Datavideo TBC-3000 change IRE?

[ENunn]

i'm transferring a japanese tape on my ag-1980. the black levels are a little crushed. i use a tbc-3000 as a tbc. is there a way i can change the ire on it? there's some dip switches inside, but i don't think any of them change ire. or maybe i'm wrong.

[aramkolt]

The IRE would really just be changed by the proc amp controls on the front. IRE would be some combination of contrast and brightness - one probably affects black level more than white though. Best bet is to use a waveform monitor/vectorscope if you can.

[ENunn]

thanks. i don't have easy access to one. the best thing i can do is using graphstudionext and the avisynth histogram. looks like there's no detail to recover regardless of how much i mess with the proc amp.

[lordsmurf]

For TBC-3000, PAL is auto 0 IRE, NTSC is auto 7.5 IRE, and this cannot be changed.

What is instead required is adjusting the proc amp for non-standard formats like NTSC-J.(Actually NTSC-J recorded to NTSC tape, as technically there is no NTSC-J VHS tape format, but it's de facto due to source IRE.)

VHS tape wasn't perfect digital 0 or 7.5 IRE anyway -- nor even many digital devices, for that matter. VHS tape natively has muddy darks, no true blacks.

Just use your eyes for balance, assuming that the monitor is properly calibrated. I rarely use "-graphs" (or "-meters") for color correction. I'm watching the content, not an algorithm. I'll know if it's wrong or right. (*Granted I have decades of experience, but still, it's not so overly complicated that -graphs/-meters are needed. Just ask for confirmations from others, such as posts here in the forum.)

[aramkolt]

If blacks are crushed and adjusting the proc amp on the TBC3000 doesn't bring them back, that suggests that the TBC3000 is clipping on the input side before the proc amp has a chance to do anything. You could always adjust the output levels on the AG1980 which are usually small holes in the main PCB over the TBC card and they usually are fairly well labeled.

The easier thing would just be to put an analog proc amp before the TBC-3000 and that should fix all of your problems without having to mess with the internal settings of the AG1980. Options are kind of limited when it comes to S-Video capable Proc Amps, but I've theorized you could just run the luma wire from S-Video as a composite signal through the composite of a composite-only proc amp and get the same result given that you are only making luma adjustments. The only real downfall there would be that the proc amp having a longer path for luma could mean you get more YC delay issues where chroma is horizontally shifted a bit compared to luma on the output side.

[lordsmurf]

Quote:

Originally Posted by aramkolt

If blacks are crushed
suggests that the TBC3000 is clipping

As an aside:
I hate the terms "clipping" and "crushed", because it has a connotation that the TBC did something wrong. That is not accurate. TBCs are science instruments, and have to be calibrated to values. Those values are specified by organizational bodies, who decades ago (almost a century ago!) decide on IRE. It's really no different that calibrating the speedometer on a car, so all speed measurement are standardized vehicle to vehicle.

Quote:

You could always adjust the output levels on the AG1980 which are usually small holes in the main PCB over the TBC card

This is not easy to get to, and not really an option if you don't want to gut the VCR on a workbench.

Quote:

The easier thing would just be to put an analog proc amp before the TBC-3000 and that should fix all of your problems without having to mess with the internal settings of the AG1980.

TBC-3000 does not legalize values beyond the IRE.

Furthermore, the issue with proc amp, before frame TBC, is that it can (and often does) falter on un-timed/mis-timed signals. If you ever insert proc amp before frame TBC, you must carefully vet every second of the captured footage, looking for timing flaws. It's tedious, and not suggested for anything of length. I would only attempt this with AG-1980P (NV-FS200), due to field TBC (multi-line TBCs), not JVC (line TBCs).

Quote:

Options are kind of limited when it comes to S-Video capable Proc Amps

Here's an idea: I'm sending you my non-working proc amps, for you to repair (hopefully). Assuming it goes well, ENunn should buy one of the SignVideo. He's a long-term hobbyist, he needs one.

Quote:

The only real downfall there would be that the proc amp having a longer path for luma could mean you get more YC delay issues where chroma is horizontally shifted a bit compared to luma on the output side.

