De-interlacing with QTGMC results in odd frame mismatching

[Cleen]

I have a video I'm trying to de-interlace a TV series using VirtualDub2/AviSynth+ with QTGMC installed, and do a final upscale with Handbrake to H265 1080p 59.94FPS.

The source is from a DVD video - mpeg2 720x480 interlaced 29.97FPS NTSC YUV 4:2:0

This is the avs script I'm running:

SetFilterMTMode ("QTGMC", 2)
FFMPEGSource2("Episode 480i.mkv")
AssumeTFF()
QTGMC(preset="Slower", SourceMatch=3, Lossless=2, EdiThreads=4)
Crop(0,0,0,-2)
LanczosResize(720,540)
Prefetch(14)

I'm exporting the episodes to Lagarith YV12 (720x540@59.94fps) mkv and then upscaling them to H265 1080p using Handbrake.

However, I noticed an episode seems to have encoding errors from using QTGMC. At 2 random points in the video, approximately 1-4 seconds have a few frames between that are corrupted and seem to jump back and forth as if they were encoded out of order.

To check, I ran a regular de-interlace in VirtualDub2 using Yadif DFR TFF, Crop (Bottom 2), and Resize (720x540,Lanczos) and it doesn't happen when de-interlacing that way. It's almost as if QTGMC isn't handling the frames' order correctly. I'm not sure why the Yadif would be fine but QTGMC wouldn't.

I've spliced together the corrupted frames in the QTGMC video with the YADIF frames for now but it's definitely noticeable, is there a way to check the source for corrupted frames?

What could I do to fix this from happening? I'm just worried that other episodes will have problems and I won't notice until I watch them, and I've already finished a decent amount of episodes.


Edit: Fixed! I downloaded a new copy of the episode that was having issues and it seemed to have solved the problem. Must've been some file corruption or something.

[jagabo]

I don't think FFMPEGSource2 is always frame accurate with MPEG 2 video, especially in an MKV container. The best way to handle MPEG 2 sources is to use the original VOB or remux from MKV to MPG then use DgIndex and Mpeg2Source("filename.d2v").

[RogerTango]

try dgdecode / dgindex or a variant... reading VOBs with ffsource is less than accurate.

Andrew