Quantcast Noisy bottom bar on VHS video? - digitalFAQ Forum
  #1  
03-31-2022, 06:59 AM
Cortez Cortez is offline
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Hello Guys,
i have this noisy bar at the bottom of the footage. I think it is a very common problem because a lot of topic was created for that.

I read them so i need just a little assistance to correclty identify the problem and define the appropriate issue handling. Maybe getting information for better understanding

My workflow is:

JVC HR-S9600 -> TBC-1000 -> ATI AIW Capture Card -> MMC 8.1

I am using the VCR with the suggested features turned on. I have two of them so i left one of them untouched because with some cassettes it works fine.

One of the suggestions in these topic were the physical adjustment of the roller.
VHS_m-loading.jpg

Its the 1 Take-Up Adjustable Guide Roller. I marked with 2 the other roller. I didn't touch it because i don't know what is the function of that (maybe adjusting the top of the screen, but that just a rumor) and it has also this tiny wheel on the top of that with screwdriver holes. It starts to spinning when i hit the play button to avoid adjusting it during playback i think.

So i started to adjust the 1 roller with tiny rotations and check the result with capturing. I could eliminate picture jumpings (my grandmother with bad eyesight also notified the jumpy pictures) and could make the bottom noisy bar as thin as possible. If i tried to rotate on full rotation from this position to both direction the bar get thicker and the jumpy picture also came back.

This is the best result i can get from this side, maybe i should try out different feature settings? Maybe set the Picture Control other than SOFT or SHARP as hodgey mentioned As you have a JVC machine, check the "Picture Control" setting in the menu, if it's set to SOFT or SHARP settings there image will be overly blurred.


For the technical background i read two terms to identify this issue: "head switching noise" and "overscan issue". I don't understand the relation of these two, LordSmurf mentioned

Again, I think you may be merging some concepts here. The "overscan" is a physical area outside the boundaries of the normal viewing area. One reason this area is exists is because it can (and usually does) contain various types of noise -- visual artifacts from closed caption pulses, head switching noise, broadcast pillars, etc.

The noise you have here is "head switching noise", which is a technical term for VCRs.


I am thinking about something like that:
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We talked about line and frame TBC earlier. It has any connection with this overscan area around the visible area or these are totally different contexts? What i thought eariler with the roller i can adjust the boundaries or if those are fixed for the image, an another rectangle for pointing at the visible area. Because of this wrong adjustment i see black bar at the bottom in the visible area from the overscan area.

From the software side until now i used MMC 8.1 only with mostly default settings. I found VirtualDub more complicated. But as i see i have to use it because the common method to solve this problem is to mask this bottom area with black color to keep the aspect ration, resolution and others. In MMC i neither set codecs, left them on default, but with HuffYUV and AAC codecs in VirtualDub i can get better quality with bigger file size?

I was confused with that many VirtualDub version but i think the best i can get is this version that was linked many times. No newer or later version.

I was also confused about these "filters" because i didn't know what are these exactly. One of them is this Masking method to remove the bottom bar, so can i say these filters are options to improve quality those MMC doesn't provide?

Finally here is a picture from the captured video, with a tiny noise bar at the bottom
Overscan.png

With the masking i will lose some picture data (at the bottom or at the top)? I don't understand why the noise bar doesn't appeare when on PC's display just playing or capturing the cassette, but visible on the captured footage.

Many many thanks my dear friends for the answers.


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  #2  
03-31-2022, 09:39 AM
latreche34 latreche34 is online now
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This has nothing to do with the VCR or the head switch noise, quite messing with the factory alignment, if you screw it you will never get it back without an oscilloscope and an alignment tape. figure out why your playback software is not displaying the entire frame and post some pictures to show the difference.

https://www.youtube.com/user/latoak34/videos
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  #3  
03-31-2022, 11:16 AM
dpalomaki dpalomaki is offline
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^+1 on not messing with alignment unless you are qualified and equipped to do so and restore it to factory specs.

Over scan is an artifact pf analog TV days and served to allow for variations in TV set alignment. Video was shot and edited with a view to "action safe" and "title safe" areas to ensure the important parts of the image would be visible on all properly aligned analog TV sets. The image portion of the TV signal was comprised of 486 scan lines, about 53 microseconds per visible line (for NTSC), but perhaps 5% (give or take a few percent) were hidden by the typical over scan adjustment both vertical and horizontal.

