Methods and apparatus for differential encoding

A data stream encoder eliminates duplicate transmission units in a transmitted data stream in which the detected duplicate may not be the immediately preceding transmission unit. A data aggregator transmits a stream of data by identifying a frame interval, or timing interval, corresponding to the time to send a frame of data in the stream. Each of the frames includes a predetermined number of blocks. Configurations identify repetition patterns in the blocks of successive frames, thus looking backward a frame interval to identify a previous corresponding block in the preceding frame. The corresponding transmission block need not be the immediately preceding block or transmission unit. For certain types of data, successive frames exhibit the same or similar patterns in the blocks of data defining the frame. Therefore, the encoder identifies duplicate blocks in successive frames, and transmits only the blocks that differ from a counterpart block in the previous frame.