Amount of interlacing differing between captures?

[volleymeister]

I'd imagine that this question has already been asked/answered, but there are so many threads about interlacing that it makes it very difficult to find this specific issue.

I've been capturing old basketball games from (NTSC) VHS tapes for the past few weeks, all of which come across as interlaced of course. The most recent game I've captured, however, seems much more interlaced than the others. In other words, the horizontal comb lines are much longer on this video than on the other videos that I've captured with the same equipment.

The end result of this is that after applying deinterlace filters in virtualdub, the finished video looks blurry. It doesn't look interlaced anymore, but it looks like there's ghosting or double-image blurring on movement scenes.

I've captured it at 29.97 fps just like all of my other captures that don't have this problem (to this degree). Is there anything I can do to reduce this? Would recapturing at a higher frame rate make any difference?

Thanks in advance.

[jagabo]

Use a better deinterlacer. The double exposure look after deinterlacing implies you used a blend deinterlace -- that just blurs the two fields together.

Interlaced video is interlaced video. If you used the same setting son the camera you there should be no differences. But if you used a progressive setting on the camcorder there will be less or no combing. If there is no motion you will not see comb artifacts. The more motion there is the more artifacts you will see. You should post samples of your "less and more interlaced" videos.

[vhelp]

i agree, interlace is interlace, two different video fields of slightly different times weaved together as one frame. a sample that shows the problem you are seeing would help. however, i believe that you may have a segment in that video that is motion replay effect or is progressive. for these you will have to segment and handle separately and join back later.

[volleymeister]

I don't know what's different about this particular tape, but something is.

Same VCR, same capture device, same capture software, same deinterlace filter.
The only thing that's different from the 10 other games I've captured without this problem is the VHS tape that I'm capturing.

I've tried both blend and other deinterlace modes, the other modes look worse than blend. Not as blurred, but more artifacts and just lower picture quality in general.

I'm not at home right now so I don't have access to the capture files. I'll try to post some pics later this evening that show what I'm talking about.

[jagabo]

If you want really superior deinterlacing you'll have to learn a bit of AviSynth. The QTGMC() filter there is the best so far.

[jagabo]

Yes, DirectShow should be your last resort.

[volleymeister]

Y'know I played around just briefly last night with Avisynth and QTGMC. What I was running into was that the filter apparently can't accept the RGB32 format that I captured these files in. I hadn't had time to try to figure out if I could convert these files in Avisynth prior to applying the QTGMC filter, or if I should just recapture them.

I see that QTGMC will accept YV12 or YUY2, is either of these recommended over the other?

[jagabo]

Use ConvertToYV12() before QTGMC().

WhateverSource()
ConvertToYV12()
QTGMC()

[volleymeister]

Thanks much, I'll give that a shot tonight.

[jagabo]

Oh, you may also need to specify the source is interlaced and the field order.

AviSource("filename.avi")
AssumeTFF() # or AssumeBFF(), whichever matches your source
ConvertToYV12(interlaced=true)
QTGMC()

[volleymeister]

Just encoded a few minutes of the video using QTGMC, and wow what a difference. Looks fantastic. Why can't virtualdub have a deinterlace filter this good on it's own??

[jagabo]

I don't think many people write VirtualDub filters any more. QTGMC() uses several other AviSynth filters so someone who wanted to duplicate it for VirtualDub would have to include all those other filters too. It would be a very big job.