1. An image converting system comprising two or more image converting devices, each of the image converting devices including an image input device, an image converter, and a line memory, wherein the two or more image converting devices output conversion results to a storage medium common to each other while synchronizing with each other, wherein each of said image converting devices converts input image in accordance with a conversion specifying means, wherein said synchronizing is realized by providing said conversion specifying means with interrupt instructions, wherein said interrupt instructions and conversion specifying means are stored in said storage medium, wherein said image converting system further comprises a computing device, said computing device being configured to read and write said conversion specifying means, thereby while one conversion specifying means is being processed by one of said image converting devices another conversion specifying means in said storage medium can be rewritten by said computing device.