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Jason O'Hara
converting 24PF (Canon) to 30P using compressor?
on Jul 17, 2016 at 12:01:55 am
Last Edited By Jason O'Hara on Jul 17, 2016 at 12:04:55 am

I have some footage that was recorded with a Canon HV30 in the 24PF mode, which I understand encodes the 24p image in a 60i HDV stream, which I need to convert to 1080/30p (ProRes)

I am still using FCP7/compressor, though I expect it can handle these dated formats.

What is the most effective way to extract a true 24p stream from the 24PF footage encoded as HDV/60i?

Once I achieve that, I am familiar with performing a frame rate conversion to 30p using "frame controls" in Compressor, so I assume these 2 steps in sequence are the most effective method for converting my footage?

Any direction is much appreciated


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Shane Ross
Re: converting 24PF (Canon) to 30P using compressor?
on Jul 17, 2016 at 10:04:20 am

First off, I'll give you the link to this thread:

http://www.dvinfo.net/forum/canon-cinema-eos-camera-systems/524694-24p-vs-2...

Second, I'll say that converting 24p to 30p won't be smooth...at all. It'll look stuttery no matter what you do. Because the only way to get 24P to 30p is to repeat frames...6 of them per second, and that will stutter, no two ways about it. NEVER shoot 24p if your intention is to deliver 30p. It goes well into 60i (30 interlaced frames, 60 fields) as you know as 24PF is 24frames in a 30fps interlaced stream...just like telecine-ing film to tape. The extra repeated frames are divided up into the fields for a more smooth conversion.

But you have 24p in 60i that you want to make 30P. So first you need to REVERSE TELECINE the footage to 24fps (23.98) and then make 30p. That won't look good, just so you know. Not at all. And there's nothing you can do to fix it. I've had to deal with this before, delivering a show 30p and 1/3 of the footage was 23.98. It stuttered, and I had to get special permission to have it be acceptable.

[Jason O'Hara] "What is the most effective way to extract a true 24p stream from the 24PF footage encoded as HDV/60i? "

Compressor. You'll need to set the frame rate to 23.98, and then in the FRAME CONTROLS of the INSPECTOR, choose REVERSE TELECINE. You'll have to test settings to make sure you get them right. And you can get good 23.98.

But then going back to 30...well, I've said it. It won't be smooth.

[Jason O'Hara] "I assume these 2 steps in sequence are the most effective method for converting my footage?"

Yes, I believe it'll be better than simply trying to de-interlace the 60i footage, that might look even worse. So yeah, test everything.

Shooting 24PF was not the wisest idea in this case. Although I suspect that you shot that not knowing the delivery spec of 30p. Which is a VERY odd delivery spec....unless it's for the web. Then it makes sense.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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Jason O'Hara
Re: converting 24PF (Canon) to 30P using compressor?
on Jul 17, 2016 at 5:56:57 pm

very helpful. thank-you.

Indeed we're well aware one should never mix frame rates, this HDV/24pf footage (in a 60i wrapper), along with some other DSLR footage in 24p (23.98) is archival footage we are looking to integrate in our doc - which was shot entirely in 30p (29.97), so wondering what is the optimal (though necessarily imperfect) method of conversion.

The reverse telecine you recommend, does an excellent job creating what appears to be a perfect 23.98p file from the 24pf, which assumably can now simply be treated the same as the other archival 23.98p content, to do a frame rate conversion in compressor from 23.98p to 29.97p using "frame controls" as described here:
http://www.kenstone.net/fcp_homepage/converting_frame_rates_compressor.html

This works fine when there is little motion in the frame, but where there is motion, the conversion artifacts are brutal at both "better" and "best" settings. Will an Alchemist or Terranex handle this conversion any better? The consensus online seems to be that with time - Compressor will do as good a job as this hardware, but so far - my results with compressor have been unsatisfactory.

I have been extremely impressed by footage we've slowed to 50% using Twixtor - the interpolation of the missing frames seems to be utilizing a more sophisticated engine than "frame controls" in compressor - could Twixtor be the optimal solution? Thanks!


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Shane Ross
Re: converting 24PF (Canon) to 30P using compressor?
on Jul 17, 2016 at 8:03:40 pm

[Jason O'Hara] "This works fine when there is little motion in the frame, but where there is motion, the conversion artifacts are brutal at both "better" and "best" settings. Will an Alchemist or Terranex handle this conversion any better?"

What are the artifacts? Going from 24p to 30p should only repeat frames, not make any odd artifacts. And no, Alchemist nor Terranex couldn't do any better in terms of frame repeats. NOTHING you can do can make smooth 24p to 30p, beyond repeating frames. It's not a clean conversion. Can you post a pic of the artifacts?

Twixtor MIGHT do something better, by creating in-between frames. But even then, I've noticed that the in-between frames can at times look wonky.

Shane
Little Frog Post
Read my blog, Little Frog in High Def


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