Properly using Decomb & Interpreting the Debug output

[Bulletproof]

I don't know which forum this thread belonged to, but since Decomb is an Avisynth plugin I think it would be best here. I can't seem to get Decomb to properly IVTC a video I have. I am trying to do this WITHOUT post-processing becuase I know another program that can do the IVTC properly but it is much slower.

These are the settings I'm using:

Telecide(guide=1,gthresh=15,post=false,chroma=true)
Decimate(cycle=5)

I had also tried the parameters given in Doom9's Decomb guide with no luck. I seem to get alot of interlaced frames during Scene changes, using the other options such as reverse does not seem to help. I also get some Mouth interlacing too. Also, you need the proper field order for doing IVTC, but how do you set the field order in Decomb and figure out which one it uses by default? And I'm also trying to understand how the parameters actually work.

I want to know what gthresh does exactly, from my understanding it is the threshold in which Decomb decides when to change its patterning, but what I need to know is whether raising it higher will make it change the patterning easier or whether lowering the threshold will make it harder to change the pattern (less sensitivity). And I also wanted to know the difference between threshold and dthreshold and whether those two have any effect if your not using post processing. I also don't seem to know how to interpret the debugview output, if someone could explain these things to me I would be greatful.

[manono]

Hi-

I can answer some but not all of those questions, although I'm not sure why you're not willing to use post processing. I like to have the insurance, and there are usually a few interlaced frames that sneak through.

how do you set the field order in Decomb and figure out which one it uses by default?

From the Help File:

"reverse (true/false, default false) is used to reverse the sense of Telecide's field matching, i.e., instead of matching on the second field, match on the first field.

swap (true/false, default false) is required if the result of Telecide comes out field-swapped; some capture cards require it."

what I need to know is whether raising it (Gthresh) higher will make it change the patterning easier

The higher you go, the more likely it is that field matching will be overruled by pattern matching. With nice clean sources, you can go up to 90 or so. Ordinarily I don't go higher than 60.

If you use Post=false, then neither Threshold nor Dthreshold does anything. But I'm not entirely sure of the difference between the two either. And I've never used dbugview. I hope I've answered some of them for you. Anyone else want to add to or correct anything?

[Guest]

Hi manono! Good explanation. Permit me to add:

threshold is a threshold used to decide if a frame is combed.

dthreshold is the threshold to be used for deinterlacing if the frame was decided as combed. This allows the user to fine tune the decision process. You might set dthresh lower than thresh to do a really thorough deinterlacing job on frames that are decided as combed.

[daiyam]

Hi

Before ITVC, you can use an deinterlace filter like TomsMoComp (the most powerfull deinterlace filter, I have tested)
I will converted the interlaced film into a progressive film and you will have no problems with interlaced frames.

(Sorry for my English):rolleyes:

[WarpEnterprises]

Maybe it's not good to set guide=1 as Telecide then assumes to do NTSC 3:2 pulldown removal.
Try with guide=0.
The field order is kept by avisynth itself.
So you have to try a
ComplementParity
before Telecide if it seems your output is wrong.
You can check by doing only a
SeperateFields
on your video and looking if the movement in the result is ok.

@ daiyam
TomsMoComp is for TRUE interlaced material only (and there really good). If used in a telecined video it will destroy the possibility of IVTC!