Those solutions are not always cooperative with consumer sources like VHS. That's the main difference. The TBCs aren't "the same" as options generally suggested for this task. While I'm glad you found a solution that works, and it's definitely decent, it's not going to be what everybody needs. I refer to as a "closed loop" for a reason, aka single workflow within a device. But if/when there are issues, it becomes an expensive capture card, and external TBCs will be needed. Given the non-consumer source intended, errors are likely with anything other than out-of-camera originals. Sometimes not even out-of-VCR, as even 1st gen VCR recordings could have awful issues.

I wish I could say it's an upgrade, but it's not. It's just different.

And so does your suggested gear, not always cooperative with consumer tapes. As always being said tapes are case by case scenario and every tape has its own problems, but the majority of consumer tapes can be transferred with proper gear whether consumer components or a full fledged pro device, I'm looking forward for someone to send me a problematic tape so I can tinker with its issues, The learning never stops.

As to cost, actually both methods are expensive but the consumer one can be even more expensive, a fully working TBC-1000 is over $2000 and if it doesn't fix the tape you have to get another TBC and hope it will fix it.

I don't disagree with that -- aside from the word "majority". What % is retail, vs. VCR, vs. camera-shot? The first two don't work well with certain workflows, and the latter is indeed case-by-case due to recording gear used. Mostly the era: camcorder quality, tape grade. It is messy. Camera-shot perfection (as "perfect" as you can expect for VHS, at least) is generally okay-ish with lesser TBCs, though you'll still want to scrub it for errors. Actual frame and line TBCs (not "also has TBC" devices) specifically made for consumer sources generally has less hand holding, less monitoring, and "just works". Generally, few narrow exception always exist.

I wish I could do this for you. I'd have to recreate some bad 90s methods to crank those out. Every project has bad tapes like this, and I have a library of bad tapes that took decades to build.

People overly focus on that exact TBC model. It's good, excellent even, but not perfect, not the best. But the best are rare units.

"But the best are rare units."

Such as......?

I guarantee you the reason the Datavideo TBC-1000's and the AVT-8710's are so incredibly expensive is because those were the two touted around video forums as the best money can buy. Some insight is appreciated.

Several are Cypress variants (and possible reverse engineer + upgraded Taiwan-origin knockoffs) that you've never heard of, from companies that long ago disappeared. And in each case, certain sub-versions/variants therein.

The most "common" (not really) TBC is the 4th gen DataVideo TBC-3000, and 2nd gen 4000/6000 (using modified 3000 boards). The production run was more limited, especially on the 4/6 models. It had almost perfect transparency, strength, somewhat decent/accurate proc amp, and luma/chroma values were accurate. I have 3 of these, and it took years to hunt and acquire. The monkey wrench here is condition, not just acquiring the right variant.

These TBCs are generally unobtainium.

The main reasons the TBC-1000 and AVT-8710 were so suggested is
(1) sub-$1k price
(2) easily obtained new
(3) my posts in forums, along with various guides

- First has been gone for years, add inflation, etc. Now about double that max.
- Second has been gone for well over a decade, nothing good new since 2000s.
- Advice still applies, but there are many adds for latter TBCs, more TBCs, budget/frankenstein setups, etc.

The 1T-TBC, for example, can be considered a AVT-8710 "clone", but it has both "green" and "black" (mostly black, post-2010, bad!!!) versions. That TBC is less fiddly than AVT-8710, due to construction, but cost more at the time, almost double that I recall. Not that it was 2x the TBC, but rather sold to a market that afforded 2x the cost. The last time I saw a good 1T unit was back in early 2020. Several actually, dripped into my workflows into 21. Lots of junk units in 2021-2022.

I could go on ... but time doesn't allow. :2cents:

It would be good to capture those using a simple DAQ, similar to what this guy has in mind, so that you can "play" the S-Video signal back through a TBC and capture card you're testing, long after the physical tape has crumbled to dust.

Has anyone done this kind of thing? There's the Domesday Duplicator but it captures the RF from the video head(s) instead of the S-Video signal coming out of the VCR.

I don't see anything special about that link, Using FPGA is not new, it's over a decade old and real devices do exist not just math formula's, His approach is to sample at 16MHz, As I mentioned in post #34 SingMai samples at 27MHz, that's almost twice or 4 times a consumer card. The wheels has been invented and re-invented several times throughout the years. The only exception that VHSdecode has a completely different approach since it grabs the head RF signal which it was never done before, only if they have a working model.

Can the SingMai save the raw voltage samples to disk?

The raw samples are the actual digital signal, Samples are just pixels in a scan line, each scan line has a number of 720 pixels in a 480 scan lines raster. The chroma resolution is different it is sampled as 4:2:2 not 4:4:4 to save data, there isn't enough chroma details to begin with anyway. The VBI and HBI signals are also digitized and used to assign each pixel a H and V positions in the raster.

The frequency oversampling of pro devices has something to do with the way ADC chips work, dithering and bit depth and that kind of stuff, Supposedly oversampling produces clean signal at 14bit and 12bit, The final resolution is always 720 samples @ 10bit or 8bit.

I don't want the pixels, I want the raw analog voltages from the luma and chroma wires sampled at a sufficiently high frequency and bit depth to capture all of the information in the signals, and then be able to replay them back through the TBC and capture card as I explained above.

You can't store voltages, they have to be digitized first. But they are not actually voltages, it's frequency. if you want to keep the frequency as analog just store the tape and watch it as is whenever you like but it will degrade and wear out, that's the whole idea behind digitizing tapes.

That's what capture cards exactly do, they take the Y and C signals and digitize them.

