Horizontal Red and Green Lines (GV-USB2)

[fundo]

Hello there!

I have some trouble with my current setup for digitizing VHS family tapes. I'm located in Germany, the tapes are PAL. I'm using a Panasonic NV-HS830 directly connected to the capture card via S-Video. As far as I understand, this device doesn't feature any TBC functionality, but I'm not sure. How can I confirm?

For capturing, I have tried:

• EasyCap: Overall low quality, 4:2:0 subsampling
• Hauppauge USB-Live2: Good quality, audio clipping, settings are not persisted (probably a defective device?)
• I-O Data GV-USB2: Good quality

The GV-USB2 is the clear winner for me. Sadly, I am observing horizontal red and green stripes, but only when capturing with the GV-USB2. The stripes are barely noticable at original playback speed because the red and green parts are alternating. Interestingly, the occurrence and distribution of these stripes is the same when capturing the same scene repeatedly. But after a reboot of my PC and the VCR, the pattern changes. Sometimes, it is gone almost entirely. The capture settings are the same every time, and I haven't (yet) investigated whether it is the restart of the VCR or the PC or the capture device changing the pattern. I am capturing with VirtualDub2, but capturing with AmaRecTV gives the exact same result as long as I don't restart my setup.

I have attached two clips and frames of the same scene. Both are recorded with the same hardware and software setup, but a restart of my system has happened in between. The stripes are visible in capture_1 (and the respective frame), especially in the sky.

What could be the root cause for this behavior? Is it the lack of a TBC? Then why am I not seeing it with other capture devices? Or is my capture card defective? Any advice or hint is welcome!

Thank you in advance, and please let me know if I missed out on sharing some crucial info.

fundo

[fundo]

Hello again, I have now tried several times to reproduce the case in which the recording doesn't show the lines. Sadly, I have failed. I have power cycled the VCR, the capture device, the PC multiple times in all possible combinations. The lines are now there in every recording, and recording the same tape multiple times leads to the same pattern. Just to add some more clarity as to what I'm talking about, I'm attaching a frame where it is more obvious. The pattern appears in bright areas, especially the sky, and it also appears on vertical edges, especially those between dark and bright areas. Does anyone have a hint for me?

[Attachment 87996 - Click to enlarge]

[Sharc]

The HS830 has no TBC, therefore you get the horizontal wiggling. Watch the jittery poles.
The horizontal stripes are probably baked onto the tape by the camera. Maybe PAL Hanover bars, but I am not sure. Also, the 2 fields come with a sligtly different hue.
For capture_1 you should probably adjust the luma level (-> 'brightness' and 'contrast' procamp settings of the GV USB-2).
You can improve the stripes in your capture using vinverse().
Something to begin with:

AVISource("capture_1.avi")
ConverttoYV16(interlaced=true)
levels(32,1.1,200,0,235,coring=false)  #for demo only. Should be set right with the procamp settings of the GV-USB2
separatefields()
vinverse()
weave()

As your HS830 has no TBC you could use a DVD recorder in passthrough as a "TBC workaround" to eliminate the wiggling/jitter.

[fundo]

Hi Sharc, thank you so much for your analysis and your sample script! You're right, the proc amp settings are not optimized for this tape, yet. Your observation with the hue being different between the two fields holds true even for the recording in which the combing doesn't appear (capture_4.avi in the original post). Thanks a lot for the hints. I'll deal with those things later.

Thanks for pointing out that the jittery poles indicate that a TBC would be helpful. I'll try to get my hands on one of them. There seem to be many threads like this. Is there by any chance a thread which explains which models are generally appropriate?

But now, back to the color combing. I don't think it is baked into the tape, else I wouldn't be able to occasionally (very rarely!) record the same scene without the lines using the exact same setup and configuration (see capture_4.avi in the original post). In order to confirm this, I just wanted to switch from S-Video to Composite or maybe to a different (worse) VCR that I have access to. And out of the blue, before I even started this test, the lines are gone again in the original setup. See capture_9.avi and attached capture_4_frame_59.png, but it's especially obvious in clip_2_capture_2_frame_50.png.

I have checked what is required to trigger the combing again. I have rewinded the tape, ejected the tape, power cycled the VCR (pulling the plug), restarted VirtualDub2. Only after power cycling the capture device, the issue reappeared. Switching to Composite, the issue is still there. I have tried power cycling the capture device and the VCR again multiple times in any potential order, but the issue is there every time (Composite and S-Video).

To me, it looks like it is an issue with the GV-USB2 unit I have. What do you think?

[Aquilsas]

Hi there,

I've had the exact same issue with my GV-USB2, although I'm now sure it's not a device/hardware problem but something regarding my PC (O.S. maybe? Drivers?), as my Pinnacle 710 also produces that horizontal lines. In addition, I have recently lent my GV-USB2 and the person using it doesn't have this problem on his laptop.

[Sharc]

Hanover bars of PAL video:
https://en.wikipedia.org/wiki/Hanover_bars

[jagabo]

It looks like Hanover bars to me.

SeparateFields()
MergeChroma(Blur(0.0, 1.0).Sharpen(0.0, 0.7))
Weave()