A system for transmitting digital data representing an original over plural transmission links, at least some of which have limited bandwidth, including a digital data source storing digital data representing the original, a digital data receiver receiving the digital data representing the original via one of the plural transmission links having limited bandwidth and a digital data transmitter operative to transmit the digital data representing the original to the receiver over a transmission link having a limited bandwidth in plural blocks which are sequentially transmitted at a rate determined by the limited bandwidth, each block being an incomplete collection of data which includes parts of multiple frames, each frame being viewable in a selectable order by the receiver even when less than all of the plural blocks have been received, receipt of subsequent blocks by the receiver being used to cumulatively improve the quality of the digital data viewed by the receiver.