TBC Issue?

[stiltzkin]

Hi there,

I hope the Capture forum is the right place to post this. I'm new here and also new to the process of digitizing VHS tapes.

I recently picked up a Panasonic AG-7650P for very cheap at auction, and I've been very happy with the results from it so far. It does a fantastic job on my home movies. I'm using a Diamond VC500 for capture.

However I've noticed that on a particular tape, which is a commercial release, I'm getting some pretty bad jitter on the top ~55 lines of the frame intermittently throughout the video. This is not constant throughout the whole playback of the film; it only appears in certain scenes and it comes and goes. Here's a screenshot:


[Attachment 50623 - Click to enlarge]

I attached two video samples from the same scene. The first sample is with the TBC enabled on the Panasonic. Notice the lines skewed out of place at the top of the frame.
The second sample is with the TBC disabled (set to Bypass). Obviously the video quality suffers tremendously and the frame is warped to the left as it's not being corrected. However, the skewed lines disappear and I don't see any damage to the video near the top.

So my noob question here is: what does this indicate?

Would this point to a problem with the TBC? I haven't noticed this issue yet on any other tapes, although I'm still testing.
Would it indicate damage to the tape I'm trying to play back, which is confusing the TBC?
Would it indicate something else, like a dirty playback head, etc? I am getting what I'd consider stellar quality video from this thing other than those lines when playing this tape.

I've tried my hand at eliminating the jitter in Avisynth using DeJitter and some other filters, but haven't had much luck. It would be much better to eliminate this problem at the source, in hardware.

Very much appreciate your suggestions!

[Brad]

Probably Macrovision confusing the line TBC. Macrovision lives in the Vertical Blanking Interval above the active video area.

This page says the TBC in your VCR blanks out the VBI: https://www.cameratim.com/electronics/panasonic-ag7650-ag7750-vtrs/modifications#tbc-v...tical-blanking

So I guess it does this VBI regeneration after the line correction has already processed the raw signal containing MV.

I assume this is also why the bypassed video sample is blown out, unless you changed proc amp settings between the two captures.

[Eric-jan]

Looks like this is in the recording/tape itself, because you see it change at different scenes/camera positions.
so it's no fault in the capture.
at least in the 1st mkv clip, the 2nd clip i don't know.
You know for sure all hardware is allright ? no misallinement ?

[stiltzkin]

Probably Macrovision confusing the line TBC. Macrovision lives in the Vertical Blanking Interval above the active video area.

This page says the TBC in your VCR blanks out the VBI: https://www.cameratim.com/electronics/panasonic-ag7650-ag7750-vtrs/modifications#tbc-v...tical-blanking

So I guess it does this VBI regeneration after the line correction has already processed the raw signal containing MV.

I assume this is also why the bypassed video sample is blown out, unless you changed proc amp settings between the two captures.

Thanks for this info, that's interesting. I did not change any proc amp settings between those captures, so that would seem to support your statement. Is there a reference I can look at somewhere to see if this film indeed had Macrovision? I'll have to try some other commercial releases.

Looks like this is in the recording/tape itself, because you see it change at different scenes/camera positions.
so it's no fault in the capture.
at least in the 1st mkv clip, the 2nd clip i don't know.
You know for sure all hardware is allright ? no misallinement ?

That was my suspicion, that this has something to do with the tape and not the deck. I have not opened this unit; it seems to be in great condition and I've done some home tape captures from it that look fantastic. That's all I have in support of it being in good mechanical shape.

The distorted lines are not that bad, and the film would be watchable, except that I think they are heavily confusing QTGMC in my script, so in scenes where the lines show up, the deinterlacing produces really choppy, bad video. That's more of a problem than the visual distortion itself.

[stiltzkin]

Here's two more samples from a different scene where the distortion shows up, again with and without the TBC. I captured these one after the other just to double check that I hadn't changed any proc amp settings. I also realized I had a lingering Crop() command in my script before I posted the previous samples, and it's probably better to post unaltered video.

[Brad]

I started a thread; maybe you can tell me if the wording makes any sense: https://forum.videohelp.com/threads/394768-Tricks-to-check-if-a-tape-has-Macrovision

Both of your uncropped samples have the "white block" in the head-switching area that's a clue your tape is MV-protected.

[stiltzkin]

I started a thread; maybe you can tell me if the wording makes any sense: https://forum.videohelp.com/threads/394768-Tricks-to-check-if-a-tape-has-Macrovision

Both of your uncropped samples have the "white block" in the head-switching area that's a clue your tape is MV-protected.

Yup, you were right. And yes, your new thread makes sense as well. I can see it on the 7650 just by fast forwarding and looking at the top of the frame - the telltale white blocks fading in and out are right there (see attachment).

So - is there anything I can do about this? Since the TBC is not fully bypassing it, is there any value in looking at an external Macrovision defeat device?

I determined that this was not in fact messing with the deinterlacer at all, avisynth was just defaulting to the wrong field order. So the capture is almost perfect now.

[Brad]

is there anything I can do about this? Since the TBC is not fully bypassing it, is there any value in looking at an external Macrovision defeat device?

Trouble is, you have to disable the VCR's TBC. Chaining a Macrovision remover after the fact won't help with the skewed lines, as the skew is already baked-in at that point.

I don't know of a good solution that isn't expensive or difficult.

[KarMa]

See here https://forum.videohelp.com/threads/394628-What-s-the-best-Capture-Card-Software-combo...re#post2562665

And proof it doesn't care about macrovision. https://forum.videohelp.com/threads/394768-Tricks-to-check-if-a-tape-has-Macrovision#post2563844

[oln]

Using a Panasonic DMR-ES10/15 or other DVD-Recorder for TBC passthrough (with VCR tbc off) with a card that doesn't mind macrovision is one not too expensive option. The DVD-Recorders typically re-create the macrovision signal so you would need a capture card that doesn't mind it, the VC500 may be fine for that.

