Quantcast Jitter on capture, but not on tv? - digitalFAQ Forum
  #1  
04-09-2017, 11:16 AM
tnxyz tnxyz is offline
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hey everyone!

i'm new here and don't have the in-depth knowledge about digitizing vhs and, frankly put, i need your assistance. please spare with me.

i'm trying to digitize a couple of home videos, using a blaupunkt rtv-965, s-vhs, elgato video capture via virtualdub and the huffyuv codec. my issue is that i get hoizontal jitter on the actual digital picture whereas it plays just fine on tv (played side by side). not constantly, but when the person filming is moving.

i really don't know what issue is. is it the output from the vhs recorder/player or the elgato hardware?

when i adjust the tracking in real time, it's visible on tv as well as on my computer.

i'd be really grateful for any advice you're willing to offer.

best regards,
tn

Last edited by tnxyz; 04-09-2017 at 11:32 AM.
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  #2  
04-10-2017, 03:08 AM
sanlyn sanlyn is offline
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Your TV is a very forgiving device that isn't trying to translate and render a new, hard digital copy of your VCR's signal. Your capture device and capture software are a different story and aren't translating the analog input signal in the same way. Defects in the signal are interpreted as defects in the digital domain -- it isn't your capture card's job to clean up your signal's frame timing for you. That would be a task for an external frame-level TBC designed to correct signal timing in analog source. Your VCR has an internal line-level tbc that cleans scanline timing sync within frames -- that is, it corrects image errors but doesn't 't correct frame flow errors. VHS capture requires both types of tbc. You need a frame sync tbc.

That's the guess analysis anyone can offer without an actual video sample of what you refer to as "jitter'.
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04-11-2017, 07:02 AM
tnxyz tnxyz is offline
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sanlyn, thank you for your input.

although i was aware of the fact that tvs tend to sugarcoat the analog signal, i regarded it as normal since i have this "jitter" on almost every home video, but this is the first time a tape plays smoothly on tv. on second thought i'd identify it as tearing though.

i will provide a sample, possibly tonight or tomorrow.

again, thanks a lot!
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04-11-2017, 05:14 PM
tnxyz tnxyz is offline
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here's a short sample of the particular passage.


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File Type: mp4 vhs_distortion.mp4 (11.06 MB, 29 downloads)
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04-11-2017, 05:53 PM
sanlyn sanlyn is offline
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Thanks for the sample. That disturbance isn't jitter. It's frame skew.

A tape or portions of it can be in such terrible shape that it sends signal spikes and timing disruptions that capture devices often translate as copy protection garbage. That's the way it looks to me. You would need an external frame-level tbc that can defeat copy protection by rebuilding the signal. I had a few home-made, non-copy protected tapes that gave me similar effects during capture. I fixed it by inserting my AVT-8710 into the capture chain. The hassle is finding an AVT-8710 or TBC-1000, or similar device, that hasn't been burned up or still has good circuitry. A pass-thru unit such as a Panasonic ES10 likely won't do the trick.
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04-11-2017, 06:14 PM
tnxyz tnxyz is offline
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first of all, thanks for the clarification, sanlyn!

but dang, i thought an ES10 in pass-thru could fix it since i could get one for just a couple of bucks.
i guess i'll just give it a try and should i get the same results, i'll have to invest some more to get an AVT-8710 / CTB-100.

what do you think?
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04-11-2017, 06:35 PM
sanlyn sanlyn is offline
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You can try it, but like most pass-thru's the ES10 won't defeat copy protection. Tell you what, however -- an ES10 is so handy it's unbelievable. For one thing, you're not tied to that one VCR for a line tbc. If your super-player won't track a tape, often a lesser player will and could make use of the ES10's rather hefty line tbc and decent frame sync. My ES10 has come in handy countless times with bad tapes and a different VCR.
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04-11-2017, 07:42 PM
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i'll give it a try, because what kinds of tapes are more sacred than personal / home tapes?

i'll definitely provide you with an update on how that turned out.

however, if this fails to give me clean(er) results, do you have any idea how to purchase one of those external and preferred TBCs in europe?
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04-12-2017, 07:23 AM
sanlyn sanlyn is offline
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For a pas-thru legacy DVD ES10 or ES15, a European PAL version is required. The ES15, by the way, is rated second to the ES10 but is still effective. Other units have been used such as older 2004-2005 Toshiba RD-X series but they aren't as powerful.

