Digital Video Recording in the 625-Line System

Multiple generation copies of videotape recordings are, even today, still subject to considerable reductions in quality. At the present time, it is difficult to foresee any progress being made in the tape, head, and amplifier fields which will bring about any noticeable improvement, as long as the analog FM recording method is retained. On the other hand, recording with digitized video signals would bring definite improvements without incurring any basic disadvantages such as increased tape consumption. The quality of copies (generations) would, with the exception of dropouts, no longer be influenced by the machine. At the moment, tape recorders with rotating head arrangements offer the highest storage density by far and, for this reason, are particularly suitable for digital video recording. Wavelengths of approximately 1 μm, using a corresponding code of 2 bits/μm, can be read with certainty. A track width of 40 μm yields a S/N ratio better than 26 dB and a corresponding BER (bit error rate) of about 10⁶. Including safety margins, a recording density of 3 Mbit/cm² can be achieved. Assuming that a future European digital video system will use a data rate of approximately 160 Mbit/s, a transport velocity of about 24 cm/s is required when 1-in tape is employed. A tape speed close to 24 cm/s is customary for the present generation of helical-scan machines in the 625-line system, recording analog signals.

Print ISSN

0036-1682

Published

1981-02

Content type

Information

DOI

10.5594/J01501