That's not a downside, that's a fatal flaw that makes it untenable.

[aramkolt]

Disagree on a few points:

There's no reason you'd want a TBC to "clip" illegal levels on the input side (especially black levels) if they have a built in proc amp meant to correct signals coming in. I can kind of see where they need to limit the maximum brightness value on a scale since it only goes up to 255 in a full range 8 bit system (or 235 for limited range), but we know that the TBC itself is capable of assigning digital values down to zero because it does that when in PAL mode. Arbitrarily assigning the digital equivalent of anything less than 16 (which is the equivalent to 7.5IRE) to 16 instead loses all of the data below 16 unnecessarily. Not saying it makes the TBC unusable, it just isn't ideal and causes situations such as what ENunn is experiencing where more equipment is needed that otherwise wouldn't be. I think we've

Agree that YC delay issues *could* be severe if passing only luma through a proc amp, but we don't know for sure that it actually happens until someone tries it. There are also TBCs that can correct the YC delay which can be very useful for second or more generation dub capturing I've found, though that's not something that any of the "recommended" TBCs can do though. The most common ones that have the feature are the For.A FA300/310, IVT-7, some DPS units, and some Snell and Wilcox units, but I'm sure there are others.

[lordsmurf]

Go back to why this gear exists. It's not to convert NTSC-J tapes. That's just how it's being used now, some 20-30 years later. These were made, decades ago, for a specific use-case/workflow, being purely for NTSC North America or PAL Europe/Australia (not even Asia).

The non-recommended TBCs are not recommended due to how those overall handle consumer analog formats, having been created for studio/broadcast use. So the features differ.

Sometimes modern users try to make old square gear fit into new round holes. For me, having "been there, done that" is quite helpful at times. I know the historical context, because I was there, buying/using it when new in 90s/00s. I know how it was used then, and how it can be used now.

Realize that I don't adore legalizing. But I understand why.

[vwestlife]

Quote:

Originally Posted by lordsmurf

It's really no different that calibrating the speedometer on a car, so all speed measurement are standardized vehicle to vehicle.

Off-topic, but almost all car speedometers overread by a few MPH / km/h (sometimes up to 10%), so that even if your tires are bald and/or low on air, the speedometer won't underread:
Need for speed: why some speedometers lag behind reality

[aramkolt]

Regardless of whether it is an NTSC-J tape or regular NTSC tape, in an ideal world, you don't want your TBC to clip incoming luma at 7.5IRE. There's not too much point in having a Proc Amp on the TBC if it only adjusts after the levels have already been clipped at the input. I think most of us have probably transferred a tape that has IRE signals that are either recorded or played back below 7.5IRE and that information is just lost without an additional device in this situation.

Now I'm kind of curious if it also clips hot white levels at the input as well.

[lordsmurf]

The TBC-3000 doesn't clip to IRE, it adjusts. Have you used one before?

[aramkolt]

I have not used one, but the way I'm reading it, the original poster is saying that he can't adjust the black level up without crushed blacks with the digital proc amp of the TBC-3000 when used on an NTSC-J tape, so that implies that the clipping is occurring on the input side before the digital proc amp has a chance to bring the levels up.

The other possibility here is that, perhaps, the AG1980 is doing the clipping on the output side which I suppose is possible since I haven't tried an NTSC-J tape myself in one. I do have some NTSC-J VCRs, so perhaps I will have to figure out a way to make an NTSC-J recording and then play it back on the AG1980. Suppose the only real difference is the black level which I should be able to to adjust down using a Proc amp when making the "NTSC-J test tape" recording.

On a side note, I do wonder if AGC (while recording) on a regular NTSC VCR would increase the black level to 7.5IRE on the recording it makes if you feed it a Zero IRE source.

[lordsmurf]

But NTSC-J is not the spec of the TBC, nor the intended use-case/purpose. It can be used for NTSC-J, but the consequence is offset IRE/luma. Therefore adjust in proc amp, and done. You can't use the TBC "wrong", then blame it for not doing what it wasn't designed to do. That's all I'm getting at.

Other TBCs are more multi-format friendly (especially Cypress), never DataVideo.