telecide() and decimate() usage, question regarding current project.

[Aesop]

Howdy all,
I have a project at the moment with an interlaced NTSC source.

In looking at the source material field by field I see a duplication pattern of 2/3/2/3/2/3 .... telecide() produces a progressive stream where every 4th frame is a duplicate, telecide();decimate(cycle=4) removes the duplicates but the final output seems "jerky". Is there something wrong with my setup here?


LoadPlugin("E:\c\GORDIA~1\mpeg2dec3.dll")
LoadPlugin("E:\c\GORDIA~1\avisynthplugin\decomb yv12.dll")
LoadPlugin("E:\c\gordia~1\avisynthplugin\convolution3d yv12")
mpeg2source("Y:\Two Towers 30fps tester.d2v")
Telecide()
Decimate(cycle=4)
BilinearResize(640,272)


Is it possible to perform a decimate on a field basis rather than a frame basis? such that removing every fith field would produce a pattern of 2/2/2/2/2 ... ???

Any comments appreciated :)

[DJ Bobo]

and what's with decimate(cycle=5) ?

[Aesop]

I don't know if anything is with it at the moment.

why who were you expecting?
;-)

[Guest]

2/3/2/3... would imply 2 extra fields per 10, or 1 extra frame per 5. So use Decimate(cycle=5). That should fix your jerkiness.

Sometimes people answer cryptically to stimulate your thinking. :)

You can decimate on a field basis by separating fields first and weaving afterwards, but I don't recommend it because it is not needed and will not be reliable due to the spatial shift of alternate fields. Also, obviously, if you did that you'd not use Telecide, so you'd lose the benefit of pattern guidance. Might be fun to play with though as a wacky way to do IVTC. :)

Just try cycle=5 and report back.

[Aesop]

Thanks for the responses ;-)

Have had some luck with things ;-), the .d2v was producing 23.976fps source rather than 29.970fps. loaded it back into DVD2AVI and it claimed the "forced film" was not enabled so I don't quite know how or when that happened, just a piece of strangeness I was not expecting...

Spotted it when I realised that the jerkiness in the encodes was probably more to do with the 18fps output, then I wondered why it had such a number...

But anyway things are much better now. I tried telecide();decimate(cycle=5) and it is producing a decent result ;-) But I am still trying to figure out exactly what it is that telecide is doing. When I look at these things I tend to pull them apart into fields then do some manual frame matching. Then I look at the docs for telecide operation and work that out manually too. Much confusion follows.

What I would like to know is what exactly is happening to that field triplet, and how is it being treated in oder to retain 30fps. the way I see it, if that field could be dropped there would be a nice 25fps output with only a little juggling of field orders in successive field pairings...

trying to fathomth Debug output at the moment ;-)

[Guest]

Originally posted by Aesop
What I would like to know is what exactly is happening to that field triplet, and how is it being treated in oder to retain 30fps. the way I see it, if that field could be dropped there would be a nice 25fps output with only a little juggling of field orders in successive field pairings...The theory of operation appendix to the help file tells you everything you need to know. The reason Telecide doesn't do the field dropping is because it would not then be generally applicable to PAL, NTSC, etc. Its job is to recreate progressive frames where possible. That is all.

Sure it would be possible to make an IVTC work as you suggest, and it has been done. But such solutions limit their applicability. It has not been conclusively shown that the limited solutions work any better, although you'll certainly get a lot of opinions about it. The Decomb approach seems to offer a reasonable tradeoff between flexibility and effectiveness.

Use show=true instead of debug=true. It's much more user friendly. :)

[manono]

Hi-

Spotted it when I realised that the jerkiness in the encodes was probably more to do with the 18fps output, then I wondered why it had such a number...

Because you IVTC'd after using Force Film in DVD2AVI. If you plan to IVTC, then use no Field Operation. But there's a lot of confusion evident in your posts, so I may be misunderstanding something.

What I would like to know is what exactly is happening to that field triplet, and how is it being treated in oder to retain 30fps.

If you're asking how 24fps film material is telecined to 30fps, then the little picture in This Tutorial (http://www.doom9.org/ivtc-tut.htm) may help. Forget all that field stuff. Decomb can handle your video with one hand tied behind its back.

If you, for some reason, really want 25fps output, then just add AssumeFPS(25) at the end of your script. But you'll have to shorten the audio, as otherwise it will become asynch.

[Aesop]

Howdy,

Because you IVTC'd after using Force Film in DVD2AVI. If you plan to IVTC, then use no Field Operation. But there's a lot of confusion evident in your posts, so I may be misunderstanding something.

I was suffering from a bit of confusion myself ;-) I was working on a 30second "tester", I changed the 30 seconds snip to something including a long pan shot so as to see what the frame progression was like... somewhere in there I must of turned on "Forced Film" or something, which was stuffing up my predictions.... If I had spotted it sooner I would not of made the original post ;-)

Sorry about that...

Aesop :p

[Guest]

>Sorry about that...

Don't be sorry. A lot of good info came out and you probably learned quite a bit about IVTC, etc. Sometimes mistakes can be serendipitous.