RE: [AV Media Matters] Digest for AV-Media-Matters@topica.com, issue 237

[tony gardner <anthony.gardner@cec.eu.int>]

>Commenting on Anthony Gardner's post, is it ever possible to
>duplicate anything at "100% of the original quality"?

Yes it is - once you have chosen the original digitilization
standard on the storage mediaum (number of pixels, bits per sample,
data format(Mpeg ...)) then a digital copy is bit by bit identical
to the original and - after hundreds of generations - will be as
good as the original. The same as copying files on your computer.

You only lose quality if you decode the digitilized information to
some other standard (eg SDI digital video) and then re-encode. In
this case, the deterioration depends on whether the new
digitilization follows the same standard or a different one, and the
degree and type of compression. If it follows the same standard then
deterioration is minimized and small. If compression is zero, then
the process (with a little care) is transparent. This is the
argument for using uncompressed video in archive applications.
However, in practice, using the 50Mbps and DB formats in a digital
interconnection environment, any deterioration requires measurementy
and comparison equipment to see - it is not visible as picture
distortion. DVD-V, transition by Digital TV transmission and
analogue tapes will show visible deterioration.

>Access on video, of course.  But as long as it is still
>feasible to print >from film to film, I'm not sure why suggest "preservation" on
>any video or >data format.  (Anymore than I would suggest someone preserve
>video on >film.)

Surely a film to film copy has much inherent quality loss? The
judgement is the technical quality of a digital transfer to data
tape at the appropriate bit rate compared to the film copy, - and
the relative costs.

Incidentally, transferring video to black and white film, with
seperately encoded colour difference signals was seriously suggested
and demonstrated in the UK by Thames TV, the argument being that the
support (film) is inherently better than magnetic tape. It was known
as 'FILMMAC' and was a derivative of the 'MAC - multiplexed analogue
component' video systems being touted at the time.

>salesman is trying to rush me into some short-term solution.
>And insult me and my views about compression in the process.

I hope I have not been insulting! It was certainly not intended.
Incidentally I am an end user in a non profit making broadcast
studio facility: I have no connection with any manufacturer
whatsoever. I am not a salesman.

Tony Gardner
EC A/V Faciltiies, Brussels, Belgium.
These views are my own.