[lordsmurf]

Using a Panasonic DMR-ES10/15 or other DVD-Recorder for TBC passthrough (with VCR tbc off) with a card that doesn't mind macrovision is one not too expensive option. The DVD-Recorders typically re-create the macrovision signal so you would need a capture card that doesn't mind it, the VC500 may be fine for that.

The ES10/15 does not defeat/remove Macrovision. It obeys it.

The VC500 has issues, including AGC.

It's really not possible to avoid a true TBC. Many try, many fail.

[Brad]

Using a Panasonic DMR-ES10/15 or other DVD-Recorder for TBC passthrough (with VCR tbc off) with a card that doesn't mind macrovision is one not too expensive option. The DVD-Recorders typically re-create the macrovision signal so you would need a capture card that doesn't mind it, the VC500 may be fine for that.

With NTSC Macrovision tapes, the Panasonics blow out brights, clipping them internally: https://forum.videohelp.com/threads/364477-Panasonic-DMR-ES15/page2#post2341556

At least, the North American models do. Maybe the Euro models don't do it even with NTSC content.

The VC500 reacts the same way, as seen In this thread's samples of the TBC-bypassed captures and from my own experience.

KarMa's suggestion is a potentially "good enough" solution, if the raw VCR playback jitter of this tape remains below the level of what the capture card can handle. The result may be relatively horizontally stable. More jittery playback is too much for the card to straighten, as shown in his Video8 screenshots: https://forum.videohelp.com/threads/381533-Video8-Player-vs-Digital8-Camcorder-for-capturing-Video8

[oln]

Yeah there may be a PAL vs NTSC difference then, I shouldn't have assumed that it would nescesarilly work the same in NTSC and PAL. Granted, it's possible there may be differences between macrovision versions too, I've only really needed the ES10's jitter correction on home-recorded tapes. I don't remember had issues with the VC500 blowing out whites on macrovision either with PAL, but I can see it on the posted video and other NTSC samples. Maybe it has something to do with NTSC using 7.5 IRE for black level and some of the macrovision signal macrovision stepping below that but still staying above 0 IRE to not screw with Horizontal sync and thus making the AGC think the black level is lower than it actually is.

EDIT: Seems macrovision does dip lower than 0 IRE and down to the same level as the bottom of hsync.

[jwillis84]

Those look like VBI lines to me, teletext or something, maybe close caption.

[stiltzkin]

It's really not possible to avoid a true TBC. Many try, many fail.

A "true" TBC is what I hoped that I was getting with this Panasonic, but I guess that's not the case? As a matter of fact, when I saw this VCR at auction, I checked to see if it was in your very nice VCR Buying Guide list over at DigitalFAQ, and it was, listed as having "full-field (multi-line) TBC instead of a standard line TBC."

What would you recommend? I've seen the DataVideo TBC-1000 mentioned in some posts on this forum (probably your posts) from years ago, but I no longer see anywhere I can buy one online. Unless you've got more to sell?

[stiltzkin]

I've since added a JVC HR-S9500U to my collection. Here's the same problematic scene captured on the JVC with the TBC turned on:


[Attachment 51301 - Click to enlarge]

See attached clip, as well.

Turning the TBC off gives basically the same result as the Panasonic.

So - what gives here - is this an issue with this particular tape? Are these decks not capable of dealing with the variant of Macrovision on this release? My capture card shouldn't care about Macrovision at all. Is something else wrong with my setup? Not sure how to proceed.

[lordsmurf]

You need this chain:

S-VHS VCR (for stable transport), probably still better/higher with-TBC mode
> ES10/15 for anti-tearing, line TBC(ish)
> external framesync TBC
> known-good quality capture card

Also via s-video, not composite.

But you also need to realize that not all copies of commercial titles act the same. You may just have a bad copy of the tape. It happens. The most common issue if the MV signal is corrupt in some weird way, and nothing can correct it. It's not unusual for the tape to even play badly direct from a plain VCR to the CRT TV, as it was designed to do. Again, it happens.

Inversely, sometimes all copies of a title are fubar. That also happens.

DataVideo TBC-1000 is fine, good TBC, but there are also some others (example: green AVT-8710).

Nothing here is something I've not seen before.

[stiltzkin]

I've gone ahead and ordered another copy of this film - hopefully should help address whether or not this is an issue with this particular tape. $5 VHS is significantly less investment than a >$500 piece of equipment that I don't seem to need for any other tape but this one.

[Eric-jan]

@stilzkin: since you have a second version soon of the tape, at the price of you sending me that tape (if it still has MacroVision) i can transfer it for you, my combo recorder defeats MacroVision. and i capture over component video into ProRes422 LT (virtual lossless) or i also convert to MP4, by WeTransfer i can send you the file, the capture will be in progressive mode, NTSC or PAL, i can do both.

btw. tape (VHS) recorded speed should be normal.

[stiltzkin]

@stilzkin: since you have a second version soon of the tape, at the price of you sending me that tape (if it still has MacroVision) i can transfer it for you, my combo recorder defeats MacroVision. and i capture over component video into ProRes422 LT (virtual lossless) or i also convert to MP4, by WeTransfer i can send you the file, the capture will be in progressive mode, NTSC or PAL, i can do both.

btw. tape (VHS) recorded speed should be normal.

Thanks, I appreciate the offer! Let me take a look at this second copy when it comes in, and if the problem is with my equipment and not with any one particular copy, I might be interested in that.