The AVT-8710 and DataVideo units such as the TBC-1000 accept both PAL and NTSC. The reason for the popularity of those products was that they were optimized for work such as analog source capture and were even more ideal for that purpose than most pro shop units, besides costing far less than pro gear. But that was during the hayday of VHS transfer. Since those days the same products have either changed hands or stopped manufacture. The newer units had serious quality control issues that most readers here are familiar with. If you can find a unit that definitely works as intended you've found what many newcomers are looking for, but at a premium price. My ancient AVT-8710 is a black and green 2004 issue that still works, but those are tough to find. So caution is advised. If you find a cheapie at a low price on an auction site, be very wary of its condition. There are many complains about such units, and newly made units are a lottery because of poor quality control. You can often find certifiably working 8710's and DataVideo units sold in digitalfaq's marketplace forum.

If only one or two tapes are at issue it's probably cheaper to use digitalfaq's lossless transfer service as a far more economical option. I don't work for their service but I've used them in the past, and they make transfers at a pro level the way it's supposed to be done. The average transfer service typically does horrible work.
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04-13-2017, 06:12 PM
tnxyz tnxyz is offline
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again, thank you for all your assistance!

i got my hands on an ES10, set it up in pass-thru mode and voilą -- it fixed the issue!
i attached another sample.

by its nature, the ES10 cuts off a few pixels on the left, but i could live with that.

however -- and i don't know what the proper term is -- the horizontal line (timing error? tracking error?) at 2.280 bothers me.
is there any way to fix it?


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File Type: mp4 vhs_distortion_pass-thru_es10.mp4 (10.71 MB, 19 downloads)
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  #11  
04-13-2017, 06:29 PM
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Quote:
at 2.280
Where?

Post a still on what you're talking about.
Hint: Greenshot works well for snapshot with markup.

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  #12  
04-13-2017, 06:48 PM
tnxyz tnxyz is offline
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here's a still of the frame i'm talking about.
it's the line in the upper part of the video.

sorry, i should have posted it in the first place.


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File Type: png vhs_horizontal_error.png (919.9 KB, 12 downloads)
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  #13  
04-14-2017, 03:12 AM
sanlyn sanlyn is offline
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From the looks of the tape damage, you're lucky you have a stable video at all. Looks as if the ES10 is earning its keep.

There are horizontal black lines in frames 57-58, 333-334, 339-340, and a little guy in the upper right sky in frame 462. VirtualDub's frame counter is handy for describing this sort of thing.

There is magenta moire discoloration in the brights, and alternating frames have additional magenta stains.

The upper-left border has visible flicker, especially the first 4 seconds, but that's easy to fix.

Of course you have black side borders, as standard def SMPTE standard in most viewing systems populates only 704 pixels of a 720-pixel frame. While that doesn't sound like much, is actually 97.8%. There's an unstable twitter in the right border, but that can be fixed too.

If you're setting your capture luma levels, the black level values are high at around RGB 28 and the image looks washed out. Apparently you might have allowed the black borders and head-switching noise to affect your capture histogram if you're using one (if you aren't, better get used to checking with it). Somewhere you do have zero-level blacks but only in alternating fields, and I can't tell where they're coming from offhand. It's possible that the IRE output levels in the ES10 aren't adjusted properly, but without notes on the capture-time levels setup or your ES10's menu, that's just a guess.

Watch your encoding. Your sample is interlaced video encoded as progressive. If your final target output is for DVD or BluRay, the 44.1 KHz audio is invalid for those formats.

There are Avisynth filters that can help with almost all of these disturbances, but you'll find that working with lossy encoded long-GOP video will have a considerable quality cost after post-processing. But I understand that the mp4 is a demo only.

Last edited by sanlyn; 04-14-2017 at 03:37 AM.
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