage from my HVX170 yesterday, I did the following test and I am curious where my downfall may be in attempting this:

I shot at 720/25P (actually shooting at 24.98) & set the syncro scan to 50.

I then dropped the the footage into a FCP timeline that was set to the FCP PAL sequence default. I enlarged the footage to 100% to create a 4:3 image and crop the sides.

Basically, the footage does not seem to have any huge apparent issues on my Apple Cinema display. I tried a bunch of different things shooting-wise hoping to exploit any strobing with movement, etc.. It did hold its audio sync as well.

I then made a PAL dvd of the material and played it back on my Sony PVM-20L5. In 575/50i mode the entire image did appear to be a bit "strobey" but not particularly on the movement so I am not sure if that is the monitor itself. I am told this is normally what a PAL dvd will do on an trinitron monitor, even though monitor is registering the PAL signal.

So then I shot some material using an EX1 in true 50 hz PAL mode & shot some 25P & 50P material.

In comparison, the 25P EX1 material looks extremely similar to my 24.98 FPS modified to 25 HPX170 material, I think. They both exhibit the same behavior on my trinitron monitor.

Edited by Clay Walker, 01 October 2008 - 12:47 PM.

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