Re: Analogue artifact estimation

> Reverse 3-2 pulldown looks fairly straightward, but there is the
 > problem of working out which fields go together to make the original
 > frames.  As long as field dominance, (I know that's the wrong term,
 > but the correct one escapes me, and you know what I mean), doesn't
 > change partway through, this should be obvious at the first scene
 > change, because there is going to be one combination that is obviously
 > wrong, and simply doing an RMS of the differences between lines should
 > reveal that one.

It is seldom the case that there is "one" correct frame order for 
inverse telecining. The reason is that most video sequences are spliced 
together from many sources, often after they have already been converted 
to ~30 fps. So the frame order changes, and there may be no proper way 
to compensate for it, since depending on where the change occurs, some 
fields may be completely missing, etc. Another fun factor is that CG 
sequences that are originally rendered at ~30 fps are becoming more 
common. They cannot be ivtc'd at all, and are stuck in the middle of 
what is otherwise a ~24 fps source.

This is the reason that, to my knowledge, there are no good automatic 
ivtc filters, though there are certainly a number which will work except 
for the ugly cases listed above.

But, I agree, all these ideas are pre-processing stages, and should be 
relatively independent of whatever codec is then used to compress the 
"corrected" video sequence.

The only real question, to me, is whether or not the codec can handle a 
variable framerate. This might provide a simple solution for the CG 
sequence problem. I doubt that it would be that difficult to make a 
codec do so, given the proper support from whatever muxer is being used.

--- >8 ----
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