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10th July 2009, 23:05 | #1 | Link |
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Quick Deinterlacing Question...
Well, I think it's quick anyway
Basically I've got a PAL DV file which was dubbed from a PAL BetaSP which came from a film source. The original film was shot at 24fps but I'm assuming they did the 4% speed-up when doing the telecine at 25fps. Anyway I'm trying to deinterlace this sucker the best way possible. Once I get to real 25p I'll convert it back down to 24p. Here is a frame from the source: My first try in VDub was with the filter "deinterlace - PAL movie v1.1 (normal)" and it seems to be doing the right thing. Here is the same frame after filtering: My question is, why am I still getting (albeit minor) comb artifacts on the edges? My paranoia says that I must be doing something wrong - or is this "normal" when deinterlacing, to have some minor artifacts still? Am I approaching this in the right way or should I be doing something else? Here's a short clip of the material: http://rapidshare.com/files/254364852/Clip1.rar.html Many thanks in advance for any help! Leo Last edited by LeoH; 11th July 2009 at 22:04. Reason: Added clip link |
10th July 2009, 23:17 | #2 | Link |
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Obviously the deinterlace filter you used didn't catch all combing artifacts. If that filter has options, try to tweak the parameters.
If you can't get acceptable results with that filter, I highly recommend you give Yadif or TDeint a try BTW: Most deinterlace filters leave a few artifacts here and there. But the question is: Are they visible at normal playback speed?
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10th July 2009, 23:25 | #5 | Link |
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Thanks for the fast reply! Well, this particular filter has no options except for "swap fields first" which didn't seem to help. It actually does a pretty good job with the whole film - aside from the minor comb artifacts on the edges. But since this material is from film, shouldn't the fields simply fit back together into one seamless frame? I don't want to use any filters that interpolate or are destructive to the original source if possible. Thanks again!
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11th July 2009, 00:15 | #7 | Link |
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OK, here's a short unprocessed clip of the material:
http://rapidshare.com/files/254364852/Clip1.rar.html I think a field matcher sounds like the right ticket possibly, but feel free to let me know what you think of the clip. Many thanks!! |
11th July 2009, 00:43 | #8 | Link |
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This is not only field shift, it also has additional distortions. Like that weird color ghosting between the fields:
But "decomb telecide" to fix the field shift followed by Yadif to clean-up the remaining combing artifacts seems to give reasonable results: http://www.mediafire.com/?yaykindhzeq
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11th July 2009, 01:28 | #9 | Link |
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Thanks Mulder
Yeah the video has other problems, but I was trying to focus on just getting it back into progressive frames first. Decomb telecide and Yadif do seem to work nicely! What script did you use? I've tried this with just the Decomb filter: AssumeBFF() Telecide(guide=2,post=2,vthresh=50) Seemed to produce reasonable results but maybe I should try Yadif for the "post" part. Thanks again! |
11th July 2009, 12:06 | #10 | Link |
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I simply used "Decomb Telecide" (in "PAL/SECAM" mode) followed by Yadif (in Non-Bob mode). This was done in Avidemux.
But I think you can simply append Yadif(mode=0,order=0) to your script and see whether that does help or not http://avisynth.org.ru/yadif/yadif.html
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11th July 2009, 21:59 | #11 | Link |
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I've tried Yadif after Decomb Telecide and it does produce nice results. There were still a few very minor comb artifacts on certain rounded edges, so I tried running "field bob" in VDub in conjunction with the AviSynth script of Decomb Telecide and Yadif. That seemed to take care of all the jagged edges and I don't think the quality suffered. Of course now I'm noticing all the other weird problems with the video - like the frequent wobble across the middle of the screen.
One thing at a time for now... |
11th July 2009, 22:18 | #12 | Link |
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I think if you use "Field Bob" in VirtualDub, which basically throws away one field (half of the lines) and then interpolates the missing field, you can drop Yadif.
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11th July 2009, 22:53 | #14 | Link | |
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Quote:
Only "smart" (motion adaptive) deinterlacers don't blindly interpolate all the pixles of one field, but try to keep as many pixels as possible. This is possible because in areas where there's no motion, we can simply weave the fields with no visible combing. As far as I understand, Yadif does not work like that. In interpolates all pixels of one filed, but uses a very smart method to do that.
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12th July 2009, 01:53 | #15 | Link | |
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Quote:
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12th July 2009, 02:03 | #16 | Link | |
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Quote:
After that process we (ideally) get the original progressive frames back. No interpolation does happen. Of course Decomb Telecide only works with Telecined or filed-shifted material. It does not work on "true" interlaced video at all! In your case the video appears to be field-shifted and Decomb Telecide does restore the video pretty well. Unfortunately there are some filed distortions, which cause these minor combing artifacts shown in your screenshot. Putting a deinterlacer (e.g. Yadif) behind Decomb Telecide removes those artifacts. Of course you could skip the Decomb Telecide filter and only use Yadif. This should remove the combing too. But you probably get better quality, if the deinterlacer bases its decisions on the "fixed" stream instead of the field-shifted one. The same way we could simply deinterlace a Telecined stream, but we certainly shouldn't do that! BTW: Maybe one of the Avisynth gurus could write a script to fix your field distortions in a smarter way Appending Yadif is the quick and dirty solution to clean-up the remaining combing...
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12th July 2009, 03:18 | #17 | Link | |
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Quote:
UPDATE: I think I've found the perfect solution! It's an AviSynth plug called "Vinverse" - the description reads "An effective Function against (residual) combing, by Didée. Useful after deinterlaceing." Well, I've tried it and it seems to work like a charm. My residual combing problems appear to be gone and edges are smooth! Last edited by LeoH; 12th July 2009 at 04:00. |
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12th July 2009, 04:54 | #18 | Link |
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Wrong. It has a post processor that catches combed frames that slip through the field matching process. That is enabled by default.
The post processor in Telecide() will test if the frame has combing and apply deinterlacing only to the combed frames. Yadif will act on all frames, whether combed or not. That is not good. Your post is borderline FUD. Last edited by Guest; 12th July 2009 at 04:57. |
12th July 2009, 05:23 | #19 | Link | |
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12th July 2009, 12:21 | #20 | Link | |||
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Quote:
But basically the idea of an Inverse Telecine filter is to restore full frames by merging fields in the correct order/pattern, instead of interpolating. If there's an (additional) post processor in Decomb Telecide to catch remaining combing artifacts, good. Will try to keep that in mind Quote:
If you know a better one (maybe Decomb Telecide's post filter can be tweaked to give better results on LeoH's source), I think it would be welcome (BTW: TDeint has a similar option to only process "combed" frames, so it can act as a post-processor too) Quote:
Even if the fields are merged in the correct pattern, they don't fit perfectly together, because of these distortions. Maybe the "correct" solution would be to shift each odd (even) line horizontally until it fits...
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