Various embodiments provide example apparatus, method, and computer program product. The example apparatus includes: at least one processor; and at least one non-transitory memory including computer program code; wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to: define a derived image item; and define a single stream item property, wherein the single stream item property is used to indicate that input image items of the derived image item are concatenated in encoded domain to obtain a single stream and are to be decoded by a single decoder.