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interlaced from the telecine!?


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#1 seth christian

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Posted 22 January 2006 - 02:04 AM

does telecining film to a QT ..digital format of any kind,
always end up being interlaced??

Shouldn't a guy be able to get it uncompressed
AND progressively rendered?

Or do you have to get a file full of sequence
images?

I'd appreciate this process being cleared up for me,thanks.
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#2 Joshua Reis

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Posted 22 January 2006 - 03:39 AM

does telecining film to a QT ..digital format of any kind,
always end up being interlaced??

Shouldn't a guy be able to get it uncompressed
AND progressively rendered?

Or do you have to get a file full of sequence
images?

I'd appreciate this process being cleared up for me,thanks.


Hi, to answer your question, yes. If transfering directly to a hard disc, one should be able to be given a Progresive frame format. For example, if you shot at 24 fps, you can obtain a native 24P quicktime movie. However, even if you were given a 29.97 interlaced quicktime (or even a 29.97 NTSC digibeta tape), via a quicktime editing program (Final Cut, Cinema Tools, After Effects, etc.) you can perform a 3:2 pull up and obtain your native 24 fps frames. Without getting into the details, the pull up process is a matter of throwing away the redundant fields that make up the extra frames, so it is a lossless process - no degredation to the image. Whether you are given a Quicktime file or image sequence is dependant upon the telecine facility. Hope this helps.
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#3 Michael Most

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Posted 22 January 2006 - 01:31 PM

Hi, to answer your question, yes. If transfering directly to a hard disc, one should be able to be given a Progresive frame format. For example, if you shot at 24 fps, you can obtain a native 24P quicktime movie. However, even if you were given a 29.97 interlaced quicktime (or even a 29.97 NTSC digibeta tape), via a quicktime editing program (Final Cut, Cinema Tools, After Effects, etc.) you can perform a 3:2 pull up and obtain your native 24 fps frames. Without getting into the details, the pull up process is a matter of throwing away the redundant fields that make up the extra frames, so it is a lossless process - no degredation to the image. Whether you are given a Quicktime file or image sequence is dependant upon the telecine facility. Hope this helps.


Telecine is a real time process. In order to do this, it uses video formats. The only current 24 frame video format is 1080/24p. NTSC, which is the only standard definition choice, is 60i. There is no way to get this into any computer system I know of in real time while still removing 3:2 pulldown, so the only way to get standard definition, 24fps Quicktime files is to create them either on tape or on a computer at 60i, then take the pulldown out. If you are getting files from a video facility that are 24fps, what that means is that they were either transferring in HD, or transferring to SD tape and ingesting that into an editing system that is removing the pulldown.
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#4 Phil Rhodes

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Posted 22 January 2006 - 04:17 PM

Hi,

This is easily solved - have it done at whatever highest rate the telecine will do - 30fps, producing 30p, is most common - and then it's a two-click operation in any competent NLE to "interpret as" 24 frames a second. This has the benefit of making your transfer slightly faster. This is a much better idea than working on a pulled-down intermediate format, the extraction of which will not be lossless unless you are working with uncompressed video.

This also makes timecode extraction a lot easier than trying to back-figure pulled-down timecode (although the timecode in the file itself will be garbage.)

Phil
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#5 Sam Wells

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Posted 26 January 2006 - 12:48 PM

This is a much better idea than working on a pulled-down intermediate format, the extraction of which will not be lossless unless you are working with uncompressed video.
Phil


Phil can you define exactly what losses in the signal occur here ?

Thanks

-Sam
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#6 Phil Rhodes

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Posted 26 January 2006 - 03:15 PM

Hi,

If you're going, for example, from DV to DV, then you're losing a generation in recompression.

If your original on the hard disk is uncompressed (as one would hope), you shouldn't lose anything worth worrying about. Even in these circumstances, though, it's terrifyingly easy to have codecs start to crop and alter colourspace, etc.

Phil
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#7 Sam Wells

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Posted 26 January 2006 - 04:22 PM

Understood, but where does deinterlacing per se play into this ?

-Sam
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#8 Phil Rhodes

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Posted 26 January 2006 - 04:29 PM

Hi,

If you're deinterlacing something, you'll be decoding it, and reencoding it to something else when you're finished. Not a loss free process, unless you're uncompressed throughout.

Of course if you start compressed and then output uncompressed, you could probably take the position that you're no worse off than you were...

Phil
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#9 Thomas Worth

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Posted 26 January 2006 - 04:40 PM

This is easily solved - have it done at whatever highest rate the telecine will do - 30fps, producing 30p, is most common - and then it's a two-click operation in any competent NLE to "interpret as" 24 frames a second.

