Quote:
Originally Posted by Katie Boundary
IVTC is a form of deinterlacing.
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That is simply not true (i.e., wrong). IVTC involves the removal of redundant fields and, if the video is viewed directly without re-encoding, IVTC involves zero loss and produces zero artifacts.
By contrast, deinterlacing
always involves degradation of the video because you must manufacture fields that were not there in the original. You do this either through duplication, blending, motion estimation, or some other technique.
I am bothering to post this in what has become a thread that is increasingly filled with strange statements because, unfortunately, a lot of people new to dealing with video make the mistake of conflating IVTC and deinterlacing and will often use a deinterlacer on telecined footage and then wonder why they get such horrible results.
So, deinterlacing and IVTC are two completely different things, and you cannot use the tool for one of them to solve the other one's problems. They are orthogonal.
One thing that was correctly stated in this thread by one of the doom9.org experts is that you
must do IVTC before applying any temporal filter.
That is 100% correct, and should be obvious.
Why is it obvious? Because if you have a filter that looks at adjacent frames (or, sometimes, a bunch of nearby frames), the total lack of any change whatsoever between some nearby frames or fields, but not others, will completely blow up the algorithms.
As a corollary -- one I found out first-hand when I started encoding VCDs and SVCDs 20+ years ago -- is that encoders have the same problem as temporal filters when you try to encode telecined material without first doing IVTC. In fact, if you try to encode telecined footage, you will need integer multiple larger bitrates to get the same quality. I still remember spending half a day trying to encode the Elton John music video "I'm Still Standing" onto a VCD back in the late 90s. It was shot on film and the capture I made off satellite was telecined. I encoded that telecined video to SVCD and all I could see was "mosquito noise." It was awful. After lots of research and dozens of encodes, I discovered the IVTC built into TMPGEnc. I used it, and the results were a hundred times better (they still look good, even by today's SD standards).