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1080i to 720p to NTSC
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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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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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[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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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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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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