Posted by ptravel on 10/31/99 11:52

mmaker@my-deja.com wrote:
> PTravel wrote:
> > Bits don't get corrupted during a firewire transfer,
>
> Yes they do.
>
> > and drop-out, i.e.
> > uncorrectable data loss, is incredibly rare for digital video media.
>
> No they're not.

Simply saying so doesn't make it so.

>
> > In the
> > 200-300 hours of digital video that I've shot, I've never had a single
> > instance of drop-out -- not one.
>
> Really? Your deck actually tells you when it gets an uncorrectable
> error?

No -- drop out is obvious when it occurs.

>
> Or are you just guessing you've never had a dropout because you've
> never noticed it?

See above.

>
> > There is no generation loss when copying digital video.
>
> Here's an idea: take a DV file, record it from tape to tape a hundred
> times, capture it back into your computer, then do a bit-by-bit compare
> of the original file and the hundredth-generation copy. I think you'll
> be surprised by the result.

I think you'd be surprised by the result. I have no intention of
wasting that kind of time. Drop out is exceeding rare -- I've never
experienced it, and those who I know who have rarely experience it and
shoot far more video than I do. Nonetheless, drop out is not the same
thing as generational loss.

>
> > Both hard drives and digital tape employ error correction,
>
> But one can do something _before_ dropouts become a problem, for
> example by moving the data from that block to a different block... and
> the other can't.

So what? How often is a hard drive read, versus tape? The recording
density is far greater for hard drives than tape.

>
> >which is one of
> > the reasons why drop-out is so rare for digital video tape.
>
> Except it's not. When DV error correction can't fix a block read from
> tape it simply replaces it with the same block if it's video, or
> silence if it's audio. If the camera is stationary and there's no
> movement in that block of pixels you probably won't notice, but you
> still got a drop-out and you still lost the bits.

DV cameras don't replace drop-out with anything, and when I say I
haven't experienced drop out and don't know anyone who has encountered
as anything but a freak occurence, I'm not referring to stationary
cameras.

>
> Mark

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