Avisynth + Decomb: how to find out which option to use?

[ChAoS Overlord]

First of all, I'd like to thank doom9 for writing a decomb guide, it's what I really wanted to see on the site!

Still something is not clear to me, doom9 states the following

Telecide recovers progressive frames by field matching and by default it will post process every frame and deinterlace parts of a frame where combing (interlacing) effects can still be found.

FieldDeinterlace contains the postprocessing functionality of Telecide and should only be used on purely interlaced streams that have not been telecined. Most DVDs have been telecined in some way and are based on progressive sources so you shouldn't use this option on such clips. Truly interlaced clips are stuff you capture with your camera, and TV shows originally shot for TV (modern TV series are now often shot on film - 24fps progressive rather than 29.97 or 25fps interlaced).

Decimate well remove duplicate frames after postprocessing and adjust the framerate accordingly. If you have an interlaced or telecined PAL source this parameter is useless as you want to keep the original framerate.

I really want to do this right, but what I don't get is how I can figure out if the movie is a purely interlaced stream (FieldDeinterlacing) or the other things, how can I figure out/with which program which of these three options I should use, because it really isn't clear to silly old me

Thx in advance for sharing your insights with me guys

[manono]

Hi-

You didn't say, so I'll assume this is an R1 NTSC DVD. It's easy enough to find out what kind of source material you have. First, make your .d2v without Force Film (30fps). Then you can either open it in GKnot, or make an .avs from that, but without IVTC or any other changes, and open that in Nandub or VDub.

Then, either way you've done it, scroll through it and find a scene with some movement. Then look for the interlacing. If, out of every 5 frames, you see 3 progressive frames (no interlacing) and 2 interlaced frames, then it has been telecined and you can IVTC it (and bring it down to 24fps in the process). In that case you would use the Telecide-Decimate combination. If, on the other hand, you see that all the frames are interlaced, then you have no choice but to deinterlace it and keep it at 30fps. So you would use FieldDeinterlace by itself.

You should probably check in several places to see that it's the same. Sometimes they mix up telecined and non-telecined material (rare). If that's the case, then you have some hard choices to make-come back if you find any like that.

[ChAoS Overlord]

Oh I forgot to mention most of my material is R2, cause I live in Europe, so that would be PAL.

Thx for the info, it was really good!

[manono]

Hi Again-Gee, all that work for nothing. Oh well-maybe someone else can use it.

Not having worked with PAL material before, then I'm less sure of my ground here. First, don't use Decimate. You will always want to keep your stuff at 25fps. Telecide will reconstruct progressive frames so you can use that still (but I have no idea if that 3 progressive and 2 interlaced pattern still holds). And if you have a pure interlaced source then you can still use FieldDeinterlace.

Read the help file that comes with Decomb for more information. Someone please correct me if I've said anything obviously stupid.

[Zoltan]

@ChAoS Overlord:

You did not mention why exactly you want to decomb()? If you have a PAL stream then forget about this telecine() and decimate(5) stuff. PAL uses 25 fps and that's it. R1 NTSC DVDs may have Telecined, iVTCd or pure 29.97 fps streams. See this thread in this forum for more details on how to handle those DVDs.

Again, forget this decimate stuff for PAL DVD to PAL SVCD conversions. If you see that vertical edges (like a door ot stg else) show up many horizontal lines (like a comb) during horizontal movements on your TV set, use a de-interlace filter instead.

Regards,
Z

[trbarry]

If PAL material is properly telecined from a progressive source then it should already look fine. But if it is from a video capture, say a movie of TV, then sometimes there is a phase shift so the even and odd fields may appear as:

1 2 3 ..
2 3 4

which looks the same as interlace on moving scenes. But it can be IVTC'd with no decimation by:

GreedyHMA(1,0,2,0,0,0,0,0) or
GreedyHMA(0,0,2,0,0,0,0,0)

depending upon the TopFirst parm, whichever works best. This automatically adjust for the phase shifts without adding the artifacts or softness that may come with deinterlace. So effectively it is IVTC for PAL.

I'm almost certain that Decomb has a similar option but I don't know how to specify it.

- Tom

[ChAoS Overlord]

Also do I put the FieldDeïnterlace before or after the bicubic resize? I always put it before, normally...

[trbarry]

No matter which program you are using you should always put IVTC/deinterlace/decomb first, before resize.

- Tom