Entropy Coding

DC and AC components finally need to be represented by a smaller number of bits:

• Categorize DC values into SSS (number of bits needed to represent) and actual bits.

      --------------------
         Value       SSS   
           0          0   
          -1,1        1   
       -3,-2,2,3      2     
      -7..-4,4..7     3   
      --------------------
  

• Example: if DC value is 4, 3 bits are needed.

  Send off SSS as Huffman symbol, followed by actual 3 bits.

• For AC components (skip, value), encode the composite symbol (skip,SSS) using the Huffman coding.

• Huffman Tables can be custom (sent in header) or default.