QTGMC Doubling Frames Instead of Interpolating?

[LucasAuraeius]

I've been racking my brain trying to figure this out but I'm at a loss. I've been trying to both upscale and interpolate this DVD to convert its framerate from 29.97 to 59.94fps. Instead of the end result being a 59.94fps video with interpolated frames, I get a 59.94fps video with DOUBLED frames. No motion interpolation. By using the same script, I've been able to successfully perform this process on some DVDs, but not others. I've compared the DGIndex logs of one DVD that's worked, and two DVDs that haven't. I can't seem to figure out what is causing this problem. To perform this process, I first created .d2v files from the .vob DVD files, then rendering the video from that. I'm able to tell that I'm getting doubled frames as early as the preview screen in VirtualDub, so the issue lies in either the script or the encoding in the DVDs. I'd greatly appreciate any help.

Here's the script:

LoadCplugin("C:\Program Files (x86)\Avisynth\plugins\yadif.dll")
LoadPlugin("C:\Program Files (x86)\AviSynth\plugins\DGDecode.dll")
SetMTMode(5,9)
MPEG2Source("D:\Movie\movie.d2v")#DGDecode_mpeg2source, FFVideoSource, AviSource, whatever your source requires
AssumeTFF()
ConvertToYV12(interlaced=true)
SetMTMode(2)
QTGMC(EdiMaxD=16, EdiThreads=8, Lossless=1, Preset="Placebo", Sharpness=0.0, ShowSettings=false, SourceMatch=3, SubPel=2, TR0=2, TR1=2, TR2=3, TrueMotion=true)
Distributor()
#add the argument FPSDivisior=2 to QTGMC to preserve the original framerate

Here's the two nonworking .d2v files on the left, then the working one on the right:

[Attachment 49129 - Click to enlarge]

I'm probably not posting the necessary info here, but I can provide whatever I need to.

[poisondeathray]

Probably that DVD's actual content is 29.97p , not 29.97i

[LucasAuraeius]

Is it possible for it to be 29.97p even when the frame type shows up as "interlaced"? In which case, how should I edit the script?

[manono]

Yes, it's possible. It's common for progressive 29.97fps sources to be encoded as interlaced.

I have no idea if that's what is really going on, but the doubling you mentioned could easily result from that. My question is, what's your obsession with getting 59.94fps out of it? Before bobbing you should understand what you have and how it should be treated and not just blindly put on a bobber.

You might post a short sample from the DVD, one with steady motion, 10 seconds or so. Also, your source is already YV12, so you don't need the Convert line in your script.

[Sharc]

On DVD the video is stored as fields and is always flagged as interlaced (by the DVD standard), even when the video is progressive. When the video is 29.97p the 2 fields are from the same point in time. QTGMC therefore produces 2 identical pictures, one from the top and one from the "identical" bottom field with no motion in between. QTGMC is a bob-deinterlacer and does not do any temporal motion interpolation. So if your video is 29.97p and you want to produce 59.94i you would have to synthesize the missing field with a temporal interpolator.

Edit:
manono was faster

[jagabo]

QTGMC doesn't interpolate motion to create in-between frames. It takes each field and converts it into a frame (using interpolation in some circumstances). With progressive frames (the two fields are from the same frame) you get duplicate frames (with minor differences) from the two fields.

[johnmeyer]

QTGMC doesn't interpolate motion to create in-between frames.

but then:

It takes each field and converts it into a frame (using interpolation in some circumstances)

These two sentences seem to be at odds with each other, and I am left a little confused.

My own understanding is that the advanced modes of QTGMC do use motion estimation (i.e., interpolating between fields/frames) which is why it is more than just another bobber (and can provide such stunning results), and is also why it is so darn slow at times.

[jagabo]

QTGMC doesn't interpolate motion to create in-between frames.

but then:

It takes each field and converts it into a frame (using interpolation in some circumstances)

These two sentences seem to be at odds with each other, and I am left a little confused.

My own understanding is that the advanced modes of QTGMC do use motion estimation (i.e., interpolating between fields/frames) which is why it is more than just another bobber (and can provide such stunning results), and is also why it is so darn slow at times.

It doesn't convert 30p to 60p by creating in-between frames with motion interpolation. It uses motion interpolation techniques to help fill in the missing field between existing fields and stabilize the image. But if there's no motion between two successive fields there's no motion to interpolate. So you get duplicate frames (aside from minor artifacts).

[Cornucopia]

So, Field-based interp, not Frame-based.

Scott

[johnmeyer]

It doesn't convert 30p to 60p by creating in-between frames with motion interpolation. It uses motion interpolation techniques to help fill in the missing field between existing fields and stabilize the image. But if there's no motion between two successive fields there's no motion to interpolate. So you get duplicate frames (aside from minor artifacts).

I think I understand: being a deinterlacer, it doesn't try to do anything in the way of motion estimation if it determines the video is progressive.

[dannyboy48888]

Its totally possible. On the Andromeda DVDs its actual 29.97p but shows as interlaced in dgindex and mpc-hc plays it at 60fps. Legends of tomorrow s01 DVD is encoded the same instead of soft telecining (tdecimate works for it). Point is on non familiar stuff I have to make a sample clip as sometimes what the streams says to do and what looks right are 2 different things.

[LucasAuraeius]

Thanks guys for your input, this thread taught me a lot about how QTGMC works. In the case of progressive DVD content, which temporal interpolation process should I use with Avisynth? Is there one that detects scene changes well? I'm completely ignorant about Avisynth scripts outside of QTGMC.

[jagabo]

In the case of progressive DVD content, which temporal interpolation process should I use with Avisynth?

None, they all create annoying artifacts when they mis-identify motion. They're pretty much only useful for panning shots. If you really want to try one, InterFrame() has tunings to let you select for smoother motion with more more warping artifacts, or less smooth motion (blended/duplicate frames) with fewer warping artifacts.

[Sharc]

Thanks guys for your input, this thread taught me a lot about how QTGMC works. In the case of progressive DVD content, which temporal interpolation process should I use with Avisynth? Is there one that detects scene changes well? I'm completely ignorant about Avisynth scripts outside of QTGMC.

First of, you have to be sure that your 29.97 DVD video is really progressive content and not telecined film. Have you visually analyzed it, e.g. by stepping through the frames or fields? If you should have some doubts post a sample of a few seconds duration of a scene with motion.

[jagabo]

By the way, most TV shows are shot on film. So the likelihood of you have 30p is very very low.

[manono]

By the way, most TV shows are shot on film. So the likelihood of you have 30p is very very low.

Hehe, a sample was requested a couple of days ago. Unless and until one is produced, all we have to go on is his guess as to what he has, yet he's here asking for help with it so I don't know how much stock we can place in what he says about it.