During the transformation of data, for example the decoding of encoded and transformed data, there is front-end processing (FE) to generate a data block for subsequent back-end processing (TR), this front-end processing may include run-length decoding (RLD). Auxiliary data (AUX) indicating the structure of the data block (MB) is also generated during the front-end processing. Typically, the auxiliary data is indicative of the location of zero coefficients within the data block. The implementation of the back-end processing (TR) is adapted to the structure of the data block (MB) based upon the content of the auxiliary data (AUX), thereby making the implementation more efficient. For example, the content of the auxiliary data can determine which shortcuts can be applied during the implementation of an inverse discrete cosine transformation. Generation of the auxiliary data during the front-end processing (FE) is less onerous than investigating the structure of the data block just prior to inverse transformation, because the former involves taking action only for non-zero coefficients, whereas the latter involves checking all coefficients in the block. |