bad VHS = dropped frames?

[Desabells]

This may seem like a stupid question but I am new to this so please forgive my ignorance. I own a recording studio so I mainly deal with audio. Video is a new area for me. I have noticed that when capturing from VHS that everything is fine if the VHS is good quality but if the tape displays some problems then I get dropped frames. Could someone tell me why this is? I mean, when dealing with audio, if someone wants me to transfer an old LP to CD, then the computer captures the audio exactly. Including the flaws (scratches, etc.) but the flaws do not make the computer act up. So why is video different? Why would the flaws in a VHS tape cause you to drop frames?
Thanks in advance for any assistance.

[Dragonsf]

A video stream is composed of "frames", whereas analog audio is just a stream of analog values (which become "samples").To digitize a video frame, the converter must know where a frame starts and ends.And within a frame, it needs to know when a new line will start.This is done by a synchronization signal.So, a video signal is composed of more than one signal: sync, color info and brightness info.
If your source is a bad, parts of the sync signal is weak/absent and the converter can't recognize this frame.Some converter will drop/ignore this particular frame, other will produce bad frames.

[stevedore]

Also being new to this, I had exactly the same problem, even with VHS tapes that seemed to be in fairly good condition.

From reading on this forum, it seemed that I needed a timebase corrector. I acquired one, and it has solved ALL of my VHS capture problems. A legitimate bad spot on the tape will show up in the capture, but it doesn't seem to drop any frames.

Steve.

[Desabells]

DragonSF, thanks for the explanation. I figured the reason must have something to do with sync.
stevedore, could you give me some info on the timebase corrector? What you bought and where you purchased it?

[stevedore]

The timebase corrector I bought is the Datavideo TBC-3000. I got it on Ebay for about $250. This model has adjustments for tint, brightness, contrast, & color that are applied during the processing. The same company makes the TBC-1000, which I believe performs the same timebase correction, but lacks the adjustments, and is less expensive. The TBC-3000 also has 2 channels, although I'll never use more than one. Given the choice, I would have bought the TBC-1000, but the TBC-3000 showed up on Ebay when I was shopping. As soon as I'm done with my VHS capturing project, I'll probably put it back on Ebay.

I bought my ADVC-100 from 4videoequipment.com; they also sell the TBC-1000.

Good luck.

[Desabells]

stevedore,

Thanks for the info. I have just ordered a Datavideo TBC-1000. I had already decided to buy the Datavideo brand and now I feel more confident about my choice after you stated you own the TBC-3000. I own the Datavideo DAC-100 analog to digital convertor already and I am very pleased with its performance so I feel like I am sticking with a brand I can trust.
Thanks again and I'll let you know if it fixes the problem. Even if it doesn't, I feel from my recent research that a TBC is a good investment. So I'll be happy no matter the outcome.