I always telecine this way when it's for my own projects. Your 30p footage is then captured and "interpreted" in the NLE as 24p, without any recompression. No need to throw away redundant frames or reconstruct the original 24 frames from pulled down 60i. The only caveat is that audio has to be synced in editing.

An even better method is to telecine to PAL @ 25fps. This can also be conformed to 24p in the NLE. The advantage of PAL is the 25% resolution increase. After downsampling to NTSC you will have a slightly better image, or you can use the extra 100 lines for timecode / keycodes and recover the original "clean" frame at full NTSC resolution.
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#10 Sam Wells

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Posted 26 January 2006 - 08:25 PM

If you're deinterlacing something, you'll be decoding it, and reencoding it to something else when you're finished. Not a loss free process, unless you're uncompressed throughout.


I deinterlace Quicktime DV stream .mov with no decoding, it's the same thing but de interlaced.

Looks better not worse


-Sam
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#11 Jamie Metzger

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Posted 27 January 2006 - 01:28 AM

Everyone posted some great info.

Do you guys think you can post a really good solution to this problem, after everyone's got their opinions posted?
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#12 Phil Rhodes

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Posted 27 January 2006 - 07:14 AM

Hi,

> I deinterlace Quicktime DV stream .mov with no decoding, it's the same thing but de interlaced.

I promise you, you don't.

You can't deinterlace it without decompressing it; you can't write it back to a Quicktime DV file without recompressing it.

Phil
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#13 Thomas Worth

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Posted 27 January 2006 - 08:18 AM

You can't deinterlace it without decompressing it; you can't write it back to a Quicktime DV file without recompressing it.

Phil's right -- as soon as you do anything to manipulate the picture, whether it be deinterlacing, adding a fade, color correction, whatever -- it needs to be compressed again, going through an additional generation loss. There's nothing that can get around this. It is inherent to the way compression works. A way to minimize the generation loss is to transcode the video into a lossless format like HuffYUV or using QuickTime's "Component Video" codec before manipulating the image. You won't be able to edit and view your footage on a monitor through FireWire, though.

Do you guys think you can post a really good solution to this problem, after everyone's got their opinions posted?

I'm telling you, running the telecine at 30fps and doing a 1:1 transfer is the only option if you want to edit true 24p in a DV NLE without having to recompress the video. Stop thinking about the DV tape as a delivery or playback medium in this case and think about it more like a disk, simply transporting your video from the telecine to your NLE. The NLE doesn't care what frame rate the video is on the tape. That can be decided later, without any recompression. Again, I will warn you that this technique will only work for you if you can sync up the sound later in the NLE. Forget about sound if you're going to telecine this way.
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#14 Sam Wells

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Posted 27 January 2006 - 03:38 PM

IOW if I take an interlaced QT .mov - select deinterlace in the Movie Properties and play it, it has now gone through a decompress / recompress cycle ??

It's kinda hard to see the quality hit @ 720x480

-Sam
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#15 Phil Rhodes

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Posted 27 January 2006 - 04:04 PM

Hi,

> IOW if I take an interlaced QT .mov - select deinterlace in the Movie Properties and play it, it has now gone
> through a decompress / recompress cycle ??

Yes.

> It's kinda hard to see the quality hit @ 720x480

Shoot a resolution chart, capture the frames, and side by side them.

Phil
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#16 Sam Wells

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Posted 27 January 2006 - 09:23 PM

I'm not questiong you on this, really.

In any case, DVCam etc is becoming academic for me anyway.

Since I've seem to have stolen the thread - well who knows maybe this will be useful to someone -
A question: If I WANT the "ghost frames" from a 3:2 pulldown subsequently played out at 30p (say for DVCPRO HD) *is* there any way I can get this 'artifact' - which in fact I'd like without compromising the picture overall as the decompress / recompress cycle we've discussed would seem to do ??

-Sam
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#17 David W Scott

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Posted 15 March 2006 - 03:47 PM

Hi,

This is easily solved - have it done at whatever highest rate the telecine will do - 30fps, producing 30p, is most common - and then it's a two-click operation in any competent NLE to "interpret as" 24 frames a second. This has the benefit of making your transfer slightly faster. This is a much better idea than working on a pulled-down intermediate format, the extraction of which will not be lossless unless you are working with uncompressed video.

This also makes timecode extraction a lot easier than trying to back-figure pulled-down timecode (although the timecode in the file itself will be garbage.)

Phil


Question for Phil and Thomas:

What NLE are you guys using? I am looking for a way to "interpret" 30fps footage as 24fps footage in Final Cut Pro.

I used to be able to do this trick in Premiere with a DPS Perception system, but since moving to FCP I haven't been able to find a way to make this work. Ideas? :blink:

Thanks,

Dave
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