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Matt Smith
1080i to 720p to NTSC
on Aug 29, 2011 at 8:44:51 pm

I have what is, admittedly, a goofy work flow that I'm forced to deal with. And I'm struggling. I'm sure I've omitted some useful info in the description below. Let me now if you need more info. I'm grateful for any help.

Background: We produce a television show that airs in standard definition (NTSC anamorphic).

The video we shoot for the show ourselves is 720p (DVCPROHD). So that's our editing format during the week in FCP 7. (That said, everything ultimately ends up being imported into an Avid Newscutter/ISIS system when the show is assembled on the weekend, with studio segments.)

Each week a client delivers source video to us via ftp that we also use in the show. We have no say in that video format — it comes to us as 1080i, h.264, 29.97.

Issue: This 1080i video is the source of my problem. Using Compressor, I can't seem to produce good results transcoding this 1080i video to either 720p or directly to NTSC. Either way I get those nasty saw tooth edges. I've tried exporting just about every way imaginable, using the various frame control options in Compressor. Deinterlaced, lower, upper. Nothing seems to rectify the problem.

Here's a FCP screen cap of the 1080i properties:


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Chris Tompkins
Re: 1080i to 720p to NTSC
on Aug 29, 2011 at 10:35:16 pm

I assume you don't have hardware for the conversion?
An I/O Card like the Kona 3?

It'll look decent with Compressor, Select the conversion to 720p
Turn frame controls on to best.

Chris Tompkins
Video Atlanta LLC


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Chris Tompkins
Re: 1080i to 720p to NTSC
on Aug 29, 2011 at 10:41:02 pm







Just assuming 60p Choose which ever Frame-rate you are cutting.

Then import the rendered file into edit. Should look Much better.

Chris Tompkins
Video Atlanta LLC


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Matt Smith
Re: 1080i to 720p to NTSC
on Aug 29, 2011 at 11:17:59 pm

Thanks Chris. Under frame controls>output fields, are you suggesting I keep it same as source? Or should I select progressive?


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Rafael Amador
Re: 1080i to 720p to NTSC
on Aug 29, 2011 at 10:39:57 pm

Sure that's not 1080p24 with added Pull-down?
rafael

http://www.nagavideo.com


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Matt Smith
Re: 1080i to 720p to NTSC
on Aug 29, 2011 at 11:20:50 pm

Rafael — the 1080i video is from a live broadcast. So I can't imagine it would be 24p.


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Chris Tompkins
Re: 1080i to 720p to NTSC
on Aug 29, 2011 at 11:29:54 pm

I'd try progressive for the output fields.

Chris Tompkins
Video Atlanta LLC


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Rafael Amador
Re: 1080i to 720p to NTSC
on Aug 30, 2011 at 12:04:47 am

[Matt Smith] "Rafael — the 1080i video is from a live broadcast. So I can't imagine it would be 24p."
And what´s the problem on life-streaming from a camera shooting p24?
That´s plain 1080p24PSF.
1080 stuff (1080p24, 1080p30,1080i60) is ALWAYS streamed as 1080i60. That´s the SMPTE standar.

Have a look to this thread about 1080 streaming:
http://forums.creativecow.net/readpost/8/1141042
So, take the pull-down if you want to process
rafael

http://www.nagavideo.com


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Matt Smith
Re: 1080i to 720p to NTSC
on Aug 30, 2011 at 12:03:55 am

Just had an interesting discovery. I transcoded the file using the "Apple ProRes 422 for Progressive material" preset. And the video looked good, though still 1920x1080. But using that very same preset, and only changing the size to 1280x720, produced bad video.

And that's the hitch: I need to bring the video down from 1080 to 720.


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Rafael Amador
Re: 1080i to 720p to NTSC
on Aug 30, 2011 at 12:22:41 am

Matt,
I don´t want to mislead you (I´m far from my Compressor); just wanted to point you out that your stuff coud be any of three flavors (p24,p30 or i60)if was streamed.
You must find out which one is your footsge.
rafael

http://www.nagavideo.com


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Matt Smith
Re: 1080i to 720p to NTSC
on Aug 30, 2011 at 12:25:47 am

Forgive me if my knowledge base is limited, but by streaming are you referring to an online stream of some sort? None of this is streamed video. It's all broadcast video.


