In the case of determination means (10) for determining the quality of a data signal (DS), which data signal (DS) consists of data blocks, wherein each data block is at least two-dimensional in structure and comprises at least two data zones, there are provided validity assessment means (7) for assessing whether data zones of at least one data block are valid or invalid and for generating and outputting validity information (QI) representing the assessment result and validity information processing means (9), which are designed to determine the quality of the data signal (DS) on the basis of the validity information (QI).