Help with VHS Capture Setup

[LMotlow]

I own an AVToolbox AVT-8710 and rarely use it.

I'm curious to know why you don't just leave it in the device chain when capturing? Since each offers its own advantages It would seem practical to always use both to ensure the best possible quality. Regardless of if the tape really needs it.

Signal degeneration, perhaps?

You guessed it. While the effect might not be noticed right off -- although some folks see it immediately -- consider that every electronic component, connector, wire length, filter, etc., etc., that's in the circuit chain has an effect. Simple resistance and inductance/capacitance itself introduces noise and color shift. Might be a teentsy bit, might be considerable. But it happens. For best results, use only what's needed.

A line TBC, on the other hand, is essential in my opinion, whether in the VCR or the DVD recorder.

If you're thinking of getting a standalone box with a line TBC, they're absurdly expensive.

I'd be more than willing to take that AVT-8710 off your hands for free if you really think it's that useless.

The AVT isn't a line tbc. But sometimes it really is needed, so it isn't quite useless.

I have zero experience here, but I still don't understand how an external DVD recorder can be almost as good as an internal VCR TBC,

The key word used above is "almost".

.....While an external DV converter box is terrible.

There are lots of cheap so-called DV "converter" boxes. They were/are very popular with the Walmart crowd. They're terrible. But why take someone's word for it? Try one.

One issue I've also thought of with the DVD recorder thread is that most of the tests there seem to have been captured on a pro-grade S-VCR with the TBC turned off, but it's probably still affecting the final results. So I'm wondering if this might be making the DVD recorder results seem better than they are.

No, off means off. It doesn't mean partially-off, doesn't mean hiding in the background. It means off.
Not all of the VCR's used were pro machines.

I wonder what would happen if I tried the same DVD recorder with my JVC HR-S5902U.

With one of the recommended DVD machines used as pass-thru, you'd probably see improvements similar to those in the posted tests.

Maybe I should just forget it all and simply get a better S-VCR with TBC? I'm going to be checking out some resale shops in the area, but I'm sure I'd be extremely lucky to find anything "pro-grade" there.

A high-end unit with tbc is probably the best way. A few things to remember: (a) high end machines in good shape are not cheap. From reputable sellers they cost from ~$350 to ~$1800 and up depending on condition. Some are even "new" or nearly so. (b) All high-end and prosumer VCR's are not equal, nor do they all work in the same way, nor do they all produce the same image from the same tape. Model for model, each has its strong and weak points: Panasonics tend to retain more detail with effective but milder noise correction, while JVC has stronger noise reduction with less detail retention. Ergo, some tapes look "better" on one machine than on the other, depending on your ultimate intent and your personal preferences. (c) 6-hour and 4-hour tapes are a bad idea with JVC machines other than their $4000 DV units. (d) The fancy ones aren't foolproof, and they require expert maintenance. (e) Contrary to popular myth, they aren't always the best choice for all the tapes in the world. Sometimes a lesser but decent VCR can give surprising results with problem tapes. Message: don't depend on one VCR alone. What do you do if you think your single player's highly touted tbc or noise reduction is over-doing it? You might need an alternative.

And...
(f) You're over-thinking this. Try something and see what happens.
(g) Don't worry about tbc's just yet. Go bareback, no protection. Then you'll understand.

[manono]

I'm curious to know why you don't just leave it in the device chain when capturing?

LMotlow has it right - it softens the picture a bit. I appreciate the offer to buy it from me but I do need it sometimes, if rarely.

While an external DV converter box is terrible.

I'm not one of the ones that think they're terrible. Sure, DV isn't lossless, and I do a lot of post-capture work trying to improve my VCR captures, but with the ADVC-300 you never have to worry about out-of-synch audio, and you can easily control gain, contrast, brightness, saturation, and other things when capturing. And DV AVI is easy to work with.

[Skiller]

At the German doom9 forum we have discussed and actually tested the whole TBC topic to death. The essence is, Panasonic DMR-ES and DMR-EH DVD/HDD recorders have excellent jitter stabilizing (TBC) capabilities – actually completely unmatched by all "real" standalone TBC boxes we tested, which are, in my opinion, overrated obsolete pieces of hardware from the 90's anyway. Standalone TBC boxes digitize and re-output the incoming signal so that the output is a constant stable signal but they do not correct line jitter. So while they remove junk like Macrovision from the signal and clean the sync pulses, nothing gets stabilized visually. Line TBCs, like those in S-VHS decks, do that. They stabilize line jitter. The Panasonic DMRs do that as well (and just as good if not better in case of the DMR-ES 10).


