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.

Branko Bubenik