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Rafael Amador
Re: 1080i to 720p to NTSC
on Aug 30, 2011 at 12:38:47 am

Same.
How you think Hollywood movies (p24) are broadcasted?
rafael

http://www.nagavideo.com


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Bret Williams
Re: 1080i to 720p to NTSC
on Aug 30, 2011 at 4:11:16 am

Have you tried editing the footage all together in a 720p60 sequence? This will solve your problems I think.

Drop the 1080i footage in a 720p sequence. Each field will get mapped to a frame. FCP does this quite well. The scale down will look great and it's a fairly quick render. For the most part it will play in real time anyway if you set your sequence to unlimited rt. But depends on processor and drives, etc. Mix in your 720p30 footage as well. FCP will simply repeat every frame. The above is essentially why 720p works on LCDs for interlaced broadcast footage. 720p is 60 fps in broadcast. So if it is upscaling a 480i signal or downscaling a 1080i signal, then there isn't any temporal data lost and there's no need for frame blending. Keeps it simple. I think it's also part of the reason 480i looks so jaggy when upscaled on an HDTV.

The big reason this works for your production flow is you're going back to ntsc interlaced broadcast. Take your final 720p60 QT into After Effects (faster, and my preference) or Compressor and render the file out to a 720x486i (or 480i) 16:9 file. The 60 frames will get mapped to fields, reinterlacing the 1080i and leaving the progressive stuff progressive because mapping 2 duplicate frames together leaves a progressive image. With this workflow you can also seamlessly add 24p into the mix. FCP dutifully repeats every frame like 30p, but repeats every forth frame 4 times instead of two (or whatever the math). Anyway the result when you go back to 480i is the 24p will have real interlaced pulldown.

I use a matrox mxo2 mini. With a 720p60 sequence, it actually interlaces the frames on the fly for the SD output. I would assume blackmagic and aja do the same. So you could skip the final step if you're going out to tape and just output to your deck as interlaced ntsc.

The single little caveat with this whole approach is that since the frames are eventually going to get interlaced, you could end up with a cut that occurs between fields. It's only noticeable if you go frame by frame, but to be perfect, just make sure cuts occur on the 1st, 3rd, 5th, 7th, ... etc. frames. If your sequence starts at 00, then you'll cut on even frames for example, which is usually the case.


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Bret Williams
Re: 1080i to 720p to NTSC
on Aug 30, 2011 at 4:15:04 am

Oh, and I'd do a simple convert of that 1080i h264 footage to 1080i ProRes 422 before you do anything.


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Matt Smith
Re: 1080i to 720p to NTSC
on Aug 30, 2011 at 4:23:17 am

[Bret Williams] "Oh, and I'd do a simple convert of that 1080i h264 footage to 1080i ProRes 422 before you do anything."

Hah! I was just about to respond to that effect. So I obviously need to get out of h264. But if I transcode to ProRes 1080i, I can simply edit that into my 720p60 sequence? Makes sense. I'll give it shot. Thanks.

But I confess, the tech nerd in me still wants to figure how to get the 1080i video to look good at 720p.


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Bret Williams
Re: 1080i to 720p to NTSC
on Aug 30, 2011 at 3:07:46 pm

Drop it in a 720p60 sequence and it should look fine. 720p and 1080i are pretty compatible and comparable in quality. It's mixed and matched all the time on your broadcast TV all the time. You're usually seeing either 1080i or 720p60. One is lower rez progressive and one is higher rez interlaced. If you're trying to convert 1080i to 720p30, then yeah, you'll probably get cruddy results unless you really know what you're doing in compressor with frame blending and all that. But even then you'd be taking 60 images/fields/moments in time and converting that to 30 moments in time. You'd either get stuttery motion, low rez, or interlacing artifacts because the interlaced frames are now being dealt with as progressive. I wouldn't do that unless someone insists that the whole show be progressive for some reason. If it were a drama where all the cameras and elements are supposed to match, I guess that would make sense, but if they're shot at different formats and rates that's probably never going to happen anyway.


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Matt Smith
Re: 1080i to 720p to NTSC
on Sep 22, 2011 at 11:28:39 pm

Just wanted to circle back and offer a massive thanks to Bret on this issue. Dropping the 1080i into a 720p60 sequence is THE ONLY thing that's worked so far. And it works like a charm. So again, my deepest thanks for your input.


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