TBC hardware: "velocity error correction" (calling jagabo)

[PuzZLeR]

Ok, granted, perhaps this is confusing.

I meant 0+ to be > 0.

[lordsmurf]

I'm not following you.

Going back to delay, video is analog, and audio is not 100% perfect anyway. A delay of a frame or two isn't going to do anything. Video already varies as it is, as we're only talking in rounded numbers anyway. Even "25fps" is not exactly 25.0∞. Hardware has to on-the-fly vary values to maintain the sync.

I just bought "Video and Camcorder Servicing and Technology" for a few bucks. It actually looked decent from the previews I saw.

[PuzZLeR]

Either you don't understand the simple concept of a "buffer", which you can research on your own, or this is another silly attempt to troll me, like you try thread after thread.

[pandy]

Either you don't understand the simple concept of a "buffer", which you can research on your own, or this is another silly attempt to troll me, like you try thread after thread.

Buffer size for 1 line is (depends from sampling rate and bit depth) somewhere between few hundred bytes and less than 10kB.
As video slicer knows exactly where horizontal sync pulses are in incoming signal and as it also knows where it should be then it is able to compensate most if not all problems related to timing - in all consumer VCR technologies 1 video track on tape is exactly 1 video field long as such 1 line error is quite linear and relatively easy to correct.

[lordsmurf]

Either you don't understand the simple concept of a "buffer", which you can research on your own, or this is another silly attempt to troll me, like you try thread after thread.

Stop being an ass. I don't remember you being this way in years past.

I never "troll" anybody, and honestly have no idea what you're going on about. You're rambling, and I'd honestly like you to clarify. Otherwise, I'll just ignore this thread, as it seems others have done.

At very least, thanks for mentioning "that book". It looks nice.

As far as I know, standard VHS frame buffer is a whole field, not just a line. But all buffers vary, hence "line TBC" (JVC) and the field TBC (multi-line) used by Panasonic. Not that it matters, seeing as how both correct timing fairly well.

davideck may be useful in this thread.

He and I use to disagree, and it was because of simpleton terms ("TBC") instead of calling them what they were ("frame sync TBC", "frame sync", etc). Perhaps "velocity error correction" is yet again another refinements in definition, but for purpose of practicality it means little.

[PuzZLeR]

I don't remember you being this way in years past. I never "troll" anybody, and honestly have no idea what you're going on about.

Then I'll take the blame for expecting someone like you to have understood what I meant already several posts ago. Perhaps “trolling” may be a strong word towards a long term member, but I don’t believe I’m being difficult when I was pointing out that this chiming in of yours was rather unnecessary, and rather frequent activity from you towards me, and towards several others who’ve disagreed with you on VHS capture (VCRs, video formats, processing, including TBCs, etc).

I will agree with you on the SignVideo proc amp. Very nice.

You're rambling, and I'd honestly like you to clarify. Otherwise, I'll just ignore this thread, as it seems others have done.

Well, maybe you yourself expected more from me. I can take that as a compliment then.

I was referring to a buffer in how you'd need to hold on to a few bits of info to process, whether it's 100+bytes, or 10kb that Pandy mentions, or even the whole capture itself, after the fact, which can be a "buffer" in some capacity. Perhaps haphazard in delievery, but at least Jagabo, whether he agrees or disagrees, at least got my gist long before.

Now for sure I feel like I'm rambling...

At very least, thanks for mentioning "that book". It looks nice.

Who are you thanking? Me? I'm touched.

Well, my friend, it's clear that you didn’t read the thread properly before you chimed in, which would have alleviated our audience of some of my so-called “rambling” in the first place.

As far as I know, standard VHS frame buffer is a whole field, not just a line. But all buffers vary, hence "line TBC" (JVC) and the field TBC (multi-line) used by Panasonic. Not that it matters, seeing as how both correct timing fairly well.

Fairly well?

Uh oh. And this may be the problem you have with me, when I post that, no, these TBCs you support, stand-alone and onboard VCRs, don’t perform “fairly well”. There’s enough evidence to suggest otherwise. Sorry.

For onboard TBCs, the JVC’s line-based and the 1980’s full-field/half-frame based both do major damage to captures – bad spots, more jitter, color banding, messing up field order, etc. Also, the full-frame stand-alone TBCs: the DataVideo TBC-1000 softens video, and the AV Toolbox AVT-8710 has multiple serious issues such as morphing among others.

