TBC's with horizontal line dropout compensation?

[aramkolt]

I've seen a few models of TBC claim to have "dropout compensation" or "DOC" which I believe means they take any missing horizontal lines and replay only the missing lines from the prior frame. Without that, you get a sort of darkened or discolored horizontal line in your final output when there are magnetic dropouts on the tape.

I know that they are due to the tape itself because I can play the tape back and it will have those missing lines in the same frames each time they are played back.

Seems that prevention of horizontal line dropouts is one of the best things at least I could do to improve my captures, so wondering if anyone has solutions that work particularly well for that?

I believe the DVD recorder passthrough like the DMR-ES10 can reduce them (since it essentially digitizes it, then converts back to analog I believe), but some details are also lost and I'd prefer to keep devices in the chain to a minimum if there otherwise isn't any tearing/flagging going on.

So my question is mainly whether anyone has had good experience from standalone TBCs having excellent "horizontal line dropout compensation" or if there's some setting within the JVCs that allow them to handle the line dropouts better?

Also, do the recommended TBC-1000 and AVT-8710 do anything for these line dropouts? I figured they would advertise this function if they had it?

[lordsmurf]

I'm sure you're referring to DPS (Leitch) units here. I wanted to see what DOC could do, about 15-20 years ago (mid 2000s), and bought (and immediately resold that year) multiple TBCs for testing. All disappointing results, most of them make quality worse or added errors, since not made for consumer analog sources like VHS.

DOC is internal to VHS VCRs.

DOC in TBCs is mostly intended for players that lack DOC, such as U-matic, and incorporated into special broadcast (rackmount, "pizza box") TBC appliances. Very often, the DOC is a separate component, either added to the TBC housing, or as external unit.

DOC is not really a function of TBCs.

TBCs like DataVideo TBC-1000 and AVT-8710 are frame TBCs, whole-frame corrections, advanced frame stores. DOC is not something those address.

DVD recorders may have DOC as a function to help MPEG encoding, but I've never seen it. It's pretty easy to generate false dropouts with the Samsung 5000W, and nothing I have will correct for it. Nor do I expect it to.

Avisynth work has developed around this issue, but it is extremely fiddly. I've never been able to use the same script twice, which is a reason I've never bothered to share it. (Noting it's based on work by others, my Avisynth-fu is not the best at from-scratch scripting for complex operations.)

[aramkolt]

Yeah, it's interesting that some TBCs claim to have this function and have a separate "DOC" BNC connection which is essentially the same RF tap that VHS-Decode uses, so I think you could add that to just about any VCR. I think the way it works is that the drop in the RF tells the TBC which lines aren't there in the current frame and to replay them from the prior frame.

Seems all VCRs kind of handle dropouts differently internally. The JVCs I've tried seem to have visible dropouts present in the raw output by repeating the same line until it gets a good signal to continue, so it doesn't pull the lines from prior buffered frames (which would look more natural).

DPS ones I don't believe have the separate "DOC" port, so I'm not sure how it knows if there is a dropout. With the JVCs repeating the last known good line in their output, the TBC wouldn't see that as a dropout since it's getting good lines and they don't know that they were just repeated. It's almost like if you were having the TBC do the dropout correction, you'd want the VCR to pass the dropouts along in the signal so the TBC knows to substitute the line from the previous frame.

I'm planning to try a variety of VCRs and in-line equipment to see if I can narrow down specifically if certain brands handle dropouts better, though I wouldn't be too surprised if the winner is a DMR-ES10 passthrough at the cost of loss of detail.

I do want to try a TBC with a DOC port as well just to see if that theoretically works the way I think it does or not.