TBC testing: How to display line and frame time base errors live?

[aramkolt]

I am attempting to test a bunch of time base correctors on an identical starting signal using a distribution amplifier to each TBC device.

The issue I'm running into is figuring out how to display the output of each TBC in real time that shows line and frame time base errors without the display itself internally correcting or tolerating them. I thought I could accomplish this by using small analog input LCD displays from Marshall (Such as the V-R563P), but it turns out that those internally correct line-time base errors and they seem extremely tolerant to unstable signals, so that isn't going to work for my application. It's actually kind of too bad that they don't have some sort of digital output as I'd not be surprised if they'd be among some of the best line TBCs out there.

What I want is some sort of ideally "small" screens that will show the sort of flagging that is typical with many capture cards when a line TBC isn't used and that will drop the signal if the image gets too unstable. I want the wobbly/to screen flagging displayed on those screens so I can see in real time what each TBC is doing to correct things and which is the last to drop sync with an extremely poor input signals. The idea behind the screens being small is that a single video camera could then grossly show which TBCs struggle with the same signal and when each drops out completely.

Alternative options would be:

- Some way to record an analog composite signal with time base errors preserved) to then play back to each TBC individually. That would guarantee an identical starting signal. Someone mentioned using something called a DAQ to accomplish that, but info is rather scarse and the software doesn't look particularly user friendly.

- multiple capture PCs with the same type of capture card to record from each TBC in real time (to capture output simultaneously from all of the distribution-amp fed TBCs at once) - That'd be complicated/expensive to set up for the purposes of this test. However, the actual screen comparison could be done with a 4x1 multi viewer to a 4K display in real time (1/4 of the screen is showing each PC's full screen output) and that 4K output could then be recorded for the actual comparison posting.

- CVBS_Decode can capture a raw composite signal, but I don't think it can play the captured signal back as analog unfortunately.

At this point, I am highly considering getting like 4 elgato video capture devices and running them all at once (on some older laptops) to each TBC "under test" being fed by the distribution amplifier. I get that they aren't ideal for actual capturing, but they will display static for a while before dropping out and I believe they will still show flagging/line time base errors in their captures if present.

After I narrow down which TBCs yield the best signal stability for particularly unstable signals (and show if they have any bonus line TBC abilities), I would then do other tests as far as preserved image quality (probably mostly with pattern generators or a DVD for the identical signals) all with the same capture card and using an VM-700T for some other statistics in terms of measurement of residual jitter, signal to noise ratios etc. I'll have to come up with some sort of audio sync test, or at least frame drop statistics for mechanical media as well.

Any thoughts on the actual testing would be appreciated, or if there's some test that a "grand comparison" of TBCs should have that you think I might miss, let me know. I'm still looking for VHS tapes to be used in the test if you have any tapes that are very jittery or have extreme flagging that you'd like to donate (I can convert them to digital with whatever hardware combo works the best for free as well), please PM me.

[lordsmurf]

This can be accomplished with specific playback and ingest hardware. External TBCs are injected for that half of the signal. But I find it more difficult for minimal reason.

[gunzel]

I was using a cheap reversing camera screen from eBay, something like this: https://www.ebay.com.au/itm/166328488335 while I didn't have a proper TV.

I'm not sure how tolerant they are of errors because I don't see many in what I've been doing so far. They just take a composite in, and they are pretty cheap, probably even cheaper on Aliexpress. You'll have to sort out power (12V) and the aspect ratio is wrong, but it doesn't sound like that's what you are looking for.

[latreche34]

You will be better off with a studio monitor that split the screen horizontally and vertically, Thos often are expensive and require maintenance and calibration, Another alternative is a video vectorscope and waveform monitor that is designed for analog SD video.

[aramkolt]

All good points, thank you all.

While I do maintain that the ideal test setup would be a split/distribution amplified starting signal or a digitally re-produced analog signal that still contains time base errors, it adds extra variables like not having the exact same capture card for each TBC. Viewing a bunch of small screens via a camera could also make for some odd viewing angles. I do believe the playback will be slightly different from playback to playback, but it's probably not enough to matter significantly. That, and I won't be able to get frame drop statistics if I am just viewing live.

