Proc amp recomendation?

[lordsmurf]

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Originally Posted by latreche34

I don't understand why people are too worried about levels, The levels are always within a margin of tolerance by design,

No. Levels fully depend on factors.

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They can only be screwed up during camera shooting when there is an idiot behind it, such as using wrong setting for the scene conditions or wrong white balance, Also low end camcorders with poor performance in indoor conditions,

Wait, no, stop, halt. For starters, I'm not sure I'd call my parents idiots.

Take off the 21st century blinders (2000s-2020s), and go back to the 20th century (1970s-1990s). Back then, things like auto white balance were terrible, and the instructions and controls to manually set values (WB, etc) were obtuse or non-existent. I actually still have one of our 80s family camcorders (I think it's the 2nd unit from 1984-ish), and it's a confusing beast, in addition to being the size of two basketballs that weighed at least 10 lbs.

We were early VHS adopters. They shot family Christmas with my grandmother (who's been gone for decades now; aunts and cousins now gone too --- we cherish those tapes now), my high school and college graduations, etc, and it's all on VHS. And none of it looks great. Back then, those cameras were at least $1k, and we weren't rich by any means -- back then, you'd save and buy (or use layaway), not plop down credit cards.

One of my regrets is that we didn't switch to Video8 then Hi8 in later years. VHS and VHS-C (even S-VHS-C) home camcorders sucked. But only in hindsight, seeing how much better those tapes look when digitized, something that obviously wasn't know at the time.

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And those will be baked in the tape anyway and cannot be corrected by a proc amp no matter where it sits. Proc amps are good for touching up the levels but not for correcting baked in mistakes.

Best case, value issues can be corrected.
Worst case, value issues can be made less worse.
Though noting many tapes are fine as-is, proc amp not needed. But when it is needed, it's really needed!

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Originally Posted by aramkolt

Shouldn't the proc amp be placed before a frame TBC in the chain

No, never.

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My logic is that if illegal analog video signal levels come into a TBC, there's potential for the TBC to clip them

Clipping is not a function of TBCs. The exception is certain TBCs that have proc amp (certain BV), but even that is unusual.

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I also don't get what the difference would be if you were to use a hardware proc amp after the TBC versus just using the software proc amp controls for your capture card at the time of capture since they are both in the same place in the capture chain then?

No. The software proc amp is post-digitize. It's too late, baked in, just use an NLE for correction instead of weenie crappy driver sliders.

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My understanding is that standalone proc amps shouldn't be able to clip anything because the signal stays analog throughout the device.

Cheap junk proc amps existed, and did everything from clip to distort colors. Same as anything else: random VCRs, random TBCs, random proc amps = random quality.

[latreche34]

I can agree on can be made less worse, but proc amp is not magic, You change the gain for one area and screw the rest of the frame or vise versa, You can't have it both ways.

[lordsmurf]

Quote:

Originally Posted by latreche34

I can agree on can be made less worse, but proc amp is not magic, You change the gain for one area and screw the rest of the frame or vise versa, You can't have it both ways.

Yep, that's it.

For anything more advanced, you need HDR. But to enable HDR to have something to work with, you generally want to pre-adjust with proc amp in analog domain.

It's all about give and take.

[aramkolt]

I'm not quite sure that the software setting proc amp settings at capture are "post digitization" - but rather "as it is being digitized"- How would one go about testing that? I'm envisioning a known hot signal with luma levels that are in the 130 IRE+ range which would be easy to produce with a proc amp before the card.

Question is, how do you prove that the automatic gain control on the card doesn't kick in and bring the levels down before the software proc amp settings take effect?

That also brings up the question - if the automatic gain control on the capture card is ideal (which AIW cards are purported to be) - wouldn't a proc amp almost never be needed? Only scenario I can think of would be a very low dynamic range such as a a super dark scene where you'd want to expand the limited range of values (while still analog and not 1's and 0's).

Orrrrrrrr are you saying that AGC is also post-digitization?

If everything was done post-digitization (AGC and software proc amp settings), you should see a flat topped clipped waveforms when viewing the recorded 130IRE signal described above that has then been brought down to 100IRE in the captured file?

[latreche34]

Digital proc amp should be part of the analog to digital conversion process to be effective, Either be part of the TBC itself or part of the capture card if it's connected directly to the VCR, If you have a TBC without proc amp that converts back to analog you're out of luck. If proc amp important to you get a separate proc amp before the TBC (digital or analog), get a TBC built in proc amp, or get a capture device built in TBC.

