Scan conversion apparatus, image encoding apparatus, and methods of controlling them

Abstract

Using scan conversion processing of changing the scan order for each block, parallel scan conversion processing is executed if possible. A scan status holding unit holds statistical information based on the appearance frequency values of coefficients in a block. A scan order holding unit holds coefficient position information in which the coefficient positions in a block are arranged based on the scan order. A significant data position information generation unit scans one block data in accordance with coefficient position information, and generates information representing nonzero/zero for each data position. Based on the statistical information and the information generated by the significant data position information generation unit, a parallel number determination unit determines whether to process two blocks in parallel or process one block. In accordance with the determination, a scan conversion unit scan-converts two input blocks in parallel or scan-converts only one of the blocks.