Regarding the ADVC 300... German VCR enthusiast Volker Schauff discovered, like 8 years or so ago, the ADVC 300's TBC is dodgy and does not help at all, sometimes it even completely trashes the picture and goes nuts. There is also a bug with audio sync; very slowly the audio constantly drifts off until the offset reaches -40 ms (-33 ms for NTSC) and then a frame is duplicated to keep sync. Here is his review (definitely have a look at the sample pictures!).



So my honest recommendation is, ditch the ADVC 300 because of the destructive TBC that cannot be switched off and get a Panasonic DMR-ES 10 and use something else for capturing to the PC (ADVC-110 would be OK-ish).

Since the ADVC-300 does nothing or next to nothing about straightening out squiggly horizontal lines in a capture, I'd say the right DVD recorder used as a pass-through device is infinitely better. I usually use an S-VHS VCR with a built-in line TBC to capture losslessly these days, but the DVD recorder gives similar results.

I agree 100%.

[Brad]

Regarding the ADVC 300... German VCR enthusiast Volker Schauff discovered, like 8 years or so ago, the ADVC 300's TBC is dodgy and does not help at all, sometimes it even completely trashes the picture and goes nuts. There is also a bug with audio sync; very slowly the audio constantly drifts off until the offset reaches -40 ms (-33 ms for NTSC) and then a frame is duplicated to keep sync. Here is his review (definitely have a look at the sample pictures!).

Wow, thanks for the link. But the Panasonic MN673744 chip used by the ADVC-300 for TBC is also used in at least some of Panasonic's own DVD recorders: 2003 DMR-E80H teardown.

[Brad]

Here you go. While searching for something else I found an old thread which links to a Japanese site that amazingly still has all its test images and video samples up. In case it does go down in the future, I've attached the three video samples showing 8mm tape playback.

Canopus ADVC-300 (supposed TBC always on)


Roland VMC-1 (TBC on)


Roland VMC-1 (TBC off)


As you can see, lines are straightened in the middle image. But the dropouts are always in the same place (through the "NTT" text and bottom circles, most clearly).

Both units contain the MN673744 chip, so I guess Canopus failed to use it appropriately. I don't buy the German reviewer's explanation that the chip was secretly found to be faulty and possibly fixed, unless there are complaints about their DVD recorders from the same time period. [EDIT: Reading further into his review, I see he actually mentions the VMC-1 and says it suffers from "similar symptoms." Confusing.]

The video samples use Canopus' FOURCC. I forced Cedocida to decode them like so:

A = AVISource("tbc8_advc300_b.avi",fourCC="DVSD")
B = AVISource("tbc8_vmc1.avi",fourCC="DVSD")
C = AVISource("tbc8_vmc1_notbc.avi",fourCC="DVSD")

Interleave(A,B,C)

[DoDanger]

As you can see, lines are straightened in the middle image. But the dropouts are always in the same place (through the "NTT" text and bottom circles, most clearly).

Aha! So "dropouts" was the word I was looking for. Would a better VCR help reduce this issue or is this something you can only fix with post processing?

Both units contain the MN673744 chip, so I guess Canopus failed to use it appropriately.

This might answer my question as to why a DVD recorder is a better TBC than the Canopus ADVC-300.

One issue I've also thought of with the DVD recorder thread is that most of the tests there seem to have been captured on a pro-grade S-VCR with the TBC turned off, but it's probably still affecting the final results. So I'm wondering if this might be making the DVD recorder results seem better than they are.

No, off means off. It doesn't mean partially-off, doesn't mean hiding in the background. It means off.
Not all of the VCR's used were pro machines.

I meant that the overall playback on a pro VCR --even with the TBC turn off-- would probably still be improving the footage before it ever hit the TBC device.

And...
(f) You're over-thinking this. Try something and see what happens.
(g) Don't worry about tbc's just yet. Go bareback, no protection. Then you'll understand.

Isn't that kind of what I'm doing already, just with faulty protection. Yes, I'm overthinking this a lot, but it's because I'm paranoid. I'd like to ideally make digital backups of all my old VHS tapes, then throw them out and never have to deal with this ever again. But I know it's never that simple and I'm afraid I'm going to make some stupid amature mistake that'll only be discover after it's too late. This probably means I should really get a pro to do it, but I like to get hands on with this stuff and know exactly how it's being done.

