[AV Media Matters] DV recording robustness-another perspective

[e.ha.zwaneveld@nfb.ca]

Greetings,

Recent comments from Peter Brothers and Bob Curtis on the DV video
format prompted me to share their observations with Horst
Schachlbauer, who is the Project Leader of the European Broadcasting
Union (EBU) / Future Television Archives project. This project is
the result of an urgent request by member broadcast organisations
faced with the problem of having to save millions of hours of
valuable television legacy content for the future and expecting an
ever increasing amount of program content to be archived as digital
television broadcasting becomes reality. The EBU is supported by 118
members in 80 countries (69 active members in 50 countries and 49
associate members in 30 countries). The EBU Headquarters in Geneva
hosts around 10,000 visitors and delegates from member organisations
every year. In television, 20 satellite channels relay 70,000
transmissions per year (including 25,000 news items and 7,700 hours
of sports and cultural programmes). Eurovision is received by 255
million homes or a potential of 640 million viewers.

I quote:
"I would not be so pessimistic about DV tape. Current headlife shows
fabulous figures ( more than 2000 hours, in a reference installation
6000 hours are quoted. ). If you look at the construction of the
total head/tape path plus elastic parameters of the 4-layer DV tape,
there is some reason to be optimistic. By the way, forecast for
future longitudinal Mass Data Storage media is going in the
direction of thin tape as well. Evaporated tape requires careful
future scrutiny however.

As far as "cloning" on digital recorders is concerned, the error for
off-tape with modern DVTRs is at about 10-5. FEC will take it beyond
10-11 after correction. Concealment is not as granular with
compressed formats as it is with linear ones, but what is a
macroblock substituted from a previous field from time to time. It
is hardly conspicuous.

In analog, there is no correction. Coarse concealment in the form of
the substitution of a whole line or a fraction of it is the norm.
And every copy will deteriorate the quality of the content to be
preserved, not just in terms of increased S/N but also in terms of
reduced Y/C bandwidth due to concatenated filtering effects.

Analog is becoming nostalgia now: digital is the future

Analog will be dead soon...long live digital!!!"

I hope that this additional perspective will be of help in this
discussion.

Best regards,

Ed H. Zwaneveld,
Technological Research and Development,
National Film Board of Canada
125 Rue Houde, T-3
Saint Laurent, QC, Canada H4N 2J3
Tel: +1-514-283-9143
Fax: +1-514-283-0278