Abstract: Method and system for indicating that at least one row or column of a DVD data block has an uncorrectable number of errors, by marking or flagging the corrupted codewords of a codeword with defect detect signals. When a column (or row) of the data block is found to contain more than a thereshold number of errors, a selected number w of distinguishable codeword values (DSVs) “x” is associated with at least one column (or with at least one row) of the block. When the block is further processed and the presence of more than a threshold number of DSVs is sensed, the system interprets this occurrence as indicating that an uncorrectable group of errors has occurred in a column and/or row of the block.