| 摘要 |
<p>According to the present invention there is provided apparatus for reading and writing data to a storage medium, wherein data is divided into fragments of predetermined length and each fragment comprises a marker, the apparatus comprising: means for detecting markers; means for extrapolating from the position of known markers to establish the position of an undetected marker. The present invention reduces the likelihood of data being unrecoverable as a result of unidentifiable marker patterns. Where a marker pattern is not detected, but a previous marker pattern within the data track has been successfully detected, the position of the missing marker is extrapolated from the position of the previous marker, using a knowledge of the relative spacing of markers which is predetermined by the data interchange format. In the embodiment to be described, each data fragment comprises a header containing ancillary information wherein the headers of the data fragments comprise the markers. Preferably, the extrapolation is done from the position of already-detected markers. to establish the position of subsequently undetected markers. Optionally, the extrapolation may be done in reverse from the position of subsequently-detected markers to establish the position of previously undetected markers. The apparatus may comprise means for setting a limit on the number of consecutively undetected markers whose position will be established by extrapolating from the position of a known marker. <IMAGE></p> |
