IVTC has interlace artifacts or jerky movement take your pick?

[clashradio]

Hello,

Somewhat new to AVISynth and I've got my feet wet deinterlacing via QTGMC, now I tried my first Inverse Telecine project. It should be a simple 29.97fps to 23.976fps conversion. Source is NTSC laserdisc captured at 480i. Goal is 720p BD delivery. I'm having what I think is called combing artifacts. I've searched this forum and tried a handful of plugin options TFM(pp=0), ConditionalFilter(last, QTGMC(FPSDivisor=2), last, "IsCombedTIVTC"), SelectEven(). TDecimate(mode=2)

Depending on which option(s) I use I either get combing artifacts with smooth playback, or no combing artifacts yet get every 20th frame is a duplicate frame with the 22nd frame looking jerky due to the lost 21st frame.

I figured this project would be as standard as they come being how the original source is film shot at 24fps with 3:2 pulldown. Attached is a still of the combing artifacts, and a clip with the script I used. This script doesn't have the combing artifacts but has the duplicate frames).

TDecimate(mode=2) gets rid of the combing, yet causes the duplicate frame/jerky issue. Changing to AssumeBFF() gets rid of the duplicate frame, yet causes combing.

Any help is much appreciated. I've tried every combination I ran across from reading about this issue.

a = LWlibavAudioSource("1.avi")
v = LWlibavVideoSource("1.avi")
AudioDub(v,a)
AssumeTFF()
TFM()
TDecimate(mode=2)
nnedi3_rpow2(2, cshift="spline36resize", fwidth=1280, fheight=870)


[Attachment 58975 - Click to enlarge]

[davexnet]

Post a clip of the source, at least 10 seconds

[jagabo]

Yes, we need a sample of the source. Are you sure it's TFF? Also, in this particular case the subtitle may have confused the decimation. At least as an experiment try cropping it away before TDecimate()

[clashradio]

Here is a ten second clip. I'm pretty sure it's TTF; I used the script below and got nasty results with BFF. I'll try to crop out the subtitles and see if that helps. I chose 1280x870 because it made it easier to go from letterbox to anamorphic when I cropped out of the black bars in Vegas.

AviSource("input.avi")
AssumeTFF() # or AssumeBFF()
Bob()

[jagabo]

Both times in that clip the problem occurred when the subtitles appeared. I think that's the problem. But you should upload a sample of your source, not processed videos.

If the subs are the problem you can work around that by splitting the video into top and bottom parts, IVTC'ing them separately, then stacking them back up.

[clashradio]

I uploaded the processed video just to show what issue I'm having. I think you're right about the subtitles being the cause. When I scroll frame by frame, the first frame of the duplicate doesn't have the subtitle then the next frame does, even though it's the same frame as the previous.

I've uploaded a raw ten sec capture of the same clip.

[jagabo]

Try:

AssumeTFF()

top = Crop(0,0,-0,332).TFM().TDecimate()
bot = Crop(0,332,-0,-0).TFM().TDecimate()

StackVertical(top, bot)

[clashradio]

Wow that worked thank you. No more interlace artifacts and duplicate frames. Just curious; the subtitles are still there. Not a problem because I'm cropping in Vegas anyways. But the subtitles are what was causing the issue. How did this top/bottom cropping fix the problem?

[jagabo]

The subtitles were added after the video was telecined and are not coordinated with the 3:2 pulldown pattern of the film. They interrupt the pulldown pattern making the full frame difficult to IVTC properly. Splitting the top and bottom portions of the frame allows them to be IVTC'd separately.

[clashradio]

Thank you jagabo never would have guessed that. You saved me a big headache.

[clashradio]

Upon viewing the complete project I noticed a few scenes that didn't get IVTC'd properly. I seems like it's mainly when there are other objects with defined straight lines in the scene. I know you guys like an uploaded clip of unprocessed video, but I want to show an example of what's happening. Attached in a captured frame with a box and a grate with vents, and the video clip is a control panel with terrible interlace artifacts.

This video has subtitles which caused IVTC problems, later resolved by jagabo. Below is the script. Is this interlacing artifacts common with IVTC? I've never viewed a complete movie, only test clips here and there. Do I need to add any extra mode to TDecimate?

a = LWlibavAudioSource("1.avi")
v = LWlibavVideoSource("1.avi")
AudioDub(v,a)
AssumeTFF()
top = Crop(0,0,-0,332).TFM().TDecimate()
bot = Crop(0,332,-0,-0).TFM().TDecimate()
StackVertical(top, bot)
nnedi3_rpow2(2, cshift="spline36resize", fwidth=1280, fheight=870)

[jagabo]

Yes, TFM's post processor sometimes mistakes thin horizontal lines that are truly part of the video as residual combing and deinterlaces it. One way around that is tune the comb detector's threshold TFM(cthresh=-11). Or you can turn off the post processor with TFM(pp=0). But if the video has orphaned fields, or some other reason the field matching doesn't work, interlaced frames will slip through. Sometimes you can provide an alternate clip to be used by the post processor, TFM(clip2=QTGMC(FPSDivisor=2)) -- the post processor will still kick in but the alternate clip may result in fewer artifacts. Or, if you know where those frames are, just treat the section differently.

[clashradio]

Ok thanks for the suggestions. I'll play around with the different thresholds and if that doesn't work I'll tackle each problem scene with a different script. Seems like when I swapped fields the interlacing disappeared.