Can TBC errors cause interlacing artifacts?

[binister]

I have captured a very old VHS tape that is exhibiting some strange interlacing artifacts when played back on my TV.

For reference, all of my other captures/conversions look fine.

The tape has some major compounded TBC errors on it and I am wondering if that is contributing to the problem. I have only done some minor level tweaking in AVISynth on the footage but the resulting mpeg and DVD exhibit obvious interlacing artifacts (combing) when played back on a TV. The strange part is the interlacing artifacts appear on objects that aren't moving however it is along the same horizontal axis that the TBC errors appear. The more pronounced the TBC error the more pronounced the artifacts.

If I play the DVD in VLC I see the same artifacting until I enable the blend deinterlacer at which point the footage is properly deinterlaced and the artifacts disappear.

It is almost as if the DVD footage isn't flagged as interlaced or something. Both my LCD and plasma sets don't appear to be deinterlacing the footage properly. Any ideas?

[yup]

binister!
Upload 5-10 captured frames or short clip using lossless codec (huffyuv).
yup.

[2Bdecided]

Yes, of course TBC artefacts can look like interlaced combing on objects that aren't moving - if the two fields shift apart horizontally that's exactly what will happen.

Cheers,
David.

[yup]

2Bdecided it is true even for full frame Time Base Corrector? Or You speaking about TBC which have some VCR and frequently not full frame?
yup.

[Mug Funky]

there's no such thing as full frames in the composite signal...

sometimes bypassing the TBC will give better results depending on the equipment used.

also, double-check the tracking on the VCR, as this could definitely be a variable.

what's got me is that you're seeing interlace on a TV that should not show it. are you resizing vertically at some point? or do you mean that you're seeing jittery horizontal movement on otherwise static objects?

come to think of it, a motion-adaptive deinterlacer in your LCD or plasma could be the cause - if the timebase jitter is constant enough the deinterlacer will assume it's static detail and pass it through untouched.

maybe abusing depan or mvtools could help here, or simply moving the 2nd field by the right amount (if this amount doesn't change).

[binister]

Here are some clips:

1. HuffyUV encoded DV AVI (16 MB).
http://rapidshare.de/files/39897088/post.avi.html

2. MPEG2 encoded (via CCE) .mpv file (1.4 MB).
http://rapidshare.de/files/39897104/post.mpv.html

You can see the artifacts on the borders of the curtains and sliding door in the back when these clips are played back on a DVD player. Notice the significant TBC errors along that horizontal plane.

I checked the frame parity of all clips with GSpot and they are all interlaced BFF clips.

I downloaded Smart Deinterlacer for VirtualDub to see if I could recreate the problems in VDub and it looks like it might just be a limitation in my HT DVD players. If I set the motion detection value to a low number (meaning small interframe movement is deinterlaced) then the clip looks correctly deinterlaced in VDub. If I set the motion detection value to a high number (large movement required for deinterlace to occur) then I see the same artifacts that I see on my HT screens.

The deinterlacer in my DVD player and PS3 must be using an adaptive deinterlacer that isn't sensitive enough. I know they are doing some deinterlacing because obvious movement is deinterlaced.

Thanks for the help.

[2Bdecided]

You need to re-transfer that on a VHS machine that includes a TBC, or from the VHS via a stand-alone TBC - never mind the "interlacing artefacts" - the vertical lines look like jelly! A good TBC should fix this.

cheers,
David.