Re(2): [AV Media Matters] Compression discussion.

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

>compression in the video domain has gotten so darn
>confusing that it is hard to define exactly what you are saying no to.

I agree, especially as the picture quality depends on the coder for a given
MPEG level, and so is a question of operational judgement, good design and
the right ancillary equipment before coding.

>
>BUT
>
>From an archival perspective there are many other concerns that may not
>exist in current broadcast operations.  The needs are different and
>therefore the requirements are somewhat different as well.  For one
>thing ... one of the goals is to "pass the flame" on in
>an intact fashion.  Why?  Well because we cannot anticipate now what
>technology may evolve in the near and not so near future - and so
>keeping the original content in a fashion that is as close to the way it
>was in origination becomes very important. ...
>If you already have high bandwidth should you reduce it for
>archival storage?  I think that the answer is clearly no.  Materials
>that have been acquired in already reduced bandwidth is another issue -
>if you have already lost it.... there is no going back.

This is the core of the argument. I do not accept your 'clearly no'
statement - only that what you do, how you compress takes into account these
points seriously, and that a reasoned intelligent judgement is made. As far
as possible short term conveniance and cost must not be allowed to determine
the issue. The archivist has indeed a responsibility to keep things properly
and the accountant must accept that!

BUT
Film is different and news footage is different, but ...
For material originated in a TV studio in SDI, and post produced without any
(further) compression to the final master tape, what now for the archiving
of that? I can keep the original tape, but, as I said in another posting,
I'm not sure of the durability of availability of current uncompressed
formats. If I chose digital betacam, say, then I can get a machine when I
need one several or more years from now, (at least seing from europe). But I
have compressed but remain very close indeed to the original uncompressed
pictures - very close indeed. And I would argue that I have a good quality
headroom as well, ie I can go to any of the current lower bit rate
compression schemes for editing, versioning and transmission without
significant concatenation problems.
At the other end I would never suggest a DVD video as a suitable long term
archive of such a programme, nor any of the low bit rate streaming formats,
or AVIs or whatever.
Where my doubts are is in the middle - what about the professional 50Mbps
formats - and maybe even the 20/25Mbps? No one says there won't be some
artefacts, here and there - the decision is what you can accept. This I
would argue is largely material dependant and different say for a major TV
film series and say a based political discussion programme. (The resale
value in ten years is higher for the first than the second).
'Pass the flame on intact' is not the same as not compressing, because the
compressed version can be so near the original as not to matter, and still
be robust enough to go survive more compression in transmission etc..

I've a feeling this correspondnace could go on forever ...

best wishes
tony
                                   Tony Gardner

                Press and Communication Service
                               Audiovisual Unit
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                     anthony.gardner@cec.eu.int