The usual signal flow for an effective proc amp is as follows:
Analog video -> analog to digital conversion -> signal timing -> Proc amp -> audio embed -> digital video.

[lordsmurf]

No, TBC comes before proc amp. Do not color correct non-timed signals. You wrote that wrong to start, then stated it properly after the diagram. Regardless of A<>D

And too much is made of A<>D these days, it's become silly dogma. Same for colorspace conversions (non-lossy, or minimal lossy). These are merely processes of video, not some sort of video cooties to be avoided.

A lot of TBCs that "also have" proc amp are fairly weenie. With a few exceptions, as always.

[latreche34]

In digital that's not how it works, the signal has to be digitized, time based to a stable signal and then corrected for levels, There is no such device works that way even the AVTool, keep in mind this is all happen in digital, correcting for VBI and HBI does not affect the scan lines video data, You can sort of say it happens in parallel but in diagrams they always show it after the TBC, but certainly not before TBC. Only proc amp changes affect the scan lines video data.

In analog workflows you have to put the proc amp before TBC because every device works independent from the rest of the workflow, But most people that use external TBC use the proc amp in the capture card driver via the capture software, this was always the case, What has changed that everyone agrees with me now?

[lordsmurf]

Quote:

Originally Posted by latreche34

the signal has to be digitized, time based to a stable signal and then corrected for levels,

That's what I'm saying as well.

If you attempt to correct levels before stabilizing the time base (of the analog videotape), the timing just gets worse (essentially injecting nth gen properties), and in fact can make the signal unstable beyond TBC repair. That's actually what digital artists want, so I do inject proc amp before TBC for effects. You can do some crazy crap in the pure analog domain.

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In analog workflows

I'm not sure what you mean here.

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But most people that use external TBC use the proc amp in the capture card driver via the capture software,

I don't think "most people" ever did that. In fact, most are fully unaware of the software proc amp controls. Not that they should be using them, since it's post-ADC and redundant to better CC in an NLE.

@aramkolt
And post-ADC card/software/driver proc amp is easy to see, the luma levels have a "digital" leveling to them that vastly differs from analog levels. (I lack a more proper description at this moment, but again it's extremely obvious.)

[aramkolt]

Should the proc amps in a TBCs that have them built in NOT be used either because that is also "post digitization"? Granted, on most TBCs, that is then re-converted to analog on output (unless you're using one with SDI out).

Perhaps what is unique about TBCs is that they are allowed to output at illegal levels as high as they want (that matches or exceeds the input levels), and therefore don't cause clipping?

For those that do SDI capture from a TBC, then the proc amp controls on that are definitely post-digitization and shouldn't be used either?

I am also aware that SDI proc amps exist to legalize these levels, but I always thought there was still a ceiling that would clip above certain levels if they start out too high?

[lordsmurf]

Again, too much is made of, and misunderstood, concerning A<>D. To say that a capture card, and a TBC, and both "post digitize" is misunderstanding the fundamentals of those processes. And again, it's the difference between a signal and an image.

The clipping aspect fully depends on multiple factors.

SDI is a closer-loop system, with differences from standard workflow.

It's hard to describe some of these concepts, because it's a big concept. Sort of like saying "the car works by putting in the key", which is a simplified description of what is actually happening. It's not one I've ever really been interested in tackling, because it's mostly just trivia for users -- and I don't waste my time on trivia (unless it's a sentence or two, not a novel long).

The further irony here is that some people can tell you the trivia, but have zero idea how to apply it to a real world application. Sometimes "knowing" the concepts still doesn't mean you know how to actually do/use it. You find a lot of that in academia, and is why you hear "Those who can, do. Those who can't, teach."

[latreche34]

Quote:

Originally Posted by aramkolt

For those that do SDI capture from a TBC, then the proc amp controls on that are definitely post-digitization and shouldn't be used either?

Digital Proc amps, mixing consoles, character generators have always worked this way as I and LS mentioned, To process the signal you have to digitize it, stabilize it, then correct its levels. If you are talking about pure analog proc-amps that's a different story, I've never dealt with those and as I've read they are not as good as digital ones in terms of quality, hope this clears the confusion.

[lordsmurf]

Quote:

Originally Posted by latreche34

If you are talking about pure analog proc-amps that's a different story, I've never dealt with those and as I've read they are not as good as digital ones in terms of quality, hope this clears the confusion.

These may be analog proc amp, 1980s Archer gear.
https://www.digitalfaq.com/forum/vid...-enhancer.html

Terrible items.