Yes, the 8710 TBC does indeed have an obvious “other buffer” that holds onto frames it deems “bad” till the next one that it deems is “good”, and morphs them together creating noticeable, and unsightly, artifacts.

And none of them totally cure this quiver mentioned in this thread.

And no, it’s not due to my gear being “defective”. Well, some of it is now, but that's after the fact - and another tale.

davideck may be useful in this thread.

He and I use to disagree, and it was because of simpleton terms ("TBC") instead of calling them what they were ("frame sync TBC", "frame sync", etc). Perhaps "velocity error correction" is yet again another refinements in definition, but for purpose of practicality it means little.

And there you go again, digressing. Not trying to be mean, and I totally appreciate your fiery passion for this, but really.

Maybe I'm being extreme, but again, this feels like a preamble to your next post being that since davideck, gshelley, you, and others, have been inactive for a time, this forum deteriorated in knowledge.

If you’re in touch with them, then please, ask them to join in here. I will listen. Honestly, if this heathen is indeed chirping nonsense then I wouldn't mind being schooled by them.

[davideck]

Hello everyone! How are you LS? This has been a fun thread.

My experience with velocity errors is primarily on Direct Color Type C Professional VTRs, where timebase errors of a few nanoseconds would cause noticeable hue shifts in the color subcarrier. A linear interpolation from line to line worked very well. Attempts to incorporate a 2nd order component proved difficult to align in practice with little if any noticeable improvement. But that was long ago.

It is hard for me to imagine how a VHS scanner spinning at 30 revolutions per second and painting 525 lines per revolution could possibly create velocity errors across each line with anything near the frequency and magnitude shown in the image in post #1. Are people actually noticing these types of distortions?

[jagabo]

It is hard for me to imagine how a VHS scanner spinning at 30 revolutions per second and painting 525 lines per revolution could possibly create velocity errors across each line with anything near the frequency and magnitude shown in the image in post #1. Are people actually noticing these types of distortions?

I'm sure it's an exaggeration for demonstration purposes.

[PuzZLeR]

Hi davideck.

Are people actually noticing these types of distortions?

On a much more "micro" view yes, which would be the "quiver/wiggle/jitter", but not at that scale. Again, like Jagabo said, I too believe the demo is for hypothetical purposes.

I haven't decided whether it's an exagerrated jitter, or an exagerrated flagging myself. However, I imagine flagging would be at the transfer or even the analog-to-digital level anyway, not necessarily with the tape itself.

[davideck]

It is true that variations in scanner speed will stretch or shrink the lines. However, due to the mechanical inertia of the scanner, I would expect the distortions to be lower frequency, creating jitter or wobble in the time domain from frame to frame rather than waviness or jaggedness in the spatial domain from line to line (top to bottom) as shown in post #1. I can't say that I've ever encountered this.

It is also true that noisy or unstable sync edges can upset the sampling clock generation of a TBC device, causing it to add its own instability into the mix and making matters worse. These errors can be higher frequency, creating spatial as well as temporal distortions. This I have encountered on my own marginal tapes. While some TBC devices made things noticeably worse, others made things noticeably better.

YMMV

[PuzZLeR]

It is also true that noisy or unstable sync edges can upset the sampling clock generation of a TBC device, causing it to add its own instability into the mix and making matters worse. These errors can be higher frequency, creating spatial as well as temporal distortions. This I have encountered on my own marginal tapes.

Interesting you bring this up.

I'm not sure if you have a JVC pro-deck, but find its (line-based) onboard TBC guilty of this behavior. I've called it "overcompensating" in other threads, and yes, also have mentioned a higher frequency lower radius jitter it produces.

I can't tell with my own eyes, but, as per this thread, maybe it is indeed a left or right edge not corrected that is causing this.

Yes, this varies per tape, but honestly, I find it's better not to activate this particular TBC for a mass majority of tapes.

[davideck]

That is interesting. The JVC TBC worked great on my tapes, some of which had significant jitter introduced during record due to a faulty transport. I'm just not a big fan of the DNR. I prefer my Panasonic AG-1970.

