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Vertical lines artifacts capturing VHS

 
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Slennox
(MXO2 Mini)




Joined: 04 Jul 2005
Posts: 5

PostPosted: Fri Nov 20, 2015 2:40 pm    Post subject: Vertical lines artifacts capturing VHS Reply with quote

Hello.

Trying to get support to a common problem (but without a known solution/workaround) some users had reported regarding VHS captures. See here, here or here.

My setup is as follows:

Panasonic NV-FJ625 (composite) -> Matrox MXO2 Mini ('Capture unstable video signals' has to be checked) -> Adobe CC 2014/Vetura/whatever

I am getting vertical white lines artifacts, like some kind of noise, with every single VHS tape I've tried to capture:



They are very noticeable on reds and vivid colors in general.

None of these lines can be seen when playing the tapes directly on a monitor or a TV.

In that referred topic, user erwin9 did a comprehensive testing and it would seem the likely cause to be related to a software configuration problem instead of a hardware defect of my MXO2 mini (maybe related to the digital noise reduction filter used by the unit).

As I can easily reproduce the problem, I am open to test any new firmware or special configuration I can tweak to try to resolve this problem.

Thank you.
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Slennox
(MXO2 Mini)




Joined: 04 Jul 2005
Posts: 5

PostPosted: Fri Nov 20, 2015 2:53 pm    Post subject: Reply with quote

Another shot of video color bars captured from a VHS tape:

[/img]
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Matrox_Support_Sam
(Moderator)

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Joined: 04 Jul 2005
Posts: 6872

PostPosted: Fri Nov 20, 2015 3:50 pm    Post subject: Reply with quote

We do not have any firmware updates or fixes for this issue. It is likely you are seeing Composite signal limitation, where all video information is encoded on one channel and you experience video artifacting and/or dot crawl.

Composite gives the least quality for analog signals when compared to S-Video or Component. Depending on the source device and footage, you will likely see poorer quality, grainy image and you may be able to see color bleed using the composite signal. Overall, component signal provides much better picture quality than s-video and composite. However, S-Video is better than Composite, therefore, if you have an analog device with S-Video or Component, this would be better.
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Sam
Matrox Video Technical Support
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Slennox
(MXO2 Mini)




Joined: 04 Jul 2005
Posts: 5

PostPosted: Sat Nov 21, 2015 5:31 am    Post subject: Reply with quote

Thank you, Sam.

I've been digging around and indeed these artifacts might happen when capturing analog sources through composite signal if the capturing device cannot properly remove the luma subcarrier from the chroma (luma/chroma crosstalk). Is it possible to tweak the comb filter that should be doing that task?

The workaround should be to use an S-Video signal as input since chroma and luma are physically separated. That means I would need to invest on S-VHS equipment (my current VHS only output composite through SCART).

I'm not satisfied. I would expect MXO2 should do a better job working with the composite signal. At least to have the possibility to adjust the comb filter through configuration options.

As a workaround, and for anyone else interested, decreasing vertical resolution to 360 lines (VHS) and increasing back to 720 (PAL) might remove most of these artifacts. You might have a minimal loose of sharpness/definition though:


Before:




After:

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Matrox_Support_Sam
(Moderator)

Site Admin


Joined: 04 Jul 2005
Posts: 6872

PostPosted: Tue Nov 24, 2015 10:48 am    Post subject: Reply with quote

Although we do not have specific comb filtering setting, the Composite signal meets the specifications as mentioned in our User Guide:
ftp://ftp.matrox.com/pub/video/doc/Matrox%20MXO2%20Installation%20and%20User%20Guide_4.5.1.pdf

As mentioned, the quality you are seeing is not only due to Composite signal, but possibly with other variables such as the source device or footage.

Thank you for the workaround described, tt would appear almost as a progressive signal. We are sure it can be helpful to others.
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Sam
Matrox Video Technical Support
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