Best way to convert analog to digital?

clearvu wrote on 7/10/2003, 2:05 PM
I have a Panasonic PV-DV953. It has a pass-through feature which allows me to take, for example, a VHS tape signal and send it to my computer.

The problem that I notice is that when the tape starts being captured, the signal that is captured is VERY distorted and the audio crackles. Once the tape starts running for 3 to 5 seconds, everything is great. However, the problem reoccurs if there is a new recording section on the tape. It seems the signal gets confused and again spits out blocky video and crackled sound.

Is this problem only because of the way I'm doing my capturing? For example, I've heard of analog to digital converters such as from Canopus. Would this product experience the same problem? If not, why does my camera's converter have such a problem.

Comments

TorS wrote on 7/10/2003, 2:12 PM
Anything that happens at the very beginning or end of a tape is unpredictable. If that's where your 3 - 5 seconds are located, there probably isn't a converter in the world that can help you. Never record anything important close to the ends. Passthrough is generally looked upon as an excellent way to convert.
Tor
RBartlett wrote on 7/10/2003, 2:38 PM
You've got the digitisation chasing the sync which probably isn't running straight at the times you mention. You've got the source probably running already at full speed trying to "track" to the original speed which could just have been accelerating on the helical scan.

Where your playback deck can represent the exact dynamics and signal as it was layed down, your digitiser has to firstly be able to match its phase relationship to it and place that to fill a field or frame store before hitting the transport to DV or tape (etc).

Some dedicated TimeBaseCorrector with frame stores can be tuned to be more tolerant, or are able to adjust out of the box. Preroll is king - even with digital recording media "sources".

Ever had a VHS tape on the same VCR play OK on a portable TV but not on the old faithful main TV? Same thing. Tolerances.
clearvu wrote on 7/10/2003, 2:43 PM
The problem does always occur at the beginning of the VHS tape capturing. However, you know how when people video things the tape stops and starts again? Well, the VHS tape playback often has an almost, like, "blank" spot. It's at THAT point that the capturing problem would occur again.

The reason I'm trying to figure a way around this is that I'm looking into doing a small side business for converting VHS to DVD. If people don't want chapters or anything, I have a software that can capture the video from VHS and simply make a DVD all in one step. Do you see where my concern is? Doing things this way will end up giving a client a DVD with stuttering video and audio at the beginning of the DVD, with the possibility of it recurring at different points on the DVD if the VHS source has problems. The client, of course, will say, "hey, that noise wasn't on the original tape!".

I have already done a job for someone and had to edit all the crap out. Fortunately, they wanted menus and chapters. So I ended up having to edit everything anyway. In this case it wasn't so much of an issue because the client wouldn't notice a few seconds of missing video.


Brian
farss wrote on 7/10/2003, 5:48 PM
I do this all the time, mostly to VCD, sometimes to DVD.

You could try a Super VHS VCR with a TBC, JVC make one but its a lot more expensive than a consumer VHS VCR. But you're still going to have some issues to deal with to do a good job.

VHS doesn't need to lockup like DV and TVs are pretty tolerant of wobbly sync so your always going to have some issues, I spend most of my time chopping out the wobbly bits.

The other issue is the unstable horizontal sync. Your end up with black borders in the captured DV. The amount of fine motion in this area is not a good thing whenyou encode to MPEG so you need to mask it out. You can do that in VV but I prefer to use TMPGEnc to encode, it has a built in mask that I adjust to just get rid of the wavy borders.