Digital Dropout
 

When I play raw video at home(avi captured through premiere firewire) captured from my work computer I get a white pixelated glitch every once in a while, but not when I play raw footage that i captured through the same method (different camera though - work is an HC40, home is a trv33) at home it plays back fine on both machines. All the specs seem to be the same for the video. My home machines (tried it on two different ones) are both relatively fast and have no problems when editing video captured native to them, but these ugly dropouts show up when I use footage captured somewhere else. Any thoughts?

Thanks

Jeff

Are both sources showing the same codec, i.e. Microsoft DV AVI?

Are your Premiere project settings identical in both playback environments?

Are you able to play the clips out to a TV set/monitor, to see if the glitch is real?

David Hurdon

Both are MS DV AVI. Both have identical project settings - actually using the same project on both ends. The glitches are definitely real, I'm on a monitor and passing through a dvd burner that picks them up in the final product - my first skydive dvd's. Any more thoughts? Thanks!

Jeff

Reading your first post again, I wonder if you captured from the same tape via two different cameras. I suppose even if you used different tapes, i.e. different source material and two different cameras you might still get the result you're describing, if one of them had dirty heads or was connected by a faulty firewire cable perhaps. I recently saw dropouts on my timeline from material I was pretty sure was pristine when I logged it. I checked it in the camera's LCD and realized the heads needed cleaning at that point. After cleaning, the recaptured clip was fine. Any chance your situation is similar?

David Hurdon

I'm pretty sure its not the heads. We have a stock intro piece that we always use and it works perfectly at the dropzone, but if i bring that piece home on an external drive and put it on my hard drive, the dropout happens. Anything I capture at home though looks fine. Its most evident when I edit at home and then the final product has dropout in the intro and credits that were created elsewhere, but the middle parts are fine, no dropout. at the dropzone the intro and credits are fine. And if i capture video at home and take it there to work with it looks fine. Tried two different computers at home and get the same results. One has onboard video and the other has 64mb of vram. The one with onboard video actually has less dropout. Strange things. Monday I'll be testing it with another machine that is dedicated for video and never drops a frame at work, so we'll see how that works out. Thanks for the help!
Jeff

Here's my last stab at it, Jeff. Assuming you're keeping the clips on the external drive and moving it between your two home PCs, is it possible that the drive is the issue, perhaps overly fragmented or too fully utilized? I know it's unlikely, given your obvious familiarity with equipment and issues, but it's all I've got left.

David Hurdon

Turns out its the encoding on the initial computer. not sure what it is about it, but i took the video to CompUSA and commandeered a dual core sony, and still got the dropout. so i'm going with it must be on the source side. Thanks for all the ideas!

JEff

I share your puzzlement, Jeff. It's hard to understand how the original PC could show the material without drop outs while being the source of them. When you get it all unravelled I'd appreciate hearing your conclusions.

David Hurdon

In developing a DV decoder, I have noticed similar dropouts. In fact, their existance would crash the decoder because the corrupt data meant that "impossible" values were being generated. So, now, I assume that corrupt data can get through and deal with them accordingly.

Where this starts to get interesting is that the appearance of the dropouts depends upon the *decoder* in use. It seems that the MS DV decoder and some others make a stab at fixing the problem. They do a reasonable job but can actually end up masking a deteriorating problem (e.g., dirty heads etc). My decoder just shows you them for what they are!

I was surprised when I first saw such dropouts as they were always in the first few frames of a captured file. What I realized is that the tape transport was still getting up to the right speed and the dropouts were being generated by the camcorder. Recently, I tried viewing the signal from a tape being played at high speed and the incidence of dropouts went up quite significantly. Again, the MS DV decoder attempted to hide them whereas mine showed them clearly.

The fact that you say that two different cameras were used suggests your problem is related to this. Did you use batch capture to get multiple clips? If so, you may want to adjust the preroll time to let the tape mechanism settle before the capture begins.

John.

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