2.2.1.1 Magnetic tapes
In its present form magnetic tape recording was developed in the 1930s by AEG Telefunken and introduced for professional application in 1936. It became widely used within the German Radio. Because of World War II, however, its use was restricted to Germany. After the war it came to the United States from where it spread worldwide. In the late 1940s and early 1950s the use of this recording technology was concentrated mainly in the broadcast and recording industries. From the early 1950s onward, however, home audio recorders were developed which operated at slower speeds and employed half and quarter track formats to reduce the costs of magnetic tape. However, this was at the expense of recording quality. Also, during the 1950s, transistorised portable recording equipment became available that made sound recording possible everywhere in the world. This lead to a mushrooming of recorded sound collections, particularly in the fields of cultural, linguistic, anthropological, and ethno-musicological documentation. In the 1960s, cassette formats were developed. Of these, the compact cassette soon became the dominant format in the market, and is still in use.
In addition to magnetic tape, magnetic wire recorders were developed in the United States in the 1940s. They also gained some popularity in Europe in the 1950s and 60s.
Figure 7: Principle of magnetic audio tape recording. In such “linear“ recording, the speed of writing is the same as the speed of the tape.
After several experiments, digital audio recording on magnetic tape was introduced in the 1980s. All of these early professional and semi-professional formats are now obsolete. In 1987 R-DAT (Rotary head Digital Audio Tape), a digital recording cassette format, was marketed and gained some popularity in semi-professional and professional circles. Since about 2005, however, it has also become obsolete. Now all audio specific magnetic tape formats are, in practice, dead. Audio recording, post production, and storage have become part of the IT (computer) world with its specific carriers and formats.
From 1956 onward, magnetic tape was also used for video recording. Several professional reel-to-reel formats were developed and in use until the late 1970s. They were followed by professional analogue and digital cassette formats. For home recording, early open reel formats were available from around 1970 and, around 1980, cassette home formats became widespread. Of these, the VHS format survived until recently. For small handheld camcorders (“handy cams”), an 8 mm cassette system became popular (Video8, VideoHi8), which was still in use in the early 2000s. Digital home formats were introduced in 1996. The Mini DV format dominated handheld camcorders from the early 2000s but has also become obsolete, replaced by optical, hard disc, and solid state (“flash card”) recording systems. The same development for the last remaining professional video tape formats is under way.
Figure 8: Principle of magnetic video recording. The high bandwidths of video signals require high recording speeds, which are achieved by a fast rotating head that writes narrow video tracks across a tape moving at a much slower linear speed. This principle of “helical scan” recording is also used for digital video formats and R-DAT.
Thus, video has developed in a similar way to that taken by audio. Proprietary video-specific formats are being replaced by file formats. Recording, postproduction and storage have, like audio, become part of the IT world.
Some video cassette formats have also been used for audio only recording purposes (IASATC 04, 5.5.7).
Beyond specific audio and video formats, magnetic media are the most prominent storage media in the IT world. Magnetic tape plays an important role as a computer backup medium and hard disc drives (HDD) have seen tremendous growth both in professional and home applications. Both carrier types have become the backbone of professional digital audio and video archiving. While this publication concentrates on (traditional) audio and video tapes, the basic principles described are valid for magnetic computer media.
