Will TBC corect video/audio sync problems?

[vlakslee]

Looking over the subjects in this forum it seems that capturing old VHS tapes to a computer to make DVDs is the "holy grail" of video comversion. I have a Pinnacle Movie Box Deluxe USB 2.0. It works well on the capturing from a Panasonic AG 1960 SVHS recorder BUT with older commmercial VHS tapes the sound gets out of sync immediately. I realize that the quality of the tape is causing the problem. But would putting a TBC in line before the Pinnacle box help with the audio getting out of sync with the video or does the TBC merely correct the video portion (color, skewing etc)? One other question from a post on another thread. I read that putting a TBC in between a VHS player/recorder and a DVD recorder will removed the copy protection and "fool" the DVD recorder into recording the VHS tape. Is this true?

[Captain315]

A TBC between the two will eliminate the sync problem and will most probably defeat the macrovision too. Macrovision (in short) is a form of TBC and therefore will eliminte it. I use an AVT-8710 to accomplish exactly what you do and it works fine for me.

[Barnabas]

Yes, a TBC can really help prevent audio sync issues. I ran a test last year on a rare TV movie that was a copy of a copy. Capping 2 minutes worth without a TBC had over 200 frame drops, versus zero frame drops with the TBC turned on.

[thecoalman]

But would putting a TBC in line before the Pinnacle box help with the audio getting out of sync with the video or does the TBC merely correct the video portion (color, skewing etc)?

A TBC corrects the timing of a video, which in turn corrects how it looks. This also has the benefit of correcting A/V sync issues since the video signal is now perfectly timed for your capture card..... I posted this in another thread, it's a much better explanation that I could ever provide.

nothing is wrong with the standalone tbc you own. Those things are overrated crap. They do next nothing in terms of truly correcting picture quality.

Tape players (VTRs, VCRs, camcorders, etc.) use mechanical parts to move and read the tape. You have rollers, tensioners, a spinning helical head, gears, pulleys, etc. All are subject to slop. If there was no slop, they wouldn't be able to assemble them.

They are also subject to distorting the signal because, for example, tapes are made of mylar, which is a plastic, and will stretch. In order for the helical head to read the magnetic imprint on the tape, it must be in intimate contact with it. That means pulling the tape tightly across the head. That also means the tape will stretch slightly. Add mechanical slop of the other parts into the equation and you have a range of pressures that the tape may be applying to the head as it's stretched. Since the head won't distort, the tape must.

You also have long-term changes in tape speed across the head, called Wow. You have short-term speed variations called Flutter. You have alignment and tape registration changes with different tape brands, and they are compounded by mechanical wear.

Plus you have the usual problems like tape head magnetization after a while, and oxide buildup on the heads.

Add up all the ways a signal can be degraded, and it seems amazing that it works at all.

The effect these variables have on the signal is not only poorer video quality itself, but timing errors. Each horizontal scan read from the tape is ideally a precise time value in length, and these should fall precisely the same distance, timewise, from the previous scans, and the ones to come.

Each group of hoirizontal scans makes up a field. Two fields make up a frame. Again, the timing between fields, and between frames, should be exact.

But, we've seen from the issues above that they are not.

So what does that mean to the viewed picture? A TV set is very forgiving in matters of timing. There is an amount of "slop" built into the design. But vary the timing too much and you get a horizontal or vertical hold problem. Generally they do a good job ...with precisely timed broadcast signals.

On older sets that had a manual knob to adjust these, it was more noticeable than it is today with automatic locking circuits.

But capture from a tape, author to DVD, and play it back, and now you're feeding a signal to the TV that is timed poorly, analog-wise. But you've locked it in by authoring and when it gets to the TV, it can't correct it because by that point, it's timed beautifully again. But the actual material has changed.

The result? Vertical edges in the picture are no longer straight (horizontal scan timing issues). You also have color shifting (field and frame timing issues). These are just two examples of picture quality problems. Throw in dropped frames in the capture device, and now you have audio/video sync issues as well. Remember that non-linear editing is not forgiving, like analog television is.

Add in actual tape damage (curl, excessive stretch, etc.) and you have a horrible quality signal that is almost guaranteed to cause problems in that non-forgiving digital world

Enter the TBC. As the signal enters a full-frame TBC/Frame Synchronizer like the TBC-1000, the video information is digitized and stored in a buffer memory, one field at a time until an entire frame is stored. The timing information is discarded. Then the TBC replaces each and every horizontal line timing with its own. The timing information is determined by the length of the "retrace" area of the signal. This is also where the color information resides. It's the part of the signal you don't see on the screen.

The TBC also takes each completed field and does the same with the vertical "retrace" portion. This is where the vertical timing is stored, and is also where Macrovision pulses appear in the original source material. Line TBCs, like those found in camcorders and VCRs, do nothing to help vertical timing ...only horizontal.

The TBC then passes the clean, precisely-timed signal through a digital-to-analog converter and outputs it.

Without a TBC you wouldn't have a fighting chance of regularly capturing from various tape sources with any measure of success. If the sync issues didn't eat your lunch, the color shifts and raggedy vertical lines in the picture would ..assuming the signal wasn't MV-protected. If it was, you'd need to rely on a signal-degrading filter, such as a "corrector" or "Stabilizer" which do nothing to correct timing ...they just notch out the MV signal, and usually some of the legitimate signal as well :P

So ...a TBC is just "overrated crap"? I won't even comment on that remark.

I read that putting a TBC in between a VHS player/recorder and a DVD recorder will removed the copy protection and "fool" the DVD recorder into recording the VHS tape. Is this true?

If you read what I posted above you'll have learned that there's no fooling involved. The MV signal is history, outa here, sayonora, ........ A quick note, MV is just a video error and can rear it's ugly head when your trying to capture home video as well. It varies by device, essentially genuine video errors on older home movies are misinterpreted as MV which can be very frustrating if your just trying to capture home video since you now have a unwatchable video.