There are online books on how video is stored on tape and converted to Y-C signal for display, recording or capture, it is a good idea to read up a little bit, it's a lot of fun.

Another way of saying it, is that the tape recorded directly the OTA broadcast (NTSC/PAL). So what's contained on the tape is directly what controls the cathode ray tube at the back of your old TV. In pure analog glory. It doesn't get more direct than this. The tape is just a replay of the same broadcast, yes with some details lost due to lower bandwidth and compromises of VHS.

That's why I like the comparison with SDR (software defined radio). They do the same thing, digitize the whole RF spectrum (in practice a small-ish band of it) at a chosen bit depth and sampling frequency. Then later it can be post-processed at your leisure to demodulate or whatever, but you depend on the earlier choices made, for how much details of the original analog signal you've retained. If you didn't use a bit depth or sample rate high enough you may not be able to demodulate the more complex modulations.

Digitizing an analog signal will always be a question of where you put the limit on how granularly you've discreticized a continuous signal.
.
Will you have enough details to differentiate 0.000000001 volt from 0.000000002 volts? Or 0.00000000000001 Hz? Or 0.00000000001 dBm? Or whatever continuous/infinite list of possible values you are trying to categorize/bucketize into x finite possible digital values.

It depends on what you meant by "raw voltage", when here we are concerned ultimately by the magnetic flux of each grain deposited on a plastic tape.
I guess one could argue that the particule size acts like a "digital scan résolution" at a physics level. And if you go into quantum mechanics you could say the same about the magnetic flux of each grain is "digital". But then the Heisenberg principle throws it all into wack because the mère act of trying to measure something so small will influence the reading you get from it.

So when is it good enough? Why try to digitize at the magnetic level? You expect we have better gear today to capture this information, then letting the magic of analog be preserved all the way to the capture card and let the digitization happen at that point in the form of pixels?

At this point, it becomes mostly a philosophical debate to me. I understand the argument that implies we can get a more pure signal closer to the source before any circuit influences it. But it assumes at the practical level that we get a cleaner and more precisr way to measure magnetic quantas in 2022 than the noise imparted up to the capture card. And this hasn't been demonstrated afaik.

My own 2 cents. Hopefully I made sense 🤣

By "raw voltage" I mean the waveforms from the luma and chroma wires in the S-Video output of the VCR. I'm not concerned with how the information is stored on tape.

@jeremfg

Yes, some of what you posted makes sense, But there are facts that need to be addressed:
Video on tape is divided into scan lines, You can't capture more than say 525 lines which 480 is the actual visual frame, the rest is signaling, data such caption, teletext, and VBI. Now, yes each scan line is represented by a frequency signal lasting from the first HBI pulse to the end of the scan line, plus the chroma signal and chroma burst for timing it with the luma, You could argue that you can sample this at as high as you can but Shannon sampling theorem proved that you can't gain any more data than what's on the original frequency if you sample at more than double the maximum of the original frequency value, Meaning that if you have 12Mhz max, you sample at 24MHz, anything above 24MHz is a waste of bandwidth and the original frequency is perfectly reproduced.

Again that's what capture cards do.

Capture cards turn the signal into video frames. I don't want that, I just want the raw waveform.

@latreche34
I completely agree. I was only concerning myself of the information within a line, because yes vertical resolution is already a discrete digital notion.

And yes, the Shannon theorem is what I implied with my oversimplification of "good enough". At some point more details doesn't help. A concept hard to grasp/accept for some of the analog purists and audiophiles out there.

True. I think he only wants the ADC part of the capture card.

To which you must follow up with "what more does it do"?
In essence, nothing. A video frame is just that, an array of "voltages" numerically represented by a color and luminosity.

@traal
If you want the original raw waveforms, just take the picture frame, extract the chroma and luminescence of each pixel, and there you have it, the "raw waveform" as captured by the ADC. There's no further magic. All the information is there, lossless as offered by the digital domain.

Ok so if I have a glitchy HuffYUV capture because I didn't use an external TBC, I can play that file through the S-Video connector on my video card, connected to the input on an external TBC, and take the output of that TBC to a capture card capturing to a second HuffYUV file, and it will fix the video same as if I used the external TBC in the first place, correct?

LordSmurf, do you concur?

Don't make me say something I didn't say.

In theory, yes. In practice, no.

Your typical capture card has "smarts" in it that will result in dropped frames if it doesn't understand the signal it receives. It's trying to recognize a specific number of lines to generate a video frame for example.

That's why we use a TBC in the first place, to modify the signal, to "patch" it. Fix what was broken on the tape or the VCR. A TBC knows what the signal is supposed to look like and surimposes itself in a "I know better than you what the signal should look like". So the capture card is happy and receives a always happy perfect signal. The TBC only messes with the timing/sync parts encoded in the signal, like the "returning the electron gun to the top of the screen", aka as the vertical blanking interval.

A dumb capture card, a simple ADC, would work like you suggest. But then you can just fix the signal in software in post instead of converting back to analog again to feed it to an external TBC, and recapture again. That's the theory behind what drives the VHS-decode project. The software will not do better job than the hardware. The real advantage is that you don't need all the hardware/gear we need today.

If your capture chain flawed you can't recover a corrupted signal, My assumption on all what I've said above is the capture device either digitizes a good clean Y-C signal or it is already built in TBC so it replaces the HBI and VBI by new signals from a weak Y-C signal and add it to the video signal, This has nothing to do with waveform or pixels. The reason VHS-decode can be fixed later is because the hardware is already built in digital TBC, So it's just a matter of combining the timing data and the video data into a useable YUV signal for displaying video. You are treating the Y-C signal as if it is an original complete signal like RF, it is not.