I have visited this forum many times for advice from previous peoples issues but finally made an account to ask for help,
I am having issues removing frequency interference from a video recording of a concert video recording and was wondering if anyone could help.
Hopefully there should be a clip attached (I am new to posting here so I am not 100% sure I did everything right)
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I don't see any frequency interference. The film has been telecined (i.e., extra fields added to allow 24 fps to play on a 30 fps interlaced display). If you want to apply filters of some sort, you will need to remove those duplicate fields (i.e., perform inverse telecine using something like IVTC which consists of TFM and TDecimate).
I was wrong about telecine. I grabbed the wrong clip.
Last edited by johnmeyer; 24th Mar 2021 at 13:17. Reason: corrected my mistake in the  section
I used QTGMC instead of IVTC.
After doing QTGMC to double rate deinterlace this is frame 279, one of the worst here.
The Defreq plugin in Avisynth was designed for this, but the documentation is sparse,
nobody seems to understand it that well and it hasn't been updated since 2006
Saying that, the clip does look much better once it's deinterlaced. Perhaps some other ideas
will be forthcoming
Decoding works fine here. (using LWLibavVideoSource)users currently on my ignore list: deadrats, Stears555
Since it is telecined, I think QTGMC is going to do bad things to the clip. I'll try Defreq later today.
I posted results from Defreq not that long ago:
The guy didn't think the results were very good, so I posted this before/after still:
You have to also download his clip (in post #1) to see how much improvement I made. In my experience, you never get 100% of the interference, but often can get 80-90%, as I did with this example.
You can judge if it helped, or not. If you read through the whole thread, I provide information on how to set it. I've never found it particularly hard to use. The big problem is that interference patterns tend to change angle, width, motion, and intensity over time, so you sometimes have to apply the filter to sections of the video, change parameters, and then do the next section.
It's possible that horizontal pattern is in the original recording itself. I've seen old concerts broadcast on the TV
with that same pattern.
With my rudimentary understanding of the filter, I can reduce it a little:
Last edited by davexnet; 24th Mar 2021 at 16:01.
I couldn't improve much on davexnet's results, although it might be possible to fine tune it further using the 2nd and 3rd order parameters. Calling it a second time with different sharp settings might also provide slightly better results.
I added a few more frequencies to reduce the banding even more. But the remaining bands are more irregular. I don't know that it really looks better.
AviSource("Sao Paulo.avi") AssumeTFF() QTGMC(preset="slow") defreq(fx=0.0, fy=-10.8, dy=2.5, sharp=8.8, info=false, show=0) defreq(fx=0.0, fy=-10.0, dx=0, dy=2.0, sharp=0.0, info=false, show=0) defreq(fx=0.0, fy=9.5, dx=0, dy=2.0, sharp=0.0, info=false, show=0) defreq(fx=0.0, fy=9.0, dx=1, dy=4.0, sharp=0.0, info=false, show=0)