I do have a few CRT monitors that can do HV delay (which is good to verify if they are stripping macrovision), though being mostly CRTs, I'm not sure if they show flagging/tearing to the same degree that you get with capture cards. 12voltvids on YouTube that did show a tape that flagging/tearing errors were more obvious in HV delay mode (even with a CRT) since it seems to affect the top of the frame more and a bunch just isn't visible in regular viewing modes. I'm not sure if HV delay tells you anything about dropped frames though? I think the image has to be pretty bad to get a full roll, and that'll hopefully be one of my tests actually. I found if you completely loosen the video head from the deck , the vibrations it makes are usually enough for it to cause a continuous vertical roll. Should be interesting to see what a frame TBC does with that.

If anyone knows a way to capture composite and play it back digitally as composite with time base errors preserved, I would definitely go that route. If I knew more about DAQs, that could be the ticket. The "HackRF" can output composite and even RF TV transmissions, but it does it with digital perfection, so unless there's a way to purposely introduce timebase errors into that, I don' think it would be usable here unfortunately.

[lordsmurf]

Quote:

Originally Posted by aramkolt

split/distribution amplified

No, dual VCR output.

[Gary34]

To me it’s kinda wild that you are taking your results to YouTube. Youtube people don’t know up from down as far as digitizing analog. You are really trying to make a fair test and you are making what seems like a really good attempt at all of this. The condition of the gear is a big factor now and I’m sure there’s a bunch of other factors but the Youtube people won’t point any of that out for the most part. You could have all kinds of flaws in your testing and they well not know. They well just repeat whatever you say your outcome is.

That test that Gunzel did a while back where he photoshopped a frame to try and make it look better than a frame from other gear. If he would of posted a test like that on YouTube there would of been a bunch of people just like him that would of said ow yeah that proves it. He didn’t test anything with that but he is going to get the result he wants. He’s already got his mind made up he’s just trying to make the test results match.

With YouTube you reach the uneducated masses. If you aren’t completely sure of your testing why blast the message on YouTube? If you even mention this gear on YouTube you hear why not just get a Clearclick, decode, Elgato etc…Someone told me a Clearclick was archival quality. Just a Clearclick and a bad VCR. They are biased towards picking cheap gear. It’s not based on what is best. If the YouTube crowd was educated about this then you could post a video asking then for testing advice instead of asking here.

[lordsmurf]

Quote:

Originally Posted by Gary34

To me it’s kinda wild that you are taking your results to YouTube. Youtube people don’t know up from down as far as digitizing analog. You are really trying to make a fair test and you are making what seems like a really good attempt at all of this. The condition of the gear is a big factor now and I’m sure there’s a bunch of other factors but the Youtube people won’t point any of that out for the most part. You could have all kinds of flaws in your testing and they well not know. They well just repeat whatever you say your outcome is.

That test that Gunzel did a while back where he photoshopped a frame to try and make it look better than a frame from other gear. If he would of posted a test like that on YouTube there would of been a bunch of people just like him that would of said ow yeah that proves it. He didn’t test anything with that but he is going to get the result he wants. He’s already got his mind made up he’s just trying to make the test results match.

With YouTube you reach the uneducated masses. If you aren’t completely sure of your testing why blast the message on YouTube? If you even mention this gear on YouTube you hear why not just get a Clearclick, decode, Elgato etc…Someone told me a Clearclick was archival quality. Just a Clearclick and a bad VCR. They are biased towards picking cheap gear. It’s not based on what is best. If the YouTube crowd was educated about this then you could post a video asking then for testing advice instead of asking here.

This.

A person is smart, people are stupid. Youtube is lots of people gathered, a school yard during a pep rally, forming cliques, and yelling at each other. Nobody ever STFU long enough to even hear what the other person is saying. Lots of adrenaline, but zero communication. This goes beyond just TBCs, or even video as a topic. It's everything.

There's a reason that scientific journals don't release studies on Youtube.

The banned-from-VH user ConsumerDV has a video on Youtube, concerning TBCs, that can only be described as an orgy of fact and bullshit. As an analogy, consider a taste test of gourmet food -- but put it all in your mouth at once, then spit it back on the plate in a big lump. That's the video. Good, bad, wrong, all of it. That's what happens when newbies/students try to teach other newbies/students, but really have no idea WTF they're talking about.

While I will not dissuade aramkolt from testing, I must warn against hasty conclusions. That's the problem with Youtube, because that's the problem with people in general. What happens is faulty logic.

For example:
John like blue.
John likes bananas.
Bananas must be blue.

I like that last point. Use Youtube viewers, rather than let them use you.