TBC under control: Suggestion for a new documentation method for the digitization of analogue video

Sophie Bunz
Electronic Media Review, Volume Six: 2019-2020


The active preservation of analog video heritage has its roots in the late 1980s, when the migration of the diverse analog open reel and cassette formats was state of the art. The practice has shifted to digitization and the storage as digital video files. Nonetheless, the transfer process is still dependent on the original mostly obsolete and erratic (professional) playback devices and additional equipment, such as time base correctors (TBCs). TBCs play a very important role in the digitization process. They facilitate the compensation of artifacts such as dropouts and (sync) timing errors. At the same time, they function as processing amplifiers. Therefore, TBCs offer the possibility of optimizing the signal and simultaneously entail the risk of manipulating and altering the signal in an undesired way. This study aims to find a comprehensive and reproducible method for documentation and quality control to identify and objectify the individual key parameters of the applied TBCs as well as to ensure the traceability of the set TBC adjustments chosen for each digitization. To obtain full control of the process and to document all artifacts induced into the video image by a TBC, we have developed a specific set of test sequences. The analysis of the differences between the source signal and processed signal thus offers a characterization of the image artifacts caused by a TBC. Our test sequences will allow a well-informed decision-making process when evaluating the best TBC for a planned digitization project.

Keywords: analog video, digitization, TBC, time base corrector, quality control

Sophie Bunz
Studio for Video Conservation