Removing "interlace" artifacts

[gordonbennett]

Hello nooby here

So, I'm backing up my DVD's to my HTPC (via x264 encode) and have come across what looks like interlace in a PAL movie,
~Sample here - 7.3MB, approx. 6s

This is the worst offender, other scenes with this artifact last 2-3 s - the majority of the movie is progressive.

Separating fields gives the following field pattern - ffbffbffbffb etc (blended fields)

My question is do I need to field match, unblend/deblend or both? and if I do unblend do I need to decimate the dupe frames?
Whats the correct procedure to recover the progressive frames?

thanks in advance!

[EddyH]

Looks like someone cocked up in the telecine booth, or the machine suffered a mild voltage drop or something. Does the sound go slightly off key during those parts?

Having looked quickly at it in VLC I can't offer too much more advice I'm afraid, and not sure what you mean by the ffbffb thing. What it looks like when I skim it is that two film frames have ended up in one display one, and that they're blended into each other; whether they're actually like that or they're "whole" when seen individually and it's VLC smearing them into each other I can't tell. If it's the latter, recovery should be easy - could be there's a slight judder throwing in extra fields here and there for some reason, and getting back the full ones would be a matter of skipping that one, swapping the order, and repeat, getting proper progressive frames back out the other end (and recoding it - or those parts - as "real" progressive). If they're actually blended, something like that may still be possible, just tricky ... or completely out of the question.

Maybe the cine rig momentarily dropped into NTSC-TC mode (23.976fps) instead of running at 25fps or something, though you'd only expect one duped field every 1/2 second that way. Curious. If nothing else the slowdown it provokes is obvious. As the rest of it seems clean and clear it's not a bodged standards conversion or anything. Or maybe the encoder has fritzed and thrown in spurious pulldown flags for no good reason?

Remember you may have to alter the audio as well.

[gordonbennett]

Looks like someone cocked up in the telecine booth, or the machine suffered a mild voltage drop or something. Does the sound go slightly off key during those parts?

Thanks for taking a look, no the audio for this scene sounds ok, no drop in pitch or warbling noticed.

Having looked quickly at it in VLC I can't offer too much more advice I'm afraid, and not sure what you mean by the ffbffb thing.

What I mean by the "ffbffb" is when I separate fields (to check for interlacing) and step individually through them I get a pattern of two matching fields then a blended field which then repeats. The pattern suggests to me its maybe progressive with field blends.

What it looks like when I skim it is that two film frames have ended up in one display one, and that they're blended into each other; whether they're actually like that or they're "whole" when seen individually and it's VLC smearing them into each other I can't tell. If it's the latter, recovery should be easy - could be there's a slight judder throwing in extra fields here and there for some reason, and getting back the full ones would be a matter of skipping that one, swapping the order, and repeat, getting proper progressive frames back out the other end (and recoding it - or those parts - as "real" progressive). If they're actually blended, something like that may still be possible, just tricky ... or completely out of the question.

Yep definately blending going on here and not by VLC, getting good frames out could be tricky indeed.

Maybe the cine rig momentarily dropped into NTSC-TC mode (23.976fps) instead of running at 25fps or something, though you'd only expect one duped field every 1/2 second that way. Curious. If nothing else the slowdown it provokes is obvious. As the rest of it seems clean and clear it's not a bodged standards conversion or anything. Or maybe the encoder has fritzed and thrown in spurious pulldown flags for no good reason?
Remember you may have to alter the audio as well.

Yep the surrounding scenes are all fine, its curious that the blends start about halfway into the scene and not from the start...