I wonder what kind of timebase errors you're dealing with. Are these Camcorder tapes, or copy protected, or second generation?

Have you tried a Philips or Magnavox DVD Recorder?

[PuzZLeR]

Been away for a bit, and wanted to do some tests, but revive this discussion with some samples.

That is interesting. The JVC TBC worked great on my tapes, some of which had significant jitter introduced during record due to a faulty transport. I'm just not a big fan of the DNR.

I wonder what kind of timebase errors you're dealing with. Are these Camcorder tapes, or copy protected, or second generation?

The tapes are old, beaten up, VHS, mostly EP TV recordings here, and I've attached a few samples, each a "vignette" of clips from various tapes, each captured 5 times, and have had median methods applied to remove random playback quirks. For easy upload, each was compressed to H.264, but hopefully it's good enough for demonstration.

Notice the JVC's TBC has some serious issues: lots of jitter in high frequency, low radius, flavor, applying (skewed or overcompensating) velocity error correction or not, I don't know. Also, some bad spots (like the number in the workout video), and some color banding (such as in the top of the soccer clip), and other quirks (depending on tape). I prefer these clips with the TBC off. Am I missing something?

I wish I could show errors with the TBC of both my Panasonic 1980 units messing up field order, but one is in such bad condition now, and the other is dead. (I have no intention to replace them.)

But I did upload some stuff on this here.

I prefer my Panasonic AG-1970.

This, in theory, is appealing to me since it's like a 1980 with no DNR (of which I too am not a fan of.)

However, I've had no luck with this machine. Either it was just horrible, or likely a very abused used model by the time I got it. It now has a transport problem loading tapes, but still found a couple of these clips captured a while ago, and provide a sample. I couldn't believe how bad the quality was, even when the tapes were in better shape then.

Again, it could be likely a burned out unit causing such artifacts. (These too were captured 5x, median methods, and compressed.)

Have you tried a Philips or Magnavox DVD Recorder?

Nope. Tried pro and consumer VCRs from JVC, Mitsubishi and Panasonic, and consumer models from Toshiba, Memorex, Sharp, GE, Samsung, and others, and use a Panasonic ES15 DvD recorder as a passthrough TBC, but never tried these.

My prefered scheme is the Panasonic PV-V4520 - nice crisp clear capture - that, and the ES15 in passthrough. I can provide a sample if anyone likes.

But, if there's anything special about the Philips or Magnavox units, please enlighten me.

[Brad]

Interlaced content encoded in progressive mode. For shame!

The fact that the dots on the workout timer disappear with TBC off is bizarre.

[PuzZLeR]

Hi Vaporeon800.

Interlaced content encoded in progressive mode. For shame!

True. Very true. Just ran it quick and dirty through HandBrake at, mostly, default settings. I honestly would've taken the encode more seriously if it was part of the topic, but yeah could do better. If it's an issue, then I can upload better samples.

The fact that the dots on the workout timer disappear with TBC off is bizarre.

It's more a fact that the TBC adds them. I don't think they're part of the source. I notice this with other flat-like tiles/backgrounds as well.

[davideck]

I prefer these clips with the TBC off. Am I missing something?...if there's anything special about the Philips or Magnavox units, please enlighten me.

Both JVC captures seem to have marginal tracking during the bottom 1/4 of each field/frame. At least during the soccer section. I prefer the TBC Off as well.

The AG-1970 looks to be tracking better.

My Philips HDD/DVD Recorder had the best line by line correction that I saw with my VCRs and tapes, but the ES15 might be just as good. I've never tried one.

[Brad]

I bought the same model as your posts had mentioned, I believe. DVDR3575H?

It suffers from what I will term Funai Flicker with my camcorder tapes.
https://forum.videohelp.com/threads/374205-Weird-stuff-happening-during-VHS-to-DVD-tran...ai#post2420343

I haven't directly compared line TBC performance with my Panasonics yet.

For extremely bad, nth-gen tapes, Panasonic is preferable simply because the "Blue Background" can be disabled. The Philips gives up too easily, resulting in flashes to its blue screen where the Panasonic provides some sort of picture even when the input is completely garbled.

[lordsmurf]

I only use the Philips 3575 with hard drive as a DVD DVR.
I tested it back in 2007 on VHS tapes, even retail ones, and it was horrid.