by Paul Trilsbeek
A lot of compression algorithms in current video codecs are lossy, meaning that they throw away information that is seen as less relevant for the perception of the image in order to reduce bandwidth. This information cannot be reconstructed afterwards which is one of the reasons why archives like ours do not like to use lossy compression formats, since one never knows whether the information that is thrown away might be relevant for future use of the data. Another reason is that every time compression is applied to an already lossy compressed signal, the signal degrades. This happens both when using the same compression algorithm as well as when transcoding to a new (future) compression standard. Since codecs and file formats generally have a limited lifetime, this would mean that if an archive wants to keep their archived content interpretable in the long run, it will degrade over time because of the necessary conversion steps to the latest state of the art.
For these reasons, archives generally want to preserve data in as uncompressed a form as possible. The rapid deterioration of physical audiovisual carriers such as celluloid film and many deprecated video formats have triggered broadcast and film archives but also the film industry to start massive digitization projects. Due to the high costs of these operations and the high economical or cultural value of the material, it makes sense to store this digitized material in the highest possible quality because even if it were at all possible to repeat such digitization operations in the future (e.g. to account for new compression standards), it would be a big waste of time and money. The storage costs for these formats are substantial at this moment but will decrease with the introduction of newer, higher capacity storage technology.
A codec that is being widely used at the moment in the film and video archiving world is Motion JPEG 2000. This codec allows for lossless – i.e. reversible – compression of moving images. It is also used as the standard for Digital Cinema, albeit currently in a lossy variant. In the lossless variant, compression ratios of about 1:2 can be achieved, but the main reason for moving to lossless or uncompressed storage of video is, as stated, to prevent future degradation of the signal if current codecs become obsolete.
The MPI is currently digitizing a large collection of valuable videotapes from the German behavioral scientist Irenäus Eibl-Eibesfeldt. These recordings were originally made on 16mm film and have been transferred to Betacam SP (broadcast quality) video, which was a costly and time-consuming process. The Betacam SP tapes are now being digitized in lossless MJPEG2000 format in order to retain the highest possible quality for this material. In addition, MPEG2 and H.264 distribution copies are created to make the material more accessible over lower-bandwith data connections.