The technology described herein facilitates parallel encoding of two groups of blocks of data of a sequence of blocks of data, whilst also facilitating the use of dependent encoding across the sequence of data blocks. This is achieved by allocating pairs of first and second groups of data blocks to separate encoding units, and determining an encoding parameter value to be used for encoding the first block of each second group of data blocks. For correct reconstruction of the image, it is ensured that a block belonging to the first group of data blocks of a pair of groups of data blocks is encoded with an encoding parameter value that will cause a decoder to use the determined encoding parameter value when decoding the first block of the second group.