What problems can TBCs fix vs. not fix?
 

I have a few questions.

Are you able and willing to share samples showing how the AVT-8710 works?

I have seen a few DataVideo TBC 1000s on Ebay, but I am cautious about buying them because nobody has shown that they work other than that they power on. Some of them say that they have been tested, but they have been tested with a DVD or some other digital format, and I am working with VHS tapes, mostly from the 1980s-1990s.

If you can give me proof that I'm making a safe investment, I'm interested. I'm not in the video transfer business, I'm just trying to make sure my grandfather's homemade VHS recordings are preserved.

What problems can these TBCs fix vs. not fix?

Are the external TBCs more important to the workflow than an SVHS VCR with built in TBC?

I am debating whether to sell mine because the TBC doesn't appear to make much of a positive difference other than eliminating Macrovision distortion on commercial tapes, which are not what my project is focused on anyway.

I got this JVC 9800 and a VHS to DVD combo machine from Ebay before I fully understood the perils of that.

Thank you for your time.

Lots to unpack here. :)

And for that reason, I've made this portion of the PM a post, so others can gain knowledge from the long answer this will require...

"Professional"

TBCs are just tools needed for the task of capturing video, and are not "professional" in any way. No more so than a hammer is "professional" because it's also used by people that build houses. It's the same tool for any home DIYer or pro user.

Some people falsely believe TBCs are for "professional users" solely do to costs, and their reasoning/numbers are always arbitrary (and thus silly).
- Cars are not cheap, do only pros drive them?
- Lawnmowers are not cheap, do only pros user them?
- Collecting action figures is not cheap -- so do only comic/toy/hobby stores buy them? (And who would buy from those stores? Other stores?)

A TBC is really no different from a power drill, or hedge trimmers, or a coffee maker. It's just a tool for a task.

In actuality, the user/consumer of most TBCs is home DIY'ers, home hobbyists, and always has been. The DataVideo/Cypress type units recommended on this site were specifically created for consumer sources (VHS, S-VHS, Video8, Hi8, some others), and marketed to those users. That does not make those "consumer TBCs", as opposed to some idea of "pro TBCs" (which are not created for consumer sources, but rather pro sources like BetacamSP, U-matic and sometimes lowly S-VHS). Smaller studio operations used certain TBCs "back in the day", such as on-site duplication of marching band competition videos. And wedding videographers, school broadcast classes, etc. But also lots of home hobbyists, part of their video toolbox.

TBCs were not used by large operations that created retail tapes, as those were mostly made with contact duplication, not recording (and thus why retail tapes have added anti-copy/Macrovision, which is not adding by recording it). More on that later...

So these units were created for you to duplicate grandpa's tapes. In the analog days, it was to dupe the tape for mom, pop, auntie, bro/sis, whoever. Duplicating a VHS>VHS would create massive quality loss on the VHS-only era, so TBC was essential. The digital era is/was the same, but for different reasons. Purifying the signal became more essential, otherwise you may not get a dupe/transfer at all, or it would look far worse than the VCR>VCR method (without TBCs).

TBC pricing was always about 4x the cost of a good VCR. Back then, decades ago, realizing no inflation (so $then dollars is not $now dollars), maybe $200 for a good VCR, $800 for the TBC. That's about accurate. The average cost of a "good" VCR is now about $500 (some minimalist much less, better much more, but average), so $2000 tracks for that 4x number. Inflation for AV/photo gear is 2x+ since the late 90s, so that tracks as well. (The "used" aspect does not matter here, used/new pricing is a separate topic, and with out-of-product in-demand quality AV/photo gear, pricing doesn't drop like a used car or cell phone.)

Types of TBCs

When it comes to TBCs, lots of new users want to "see" what a frame TBC does, but that's actually backwards. Let's back up for a second...

There are 3 main types of TBC
- line
- field (essentially multi-line, sometimes referred to as "infinite window")
- frame

Line and field are essentially the same for the discussion of digitizing VHS/etc -- and no, "more lines" (multi-line) doesn't make field better, just different. There's enough RAM in the field to handle "infinite" lines per field.

While line TBCs can be more effective at correcting per-line issues, a problem often happens that partial lines are mistakenly discarded, causing "jitter" (up/down vertical bouncing; not to be confused the the jargon term "jitter", confusing!). The field TBC expects 50% of a frame, and will only output 50% of a frame. Thus it "senses" the missing line, as it zooms out to take a macro view of the field situation. The mere line TBC is myopic, focusing on each line ("can't the forest through the trees"). Again, not better, just different, as the field now sees just forest and no trees (think Bob Ross, "happy little forest", and splat splat splat with broad brush of green paints, no distinct trees).

Understanding frame TBC (actually frame sync TBC) is helped by understanding what a mere frame sync does. A frame sync grabs the frame, and immediately outputs it. Untimed, or rough timed at best. No precision, because no RAM allowance to store. In, out, in, out. Fast fast fast, slow slow slow. Not timed, though some attempt to time with a weak pathetic clock. If frames overrun or underrun this clock, it's just immediately duped/inserted/dropped. And this is why the ES10/15 type Panasonic DVD recorders are not TBCs, contain mere non-TBC frame syncs, and can still allow frame timing issues that get passed to the capture card (and dropped/inserted there as well).

Now enter the actual frame TBC. It accepts and releases to a better clock, with a RAM buffer to store. It gets released at a perfectly interval. (Noting that some "TBCs" are faulty, or just misusing/abusing the loose term "TBC" for marketing/financial gains. Those units can actually induce errors, or do nothing at all.)



To be continued soon...