STUDIES AND RESEARCH
Deterioration of Video Originals in Use
A survey of the results in the research
conducted on the degree of degeneration of audiovisual
documentation registered on audiovisual analog technology
during reproduction and re-recording.
In the introduction, the author analyses the historical
development of the registration of image and sound (mechanical,
photochemical, electromagnetic, optical digital registration)
and establishes their contribution. In order to determine
the behavior of the content of video documents in migration,
from generation to generation, that is the transfer of
information akin to genetic copying, the degradation of
two video formats was researched — VHS (an amateur video
format) and Betacam SP (a componential analog format).
Through experimentation with video documents on the VHS
format, it was found that the image completely fell apart
on the ninth generation copy (static noise overwhelmed
the image’s signal). Nevertheless, the sound quality was
still satisfactory, which shows that the degradation of
image is not linear in every frequency range, but rather
more pronounced in high frequency ranges.
The result of experimentation on the degree of degradation
of signals recorded on Betacam SP tapes during content
migration shows an unexpected stability in the recorded
image and a small losses in the transfer phase from one
tape to the other in so-called generational copying. Even
though manufacturers of Betacam television equipment guarantee
the broadcast quality of images up to the third generation,
tests showed that the image quality was very good in the
fifth generation, good in the eighth generation and still
usable in the 15th generation.
Unlike the VHS amateur format where the image was already
completely degraded in the 10th generation, the signal
stability of Betacam equipment and tapes during content
migration was established (according to signal/noise ratios
and the frequency range). About 50% of the signal was lost
in the 15th generation, therefore it can be assumed that
complete degradation would happen somewhere between the
25th and 30th generation copy.