Quantcast Image issues, only very bottom of VHS screen? - digitalFAQ Forum
  #1  
12-29-2019, 09:04 PM
Ntierney Ntierney is offline
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Setup-
Hardware
JVC sr-vs30
TBC 1000
Pinnacle 510

software
windows 10
vitualdub

I am getting a strange scrambled image at a small section at the very bottom? It seems to be black and white. Sorry brand new and after surfing this site for a very long time I can not seem to pinpoint the issue or what I need to do.

It seems to be the same or very similar to the video at the start of this link. What I am talking about is what is happing at the very beginning of the video and at the very bottom of the video.

Thanks in advance for any help. The video in the thread is titled "diagnostic".

Troubleshoot a DataVideo TBC-1000?
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  #2  
12-30-2019, 04:31 AM
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BarryTheCrab BarryTheCrab is offline
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The "issue" is called head-switching noise, almost every VCR has it, at the bottom. You never saw it before because your TV overscans the video image so the edges are off the TV screen real-estate. Some VCRs have a larger overscan scramble than others, but it's normal. I believe the best action is to mask the edges, do not crop/resize.
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  #3  
12-30-2019, 10:17 AM
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lordsmurf lordsmurf is online now
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Attach a screenshot of your error.

It could be switching noise, but I don't want to assume. The thread you refer/liked to has a specific odd (yet happening more frequently) issue with PSU and environmental acclimation.

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  #4  
12-30-2019, 10:23 PM
Ntierney Ntierney is offline
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Thanks for the reply. I will try to get a screen shot this weekend.
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  #5  
01-05-2020, 02:57 PM
Ntierney Ntierney is offline
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ok attached 2 screen shots. I can get more if needed. At the very bottom it seems to be black and white scrambled. Also I believe the 2nd image shows what it should look like prior to deinterlacing. Is this correct?


Attached Images
File Type: jpg Capture.jpg (69.1 KB, 16 downloads)
File Type: jpg Capture 2.jpg (82.0 KB, 12 downloads)
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  #6  
01-05-2020, 04:30 PM
keaton keaton is offline
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As Barry indicated, the bottom few rows of the video in those images is head switching noise. Almost all video tapes will have this. It can be cropped out and replaced with black border to preserve the pixel dimensions (i.e. 720 x 480) using avisynth or virtualdub. Removing the head switching noise will make the video much less distracting to watch, and should also save you significantly on the size of the video file, since all the moving video in that space requires a lot more data to render than a constant value of 0 (black).

A method in virtualdub is How to Properly Crop the Overscan in VirtualDub [GUIDE]

Or in avisynth, refer to these two pages http://avisynth.nl/index.php/Crop & http://avisynth.nl/index.php/AddBorders You would call crop first to remove the existing edge noise and/or black edges without video in them on any sides that need it, then call AddBorders to replace the cropped pixels with a border (default of black).

When restoring a video, after cropping the video, but before adding the black border back in, you can adjust the levels to get the most contrast out of your video, i.e. the darkest and brightest portions of the video are at or close to the legal limit of darkest and brightest when viewed in a histogram. A general rule of thumb, anyway, not always that way. A low contrast video can look washed out. Fixing contrast, not to mention the color, can really bring some life back to the video. Plenty on that topic in other forum posts. Please take time to read through some of the restoration examples that have been posted over the years. They are a fantastic fountain of knowledge and can really help you improve the video beyond what you might have thought or expected.

Regarding the second image. Yes, that is what a moving image looks like when interlaced. A caution that trying to deinterlace fast moving footage like sports can only do so much. You may not necessarily like the look when deinterlaced, even with a fantastic deinterlacer like QTGMC. You may prefer to leave it interlaced in an MPEG2 format and let your player deinterlace it for you. Again, plenty of knowledge/education to be had if you search the forum.

Best of luck to you.
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  #7  
01-12-2020, 11:56 AM
Ntierney Ntierney is offline
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Keaton, thanks that was very helpful. Does this head switching noise get cropped out on initial capture in AVI from Vitural Dub or after when performing the restoration / clean up stage?
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  #8  
01-12-2020, 02:05 PM
sanlyn sanlyn is offline
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Head-switching noise and other border cleanups are done in post processing. You either crop off bad borders and restore them with new borders in Avisynth, or crop and mask in VirtualDub.
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  #9  
01-12-2020, 07:03 PM
Ntierney Ntierney is offline
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thanks sanlyn. Thanks everyone also this is a great sight and resource.
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