Quantcast QTGMC deinterlace = lost detail? - digitalFAQ Forum
  #1  
02-29-2020, 02:20 PM
bakerie bakerie is offline
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Hi,

I'm trying to test my "workflow" and I'm probably going to post a video here so people can berate me for doing it all wrong , for now though, the one thing I've spotted easily is that QTGMC is causing a slight drop in quality and I was wondering if there's anyway around it. (I've tried various settings)

I'm using a Snell and Wilcox test pattern DVD, which I've recorded to VHS using the s-video in of the VCR. The original image is attached called "orig". The captured file is called "capd file". We can see the captured file has already lost detail on the left and right of the circle. I'm assuming this is just due to the VHS recording? The final file with de-interlacing is called "deinter". Here you can see we have now lost detail from the top and bottom of the circle.

Is this normal?
Can I prevent it?

I have two Samsung LCD TVs with brutal deinterlacring, hence why I wanted to turn the videos progressive before saving them.

Thanks!

EDIT: I was focusing so much on the circle, I didn't notice there's actually huge parts of the test pattern missing @_@


Attached Images
File Type: png capd file.PNG (918.2 KB, 29 downloads)
File Type: png deinter.PNG (819.1 KB, 30 downloads)
File Type: png orig.PNG (382.2 KB, 28 downloads)

Last edited by bakerie; 02-29-2020 at 02:32 PM.
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  #2  
03-01-2020, 12:17 AM
cbehr91 cbehr91 is offline
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Which speed of QTGMC are you using? If you're just typing "QTGMC()" in your script the default speed is "Slower", which is major overkill most of the time. The Avisynth wiki even says so. Your video will look overly smooth and plastic-y. Try fast/faster in conjunction with tweaking SourceMatch and Lossless.

Example: (Preset="Faster", SourceMatch=3, Lossless=2, MatchEnhance=0.75, TR2=1, Sharpness=0.1)

That example is meant for a fairly clean source to begin with. Source match does exactly what is sounds like. Lossless and MatchEnhance can enhance some detail. TR2 is a smoother. The higher the value the more smoothing is does. The default sharpness of QTGMC is 1.0. Obviously taking it down to 0.1 tones down the sharpness quite a bit. I'm speaking in generalities a bit because this info can be found in greater detail on the Avisynth wiki.

The real power of QTGMC is when you manipulate its core settings.
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  #3  
03-01-2020, 05:00 AM
hodgey hodgey is offline
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What's the full script you used? QTGMC won't crop the image like that on it's own. The sides being cropped off in the capture may be due to the DVD playback device, capture device or TBC. The image won't be cropped on it's own purely by being on VHS (though the TBC in a VCR may cut off a bit.) Normally there isn't detail in this area in the first place, and it would not be visible on a CRT as it's in the overscan area so video devices don't always bother dealing with it properly.
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  #4  
03-01-2020, 08:18 AM
bakerie bakerie is offline
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@cbehr91
I think I see the flaw in how I was using this now. I'm using Hybrid and hadn't appreciated that the presets changed all those parameters! I'll start playing around with this now. Thanks so much for this.


@hodgey
I can't see the option in Hybrid to show me the script it's generating? Yes, I had cropping (14 on sides) enabled, but nothing else.
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  #5  
03-01-2020, 08:21 AM
hodgey hodgey is offline
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Ah, you're using hybrid. I haven't used it but it seems it's cropping the bottom and top with the settings you are using.
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  #6  
03-01-2020, 08:27 AM
bakerie bakerie is offline
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Huzzah! Problem solved


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File Type: png Capture.PNG (865.0 KB, 28 downloads)
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  #7  
03-04-2020, 06:27 AM
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lordsmurf lordsmurf is offline
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QTGMC can also do NR, resulting in blurring.
It's why I don't use the "slow" preset, but instead "faster" in most cases.

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  #8  
03-04-2020, 10:35 AM
ELinder ELinder is offline
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Can't you bypass the NR even if you're using a preset by adding it?
NoiseProcess (0,1,2) Bypass mode: 0

Erich
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