# Interlaced video on a progressive screen



## wado1942 (May 14, 2006)

Sorry if this has been discussed elsewhere and sorry if this isn't the place to post about this but I have a question. I get the impression that all modern displays run in progressive scan mode all the time (though I'm not sure why; it doesn't take a genius to figure out how to retain interlaced fields on a progressive screen). What exactly happens when interlaced video is being run on such a display? I've done some poking on the net about this and there doesn't seem to be a simple answer. I fear each field is simply interpolated to 60p by the TV's processing, but I'm not sure. Does anything different happen with 1080i vs. 480i?

Now, let's say that I'm restoring a 90-minute concert from its original Betacam SP tapes. I'm talking quality, first generation stuff that's been well-preserved. I copied them to ProRes HQ and I want it to look the best it possibly can in our HD world. How would I handle this? My first attempt was double layered DVD 480i60 but it looked like . Then I tried deinterlacing it to 480p30 using the very clean YADIF plugin for Virtualdub, which retains a lot more clarity than typical interpolation methods. It didn't look so hot either, not to mention half the motion information is gone. My software resizing methods are likely better than anything built into a TV (Lanczos vs. Bilinear/Bicubic?). I could go with Blu-Ray but there's no 1080p60, so would I need to convert to 720p60?

I know a 480i video will never compete against 35mm scanned to 1080p24, but there has to be a way to at least preserve its quality vs. the obvious loss of quality it has now going to HDTV. It looks great on an SD display. It's sharp, relatively noise free, just a few dropouts (the occasional horizontal teardrop shaped dot) good color etc. It would really help if I knew what was happening under the hood of the typical HDTV. If it were me designing the TV's DSP, I'd use motion estimation (the same that turns movies into soap operas) combined with spatial analysis to fill in the missing lines to turn 480i60 into 480p60 without losing clarity, then resize to 1080p60, but this doesn't seem to be what's happening.

Thanks if you can offer any assistance.


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## Tom Riddle (Aug 25, 2013)

Per my understanding, interlaced streams are frame interpolated by the TV's processing to progressive. Try 720p60. Also, 480i or p content on a large HD screen will most always look bad. By large, I mean anything over 50"s.


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## wado1942 (May 14, 2006)

Thanks for the reply. So is it a simple spatial interpolation w/ field bob? That's what it appears to be at least on my TV.


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