Figure 2

Block structure of encoded read. A read partitioned into blocks of five bases, with block i containing bases _{b 1ib 2ib 3ib 4ib 5i}, showing how the two-base-encoding and ECC color calls are split into five ‘data’ colors _{c 1ic 2ic 3ic 4ic 5i}, from which the block can be called, and a ‘parity’ color (_{p + i}) which straddles the block and its downstream neighbour. The data colors are used to determine the nucleotide sequence of the blocks and the parity color is used to detect whether an error has occurred. Note that the data colors are a mixture of both color streams, with the parity color coming from the color stream of the code.