Thanks for all the great feedback everyone! I know I have a heck of a lot to learn here and I appreciate your patience with me.

[Brad]

Would a better VCR help reduce this issue or is this something you can only fix with post processing?

Different VCRs handle dropouts differently, and the behemoth "broadcast" decks that only play SP mode tapes claim to make special efforts to conceal them well. (TBC'd data from a previous field is held in memory and copied forward into the current field.) Perhaps the later prosumer models use their memory to employ the same process, but I don't think they advertised that ability. In any event, the video in that part of the image doesn't exist on the tape / wasn't picked up by the head so the best you can hope for is an interpolation of what should fill the void. There's a bit of an explanation here, with pictures a page up.

Surely this isn't a big problem found on most of your tapes?

[jagabo]

If you look at the "dropouts" you'll see they are mostly copies of the previous line from the same field. If the deck had somehow read the same line twice the rest of the field would drop down by a line. I didn't see any evidence of that. Since most of them appear on the "tbc" recording and the "no-tbc" recording, and in exactly the same places, and aren't 100 percent exact copies, the problem is most likely on the tape. Ie, they weren't added by any device in the playback chain, they're in the recording. So nothing is going to fix them.

[Brad]

If you look at the "dropouts" you'll see they are mostly copies of the previous line from the same field.

That's how simple dropout compensation is performed; see the book page linked.

[jagabo]

If you look at the "dropouts" you'll see they are mostly copies of the previous line from the same field.

That's how simple dropout compensation is performed; see the book page linked.

I know. I was pointing out that the cap made with the Roland VMC-1 with TBC disabled has the same duplicate scan lines. So the replaced lines are on the tape from a previous generation recording with a TBC, not dropouts on this tape.

[Brad]

But the TBC isn't what does the dropout compensation. The playback machine does (only it knows the RF level). The same VCR playing back the same spotty tape with near-identical dropout compensation should be expected, regardless of whether the external TBC is activated.

[2Bdecided]

Isn't it a basic part of the VHS "HQ" spec? If you have a really early VHS machine, you will see the drop outs a bright noisy white lines, whereas on a more modern (mid/late 1980s onwards) machine, they will be masked.

I remember our first deck (1985) showed all the drop outs, while our second (1991) didn't.

I sometimes wonder if it would be helpful to capture without drop-out compensation. AVIsynth could, in theory, do better drop-out compensation.

Cheers,
David.

[jagabo]

Isn't it a basic part of the VHS "HQ" spec?

None of the VHS decks I ever had did it. They were completely dumb analog devices. Junk on the tape came out as junk in the signal. They had no memory of past scan lines.

[2Bdecided]

I know you're really experienced at this jagabo, but I have to ask: are you sure? I think maybe all your VHS decks have it. When you see junk, it's because it's spread over more than one line. The "repair" you get with a one line drop-out is quite subtle.

I can't find my VCR repair manual which explains this, but a quick google found this...
http://alt.satellite.tv.narkive.com/uHDt7Txx/uk-405-line-system-fr-819-line-system-no-...-these-formats

Older VHS video recorders can handle 405 line material with few problems.
The Ferguson Videostars or their JVC equivalents are good choices. Around
1988 there were changes in circuitry that prevent them from properly
recording and playing back of 405 line material. Possibly something to do
with Macrovision.

Don't think it was related to Macrovision - I think it was the introduction
of VHS HQ. This uses line-delay techniques to "improve" the picture - and
as they line lengths are different in 405 and 625 it doesn't cope with 405
at all well. Personally I'm not sure HQ improves decent recordings at all -
it just seems to add artifical ringing-style edge... Certainly some of the
best pictures I have seen from a VHS VCR were recorded on an early 80s
Hitachi machine (first generation with electronic rather than piano key
controlled transport?) I suspect build quality and specs were higher then
(but then the machines cost massively more in relative terms?)

Even non-HQ VHS machines had problems with 405 recordings with drop out - as
the drop-out comps in VHS machines were based on line-delays (designed for
625 line recordings) Therefore drop-out comps made 405 recordings worse not
better. (I think 405 enthusiasts either use high quality tapes or disable
the DOCs on their VCRs?)

I'll post a scan of the repair manual if I can find it. It explains it pretty well IIRC.

Cheers,
David.