Degrainmedian and mixed (hybrid) video

[DoctorM]

I have a DVD I'm trying to re-encode and it contains both 29.97i and 23.976p content in the same VTS.

I'd like to use DeGrainMedian on it since it's pretty dirty, but I'm not sure if that's possible. I know in some cases it's preferable to assume interlaced because it'll still work if the material is progressive. Does DeGrainMedian work the same?

That is, should I use Interlaced=True as a blanket filter for the whole disc, or does each VOB have to be encoded separately?

[Blue_MiSfit]

Hmmm...

If you have a hybrid movie, it's surely encoded interlaced. Therefore, you can probably safely use degrainmedian in interlaced mode..

Or, you can handle the hybrid video, and deinterlace it as necessary - to either 30p, 24p, 120p, or VFR.

~MiSfit

[DoctorM]

Yikes. Oddly, it's a somewhat recent TV series. As far as I can tell from checking in DGIndex, VirtualDubMod and GSpot some VOBs are 23.976 with pulldown and others are 29.97 interlaced.
It doesn't SEEM to vary within VOBs only between them. What makes this stranger is since episodes split across VOBs, individual episodes can change between interlaced and progressive.

I did use DeGrainMedian without the interlace option set before I noticed this oddity, and I'm having a hard time finding any problems from doing that.
Anyway, thanks for the info, I'll definitely switch to interlace=true. I just hope DVD Rebuilder knows what it's doing with it. :)

[foxyshadis]

Don't use DGIndex, VDMod, or Gspot to check for interlaced! They can only tell you if it is not or might be interlaced. (And even then if it's really badly encoded, it might still be even if it says 24p Film.) It's always possible to encode something progressive as interlaced - the best automated method is to use MeGUI's interlacing check, or you can separatefields and eyeball whether every field is a new frame or not. You can handle it in several ways, by blending, dropping frames, deinterlacing everything, or creating a hybrid video. See VFR (http://avisynth.org/mediawiki/VFR).

[DoctorM]

Well since I'm recoding from DVD9 to DVD5 most of those methods wouldn't be useful.
My research does show that DVD Rebuilder actually generates a flag file so when it rebuilds it can match the pulldown pattern of hybrid sources. Pretty cool.

Really my question was how best to use DeGrainMedian with hybrid content. It seems that "interlaced=true" is the answer to that question.

[thetoof]

But, if your hybrid video has progressive frames in it, wouldn't the interlaced=true reduce the quality of the processing in those frames?

[DoctorM]

Which was exactly why I asked the question to start with.
I assume it works by separating fields, filtering and then recombining fields. Typically that doesn't have a negative impact on progressive material, just slowing processing time.

foxyshadis: How would you use MeGUI to test the file (never used the proggy before)?

[Adub]

Click on the "Avisynth Script Creator", and then load your source. Then page over and click "Analyze".

[DoctorM]

One of the discs comes up as 90% Progressive in DGIndex. Examining the video in VirtualDubMod I see combing (almost completely during the opening credits in this case).
MeGUI says something like M-in-5 or whatever.

I think I'll stick with the Interlaced=True flag for safety. It just doesn't seem right to try to process interlacing as progressive. Beside DeGrainMedian doesn't appear to have any negative effects on progressive content.

Does anyone else have experience with this?

[DoctorM]

I tested some clips side by side treating progressive as interlaced and vice versa in order to see what works best on hybrid content.

Using Interlaced=True on progressive content alters the pattern of grain removed but seems to have no effect on the final quality, sharpness or degraining.
Using Interlaced=False on interlaced content slightly softens the combing, but unfolding the fields and comparing the to the original video reveals little to no artifacts from the filtering.

The answer? Do what you want, neither seems to have a particularly negative impact (at least on the DeGrainMedian settings I used).

[thetoof]

Could you upload a small sample of the credits and another sample of your source with a high motion scene? I'd like to test a few things...

[DoctorM]

What would make this show's interlaced and progressive material different from any other? That request seems fairly random.

[thetoof]

I'm asking this because I started dealing with 24t + 30i sources a while ago and that the function I wrote, animeivtc(), can restore all this to 23,976 with no residual combing, jerks, etc etc (or create a VFR clip). So, I wanted to try some settings on your samples to see if it can be of any help.