VCR head switching noise, closed captions, VITC, and data code in analog signals is in the over scan area and would not be visible on a normal TV set. It can be visible in captures and on displays that are configured to capture this over scan area. And professional video monitors offered an option to view the over scan area. This allowed better adjustment of video signals.

Computer graphics systems were not designed with over scan in mind, and typically will show the garbage in the over scan area. However, software and modern HD TV sets and displays often give options to set/adjust and ignore the over scan area content.
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  #4  
03-31-2022, 12:13 PM
traal traal is online now
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I've been thinking about this. On a marginal tape, you can get jitter, both up and down. When the jitter goes down, the visual information is not lost because the scanlines at the bottom go into the head switching noise area, so all you have to do is move the whole field up. But when the jitter goes up, the scanlines at the top are gone and unrecoverable.

So for video capture, would there be a benefit in purposely adjusting the picture area down in order to expose some of the top overscan area and recover lost scanlines when jitter occurs?
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  #5  
03-31-2022, 02:40 PM
latreche34 latreche34 is online now
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There is no usefull video scan lines to expose, My pro gear captures at 486 so there is 6 extra lines on top of each frame reserved for signaling back in the day in a digital broadcast environment such as AR flag, Teletext, caption ...etc, and I have yet to come across a tape that has any usefull video scan lines beyond the 480 used by consumer capture devices. In fact it will be impossible because the VBI scan lines are the ones responsible to tel the capture device to start capturing the first odd video scan line, It cannot be the other way around.

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  #6  
04-01-2022, 05:04 PM
Cortez Cortez is offline
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So first i have to leave the roller at the default position and try to eliminate this bottom ?jitter? from software? I can still use the other S9600 and maybe send the messed up VCR to a service for calibration to set back everything to default. Now i believe, there are no benefits to manually adjust roller for every single tape. It is tiring and i don't want to cause any damage to my VCR.

But before that i should make two capturing with both VCR to see the difference? I used only MMC so maybe i give a try to VirtualDub also. I hope single images would be fine, just try to make snapshots where these bottom ?jitters? are more visible.
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04-02-2022, 03:17 AM
Cortez Cortez is offline
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I just started to capture test samples but VirtualDub's dropped frames increase to 26. When i played the captured video the image stopped with the sound goes on. MMC capturing is okay i think.

Now we are not talking about bottom bar noise, this has to be some technical issue.

I cut out smaller section of the video with VLC to decrease size.

VirtualDub 1.9.11 -
vlc-record-2022-04-02-10h11m46s-vd.avi-.avi

MMC 8.1
vlc-record-2022-04-02-10h12m17s-S-Video (Apr 2).mpg-.mpg


Edit:
Different tape but also CN with other cartoon. Exactly the same.

VirtualDub
vlc-record-2022-04-02-10h26m36s-vd2.avi-.avi

MMC
S-Video (Apr 2) 001.mpg



Last edited by Cortez; 04-02-2022 at 03:29 AM.
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  #8  
04-02-2022, 03:20 PM
latreche34 latreche34 is online now
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Multiple components in the capture chain complicate the troublshooting, test with one at a time to isolate the culprit.

https://www.youtube.com/user/latoak34/videos
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  #9  
04-15-2022, 09:42 AM
Cortez Cortez is offline
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Tragical. I tried three VirtualDub version (1.10.4, 1.9.11, 1.9.10) with and without frame TBC. 1.10.4 doesn't tell any audio or video information during capturing on the right side and the captured video doesn't start at all, only the the audio changes. The other two versions capturing some video but after 10 sec the picture freezing with massive frame drops.

I missed some cirtical VirtualDub setting or the the problem should be outside of VirtualDub (driver, framework, other software)?
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  #10  
04-15-2022, 11:13 AM
Cortez Cortez is offline
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Quote:
Originally Posted by Cortez View Post
Tragical. I tried three VirtualDub version (1.10.4, 1.9.11, 1.9.10) with and without frame TBC. 1.10.4 doesn't tell any audio or video information during capturing on the right side and the captured video doesn't start at all, only the the audio changes. The other two versions capturing some video but after 10 sec the picture freezing with massive frame drops.

I missed some cirtical VirtualDub setting or the the problem should be outside of VirtualDub (driver, framework, other software)?

Edit: I restored the OS to a previous state with default MS drivers and there is no frame drops and the picture don't freeze. Maybe the ATI driver has defect.
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