HELICAL TRACK MAGNETIC TAPE RECORDER FOR DIGITAL SIGNALS WITH VARIOUS OPERATING MODES

摘要

In search runs in a helical track recorder the read and recording track angles differ. This means that only track segments can be read owing to azimuth decoupling. In digital recording systems, this results in the effect where, in video recorders with considerable segmentation (e.g. 12 recording tracks per full image) and data reduction (DCT), the imagewise coherence of the data of two neighbouring tracks fails. The purpose of the invention is to reduce the interference occurring in search runs. The recorded useful data signal is usually embedded in synchronisation words, error protection data and pointers which show where the subsequent data package together with the error protection data belong in the image. According to the invention, the relationship of the head drum/tape advance phase to the tape advance is controlled in such a way that all the pointers are read in with the same frequency in an interval of several successive tracks = full images. Thus interference in search runs is reduced. Especially applicable to digital helical track magnetic tape recorders.