Coding Process

What is coded?

We have a one-dimensional array of data (usually consisting of quantized wavelet coefficients) that we want to store efficiently, but also in a progressive manner. This is achieved by coding the bit-planes from the top down, e.g. first we code bit 8 of all coefficients, then bit 7 of all coefficients, and so on until we have coded all the information.

How is it coded?

Due to the wavelet transform we hope to have reduced most coefficients to small values (or 0 in the ideal case), thus we only run-length code runs of consecutive 0 bits. Each 0 bit in the coded stream represents 2^k zeros, whereas a 1 in the coded stream is always followed by k bits (denoting some value n) and a sign bit. This is interpreted as n 0 bits followed by a single 1 bit (and the value to which the 1 bit belongs as having that particular sign).

Now, two additional things are done:


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